Co-reporter:Michael G. Sommer, Raphael Marx, David Schweinfurth, Yvonne Rechkemmer, Petr Neugebauer, Margarethe van der Meer, Stephan Hohloch, Serhiy Demeshko, Franc MeyerJoris van Slageren, Biprajit Sarkar
Inorganic Chemistry 2017 Volume 56(Issue 1) pp:402-413
Publication Date(Web):December 13, 2016
DOI:10.1021/acs.inorgchem.6b02330
The azide anion is widely used as a ligand in coordination chemistry. Despite its ubiquitous presence, controlled synthesis of azido complexes remains a challenging task. Making use of click-derived tripodal ligands, we present here various coordination motifs of the azido ligands, the formation of which appears to be controlled by the peripheral substituents on the tripodal ligands with otherwise identical structure of the coordination moieties. Thus, the flexible benzyl substituents on the tripodal ligand TBTA led to the formation of the first example of an unsupported and solely μ1,1-azido-bridged dicobalt(II) complex. The more rigid phenyl substituents on the TPTA ligand deliver an unsupported and solely μ1,3-azido-bridged dicobalt(II) complex. Bulky diisopropylphenyl substituents on the TDTA ligand deliver a doubly μ1,1-azido-bridged dicobalt(II) complex. Intriguingly, the mononuclear copper(II) complex [Cu(TBTA)N3]+ is an excellent synthon for generating mixed dinuclear complexes of the form [(TBTA)Co(μ1,1-N3)Cu(TBTA)]3+ or [(TBTA)Cu(μ1,1-N3)Cu(TPTA)]3+, both of which contain a single unsupported μ1,1-N3 as a bridge. To the best of our knowledge, these are also the first examples of mixed dinuclear complexes with a μ1,1-N3 monoazido bridge. All complexes were crystallographically characterized, and selected examples were probed via magnetometry and high-field EPR spectroscopy to elucidate the electronic structures of these complexes and the nature of magnetic coupling in the various azido-bridged complexes. These results thus prove the power of click-tripodal ligands in generating hitherto unknown chemical structures and properties.
Co-reporter:Maren Gysler, Fadi El Hallak, Liviu Ungur, Raphael Marx, Michael Hakl, Petr Neugebauer, Yvonne Rechkemmer, Yanhua Lan, Ilya Sheikin, Milan Orlita, Christopher E. Anson, Annie K. Powell, Roberta Sessoli, Liviu F. Chibotaru and Joris van Slageren
Chemical Science 2016 vol. 7(Issue 7) pp:4347-4354
Publication Date(Web):16 Mar 2016
DOI:10.1039/C6SC00318D
In-depth investigations of the low energy electronic structures of mononuclear lanthanide complexes, including single molecule magnets, are challenging at the best of times. For magnetically coupled polynuclear systems, the task seems well nigh impossible. However, without detailed understanding of the electronic structure, there is no hope of understanding their static and dynamic magnetic properties in detail. We have been interested in assessing which techniques are most appropriate for studying lanthanide single-molecule magnets. Here we present a wide ranging theoretical and experimental study of the archetypal polynuclear lanthanide single-molecule magnet Dy3 and derive the simplest model to describe the results from each experimental method, including high-frequency electron paramagnetic resonance and far-infrared spectroscopies and cantilever torque magnetometry. We conclude that a combination of these methods together with ab initio calculations is required to arrive at a full understanding of the properties of this complex, and potentially of other magnetically coupled lanthanide complexes.
Co-reporter:K. Bader, M. Winkler and J. van Slageren
Chemical Communications 2016 vol. 52(Issue 18) pp:3623-3626
Publication Date(Web):03 Feb 2016
DOI:10.1039/C6CC00300A
We report a pulsed EPR study on different transition metal phthalocyanines, elucidating the dependence of spin relaxation on solvent, ligand and metal ion. Coherence times of >40 µs and spin–lattice relaxation times of up to 2 s were found. Minimization of SOMO-environment overlap leads to increased coherence times.
Co-reporter:Margarethe van der Meer, Yvonne Rechkemmer, Frauke D. Breitgoff, Raphael Marx, Petr Neugebauer, Uta Frank, Joris van Slageren, and Biprajit Sarkar
Inorganic Chemistry 2016 Volume 55(Issue 22) pp:11944-11953
Publication Date(Web):November 8, 2016
DOI:10.1021/acs.inorgchem.6b02097
Quinonoid bridges are well-suited for generating dinuclear assemblies that might display various bistable properties. In this contribution we present two diiron(II) complexes where the iron(II) centers are either bridged by the doubly deprotonated form of a symmetrically substituted quinonoid bridge, 2,5-bis[4-(isopropyl)anilino]-1,4-benzoquinone (H2L2′) with a [O,N,O,N] donor set, or with the doubly deprotonated form of an unsymmetrically substituted quinonoid bridge, 2-[4-(isopropyl)anilino]-5-hydroxy-1,4-benzoquinone (H2L5′) with a [O,O,O,N] donor set. Both complexes display temperature-induced spin crossover (SCO). The nature of the SCO is strongly dependent on the bridging ligand, with only the complex with the [O,O,O,N] donor set displaying a prominent hysteresis loop of about 55 K. Importantly, only the latter complex also shows a pronounced light-induced spin state change. Furthermore, both complexes can be oxidized to the mixed-valent iron(II)–iron(III) form, and the nature of the bridge determines the Robin and Day classification of these forms. Both complexes have been probed by a battery of electrochemical, spectroscopic, and magnetic methods, and this combined approach is used to shed light on the electronic structures of the complexes and on bistability. The results presented here thus show the potential of using the relatively new class of unsymmetrically substituted bridging quinonoid ligands for generating intriguing bistable properties and for performing site-specific magnetic switching.
Co-reporter:J. Rozbořil, Y. Rechkemmer, D. Bloos, F. Münz, C. N. Wang, P. Neugebauer, J. Čechal, J. Novák and J. van Slageren
Dalton Transactions 2016 vol. 45(Issue 18) pp:7555-7558
Publication Date(Web):11 Apr 2016
DOI:10.1039/C6DT00839A
We report field-dependent magnetization measurements on monolayers of [Dy(Pc)2] on quartz, prepared by the Langmuir–Blodgett technique. The films are thoroughly characterized by means of X-ray reflectivity and atomic force microscopy. The magnetisation of the sample is measured through the magnetic circular dichroism of a ligand-based electronic transition.
Co-reporter:Stephen T. Liddle and Joris van Slageren
Chemical Society Reviews 2015 vol. 44(Issue 19) pp:6655-6669
Publication Date(Web):09 Jul 2015
DOI:10.1039/C5CS00222B
Ever since the discovery that certain manganese clusters retain their magnetisation for months at low temperatures, there has been intense interest in molecular nanomagnets because of potential applications in data storage, spintronics, quantum computing, and magnetocaloric cooling. In this Tutorial Review, we summarise some key historical developments, and centre our discussion principally on the increasing trend to exploit the large magnetic moments and anisotropies of f-element ions. We focus on the important theme of strategies to improve these systems with the ultimate aim of developing materials for ultra-high-density data storage devices. We present a critical discussion of key parameters to be optimised, as well as of experimental and theoretical techniques to be used to this end.
Co-reporter:Yvonne Rechkemmer; Julia E. Fischer; Raphael Marx; María Dörfel; Petr Neugebauer; Sebastian Horvath; Maren Gysler; Theis Brock-Nannestad; Wolfgang Frey; Michael F. Reid
Journal of the American Chemical Society 2015 Volume 137(Issue 40) pp:13114-13120
Publication Date(Web):September 22, 2015
DOI:10.1021/jacs.5b08344
The electronic structure of a novel lanthanide-based single-ion magnet, {C(NH2)3}5[Er(CO3)4]·11H2O, was comprehensively studied by means of a large number of different spectroscopic techniques, including far-infrared, optical, and magnetic resonance spectroscopies. A thorough analysis, based on crystal field theory, allowed an unambiguous determination of all relevant free ion and crystal field parameters. We show that inclusion of methods sensitive to the nature of the lowest-energy states is essential to arrive at a correct description of the states that are most relevant for the static and dynamic magnetic properties. The spectroscopic investigations also allowed for a full understanding of the magnetic relaxation processes occurring in this system. Thus, the importance of spectroscopic studies for the improvement of single-molecule magnets is underlined.
Co-reporter:R. Marx, F. Moro, M. Dörfel, L. Ungur, M. Waters, S. D. Jiang, M. Orlita, J. Taylor, W. Frey, L. F. Chibotaru and J. van Slageren
Chemical Science 2014 vol. 5(Issue 8) pp:3287-3293
Publication Date(Web):23 May 2014
DOI:10.1039/C4SC00751D
We have investigated the crystal field splitting in the archetypal lanthanide-based single-ion magnets and related complexes (NBu4)+[LnPc2]−·2dmf (Ln = Dy, Ho, Er; dmf = N,N-dimethylformamide) by means of far infrared and inelastic neutron scattering spectroscopies. In each case, we have found several features corresponding to direct crystal field transitions within the ground multiplet. The observation of three independent peaks in the holmium derivative enabled us to derive crystal field splitting parameters. In addition, we have carried out CASSCF calculations. We show that exploiting the interplay of CASSCF calculation (for the composition of the states) and advanced spectroscopic measurements (for accurate determination of the energies) is a very powerful approach to gain insight into the electronic structure of lanthanide-based single-molecule magnets.
Co-reporter:Yuan-Yuan Zhu, Ting-Ting Yin, Shang-Da Jiang, Anne-Laure Barra, Wolfgang Wernsdorfer, Petr Neugebauer, Raphael Marx, María Dörfel, Bing-Wu Wang, Zong-Quan Wu, Joris van Slageren and Song Gao
Chemical Communications 2014 vol. 50(Issue 95) pp:15090-15093
Publication Date(Web):13 Oct 2014
DOI:10.1039/C4CC07580C
A pair of enantiopure FeIII4 SMMs with axial symmetry was synthesized and characterized by magnetization and high-frequency electron paramagnetic resonance methods. The results reveal that the axial symmetry of the structure is broken by the interaction of FeIII4 with the disordered solvent molecules.
Co-reporter:David Schweinfurth;Yvonne Rechkemmer;Stephan Hohloch;Naina Deibel;Irina Peremykin;Jan Fiedler;Raphael Marx;Dr. Petr Neugebauer;Dr. Joris vanSlageren;Dr. Biprajit Sarkar
Chemistry - A European Journal 2014 Volume 20( Issue 12) pp:3475-3486
Publication Date(Web):
DOI:10.1002/chem.201302858
Abstract
The complexes [{(tmpa)CoII}2(μ-L1)2−]2+ (12+) and [{(tmpa)CoII}2(μ-L2)2−]2+ (22+), with tmpa=tris(2-pyridylmethyl)amine, H2L1=2,5-di-[2-(methoxy)-anilino]-1,4-benzoquinone, and H2L2=2,5-di-[2-(trifluoromethyl)-anilino]-1,4-benzoquinone, were synthesized and characterized. Structural analysis of 22+ revealed a distorted octahedral coordination around the cobalt centers, and cobalt–ligand bond lengths that match with high-spin CoII centers. Superconducting quantum interference device (SQUID) magnetometric studies on 12+ and 22+ are consistent with the presence of two weakly exchange-coupled high-spin cobalt(II) ions, for which the nature of the coupling appears to depend on the substituents on the bridging ligand, being antiferromagnetic for 12+ and ferromagnetic for 22+. Both complexes exhibit several one-electron redox steps, and these were investigated with cyclic voltammetry and UV/Vis/near-IR spectroelectrochemistry. For 12+, it was possible to chemically isolate the pure forms of both the one-electron oxidized mixed-valent 13+ and the two-electron oxidized isovalent 14+ forms, and characterize them structurally as well as magnetically. This series thus provided an opportunity to investigate the effect of reversible electron transfers on the total spin-state of the molecule. In contrast to 22+, for 14+ the metal–ligand distances and the distances within the quinonoid ligand point to the existence of two low-spin CoIII centers, thus showing the innocence of the quintessential non-innocent ligands L. Magnetic data corroborate these observations by showing the decrease of the magnetic moment by roughly half (neglecting spin exchange effects) on oxidizing the molecules with one electron, and the disappearance of a paramagnetic response upon two-electron oxidation, which confirms the change in spin state associated with the electron-transfer steps.
Co-reporter:Dr. Fabrizio Moro;Dr. David P. Mills;Dr. Stephen T. Liddle;Dr. Joris vanSlageren
Angewandte Chemie International Edition 2013 Volume 52( Issue 12) pp:3430-3433
Publication Date(Web):
DOI:10.1002/anie.201208015
Co-reporter:Francesco Piga, Fabrizio Moro, Itana Krivokapic, Alexander J. Blake, Ruth Edge, Eric J. L. McInnes, David J. Evans, Jonathan McMaster and Joris van Slageren
Chemical Communications 2012 vol. 48(Issue 18) pp:2430-2432
Publication Date(Web):03 Jan 2012
DOI:10.1039/C2CC16853G
A novel family of paramagnetic tetranuclear ferrous cubanes is reported. Two complexes from this family are described and their magnetic properties are discussed in relation to their structures.
Co-reporter:Michael Waters, Fabrizio Moro, Itana Krivokapic, Jonathan McMaster and Joris van Slageren
Dalton Transactions 2012 vol. 41(Issue 4) pp:1128-1130
Publication Date(Web):06 Dec 2011
DOI:10.1039/C1DT11880C
Bis(octacyanophthalocyanine)dysprosium(III) (1) has been synthesised, characterised and magnetically studied. By the incorporation of cyano substituents on the phthalocyanine (Pc) rings, a starting point has been created for the chemical modification of double deckers for the purpose of surface self-assembly. The modification of the rings leaves the magnetic properties of the double decker largely unaffected.
Co-reporter:Yuan-Yuan Zhu, Ting-Ting Yin, Shang-Da Jiang, Anne-Laure Barra, Wolfgang Wernsdorfer, Petr Neugebauer, Raphael Marx, María Dörfel, Bing-Wu Wang, Zong-Quan Wu, Joris van Slageren and Song Gao
Chemical Communications 2014 - vol. 50(Issue 95) pp:NaN15093-15093
Publication Date(Web):2014/10/13
DOI:10.1039/C4CC07580C
A pair of enantiopure FeIII4 SMMs with axial symmetry was synthesized and characterized by magnetization and high-frequency electron paramagnetic resonance methods. The results reveal that the axial symmetry of the structure is broken by the interaction of FeIII4 with the disordered solvent molecules.
Co-reporter:Francesco Piga, Fabrizio Moro, Itana Krivokapic, Alexander J. Blake, Ruth Edge, Eric J. L. McInnes, David J. Evans, Jonathan McMaster and Joris van Slageren
Chemical Communications 2012 - vol. 48(Issue 18) pp:NaN2432-2432
Publication Date(Web):2012/01/03
DOI:10.1039/C2CC16853G
A novel family of paramagnetic tetranuclear ferrous cubanes is reported. Two complexes from this family are described and their magnetic properties are discussed in relation to their structures.
Co-reporter:R. Marx, F. Moro, M. Dörfel, L. Ungur, M. Waters, S. D. Jiang, M. Orlita, J. Taylor, W. Frey, L. F. Chibotaru and J. van Slageren
Chemical Science (2010-Present) 2014 - vol. 5(Issue 8) pp:NaN3293-3293
Publication Date(Web):2014/05/23
DOI:10.1039/C4SC00751D
We have investigated the crystal field splitting in the archetypal lanthanide-based single-ion magnets and related complexes (NBu4)+[LnPc2]−·2dmf (Ln = Dy, Ho, Er; dmf = N,N-dimethylformamide) by means of far infrared and inelastic neutron scattering spectroscopies. In each case, we have found several features corresponding to direct crystal field transitions within the ground multiplet. The observation of three independent peaks in the holmium derivative enabled us to derive crystal field splitting parameters. In addition, we have carried out CASSCF calculations. We show that exploiting the interplay of CASSCF calculation (for the composition of the states) and advanced spectroscopic measurements (for accurate determination of the energies) is a very powerful approach to gain insight into the electronic structure of lanthanide-based single-molecule magnets.
Co-reporter:J. Rozbořil, Y. Rechkemmer, D. Bloos, F. Münz, C. N. Wang, P. Neugebauer, J. Čechal, J. Novák and J. van Slageren
Dalton Transactions 2016 - vol. 45(Issue 18) pp:NaN7558-7558
Publication Date(Web):2016/04/11
DOI:10.1039/C6DT00839A
We report field-dependent magnetization measurements on monolayers of [Dy(Pc)2] on quartz, prepared by the Langmuir–Blodgett technique. The films are thoroughly characterized by means of X-ray reflectivity and atomic force microscopy. The magnetisation of the sample is measured through the magnetic circular dichroism of a ligand-based electronic transition.
Co-reporter:Michael Waters, Fabrizio Moro, Itana Krivokapic, Jonathan McMaster and Joris van Slageren
Dalton Transactions 2012 - vol. 41(Issue 4) pp:NaN1130-1130
Publication Date(Web):2011/12/06
DOI:10.1039/C1DT11880C
Bis(octacyanophthalocyanine)dysprosium(III) (1) has been synthesised, characterised and magnetically studied. By the incorporation of cyano substituents on the phthalocyanine (Pc) rings, a starting point has been created for the chemical modification of double deckers for the purpose of surface self-assembly. The modification of the rings leaves the magnetic properties of the double decker largely unaffected.
Co-reporter:Stephen T. Liddle and Joris van Slageren
Chemical Society Reviews 2015 - vol. 44(Issue 19) pp:NaN6669-6669
Publication Date(Web):2015/07/09
DOI:10.1039/C5CS00222B
Ever since the discovery that certain manganese clusters retain their magnetisation for months at low temperatures, there has been intense interest in molecular nanomagnets because of potential applications in data storage, spintronics, quantum computing, and magnetocaloric cooling. In this Tutorial Review, we summarise some key historical developments, and centre our discussion principally on the increasing trend to exploit the large magnetic moments and anisotropies of f-element ions. We focus on the important theme of strategies to improve these systems with the ultimate aim of developing materials for ultra-high-density data storage devices. We present a critical discussion of key parameters to be optimised, as well as of experimental and theoretical techniques to be used to this end.
Co-reporter:Maren Gysler, Fadi El Hallak, Liviu Ungur, Raphael Marx, Michael Hakl, Petr Neugebauer, Yvonne Rechkemmer, Yanhua Lan, Ilya Sheikin, Milan Orlita, Christopher E. Anson, Annie K. Powell, Roberta Sessoli, Liviu F. Chibotaru and Joris van Slageren
Chemical Science (2010-Present) 2016 - vol. 7(Issue 7) pp:NaN4354-4354
Publication Date(Web):2016/03/16
DOI:10.1039/C6SC00318D
In-depth investigations of the low energy electronic structures of mononuclear lanthanide complexes, including single molecule magnets, are challenging at the best of times. For magnetically coupled polynuclear systems, the task seems well nigh impossible. However, without detailed understanding of the electronic structure, there is no hope of understanding their static and dynamic magnetic properties in detail. We have been interested in assessing which techniques are most appropriate for studying lanthanide single-molecule magnets. Here we present a wide ranging theoretical and experimental study of the archetypal polynuclear lanthanide single-molecule magnet Dy3 and derive the simplest model to describe the results from each experimental method, including high-frequency electron paramagnetic resonance and far-infrared spectroscopies and cantilever torque magnetometry. We conclude that a combination of these methods together with ab initio calculations is required to arrive at a full understanding of the properties of this complex, and potentially of other magnetically coupled lanthanide complexes.
Co-reporter:K. Bader, M. Winkler and J. van Slageren
Chemical Communications 2016 - vol. 52(Issue 18) pp:NaN3626-3626
Publication Date(Web):2016/02/03
DOI:10.1039/C6CC00300A
We report a pulsed EPR study on different transition metal phthalocyanines, elucidating the dependence of spin relaxation on solvent, ligand and metal ion. Coherence times of >40 µs and spin–lattice relaxation times of up to 2 s were found. Minimization of SOMO-environment overlap leads to increased coherence times.
![Benzene, 1,2,3,4-tetrakis[(1-methylethyl)thio]-](http://img.cochemist.com/ccimg/74600/74542-68-0.png)
![Benzene, 1,2,3,4-tetrakis[(1-methylethyl)thio]-](http://img.cochemist.com/ccimg/74600/74542-68-0_b.png)
![Benzene, 1,2,3-tris[(1-methylethyl)thio]-](http://img.cochemist.com/ccimg/74600/74542-66-8.png)
![Benzene, 1,2,3-tris[(1-methylethyl)thio]-](http://img.cochemist.com/ccimg/74600/74542-66-8_b.png)
