Co-reporter:Hendrik Leopold, Ivana Císařová, and Thomas Strassner
Organometallics August 28, 2017 Volume 36(Issue 16) pp:3016-3016
Publication Date(Web):August 17, 2017
DOI:10.1021/acs.organomet.7b00421
The synthesis and characterization of the first cyclometalated arylthiazole-based iridium(III) phosphorescent emitters of the general structure IrL2(acac) with L = 3-(4-bromophenyl)-4,5-dimethyl-1,3-thiazol-2-ylidene and 3-(4-methylphenyl)-4,5-dimethyl-1,3-thiazol-2-ylidene and acac = acetylacetonato is presented. All complexes were isolated isomerically pure and were unambiguously assigned by a solid-state structure, DFT calculations, and 2D NMR studies. Investigation of their emission behavior revealed emission maxima at 495 ± 5 nm. Quantum chemical calculations were used to calculate the energy differences between the possible isomers and to understand the emission behavior.
Co-reporter:Felix Schroeter, Johannes Soellner, and Thomas Strassner
ACS Catalysis April 7, 2017 Volume 7(Issue 4) pp:3004-3004
Publication Date(Web):March 29, 2017
DOI:10.1021/acscatal.6b03655
Recent studies have shown that anionic palladium complexes are viable catalysts for a range of catalytic cross-coupling reactions. We present a one-step synthesis of the anionic “ligandless” palladium complex [NBu4][Pd(DMSO)Cl3] together with its crystal structure. This compound has been shown to be an active precatalyst in the Mizoroki–Heck reaction. Under Jeffery conditions, activated aryl chlorides can be coupled in yields of up to 94% without the need of an additional ligand. The presence of a small amount of water was necessary for product formation. An Amatore–Jutand-type catalytic cycle is consistent with the results presented herein. For comparison with the known mixed complex [(pym-Im-Me)2PdCl][Pd(DMSO)Cl3], the cationic complex [(pym-Im-Me)2PdCl]PF6 (pym = pyrimidyl, Im = imidazolin-2-ylidene) has been synthesized and characterized using standard techniques.Keywords: anionic complex; C−C coupling; Mizoroki−Heck reaction; NHC; palladium;
Co-reporter:Vladimir N. Emel'yanenko, Maria Kaliner, Thomas Strassner, Sergey P. Verevkin
Fluid Phase Equilibria 2017 Volume 433() pp:40-49
Publication Date(Web):15 February 2017
DOI:10.1016/j.fluid.2016.11.010
•Methyl-, methoxy-, fluoro-, bromo-derivatives of phenyl-1H-imidazole synthesized.•Vapor pressures measured by the transpiration method.•Enthalpies of vaporization derived from pressure-temperature dependence.•Consistency of vaporization enthalpies tested by a group contribution method.•Gas-phase enthalpies of formation of phenyl-1H-imidazoles calculated by G3MP2.Phenyl substituted imidazoles exhibit versatile biological activity. 1-(R-phenyl)-1H-imidazoles with different functional groups R provide a convenient suitcase of molecules with tunable physicochemical properties adjustable for many practical applications. In this work, the absolute vapor pressures of 1-(R-phenyl)-1H-imidazoles (with R = H, 2-methyl, 4-methyl, 2-methoxy, 4-methoxy, 2-fluoro, 4-fluoro, 2-bromo and 4-bromo) at different temperatures have been measured by the transpiration method for the first time. The standard enthalpies of vaporization of these compounds were derived from the temperature dependencies of the vapor pressures. An internal consistency of the standard vaporization enthalpies has been proven by comparison with vaporization enthalpies of parent species, as well as by a group contribution method. A system of group-additivity values is suggested for a quick assessment of vaporization enthalpies of different 1-(R-phenyl)-1H-imidazoles. Gas-phase standard molar enthalpies of formation of 1-(R-phenyl)-1H-imidazoles have been calculated using the high-level quantum-chemical method G3MP2. The combination of experimentally determined standard vaporization enthalpies with the G3MP2 results allows for the prediction of the liquid-phase standard enthalpies of formation for the studied compounds.Figure optionsDownload full-size imageDownload as PowerPoint slide
Co-reporter:Hendrik Leopold
Dalton Transactions 2017 vol. 46(Issue 24) pp:7800-7812
Publication Date(Web):2017/06/20
DOI:10.1039/C7DT00828G
We report the synthesis of seven novel backbone functionalized N-phenyl-1,3-thiazol-2-ylidene platinum(II) complexes and their photophysical properties. Electronically diverse N-phenyl-1,3-thiazol-2-thiones were prepared by a reaction of aniline with carbon disulfide and different α-haloketone compounds. Oxidative desulfuration and salt metathesis yielded the desired NHC-precursors with hexafluorophosphate counterions. In addition, a new route for the synthesis of N-phenyl-1,3-benzo[d]thiazole tetrafluoroborate via N-arylation using hypervalent iodine species is presented. All complexes were prepared from the corresponding NHC precursor in a one-pot process using silver(I)oxide, transmetalation to platinum and reaction with the β-diketone acetylacetone under basic conditions. These complexes exhibit strong phosphorescence with quantum yields up to 72% in 2 wt% PMMA films with decay lifetimes of 8.8–12.3 μs. The influence of methyl- and phenyl-groups, and an ester-substituent at the 4- and/or 5-position of the 1,3-thiazole moiety, as well as the N-phenyl-1,3-benzo[d]thiazole-derived motif is discussed. The 4,5-unsubstituted-N-phenyl-1,3-thiazol-2-ylidene platinum(II) acetylacetonato complex served as a reference in this study to evaluate the electronic effects originating from the backbone substitution. All complexes emit in a narrow range of the bluish-green spectrum of the visible light (510 ± 10 nm).
Co-reporter:Thomas Strassner
Journal of Organometallic Chemistry 2017 Volume 845(Volume 845) pp:
Publication Date(Web):15 September 2017
DOI:10.1016/j.jorganchem.2017.05.043
Co-reporter:David Schleicher, Hendrik Leopold, Thomas Strassner
Journal of Organometallic Chemistry 2017 Volume 829(Volume 829) pp:
Publication Date(Web):1 February 2017
DOI:10.1016/j.jorganchem.2016.10.036
•Synthesis of cyclometalated ruthenium NHC complexes with three DMSO ligands.•A change in geometry from facial to meridional is confirmed by X-ray and DFT methods.•Substitution of two DMSO ligands by 2,2′-bipyridine is investigated.We present the synthesis of cyclometalated ruthenium N-heterocyclic carbene (NHC) complexes of the general formula [Ru(CˆC*)(DMSO)3Cl] and their use as starting material for the synthesis of a heteroleptic 2,2′-bipyridine (bpy) complex [Ru(bpy)(CˆC*)(DMSO)Cl]. Starting from the corresponding η6-(p-cymene) complexes [Ru(p-cymene)(CˆC*)Cl], the π-coordinated aryl ligand is substituted by three S-bound dimethyl sulfoxide ligands. In the course of this substitution, the complexes undergo a change in geometry from facial to meridional, which is unambiguously proven by solid state structure determination and DFT calculations. The labile DMSO ligands can be substituted by bidentate ligands as shown for the widely used 2,2′-bipyridine. The resulting air- and moisture-stable heteroleptic complex features two bidentate (CˆC* + bpy) and two monodentate (Cl− + DMSO) ligands.Displacement of the η6-arene ligand in cyclometalated ruthenium NHC complexes by DMSO selectively leads to a change from a facial to a meridional geometry. The DMSO complexes can serve as starting materials for the synthesis of more complex structures, e.g. by introducing bidentate ligands, as shown for 2,2′-bipyridine.Download high-res image (181KB)Download full-size image
Co-reporter:David Schleicher, Alexander Tronnier, Hendrik Leopold, Horst Borrmann and Thomas Strassner
Dalton Transactions 2016 vol. 45(Issue 8) pp:3260-3263
Publication Date(Web):03 Feb 2016
DOI:10.1039/C6DT00100A
We present the synthesis and structural characterization of novel ruthenium complexes containing C^C* cyclometalated N-heterocyclic carbene ligands, η6-arene (p-cymene) ligands and one bridging chlorine ion. Complexes of the general formula [Ru(p-cymene)(C^C*)Cl] were prepared via a one-pot synthesis using in situ transmetalation from the correspondent silver NHC complexes. These complexes react with sodium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (NaBArF4) to form dinuclear complexes of the general structure [Ru(p-cymene)(C^C*)-μ-Cl-(p-cymene)(C^C*)Ru]+[BArF4]−. Solid-state structures confirm that the pseudo-tetrahedral coordination around the metal center with the η6-ligand aligned perpendicularly to the C^C* ligand and the i-Pr group “atop” is retained in the bimetallic complexes.
Co-reporter:Maria Kaliner, Thomas Strassner
Tetrahedron Letters 2016 Volume 57(Issue 31) pp:3453-3456
Publication Date(Web):3 August 2016
DOI:10.1016/j.tetlet.2016.06.082
•New ionic liquids with surprising properties could be synthesized.•1-Aryl-3-alkyl imidazolium cations with B[ArF3,5]4 anions are reported.•Aryl substitution leads to lower melting points compared to N,N-dialkyl ILs.•Electrostatic potentials have been calculated by high level DFT calculations.A series of 1-aryl 3-alkyl imidazolium tetrakis[bis-3,5(trifluoromethyl)phenyl]borate [BArF3,5] ionic liquids were synthesized and characterized. Increasing the alkyl chain length leads to lower melting points even resulting in room temperature ionic liquids (RTILs). In comparison to their corresponding alkyl imidazolium [BArF3,5] counterparts these aryl imidazolium [BArF3,5] ionic liquids show significantly lower melting points.Download high-res image (58KB)Download full-size image
Co-reporter:Mario Tenne, Thomas Strassner
Journal of Organometallic Chemistry 2016 Volume 821() pp:100-105
Publication Date(Web):15 October 2016
DOI:10.1016/j.jorganchem.2016.04.027
•Tethering a tetrazole ring to the imidazole fragment leads to zwitterionic ligands.•These ligands were used to synthesize new neutral platinum(II) NHC complexes.•Solid state structures confirm the trans-orientation of the carbene carbon atoms.Neutral platinum(II) complexes with two bidentate 1-((tetrazolid-5-yl)methyl)-3-alkylimidazolin-2-ylidene ligands (alkyl = methyl, n-butyl) have been synthesized and characterized to investigate the electronic and steric effects of tetrazolidyl NHC ligands. Solid state structures of the complexes as well as of a ligand precursor are presented.Anionic NHC ligands create a ball-shaped environment around the platinum(II) center.
Co-reporter:Thomas Strassner
Accounts of Chemical Research 2016 Volume 49(Issue 12) pp:
Publication Date(Web):December 2, 2016
DOI:10.1021/acs.accounts.6b00240
ConspectusThis Account describes our achievements toward the development of a new class of platinum(II) complexes with interesting photophysical properties. The general motif of a strongly donating N-heterocyclic carbene with a cyclometalating phenyl group attached to the nitrogen atom together with β-diketonate based counterligands enabled us to synthesize a new class of phosphorescent emitters for use in organic light-emitting diodes (OLEDs). This Account is divided into sections and introduces imidazolium based as well as triazolium based structures and discusses the effects of structural changes on the photophysical properties. Starting from the basic methylated (substituted) phenylimidalium presursors, we initially extended the π-system of the phenyl ring to the dibenzofuran ligand, its regioisomer, and thio-derivative. As the substituents of the β-diketonate ligands turned out to have a strong influence on the photophysical properties (higher quantum yields as well as shorter decay times) a series of dibenzofuranyl-3-methylimidazol as well as diphenylbenzimidazol platinum complexes were synthesized to investigate the different steric and electronic effects, which are described in a separate section. The next section of the Account then describes other extensions of the π-system. Exchange of the methyl group against a phenyl ring, as well as the extension of the π-system in the backbone of the NHC-ligand lead to a significant improvement of the photophysical properties, which reached a maximum for the diphenylbenzimidazole (DPBIC) system. Further extension of the π-system to the diphenylnaphthylimidazol then lead to a unfavorable long decay time.The effect of substitution is discussed for cyano groups, which change the electronic situation and lead to highly emissive complexes. We are currently working on studying the effect of other substituents on the photophysical properties, as well as the introduction of additional heteroatoms into the general motif.Our initial work in that area had been on 1,2,4-triazole complexes. For the basic phenyl/methyl substituted system, two different isomers are accessible, the 4-phenyl-4H-1,2,4-triazoles as well as the 1-phenyl-1H-1,2,4 triazoles. It was interesting to note that the photophysical properties of the corresponding complexes are strongly dependent on the substituent R of the β-diketonate ligand. For R = methyl, the properties are significantly different, while we found almost identical photophysical results for R = mesityl for both 1,2,4-triazole isomers. The last section describes the synthesis of bimetallic complexes. To investigate whether it is possible to cyclometalate twice into the same phenyl ring, we synthesized dicationic NHC precursors from para- and meta-disubstituted bis(imidazole)benzenes. The bimetallic complexes show interesting photophysical properties with quantum yields of up to 93%.All experimental work was accompanied by quantum chemical calculations, which turned out to be very useful for the prediction of the emission wavelengths as well as the interpretation of the emissive states of the platinum complexes.
Co-reporter:Hendrik Leopold and Thomas Strassner
Organometallics 2016 Volume 35(Issue 24) pp:4050-4059
Publication Date(Web):December 5, 2016
DOI:10.1021/acs.organomet.6b00710
We present the synthesis and photophysical properties of six novel N-phenyl-1,3-thiazol-2-ylidene platinum(II) complexes with sterically demanding N-aryl-β-ketoiminate ligands. Diverse aryl substituents at the coordinating nitrogen atom (phenyl, mesityl, 2,6-diisopropylphenyl, 4-cyanophenyl, 1-naphthyl, and 2,4-difluorophenyl) of the N-aryl-(3Z)-4-amino-3-penten-2-ones exclusively yielded the SP-4-3 coordinated C∧C* cyclometalated platinum(II) complexes as single isomers as a consequence of the low steric demand of the C∧C* cyclometalating thiazole ligand and the bulkiness of the β-ketoiminate ligands. The formation of this isomer was confirmed by 195Pt NMR and extensive 2D NMR experiments, two solid-state structures, and the results of DFT calculations. As a proof of principle, two complexes with the sterically less demanding β-ketoiminate ligands (3Z)-4-amino-3-penten-2-onato and (2Z)-3-amino-1-phenyl-2-buten-1-onato were synthesized and isolated as an isomeric mixture.
Co-reporter:Hendrik Leopold, Alexander Tronnier, Gerhard Wagenblast, Ingo Münster, and Thomas Strassner
Organometallics 2016 Volume 35(Issue 7) pp:959-971
Publication Date(Web):March 21, 2016
DOI:10.1021/acs.organomet.5b00991
A new class of platinum(II) compounds, the 4,5-dimethyl-3-aryl-thiazole-2-ylidene platinum(II) acetylacetonato complexes, are described. Their efficient phosphorescent emission at room temperature makes them suitable for potential applications in organic light-emitting diodes. A new synthetic pathway that allows the preparation of a broad range of different N-arylthiazole-2-thiones and their subsequent conversion into the corresponding N-arylthiazolium perchlorate and hexafluorophosphate salts has been developed. Not only electron-rich (4-OMe, 4-Me, 3-Me) N-arylthiazoles but also electron-deficient ligands with a cyano or an ester group could be synthesized. From commercially available anilines N-arylthiazolium perchlorate and hexafluorophosphate salts were synthesized via ring-closure of in situ generated N-aryldithiocarbamate salts followed by a sulfur-oxidation/-substitution protocol to the air-stable carbene precursors. All reactions were performed in multigram scale in good yields. The synthesis of the corresponding platinum(II) complexes involves generating the corresponding N-arylthiazole-silver(I)-carbene complexes, transmetalation to platinum, cyclometalation, and reaction with acetylacetonate (acac). Solid-state structures of two N-arylthiazole-2-thiones, one N-arylthiazolium salt, and three N-arylthiazole-2-ylidene-platinum(II) complexes complement the analytic characterization including 195Pt NMR. The unsubstituted complex 4,5-dimethyl-3-phenylthiazole-2-ylidene-platinum(II)-acac was additionally characterized by 2D-NMR techniques (COSY, HSQC, HMBC, NOESY). Photoluminescence measurements were performed in amorphous poly(methyl methacrylate) films and revealed bluish-green emission maxima (∼500 nm) independent of the electronic structure of the thiazoles, whereas the variation of the substitution pattern at the cyclometalating aryl system led to excellent quantum efficiencies and decay lifetimes of 8.1–21.4 μs.
Co-reporter:Piermaria Pinter, Hannah Mangold, Ilona Stengel, Ingo Münster, and Thomas Strassner
Organometallics 2016 Volume 35(Issue 5) pp:673-680
Publication Date(Web):March 2, 2016
DOI:10.1021/acs.organomet.5b00982
We report a new class of C∧C* platinum(II) complexes in which excimer formation enhances the quantum yield while shortening the phosphorescence lifetime. Selective excitation of the monomer or dimer could be achieved at different wavelengths. These complexes exhibit strong phosphorescent emissions in the blue part of the visible spectrum around 450 nm with quantum yields of up to 93%. The emission behavior is controlled through the steric demand of the substituents at the 2,4-pentanedione ligand. We see dual emission with high photoluminescence quantum yields (PLQY) from monomeric and aggregated excited states.
Co-reporter:Alexander Tronnier, Ute Heinemeyer, Stefan Metz, Gerhard Wagenblast, Ingo Muenster and Thomas Strassner
Journal of Materials Chemistry A 2015 vol. 3(Issue 8) pp:1680-1693
Publication Date(Web):09 Jan 2015
DOI:10.1039/C4TC02575J
Platinum(II) complexes [(NHC)Pt(L)] with various β-diketonate based auxiliary ligands (L: 3-meacac = 3-methylacetylacetonato, dpm = dipivaloylmethanato, dbm = dibenzoylmethanato, mesacac = dimesitoylmethanato, duratron = bis(2,3,5,6-tetramethylbenzoyl)methanato) and a C^C* cyclometalated N-heterocyclic carbene ligand (NHC: dpbic = 1,3-diphenylbenzo[d]imidazol-2-ylidene, dpnac = 1,3-diphenylnaphtho[2,3-d]imidazol-2-ylidene or bnbic = 1-phenyl-3-benzylbenzo[d]imidazol-2-ylidene) were found to show different aggregation and photophysical properties depending on the auxiliary ligand. Eight complexes were prepared from a silver(I)–NHC intermediate by transmetalation, cyclometalation and subsequent treatment with potassium-tert-butanolate and β-diketone. They were fully characterized by standard techniques including 195Pt NMR. Five complexes were additionally characterized by 2D NMR spectroscopy (COSY, HSQC, HMBC and NOESY). Solid-state structures of five complexes could be obtained and show the tendency of the square-planar compounds to form pairs with different Pt–Pt distances depending on the bulkiness of the substituents at the auxiliary ligand. The result of the photophysical measurements in amorphous PMMA films reveals quantum yields of up to 85% with an emission maximum in the blue region and comparatively short decay lifetimes (3.6 μs). Density functional theory (DFT/TD-DFT) calculations were performed to elucidate the emission process and revealed a predominant 3ILCT/3MLCT character. Organic light-emitting devices (OLEDs) comprising one of the complexes achieved 12.6% EQE, 11.9 lm W−1 luminous efficacy and 25.2 cd A−1 current efficiency with a blue emission maximum at 300 cd m−2. The influence of an additional hole-transporter in the emissive layer was investigated and found to improve the device lifetime by a factor of seven.
Co-reporter:Dominik Munz and Thomas Strassner
Inorganic Chemistry 2015 Volume 54(Issue 11) pp:5043-5052
Publication Date(Web):March 30, 2015
DOI:10.1021/ic502515x
The application of environmentally benign, cheap, and economically viable oxidation procedures is a key challenge of homogeneous, oxidative alkane functionalization. The typically harsh reaction conditions and the propensity of dioxygen for radical reactivity call for extraordinary robust catalysts. Mainly three strategies have been applied. These are (1) the combination of a catalyst responsible for C–H activation with a cocatalyst responsible for dioxygen activation, (2) transition-metal catalysts, which react with both hydrocarbons and molecular oxygen, and (3) the introduction of very robust main-group element catalysts for C–H functionalization chemistry. Herein, these three approaches will be assessed and exemplified by the reactivity of chelated palladium (N-heterocyclic carbene) catalysts in combination with a vanadium cocatalyst, the methane functionalization by cobalt catalysts, and the reaction of group XVII compounds with alkanes.
Co-reporter:M. Tenne, S. Metz, G. Wagenblast, Ingo Münster and T. Strassner
Dalton Transactions 2015 vol. 44(Issue 18) pp:8444-8455
Publication Date(Web):17 Apr 2015
DOI:10.1039/C4DT03613A
Neutral cyclometalated platinum(II) N-heterocyclic carbene complexes [Pt(C^C*)(O^O)] with C^C* ligands based on 1-phenyl-1,2,4-triazol-5-ylidene and 4-phenyl-1,2,4-triazol-5-ylidene, as well as acetylacetonato (O^O = acac) and 1,3-bis(2,4,6-trimethylphenyl)propan-1,3-dionato (O^O = mesacac) ancillary ligands were synthesized and characterized. All complexes are emissive at room temperature in a poly(methyl methacrylate) (PMMA) matrix with emission maxima in the blue region of the spectrum. High quantum efficiencies and short decay times were observed for all complexes with mesacac ancillary ligands. The sterically demanding mesityl groups of the mesacac ligand effectively prevent molecular stacking. The emission behavior of these emitters is in general independent of the position of the nitrogen in the backbone of the N-heterocyclic carbene (NHC) unit and a variety of substituents in 4-position of the phenyl unit, meta to the cyclometalating bond.
Co-reporter:Alexander Tronnier, David Schleicher, Thomas Strassner
Journal of Organometallic Chemistry 2015 Volume 775() pp:155-163
Publication Date(Web):1 January 2015
DOI:10.1016/j.jorganchem.2014.04.021
•C∧C* platinum(II) NHC complexes of imidazo[1,5-a]pyridines have been synthesized.•Compounds [(C∧C*-NHC)Pt(L)] with L = acetylacetonato/dipivaloylmethanato are reported.•They exclusively form five-membered metallacycles to the aryl substituent.•DFT calculations confirm that these are favoured over four-membered metallacycles.•Seven mononuclear complexes and one binuclear complex are presented.Imidazo[1,5-a]pyridines have been used as monodentate ligands in late transition-metal N-heterocyclic carbene (NHC) complexes, but the N-aryl substituted heterocyclic ligands also allow for the formation of C∧C* cyclometalated complexes, which has previously only been shown for iridium(III) complexes. Here we present the first C∧C* platinum(II) NHC complexes of this class. A monoanionic bidentate ligand L – acetylacetonato (acac) or dipivaloylmethanato (dpm) – was used to generate heteroleptic compounds of the general formula [(C∧C*-NHC)Pt(L)]. Seven mononuclear complexes and one binuclear complex are presented. The square-planar coordination of the C∧C* cyclometalated species was confirmed by spectroscopy and additionally by three solid-state structures. The complexes have been fully characterized including 195Pt NMR and extensive 2D NMR studies (COSY, HSQC, HMBC, NOESY). From the experimental data we exclusively see the formation of five-membered metallacycles to the aryl substituent and no interaction with the pyridine part of the ligand, in good agreement with density functional theory calculations (B3LYP/6-31G(d)), which show that the five-membered metallacycles are significantly favoured over the four-membered metallacycles.C∧C* platinum(II) NHC complexes of imidazo[1,5-a]pyridines [(C∧C*-NHC)Pt(L)] with L = acetylacetonato/dipivaloylmethanato have been synthesized.
Co-reporter:Dirk Meyer, Thomas Strassner
Journal of Organometallic Chemistry 2015 Volume 784() pp:84-87
Publication Date(Web):15 May 2015
DOI:10.1016/j.jorganchem.2014.09.022
•Synthesis and characterization of a new palladium(II) complex with chelating NHC-ligands.•Complex shows catalytic activity in the CH-activation of methane.•Solid-state structure confirms a symmetrical A-frame structure.A dimeric methyl palladium(II) biscarbene complex with a bridging μ-chloro ligand was prepared by transmetalation from 1,1′-dimethyl-3,3′-methylenediimidazolium dichloride, silver(I) oxide and chloridomethyl(cycloctadiene)palladium(II). The complex was fully characterized and shows good activity in the CH-activation of methane. The solid state structure confirms a symmetrical dimeric structure with a μ-coordinated chlorido ligand.A-frame palladium(II) structure with chelating NHC-ligands.
Co-reporter:Dr. Alexer Tronnier;Dr. Gerhard Wagenblast;Dr. Ingo Münster;Dr. Thomas Strassner
Chemistry - A European Journal 2015 Volume 21( Issue 37) pp:12881-12884
Publication Date(Web):
DOI:10.1002/chem.201502087
Abstract
Two C^C* cyclometalated platinum(II) N-heterocyclic carbene (NHC) complexes with the general formula [(C^C*)Pt(O^O)] (C^C*=1-dibenzofuranyl-3-methylbenzimidazolylidene; O^O=dimesitoylmethane) have been synthesized and extensively characterized, including solid-state structure determination, 195Pt NMR spectroscopy, and 2D NMR (COSY, HSQC, HMBC, NOESY) spectroscopy to elucidate the impact of their structural differences. The two regioisomers differ in the way the dibenzofuranyl (DBF) moiety of the NHC ligand is bound to the metal center, which induces significant changes in their physicochemical properties, especially on the decay time of the excited state. Quantum yields of over 80 % and blue emission colors were measured.
Co-reporter:Mario Tenne, Stefan Metz, Gerhard Wagenblast, Ingo Münster, and Thomas Strassner
Organometallics 2015 Volume 34(Issue 18) pp:4433-4440
Publication Date(Web):September 8, 2015
DOI:10.1021/acs.organomet.5b00136
Two series of new platinum(II) NHC complexes with C∧C* cyclometalating 1-(dibenzo[b,d]furan-4-yl)-4-methyl-1H-1,2,4-triazole and 1-(dibenzo[b,d]furan-2-yl)-4-methyl-1H-1,2,4-triazole ligands and several β-diketonato auxiliary ligands (acetylacetonato, dibenzoylmethanato, and dimesitoylmethanato) were synthesized, characterized (NMR spectroscopy, elemental analysis, and X-ray crystallography for two complexes) and investigated in terms of their photoluminescence properties. All complexes are strongly emissive at room temperature in a 2 wt % complex doped poly(methyl methacrylate) film at room temperature. Using dibenzoylmethanato as auxiliary ligand leads to a broad emssion band with a maximum in the green region of the spectrum, whereas the complexes with acetylacetonato and dimesitoylmethanato ligands reveal structured blue emissions with wavelengths that strongly depend on the arrangement of the dibenzo[b,d]furan (DBF) unit.
Co-reporter:Alexander Tronnier, Alexander Pöthig, Stefan Metz, Gerhard Wagenblast, Ingo Münster, and Thomas Strassner
Inorganic Chemistry 2014 Volume 53(Issue 12) pp:6346-6356
Publication Date(Web):May 27, 2014
DOI:10.1021/ic500971z
Cyclometalated (C^C*) platinum(II) N-heterocyclic carbene (NHC) complexes are emerging as a new class of phosphorescent emitters for the application in organic light-emitting devices (OLEDs). We present the synthesis of six new complexes of this class to investigate the influence of extended π systems. Therefore, six different NHC ligands with a varying number of additional phenyl substituents were used in combination with the monoanionic acetylacetonate (acac) ligand to obtain complexes of the general formula [(NHC)Pt(II)(acac)]. The complexes were fully characterized by standard techniques and advanced spectroscopic methods (195Pt NMR). For all complexes the solid-state structure determination revealed a square-planar coordination of the platinum atom. Absorption and emission spectra were measured in thin amorphous poly(methyl methacrylate) films at room temperature. Four compounds emit in the blue-green region of the visible spectrum with quantum yields of up to 81%.
Co-reporter:Alexander Tronnier, Stefan Metz, Gerhard Wagenblast, Ingo Muenster and Thomas Strassner
Dalton Transactions 2014 vol. 43(Issue 8) pp:3297-3305
Publication Date(Web):20 Dec 2013
DOI:10.1039/C3DT53264J
Since C^C* cyclometalated Pt(II) complexes with N-heterocyclic carbene (NHC) ligands have been identified as potential emitter materials in organic light-emitting devices (OLEDs), very promising results regarding quantum yields, colour and stability have been presented. Herein, we report on four nitrile substituted complexes with a chelating NHC ligand (1-(4-cyanophenyl)-3-isopropyl-1H-benzo[d]imidazole or 4-(tert-butyl)-1-(4-cyanophenyl)-3-methyl-1H-imidazole) and a bidentate monoanionic auxiliary ligand (acetylacetone or dimesitoylmethane). The complexes have been fully characterized including extensive 2D NMR studies (COSY, HSQC, HMBC, NOESY, 195Pt NMR), three of them also by solid-state structures. Photophysical measurements in amorphous PMMA films and pure emitter films at room temperature reveal the impact of the mesityl groups in the auxiliary ligand, which led to a significant increase of the quantum yield, while the decay lifetimes decreased. The electron withdrawing nitrile groups shift the emission towards blue colour coordinates.
Co-reporter:Alexer Tronnier;Nicole Nischan;Stefan Metz;Gerhard Wagenblast;Ingo Münster
European Journal of Inorganic Chemistry 2014 Volume 2014( Issue 1) pp:256-264
Publication Date(Web):
DOI:10.1002/ejic.201301398
Abstract
Neutral C∧C* cyclometalated PtII NHC complexes have recently emerged as a new class of phosphorescent emitters with high quantum efficiencies, short decay lifetimes and high thermal stability, which makes them promising candidates for OLED applications. Herein, we report investigations on the photophysical properties of seven new PtII complexes containing a chelating NHC dibenzofuranyl ligand (3-methyl-1-dibenzo[b,d]furan-4-ylimidazole) and a bidentate monoanionic auxiliary ligand. All complexes have been fully characterized including extensive NMR studies (COSY, HSQC, HMBC, NOESY, 195Pt NMR), three of them also by solid-state structures. The extraordinary influence of the auxiliary ligands on the photoluminescence properties is demonstrated by quantum yields ranging from 0 % to 91 % in amorphous PMMA films at room temperature. DFT calculations were performed in order to investigate the nature of the emissive states in more detail.
Co-reporter:Maik Micksch, Mario Tenne, and Thomas Strassner
Organometallics 2014 Volume 33(Issue 15) pp:3966-3976
Publication Date(Web):July 23, 2014
DOI:10.1021/om5004336
We present the syntheses of 12 cyclometalated palladium C∧N 2-phenylimidazole carbene complexes with different N-1 groups as well as different substituents at the C-2 phenyl group of the cyclometalating imidazole. We investigated the influence of these substituents by comparing the catalytic performance of the complexes in the Suzuki–Miyaura cross-coupling reaction of aryl chlorides. We can show a strong dependence between the steric demand of the N-1 substituent of the cyclometalating imidazole and the catalytic activity in the cross-coupling reaction. The most active complex shows a wide substrate scope, where several aryl as well as benzyl chlorides could be coupled with different boronic acids in excellent yields using very low catalyst concentrations of 0.05 mol %.
Co-reporter:Maik Micksch, Mario Tenne, and Thomas Strassner
Organometallics 2014 Volume 33(Issue 13) pp:3464-3473
Publication Date(Web):July 1, 2014
DOI:10.1021/om500383b
We describe the synthesis, characterization, and photophysical properties of 12 neutral cyclometalated platinum(II) complexes with sterically demanding 1,2-diarylimidazole ligands and β-diketonate ancillary ligands. All complexes are photophysically active emitting in the blue-green to red region (490–590 nm) of the spectrum with quantum yields up to 58%, measured in poly(methyl methacrylate) (PMMA) at room temperature. The steric demand of the imidazole ligand as well as of the β-diketonate ligand shows a significant effect on the quantum yield but not on the emission wavelength. These can be tuned by changing the substituents at the C-2 phenyl group of the imidazole ligand.
Co-reporter:Alexander Tronnier, Alexander Poethig, Eberhardt Herdtweck, and Thomas Strassner
Organometallics 2014 Volume 33(Issue 4) pp:898-908
Publication Date(Web):February 6, 2014
DOI:10.1021/om401023f
C∧C* cyclometalated platinum(II) NHC complexes with chelating acetylacetonate ligands have been recently shown to be an interesting class of phosphorescent emitters. We sought to clarify the role of the acetylacetonate ligand by replacing one of the coordinating oxygen atoms in the auxiliary ligand with an NH group. This allowed us to study the effect on the emission, and we found that the nature of the emission process changes significantly. We herein report the synthesis of novel cyclometalated platinum(II) NHC complexes with the chelating β-ketoimine ligands (3Z)-4-amino-3-penten-2-one and (2Z)-3-amino-1-phenyl-2-buten-1-one. Due to the unsymmetrical nature of the auxiliary ligands, two isomers were always formed, which could be separated and characterized. Their photophysical properties as well as solid-state structures of representative members of this new class of compounds are given. All new complexes emit in the blue to green region of the visible spectrum with quantum yields as high as 74% at room temperature. The photophysical data of the isomers show significant differences. The new compounds have been fully characterized by 1H and 13C as well as 2D NMR (COSY, HSQC, HMBC, NOESY) spectroscopy. DFT calculations were used to determine differences between the respective isomers and to predict the emission wavelengths of the synthesized complexes. We found the reason for the different properties in comparison to the acetylacetonate complexes to be the smaller HOMO–LUMO gap.
Co-reporter:Dr. Dominik Munz ; Thomas Strassner
Chemistry - A European Journal 2014 Volume 20( Issue 45) pp:14872-14879
Publication Date(Web):
DOI:10.1002/chem.201403910
Abstract
We report a detailed mechanistic study on the CH functionalization of alkanes by palladium complexes with chelating bis(N-heterocyclic carbene) (NHC) complexes. The experimental results are complemented by detailed DFT calculations, which allow us to rationalize the regioselectivity and the catalytic activity. The study includes a library of catalysts with different electronic and steric properties, kinetic data, and isotope effects. The combined experimental and computational results favor a mechanism involving organometallic palladium(IV) intermediates. Furthermore, it is shown that at high halide loadings a different mechanism is operative.
Co-reporter:Dr. Dominik Munz ; Thomas Strassner
Angewandte Chemie 2014 Volume 126( Issue 9) pp:2518-2521
Publication Date(Web):
DOI:10.1002/ange.201309568
Abstract
Die Entwicklung effizienter aerober Oxidationsverfahren stellt die große Herausforderung bei der selektiven Funktionalisierung von C-H-Bindungen in Alkanen dar. Hier berichten wir über die C-H-Funktionalisierung von Propan mittels Palladiumkatalysatoren mit chelatisierenden Bis(N-heterocyclischen Carbenliganden) und Vanadium-Cokatalysatoren in Trifluoressigsäure. Wir zeigen, dass Halogenide eine entscheidende Rolle bei der Oxidation spielen. Neben experimentellen Ergebnissen präsentieren wir auch kinetische Daten und einen Isotopeneffekt. Die Verwendung eines Vanadium-Cokatalysators ermöglicht in Kombination mit Halogeniden die Verwendung molekularen Sauerstoffs als Oxidationsmittel. Auf der Basis der experimentellen und quantenchemischen Ergebnisse schlagen wir einen Mechanismus vor, bei dem die C-H-Aktivierung durch einen Palladium(II)-Katalysator und die Oxidation zu Palladium(IV) durch Brom erfolgt.
Co-reporter:Dr. Dominik Munz ; Thomas Strassner
Angewandte Chemie International Edition 2014 Volume 53( Issue 9) pp:2485-2488
Publication Date(Web):
DOI:10.1002/anie.201309568
Abstract
The development of efficient aerobic oxidation methods remains a challenge for the selective functionalization of CH bonds in alkanes. Herein we report the development of a CH functionalization procedure for propane by using a palladium catalyst with chelating bis(N-heterocyclic carbene) ligands in trifluoroacetic acid together with a vanadium co-catalyst. Halides play a decisive role in the reaction. The experimental results are presented together with supporting kinetic data and an isotope effect. The reaction can be run with dioxygen as the oxidant if vanadium salts and halides are present in the reaction mixture. Experimental as well as computational results favor a mechanism involving CH activation by palladium(II), followed by oxidation to palladium(IV) by bromine.
Co-reporter:Christoph Allolio and Thomas Strassner
The Journal of Organic Chemistry 2014 Volume 79(Issue 24) pp:12096-12105
Publication Date(Web):November 17, 2014
DOI:10.1021/jo501897s
Experimental results have shown that palladium complexes with chelating aryl- and alkyl-substituted bis-NHC ligands, including [(H3C-Im)2CH2]PdBr2, [(C6H5-Im)2CH2]PdBr2, and [(H3CO-C6H4-Im)2CH2]PdBr2 are excellent catalysts for the Mizoroki–Heck reaction. To better understand and improve the catalysts, a density functional theory (DFT) study of the Heck reaction has been performed at the B3LYP/6-31G* level of theory, complemented by M06/def2-TZVP single-point calculations. Different mechanistic pathways have been investigated and compared to available experimental results. The most likely mechanism is a cationic catalytic cycle involving the palladium oxidation states 0 and +II. We also looked at other oxidation states, but on the basis of the calculated Gibbs free energy a +II/+IV mechanism can be excluded. Aryl substitution with electron-donating groups at the para position (e.g., the methoxy group in [(H3CO-C6H4–Im)2CH2]PdBr2) was found to reduce the reaction barrier of the rate-determining step. This is in agreement with the experimental findings for the catalysts. The experimentally observed cis selectivity could also be explained by the DFT study.
Co-reporter:Dominik Munz
Topics in Catalysis 2014 Volume 57( Issue 17-20) pp:1372-1376
Publication Date(Web):2014 November
DOI:10.1007/s11244-014-0305-5
We report density functional theory studies on the CH-activation and functionalization of methane and propane by palladium (II) complexes with chelating bis(NHC) ligands. The combined experimental and computational results indicate that a palladium tetrahalogenido complex is the resting state of the reaction, while the CH-activation constitutes the rate-determining step of the catalytic cycle.
Co-reporter:Alexander Tronnier and Thomas Strassner
Dalton Transactions 2013 vol. 42(Issue 27) pp:9847-9851
Publication Date(Web):21 May 2013
DOI:10.1039/C3DT50841B
A series of bimetallic N-heterocyclic carbene (NHC) platinum(II) complexes with the general formula [Pt(NHC)(L)]2Ph were synthesized, which are composed of two [Pt(NHC)(L)] (L = acetylacetone, dipivaloylmethane or dimesitoylmethane; NHC = 3-methylimidazole or 3-benzylimidazole) fragments. Both fragments are cyclometalated to the same central phenyl ring in the para- or meta-position. All complexes have been fully characterized by standard techniques, two of them additionally by solid-state structures. Photoluminescence properties were investigated and very high quantum yields of 76–93% at room temperature have been observed. For a single-matrix device with an emitter concentration of 30%, a current efficiency of 25 cd A−1, an external quantum efficiency of 8.5%, and a luminance efficiency of 10 lm W−1 were achieved at 300 cd m−2. Density functional theory (DFT) calculations were performed to support experimental data and gain further insight into the photoluminescence behaviour.
Co-reporter:Dominik Munz, Alexander Poethig, Alexander Tronnier and Thomas Strassner
Dalton Transactions 2013 vol. 42(Issue 20) pp:7297-7304
Publication Date(Web):06 Feb 2013
DOI:10.1039/C3DT33006K
A series of ortho-phenylene bridged palladium bis-NHC complexes has been synthesized. Complexes with imidazolium and benzimidazolium derived NHCs and methyl-/benzyl-wingtips are reported. Bis(benz)imidazoles with a doubly brominated ortho-phenylene bridge could be obtained by an electrophilic substitution reaction. The structure of the complexes could be confirmed by three solid-state structures. All catalysts have been tested in the catalytic functionalisation of propane. The catalytic activity is highly dependent on the ligand, whereas ligand effects on the regioselectivity (n/iso) are much smaller.
Co-reporter:Maik Micksch;Mario Tenne
European Journal of Organic Chemistry 2013 Volume 2013( Issue 27) pp:6137-6145
Publication Date(Web):
DOI:10.1002/ejoc.201300688
Abstract
1,2-Diarylimidazoles are an important class of compounds. They are frequently used as ligands for photophysically active metal complexes and also display physiological activity. We developed a new, high-yielding procedure for the synthesis of 1,2-diaryl-substituted imidazoles with sterically demanding substituents at the respective ortho positions by starting from commercially available anilines and benzoic acids through the corresponding acid chlorides. The metal-free method provides access to a variety of different substituents on the phenyl rings at N-1 and C-2 as well as at the 4,5-positions of the imidazole backbone. Our new method is also suitable for the preparation of 1-aryl-2-alkylimidazoles.
Co-reporter:Thomas Strassner;Sebastian Ahrens;Michael Muehlhofer;Dominik Munz;Alexer Zeller
European Journal of Inorganic Chemistry 2013 Volume 2013( Issue 21) pp:3659-3663
Publication Date(Web):
DOI:10.1002/ejic.201300213
Abstract
The cobalt-catalyzed oxidation of methane to methyl trifluoroacetate by molecular oxygen in trifluoroacetic acid has been studied in detail. Yields of up to 50 % based on methane were obtained. The catalytic activities were highly dependent on the anions of the cobalt salts (CoII, CoIII) under investigation. Deactivation by precipitation of the cobalt catalyst could be prevented by the addition of trifluoroacetic anhydride.
Co-reporter:Mario Tenne, Stefan Metz, Ingo Münster, Gerhard Wagenblast, and Thomas Strassner
Organometallics 2013 Volume 32(Issue 21) pp:6257-6264
Publication Date(Web):October 30, 2013
DOI:10.1021/om4004576
Two series of heteroleptic platinum(II) carbene compexes of the type [Pt(C∧C*)(O∧O)] (O∧O = acetylacetonate) with C∧C* cyclometalated 4-phenyl-1,2,4-triazol-5-ylidene as well as 1-phenyl-1,2,4-triazol-5-ylidene ligands were prepared. The effect of various substituents in the 4-position of the phenyl ring (4-phenyltriazole: H, Cl, OCH3, NO2; 1-phenyltriazole: H, Cl, OCH3, CH3) was studied. The ligand precursors were obtained by quaternization of the corresponding aryl-1,2,4-triazoles with iodomethane. The complexes were synthesized by a reaction sequence starting from the triazolium precursors via the silver(I) carbenes, transmetalation with dichloro(1,5-cyclooctadiene)platinum(II), cyclometalation reaction, and finally addition of acetylacetonate. All complexes have been characterized by standard techniques such as 1H NMR, 13C NMR, and elemental analysis. Additionally, solid-state structures of seven complexes could be obtained by single-crystal X-ray diffraction. According to absorption and emission spectra, the complexes reveal interesting photophysical properties with strong emissions in the blue region of the visible spectrum at room temperature, which are sensitive to the donor and acceptor properties of the substituents at the cyclometalating ligand.
Co-reporter:Dominik Munz, Dirk Meyer, and Thomas Strassner
Organometallics 2013 Volume 32(Issue 12) pp:3469-3480
Publication Date(Web):June 10, 2013
DOI:10.1021/om400232u
Palladium bis(NHC) complexes are able to catalytically activate and to promote the oxidation of methane. The conversion of methane to methyl trifluoroacetate catalyzed by the palladium bis(NHC) complex dibromido(1,1′-dimethyl-3,3′-methylenediimidazolin-2,2′-ylidene)palladium(II) was investigated by a DFT study on the B3LYP/6-311++G(d,p)//B3LYP/6-31G(d) level of theory in combination with solvent and dispersion corrections. According to the DFT calculations the reaction proceeds by a palladium(II–II–IV) pathway without formation of palladium(0). A second redox cycle via a bromide–bromine shuttle, which mediates the oxidation of palladium(II) to palladium(IV), is proposed. Although CH activation by palladium(0) is predicted to be a very facile process, this pathway is very unlikely, due to the extraordinarily high reaction barrier for reductive elimination. CH activation by palladium(IV) has been investigated as well and might be a viable pathway comparable in energy to an activation by palladium(II) with other ligand systems.
Co-reporter:Yvonne Unger, Thomas Strassner, Christian Lennartz
Journal of Organometallic Chemistry 2013 748() pp: 63-67
Publication Date(Web):
DOI:10.1016/j.jorganchem.2013.07.011
Co-reporter:Tobias Schulz, Thomas Strassner
Journal of Organometallic Chemistry 2013 744() pp: 113-118
Publication Date(Web):
DOI:10.1016/j.jorganchem.2013.05.039
Co-reporter:Alexander Tronnier, Nicole Nischan, Thomas Strassner
Journal of Organometallic Chemistry 2013 730() pp: 37-43
Publication Date(Web):
DOI:10.1016/j.jorganchem.2012.07.046
Co-reporter:Maik Micksch
European Journal of Inorganic Chemistry 2012 Volume 2012( Issue 35) pp:5872-5880
Publication Date(Web):
DOI:10.1002/ejic.201200940
Abstract
We studied the catalytic activity of palladium(II) complexes with chelating imidazolium and benzimidazolium ligands in the Suzuki–Miyaura cross-coupling reaction. The methylene-bridged systems with aryl substituents carrying sterically and electronically different groups (F, NO2, OMe, H, Me, iPr) show good to excellent catalytic activities in the Suzuki–Miyaura cross-coupling reaction of aryl bromides. The p-methoxyphenyl-substituted bis(NHC)–palladium complex was the most active one under our reaction conditions, also in the context of a wide substrate scope. Several ortho- as well as para-substituted aryl bromides were coupled in excellent yields under mild reaction conditions.
Co-reporter:Dominik Munz, Christoph Allolio, Katrin Döring, Alexander Poethig, Thomas Doert, Heinrich Lang, Thomas Straßner
Inorganica Chimica Acta 2012 Volume 392() pp:204-210
Publication Date(Web):30 September 2012
DOI:10.1016/j.ica.2012.06.009
A series of methoxyphenyl substituted chelated bis-N-heterocyclic carbene palladium(II) complexes has been synthesized and characterized by cyclovoltammetry, spectroscopy (NMR, IR), solid state structures and investigated by quantum chemical calculations. The results confirm that a methoxy functionality in para position at the aryl substituent enhances the donor properties of the ligand compared to a methoxy group in ortho or meta position.Graphical abstractThe effect of donor substitution by methoxy groups in 2-, 3-, and 4-position of the chelating phenylsubstituted bis-NHC ligand on the palladium center was investigated in detail by a variety of methods.Highlights► Synthesis and characterization of new Pd(II) complexes with chelating NHC ligands. ► Synthesis and characterization of imidazoles and bis-imidazolium salts. ► Dependence of donor properties of the methoxy group on its position at the ring. ► CV-, IR-, NMR-data and DFT calculations explain the observed activity differences.
Co-reporter:Yvonne Unger, Thomas Strassner
Journal of Organometallic Chemistry 2012 713() pp: 203-208
Publication Date(Web):
DOI:10.1016/j.jorganchem.2012.05.019
Co-reporter:Dirk Meyer, Alexander Zeller, Thomas Strassner
Journal of Organometallic Chemistry 2012 701() pp: 56-61
Publication Date(Web):
DOI:10.1016/j.jorganchem.2011.12.014
Co-reporter:Alexander Tronnier, Anita Risler, Nicolle Langer, Gerhard Wagenblast, Ingo Münster, and Thomas Strassner
Organometallics 2012 Volume 31(Issue 21) pp:7447-7452
Publication Date(Web):October 31, 2012
DOI:10.1021/om300740d
Cyclometalated platinum(II) complexes with β-diketone ligands have recently attracted increasing interest as phosphorescent emitters for organic light-emitting devices (OLEDs). We present the synthesis of the new cyclometalated Pt(II) N-heterocyclic carbene complex [(NHC)PtII(acac)] (acac = acetylacetonate, NHC = 1-(dibenzo[b,d]thiophen-4-yl)-3-methyl-1H-imidazoyl). The complex was fully characterized by advanced spectroscopic methods (2D NMR, Pt NMR), elemental analysis, and solid-state structure determination, which revealed a square-planar coordination of the platinum atom. The photoluminescence properties were investigated in amorphous poly(methyl methacrylate) (PMMA) thin films. Quantum chemical density functional theory (DFT) computations on the singlet and triplet ground states have shown admixing of the Pt 5d orbitals with the frontier molecular orbitals (FMOs), explaining the good quantum yield.
Co-reporter:Alexander Poethig and Thomas Strassner
Organometallics 2012 Volume 31(Issue 8) pp:3431-3434
Publication Date(Web):March 27, 2012
DOI:10.1021/om3000345
We report the synthesis and characterization of a neutral pincer-type μ2-η2(1κCcarbene:2κC′carbene)-(C*-N-C*)-ligand-coordinated gold(I)-NHC complex with an emission wavelength of 452 nm. Solid-state structure analysis confirms the dinuclear structure of this complex.
Co-reporter:Markus Drees
Inorganic Chemistry 2011 Volume 50(Issue 12) pp:5833-5840
Publication Date(Web):May 27, 2011
DOI:10.1021/ic200877f
The mechanism of the Étard reaction of chromylchloride in toluene, discovered more than a century ago, has been investigated by DFT calculations (B3LYP/6-31G(d)). The formation of the experimentally observed product can be rationalized by multiple CH-abstraction reactions.
Co-reporter:Maria A. Taige, Sebastian Ahrens, Thomas Strassner
Journal of Organometallic Chemistry 2011 696(17) pp: 2918-2927
Publication Date(Web):
DOI:10.1016/j.jorganchem.2011.04.030
Co-reporter:Tobias Schulz;Dr. Sebastian Ahrens;Dirk Meyer;Christoph Allolio;Anke Peritz;Dr. Thomas Strassner
Chemistry – An Asian Journal 2011 Volume 6( Issue 3) pp:863-867
Publication Date(Web):
DOI:10.1002/asia.201000744
Abstract
Owing to numerous new applications, the interest in “task-specific” ionic liquids increased significantly over the last decade. But, unfortunately, the imidazolium-based ionic liquids (by far the most frequently used cations) have serious limitations when it comes to modifications of their properties. The new generation of ionic liquids, called tunable aryl–alkyl ionic liquids (TAAILs), replaces one of the two alkyl chains on the imidazolium ring with an aryl ring which allows a large degree of functionalization. Inductive, mesomeric, and steric effects as well as potentially also ππ and ππ+ interactions provide a wide range of possibilities to tune this new class of ILs. We investigated the influence of electron-withdrawing and -donating substituents at the para-position of the aryl ring (NO2, Cl, Br, EtO(CO), H, Me, OEt, OMe) by studying the changes in the melting points of the corresponding bromide and bis(trifluoromethanesulfonyl)imide, (N(Tf)2−), salts. In addition, we calculated (B3LYP/6-311++G(d,p)) the different charge distributions of substituted 1-aryl-3-propyl-imidazolium cations to understand the experimentally observed effects. The results indicated that the presence of electron-donating and -withdrawing groups leads to strong polarization effects in the cations.
Co-reporter:Alexander Poethig and Thomas Strassner
Organometallics 2011 Volume 30(Issue 24) pp:6674-6684
Publication Date(Web):November 30, 2011
DOI:10.1021/om200860y
We report the synthesis and characterization of a new anionic pincer-type μ2-η2(1κCcarbene:2κC′carbene)–C*–N–C*) ligand with a triazine core. Hydrolysis of one chloro substituent of the cyanuric chloride leads to the hydroxy-2,4-dichloro-1,3,5-triazine and the corresponding bis(imidazolium) salts, which, after deprotonation, serve as monoanionic ligands. Treatment of the bis(imidazolium) precursor with silver(I) oxide leads to stable silver(I)–NHC complexes with interesting photophysical properties (phosphorescent emission in the deep blue region of the spectrum). Depending on the substitution pattern of the NHC ligand, the emission can be shifted between 417 and 480 nm. X-ray structure analysis reveals the dimeric structure of these complexes.
Co-reporter:Anke Meyer, Yvonne Unger, Alexander Poethig, and Thomas Strassner
Organometallics 2011 Volume 30(Issue 11) pp:2980-2985
Publication Date(Web):May 9, 2011
DOI:10.1021/om200078h
New tetradentate O∧C*∧C*∧O-ligands and the corresponding biscarbene platinum(II) complexes are reported. They were fully characterized by 1H NMR and 13C NMR spectroscopy as well as elemental analysis. Additionally, solid-state structures of bis[3,3′-(2-hydroxyethyl)-1H-imidazolium-2,2′-diylidene]methane-1,1′-diylplatinum(II) dibromide and of bis[3,3′-(2-ethoxide)-1H-imidazolium-2,2′-diylidene]methane-1,1′-diylplatinum(II) potassium bromide are reported. The latter can be characterized as a one-dimensional chain structure formed by coordination of potassium bromide.
Co-reporter:Yvonne Unger, Dirk Meyer and Thomas Strassner
Dalton Transactions 2010 vol. 39(Issue 18) pp:4295-4301
Publication Date(Web):25 Mar 2010
DOI:10.1039/B927099J
Platinum(II) tetracarbene complexes with chelating bis(imidazoline-2-ylidene) ligands have recently shown to be an interesting class of phosphorescent emitters, although they exhibit emission wavelengths in the near-UV region with only moderate quantum yields. By changing the bis(imidazoline-2-ylidene) ligands to bis(triazoline-5-ylidene) ligands we have successfully shifted the emission wavelengths to the visible region of the spectrum. We herein report the synthesis of new bis- and tetracarbene complexes with bis(triazoline-5-ylidene) ligands, their photophysical properties and a solid state structure of a representative member of this new class of compounds.
Co-reporter:Yvonne Unger;Dirk Meyer;Dr. Oliver Molt;Dr. Christian Schildknecht;Dr. Ingo Münster;Dr. Gerhard Wagenblast;Dr. Thomas Strassner
Angewandte Chemie 2010 Volume 122( Issue 52) pp:10412-10414
Publication Date(Web):
DOI:10.1002/ange.201001316
Co-reporter:Dirk Meyer, Sebastian Ahrens and Thomas Strassner
Organometallics 2010 Volume 29(Issue 15) pp:3392-3396
Publication Date(Web):July 8, 2010
DOI:10.1021/om100488s
Platinum(II) complexes with one or two chelating bis(NHC) ligands have been oxidized by bromine as well as iodobenzene dichloride to provide the corresponding platinum(IV) carbene complexes in good yields under very mild reaction conditions. All compounds have been fully characterized by 1H and 13C NMR spectroscopy and in three cases also by solid-state structures. The NMR spectra of the novel Pt(IV) complexes show significantly shifted signals compared to their Pt(II) precursor complexes.
Co-reporter:Yvonne Unger;Dirk Meyer;Dr. Oliver Molt;Dr. Christian Schildknecht;Dr. Ingo Münster;Dr. Gerhard Wagenblast;Dr. Thomas Strassner
Angewandte Chemie International Edition 2010 Volume 49( Issue 52) pp:10214-10216
Publication Date(Web):
DOI:10.1002/anie.201001316
Co-reporter:Yvonne Unger, Alexander Zeller, Maria A. Taige and Thomas Strassner
Dalton Transactions 2009 (Issue 24) pp:4786-4794
Publication Date(Web):23 Apr 2009
DOI:10.1039/B900655A
Although examples of nickel(II), palladium(II) and platinum(II)N-heterocyclic tetracarbene complexes are known in the literature, particularly platinum(II) tetracarbene complexes are rare. We developed a new synthetic route via biscarbene acetate complexes, which make homoleptic as well as heteroleptic platinum(II) tetracarbene complexes accessible. The reported photoluminescence data show that these complexes have good quantum yields and photostability and are a promising class of emitters for PhOLEDs. Characterization of the compounds includes a solid-state structure of the homoleptic complex bis(1,1′-diisopropyl-3,3′-methylenediimidazoline-2,2′-diylidene)platinum(II) dibromide.
Co-reporter:Sebastian Ahrens Dr.;Anke Peritz Dr.
Angewandte Chemie International Edition 2009 Volume 48( Issue 42) pp:7908-7910
Publication Date(Web):
DOI:10.1002/anie.200903399
Co-reporter:Sebastian Ahrens Dr.;Anke Peritz Dr.
Angewandte Chemie 2009 Volume 121( Issue 42) pp:8048-8051
Publication Date(Web):
DOI:10.1002/ange.200903399
Co-reporter:Dirk Meyer, Maria A. Taige, Alexander Zeller, Konrad Hohlfeld, Sebastian Ahrens and Thomas Strassner
Organometallics 2009 Volume 28(Issue 7) pp:2142-2149
Publication Date(Web):March 6, 2009
DOI:10.1021/om8009238
A series of novel pyrimidine functionalized palladium(II)(NHC) complexes with aryl and alkyl substituents [1-(2-Pyrimidyl)-3-(aryl or alkyl)imidazoline-2-ylidene palladium(II) chlorides] was synthesized by transmetalation via the corresponding silver complexes. All compounds have been fully characterized by 1H and 13C NMR spectroscopy, elemental analysis, and in two cases by X-ray single crystal structures. Different solid state structures were observed for aryl and alkyl substituted ligands: for the sterically less demanding methyl substituent, a complex is formed, where two ligands are coordinated to one metal center [Pd(L)2Cl]+, while in the mesityl case a [Pd(L)Cl2] structure was observed. They show good catalytic activity in the CH activation of methane as well as in the Mizoroki-Heck reaction, where especially the methyl substituted complex shows a remarkably high activity combined with a very high selectivity.
Co-reporter:Anke Meyer, Maria A. Taige, Thomas Strassner
Journal of Organometallic Chemistry 2009 694(12) pp: 1861-1868
Publication Date(Web):
DOI:10.1016/j.jorganchem.2009.01.036
Co-reporter:Yvonne Unger, Alexander Zeller, Sebastian Ahrens and Thomas Strassner
Chemical Communications 2008 (Issue 28) pp:3263-3265
Publication Date(Web):05 Jun 2008
DOI:10.1039/B804019B
Photoluminescence measurements show that platinum(II) tetracarbene complexes, which could be obtained via different synthetic routes, are interesting lead structures for the development of blue emitters for PhOLEDs with good quantum yields and high photostability.
Co-reporter:Yvonne Unger, Maria A. Taige, Sebastian Ahrens, Thomas Strassner
Inorganica Chimica Acta 2007 Volume 360(Issue 12) pp:3699-3704
Publication Date(Web):1 September 2007
DOI:10.1016/j.ica.2007.04.037
Three octahedral complexes built from N-alkylsubstituted imidazoles and magnesium as well as calcium chloride are reported. The obtained solid-state structures differ significantly from each other, depending on the size of the metal ion and the substituent on the imidazole. A chloro-bridged structure is found in the case of tert-butylimidazole, while for the iso-propylimidazole the calcium ion is coordinated by six imidazoles. For the smaller magnesium cation, we also found a sixfold coordination, but here only three of the iso-propylimidazoles coordinate to the magnesium, the three other positions are taken by water molecules.N-substituted alkylimidazoles form complexes with calcium and magnesium cations. Depending on the substituent and the ion size different structures could be observed. We report the structures of [Ca(iprIm)6]Cl2, [(tBuIm)3CaCl(μ2-Cl)2ClCa(tBuIm)3], and [Mg(iprIm)6(H2O)3]Cl2.
Co-reporter:Sebastian Ahrens;Eberhardt Herdtweck;Sigrid Goutal
European Journal of Inorganic Chemistry 2006 Volume 2006(Issue 6) pp:
Publication Date(Web):31 JAN 2006
DOI:10.1002/ejic.200500888
The use of metal acetates has allowed the synthesis of NHC complexes without isolation of the free carbene. This route is very useful in cases where the metal acetates are readily available and has been used, for example, for the synthesis of bis(N-heterocyclic carbene) complexes of palladium(II). In the case of platinum, however, the corresponding acetate is not commercially available and is difficult to synthesize. Previously published syntheses require either an external base (e.g. NaOAc or KOtBu) or a transmetalation step. Here we present a new general synthetic pathway for platinum–bis(carbene) complexes using platinum(II) acetylacetonate as a commercially available metal precursor. Aromatic substituents greatly enhance the stability of the metal complexes against acidic media. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Co-reporter:Sebastian Ahrens, Thomas Strassner
Inorganica Chimica Acta 2006 Volume 359(Issue 15) pp:4789-4796
Publication Date(Web):1 December 2006
DOI:10.1016/j.ica.2006.05.042
Chelating biscarbene ligands are one way to extend the stability of catalysts in homogenous catalysis. Methylene bridged palladium and platinum biscarbene complexes with various counterions have been published, but until now the corresponding chloride complexes were only available by time consuming anion exchange procedures. Here, we present a new direct synthesis for methylene bridged bisimidazolium chloride salts and their platinum biscarbene complexes using dichloromethane as a reagent. Solid state structures of the imidazolium salts and the platinum complexes are reported. The new complexes were successfully tested in the catalytic CH activation of methane.We present a new direct route for the synthesis of methylene bridged bisimidazolium chloride salts as precursors for chelating NHC ligands and their platinum biscarbene complexes using dichloromethane as a reagent. Methylene bridged palladium and platinum biscarbene complexes with various counterions have been published, but until now the corresponding chloride complexes were only available by time consuming anion exchange procedures. Solid state structures of imidazolium salts and platinum complexes are reported. The new complexes were successfully tested in the catalytic CH activation of methane.
Co-reporter:Hendrik Leopold and Thomas Strassner
Dalton Transactions 2017 - vol. 46(Issue 24) pp:NaN7812-7812
Publication Date(Web):2017/06/07
DOI:10.1039/C7DT00828G
We report the synthesis of seven novel backbone functionalized N-phenyl-1,3-thiazol-2-ylidene platinum(II) complexes and their photophysical properties. Electronically diverse N-phenyl-1,3-thiazol-2-thiones were prepared by a reaction of aniline with carbon disulfide and different α-haloketone compounds. Oxidative desulfuration and salt metathesis yielded the desired NHC-precursors with hexafluorophosphate counterions. In addition, a new route for the synthesis of N-phenyl-1,3-benzo[d]thiazole tetrafluoroborate via N-arylation using hypervalent iodine species is presented. All complexes were prepared from the corresponding NHC precursor in a one-pot process using silver(I)oxide, transmetalation to platinum and reaction with the β-diketone acetylacetone under basic conditions. These complexes exhibit strong phosphorescence with quantum yields up to 72% in 2 wt% PMMA films with decay lifetimes of 8.8–12.3 μs. The influence of methyl- and phenyl-groups, and an ester-substituent at the 4- and/or 5-position of the 1,3-thiazole moiety, as well as the N-phenyl-1,3-benzo[d]thiazole-derived motif is discussed. The 4,5-unsubstituted-N-phenyl-1,3-thiazol-2-ylidene platinum(II) acetylacetonato complex served as a reference in this study to evaluate the electronic effects originating from the backbone substitution. All complexes emit in a narrow range of the bluish-green spectrum of the visible light (510 ± 10 nm).
Co-reporter:Yvonne Unger, Alexander Zeller, Sebastian Ahrens and Thomas Strassner
Chemical Communications 2008(Issue 28) pp:NaN3265-3265
Publication Date(Web):2008/06/05
DOI:10.1039/B804019B
Photoluminescence measurements show that platinum(II) tetracarbene complexes, which could be obtained via different synthetic routes, are interesting lead structures for the development of blue emitters for PhOLEDs with good quantum yields and high photostability.
Co-reporter:David Schleicher, Alexander Tronnier, Hendrik Leopold, Horst Borrmann and Thomas Strassner
Dalton Transactions 2016 - vol. 45(Issue 8) pp:NaN3263-3263
Publication Date(Web):2016/02/03
DOI:10.1039/C6DT00100A
We present the synthesis and structural characterization of novel ruthenium complexes containing C^C* cyclometalated N-heterocyclic carbene ligands, η6-arene (p-cymene) ligands and one bridging chlorine ion. Complexes of the general formula [Ru(p-cymene)(C^C*)Cl] were prepared via a one-pot synthesis using in situ transmetalation from the correspondent silver NHC complexes. These complexes react with sodium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (NaBArF4) to form dinuclear complexes of the general structure [Ru(p-cymene)(C^C*)-μ-Cl-(p-cymene)(C^C*)Ru]+[BArF4]−. Solid-state structures confirm that the pseudo-tetrahedral coordination around the metal center with the η6-ligand aligned perpendicularly to the C^C* ligand and the i-Pr group “atop” is retained in the bimetallic complexes.
Co-reporter:Dominik Munz, Alexander Poethig, Alexander Tronnier and Thomas Strassner
Dalton Transactions 2013 - vol. 42(Issue 20) pp:NaN7304-7304
Publication Date(Web):2013/02/06
DOI:10.1039/C3DT33006K
A series of ortho-phenylene bridged palladium bis-NHC complexes has been synthesized. Complexes with imidazolium and benzimidazolium derived NHCs and methyl-/benzyl-wingtips are reported. Bis(benz)imidazoles with a doubly brominated ortho-phenylene bridge could be obtained by an electrophilic substitution reaction. The structure of the complexes could be confirmed by three solid-state structures. All catalysts have been tested in the catalytic functionalisation of propane. The catalytic activity is highly dependent on the ligand, whereas ligand effects on the regioselectivity (n/iso) are much smaller.
Co-reporter:Alexander Tronnier, Stefan Metz, Gerhard Wagenblast, Ingo Muenster and Thomas Strassner
Dalton Transactions 2014 - vol. 43(Issue 8) pp:NaN3305-3305
Publication Date(Web):2013/12/20
DOI:10.1039/C3DT53264J
Since C^C* cyclometalated Pt(II) complexes with N-heterocyclic carbene (NHC) ligands have been identified as potential emitter materials in organic light-emitting devices (OLEDs), very promising results regarding quantum yields, colour and stability have been presented. Herein, we report on four nitrile substituted complexes with a chelating NHC ligand (1-(4-cyanophenyl)-3-isopropyl-1H-benzo[d]imidazole or 4-(tert-butyl)-1-(4-cyanophenyl)-3-methyl-1H-imidazole) and a bidentate monoanionic auxiliary ligand (acetylacetone or dimesitoylmethane). The complexes have been fully characterized including extensive 2D NMR studies (COSY, HSQC, HMBC, NOESY, 195Pt NMR), three of them also by solid-state structures. Photophysical measurements in amorphous PMMA films and pure emitter films at room temperature reveal the impact of the mesityl groups in the auxiliary ligand, which led to a significant increase of the quantum yield, while the decay lifetimes decreased. The electron withdrawing nitrile groups shift the emission towards blue colour coordinates.
Co-reporter:Alexander Tronnier and Thomas Strassner
Dalton Transactions 2013 - vol. 42(Issue 27) pp:NaN9851-9851
Publication Date(Web):2013/05/21
DOI:10.1039/C3DT50841B
A series of bimetallic N-heterocyclic carbene (NHC) platinum(II) complexes with the general formula [Pt(NHC)(L)]2Ph were synthesized, which are composed of two [Pt(NHC)(L)] (L = acetylacetone, dipivaloylmethane or dimesitoylmethane; NHC = 3-methylimidazole or 3-benzylimidazole) fragments. Both fragments are cyclometalated to the same central phenyl ring in the para- or meta-position. All complexes have been fully characterized by standard techniques, two of them additionally by solid-state structures. Photoluminescence properties were investigated and very high quantum yields of 76–93% at room temperature have been observed. For a single-matrix device with an emitter concentration of 30%, a current efficiency of 25 cd A−1, an external quantum efficiency of 8.5%, and a luminance efficiency of 10 lm W−1 were achieved at 300 cd m−2. Density functional theory (DFT) calculations were performed to support experimental data and gain further insight into the photoluminescence behaviour.
Co-reporter:Yvonne Unger, Dirk Meyer and Thomas Strassner
Dalton Transactions 2010 - vol. 39(Issue 18) pp:NaN4301-4301
Publication Date(Web):2010/03/25
DOI:10.1039/B927099J
Platinum(II) tetracarbene complexes with chelating bis(imidazoline-2-ylidene) ligands have recently shown to be an interesting class of phosphorescent emitters, although they exhibit emission wavelengths in the near-UV region with only moderate quantum yields. By changing the bis(imidazoline-2-ylidene) ligands to bis(triazoline-5-ylidene) ligands we have successfully shifted the emission wavelengths to the visible region of the spectrum. We herein report the synthesis of new bis- and tetracarbene complexes with bis(triazoline-5-ylidene) ligands, their photophysical properties and a solid state structure of a representative member of this new class of compounds.
Co-reporter:Alexander Tronnier, Ute Heinemeyer, Stefan Metz, Gerhard Wagenblast, Ingo Muenster and Thomas Strassner
Journal of Materials Chemistry A 2015 - vol. 3(Issue 8) pp:NaN1693-1693
Publication Date(Web):2015/01/09
DOI:10.1039/C4TC02575J
Platinum(II) complexes [(NHC)Pt(L)] with various β-diketonate based auxiliary ligands (L: 3-meacac = 3-methylacetylacetonato, dpm = dipivaloylmethanato, dbm = dibenzoylmethanato, mesacac = dimesitoylmethanato, duratron = bis(2,3,5,6-tetramethylbenzoyl)methanato) and a C^C* cyclometalated N-heterocyclic carbene ligand (NHC: dpbic = 1,3-diphenylbenzo[d]imidazol-2-ylidene, dpnac = 1,3-diphenylnaphtho[2,3-d]imidazol-2-ylidene or bnbic = 1-phenyl-3-benzylbenzo[d]imidazol-2-ylidene) were found to show different aggregation and photophysical properties depending on the auxiliary ligand. Eight complexes were prepared from a silver(I)–NHC intermediate by transmetalation, cyclometalation and subsequent treatment with potassium-tert-butanolate and β-diketone. They were fully characterized by standard techniques including 195Pt NMR. Five complexes were additionally characterized by 2D NMR spectroscopy (COSY, HSQC, HMBC and NOESY). Solid-state structures of five complexes could be obtained and show the tendency of the square-planar compounds to form pairs with different Pt–Pt distances depending on the bulkiness of the substituents at the auxiliary ligand. The result of the photophysical measurements in amorphous PMMA films reveals quantum yields of up to 85% with an emission maximum in the blue region and comparatively short decay lifetimes (3.6 μs). Density functional theory (DFT/TD-DFT) calculations were performed to elucidate the emission process and revealed a predominant 3ILCT/3MLCT character. Organic light-emitting devices (OLEDs) comprising one of the complexes achieved 12.6% EQE, 11.9 lm W−1 luminous efficacy and 25.2 cd A−1 current efficiency with a blue emission maximum at 300 cd m−2. The influence of an additional hole-transporter in the emissive layer was investigated and found to improve the device lifetime by a factor of seven.
Co-reporter:Yvonne Unger, Alexander Zeller, Maria A. Taige and Thomas Strassner
Dalton Transactions 2009(Issue 24) pp:NaN4794-4794
Publication Date(Web):2009/04/23
DOI:10.1039/B900655A
Although examples of nickel(II), palladium(II) and platinum(II)N-heterocyclic tetracarbene complexes are known in the literature, particularly platinum(II) tetracarbene complexes are rare. We developed a new synthetic route via biscarbene acetate complexes, which make homoleptic as well as heteroleptic platinum(II) tetracarbene complexes accessible. The reported photoluminescence data show that these complexes have good quantum yields and photostability and are a promising class of emitters for PhOLEDs. Characterization of the compounds includes a solid-state structure of the homoleptic complex bis(1,1′-diisopropyl-3,3′-methylenediimidazoline-2,2′-diylidene)platinum(II) dibromide.
Co-reporter:M. Tenne, S. Metz, G. Wagenblast, Ingo Münster and T. Strassner
Dalton Transactions 2015 - vol. 44(Issue 18) pp:NaN8455-8455
Publication Date(Web):2015/04/17
DOI:10.1039/C4DT03613A
Neutral cyclometalated platinum(II) N-heterocyclic carbene complexes [Pt(C^C*)(O^O)] with C^C* ligands based on 1-phenyl-1,2,4-triazol-5-ylidene and 4-phenyl-1,2,4-triazol-5-ylidene, as well as acetylacetonato (O^O = acac) and 1,3-bis(2,4,6-trimethylphenyl)propan-1,3-dionato (O^O = mesacac) ancillary ligands were synthesized and characterized. All complexes are emissive at room temperature in a poly(methyl methacrylate) (PMMA) matrix with emission maxima in the blue region of the spectrum. High quantum efficiencies and short decay times were observed for all complexes with mesacac ancillary ligands. The sterically demanding mesityl groups of the mesacac ligand effectively prevent molecular stacking. The emission behavior of these emitters is in general independent of the position of the nitrogen in the backbone of the N-heterocyclic carbene (NHC) unit and a variety of substituents in 4-position of the phenyl unit, meta to the cyclometalating bond.
![1H-Imidazolium, 1,1'-methylenebis[3-[4-(ethoxycarbonyl)phenyl]-,dibromide](http://img.cochemist.com/ccimg/889700/889618-76-2.png)
![1H-Imidazolium, 1,1'-methylenebis[3-[4-(ethoxycarbonyl)phenyl]-,dibromide](http://img.cochemist.com/ccimg/889700/889618-76-2_b.png)
![4-PENTENE-1-SULFONAMIDE, N-[(PHENYLAMINO)CARBONYL]-](http://img.cochemist.com/ccimg/856900/856899-30-4.png)
![4-PENTENE-1-SULFONAMIDE, N-[(PHENYLAMINO)CARBONYL]-](http://img.cochemist.com/ccimg/856900/856899-30-4_b.png)
![4-Pentene-1-sulfonamide, 4-methyl-N-[(phenylamino)carbonyl]-](http://img.cochemist.com/ccimg/856900/856899-29-1.png)
![4-Pentene-1-sulfonamide, 4-methyl-N-[(phenylamino)carbonyl]-](http://img.cochemist.com/ccimg/856900/856899-29-1_b.png)
![3-BUTENE-1-SULFONAMIDE, N-[(PHENYLAMINO)CARBONYL]-](http://img.cochemist.com/ccimg/856900/856899-28-0.png)
![3-BUTENE-1-SULFONAMIDE, N-[(PHENYLAMINO)CARBONYL]-](http://img.cochemist.com/ccimg/856900/856899-28-0_b.png)
![CARBAMIC ACID, [(4-METHYL-4-PENTENYL)SULFONYL]-, ETHYL ESTER](http://img.cochemist.com/ccimg/856900/856899-26-8.png)
![CARBAMIC ACID, [(4-METHYL-4-PENTENYL)SULFONYL]-, ETHYL ESTER](http://img.cochemist.com/ccimg/856900/856899-26-8_b.png)
![3-BUTENE-1-SULFONAMIDE, 3-METHYL-N-[(PHENYLAMINO)CARBONYL]-](http://img.cochemist.com/ccimg/856900/856899-23-5.png)
![3-BUTENE-1-SULFONAMIDE, 3-METHYL-N-[(PHENYLAMINO)CARBONYL]-](http://img.cochemist.com/ccimg/856900/856899-23-5_b.png)
![Carbamic acid, [(3-methyl-3-butenyl)sulfonyl]-, ethyl ester](http://img.cochemist.com/ccimg/856900/856899-22-4.png)
![Carbamic acid, [(3-methyl-3-butenyl)sulfonyl]-, ethyl ester](http://img.cochemist.com/ccimg/856900/856899-22-4_b.png)
![2-Thia-1-azabicyclo[4.2.0]octan-8-one, 6-methyl-, 2,2-dioxide](http://img.cochemist.com/ccimg/701400/701304-66-7.png)
![2-Thia-1-azabicyclo[4.2.0]octan-8-one, 6-methyl-, 2,2-dioxide](http://img.cochemist.com/ccimg/701400/701304-66-7_b.png)
![Silane, triethyl[(1E)-1-methyl-2-phenylethenyl]-](http://img.cochemist.com/ccimg/439900/439858-76-1.png)
![Silane, triethyl[(1E)-1-methyl-2-phenylethenyl]-](http://img.cochemist.com/ccimg/439900/439858-76-1_b.png)
![Silane, triethyl[(1E)-1-ethylidenehexyl]-](/data/chemimg/2068900/92992-73-9.png)
![Silane, triethyl[(1E)-1-ethylidenehexyl]-](/data/chemimg/2068900/92992-73-9_b.png)
![Phenol, 2,6-bis[(3-bromo-5-chloro-4-hydroxyphenyl)methyl]-4-fluoro-](http://img.cochemist.com/ccimg/78000/77972-42-0.png)
![Phenol, 2,6-bis[(3-bromo-5-chloro-4-hydroxyphenyl)methyl]-4-fluoro-](http://img.cochemist.com/ccimg/78000/77972-42-0_b.png)
![SILANE, TRIETHYL[(1Z)-2-PHENYLETHENYL]-](http://img.cochemist.com/ccimg/75700/75645-33-9.png)
![SILANE, TRIETHYL[(1Z)-2-PHENYLETHENYL]-](http://img.cochemist.com/ccimg/75700/75645-33-9_b.png)
![1,8-DIOXA-2-AZASPIRO[4.5]DEC-2-ENE-3-CARBOXYLIC ACID](http://img.cochemist.com/ccimg/71000/70918-95-5.png)
![1,8-DIOXA-2-AZASPIRO[4.5]DEC-2-ENE-3-CARBOXYLIC ACID](http://img.cochemist.com/ccimg/71000/70918-95-5_b.png)
![Silane, [2-(3-cyclohexen-1-yl)ethyl]dimethylphenyl-](http://img.cochemist.com/ccimg/61600/61518-54-5.png)
![Silane, [2-(3-cyclohexen-1-yl)ethyl]dimethylphenyl-](http://img.cochemist.com/ccimg/61600/61518-54-5_b.png)
![ETHANONE, 1,1'-[METHYLENEBIS(5-CHLORO-2-HYDROXY-3,1-PHENYLENE)]BIS-](http://img.cochemist.com/ccimg/60100/60011-06-5.png)
![ETHANONE, 1,1'-[METHYLENEBIS(5-CHLORO-2-HYDROXY-3,1-PHENYLENE)]BIS-](http://img.cochemist.com/ccimg/60100/60011-06-5_b.png)
![1H-Imidazole, 1-[2,6-bis(1-methylethyl)phenyl]-](http://img.cochemist.com/ccimg/25400/25364-47-0.png)
![1H-Imidazole, 1-[2,6-bis(1-methylethyl)phenyl]-](http://img.cochemist.com/ccimg/25400/25364-47-0_b.png)
![Silane, triethyl[(1E)-2-phenylethenyl]-](http://img.cochemist.com/ccimg/21300/21209-32-5.png)
![Silane, triethyl[(1E)-2-phenylethenyl]-](http://img.cochemist.com/ccimg/21300/21209-32-5_b.png)
![Ethanone, 1-[4-[(1Z)-2-phenylethenyl]phenyl]-](http://img.cochemist.com/ccimg/20500/20488-43-1.png)
![Ethanone, 1-[4-[(1Z)-2-phenylethenyl]phenyl]-](http://img.cochemist.com/ccimg/20500/20488-43-1_b.png)
![4-(4-Nitro-phenyl)-4H-[1,2,4]triazole](http://img.cochemist.com/ccimg/16800/16759-47-0.png)
![4-(4-Nitro-phenyl)-4H-[1,2,4]triazole](http://img.cochemist.com/ccimg/16800/16759-47-0_b.png)
![4-[(2S)-2-CYANO-2-({[(4-METHOXYBENZYL)OXY]CARBONYL}AMINO)ETHYL]PH<WBR />ENYL 4-METHOXYBENZYL CARBONATE](http://img.cochemist.com/ccimg/3500/3475-07-8.png)
![4-[(2S)-2-CYANO-2-({[(4-METHOXYBENZYL)OXY]CARBONYL}AMINO)ETHYL]PH<WBR />ENYL 4-METHOXYBENZYL CARBONATE](http://img.cochemist.com/ccimg/3500/3475-07-8_b.png)
![TRIMETHYL-[METHYL-(2-PHENYLETHYL)-TRIMETHYLSILYLOXYSILYL]OXYSILANE](http://img.cochemist.com/ccimg/3500/3439-16-5.png)
![TRIMETHYL-[METHYL-(2-PHENYLETHYL)-TRIMETHYLSILYLOXYSILYL]OXYSILANE](http://img.cochemist.com/ccimg/3500/3439-16-5_b.png)
![[1,1'-Biphenyl]-4-amine,N,N-dimethyl-](http://img.cochemist.com/ccimg/1200/1137-79-7.png)
![[1,1'-Biphenyl]-4-amine,N,N-dimethyl-](http://img.cochemist.com/ccimg/1200/1137-79-7_b.png)
![[1,1':3',1''-Terphenyl]-2'-amine](http://img.cochemist.com/ccimg/87700/87666-57-7.png)
![[1,1':3',1''-Terphenyl]-2'-amine](http://img.cochemist.com/ccimg/87700/87666-57-7_b.png)
![Ethanone, 1-[4-[(1E)-2-phenylethenyl]phenyl]-](/data/chemimg/1785200/20488-42-0.png)
![Ethanone, 1-[4-[(1E)-2-phenylethenyl]phenyl]-](/data/chemimg/1785200/20488-42-0_b.png)
