Co-reporter:Iliya V. Getmanskii, Vitaliy V. Koval, Ruslan M. Minyaev, Alexander I. Boldyrev, and Vladimir I. Minkin
The Journal of Physical Chemistry C October 12, 2017 Volume 121(Issue 40) pp:22187-22187
Publication Date(Web):September 18, 2017
DOI:10.1021/acs.jpcc.7b07565
A new metastable ultralight crystalline form of aluminum has been computationally designed using density functional calculations with imposing periodic boundary conditions. The geometric and electronic structures of the predicted new allotrope were calculated on the basis of a diamond lattice in which all carbon atoms are replaced by aluminum Al4 tetrahedra. The new form of crystalline aluminum has an extremely low density of 0.61 g/cm3 and would float in water. The new aluminum form is a semimetal and shows high plasticity.
Physical Chemistry Chemical Physics 2017 vol. 19(Issue 38) pp:26145-26150
Publication Date(Web):2017/10/04
DOI:10.1039/C7CP04158F
A correlation between the long-range characteristics of the magnetic response of toroidal boron-based structures is given, involving the uncoordinated B16 cluster and the hypercoordinated [Co@B16]−/3− counterparts. It is found that the perfectly symmetrical doubly aromatic systems share common features, involving a continuous shielding region for the orientation-averaged response (isotropic), and a long-ranged shielding cone under a perpendicularly oriented applied field (Bextz). In contrast, the conflicting aromatic structure given by the slightly distorted species, exhibits an enhanced deshielding cone under Bextz, which dominates the isotropic character of the response. In addition, [Mn@B16]− and [Cu@B16]− clusters were evaluated, denoting the role of the coordinated metal atom in such property. This information is valuable to account for a global magnetic response driven by the bonding pattern acting in each respective compound, and for the possible characterization of intermolecular aggregates or extended structures via NMR experiments.
Co-reporter:Xue-Mei Luo, Tian Jian, Long-Jiu Cheng, Wan-Lu Li, Qiang Chen, Rui Li, Hua-Jin Zhai, Si-Dian Li, Alexander I. Boldyrev, Jun Li, Lai-Sheng Wang
Chemical Physics Letters 2017 Volume 683(Volume 683) pp:
Publication Date(Web):1 September 2017
DOI:10.1016/j.cplett.2016.12.051
•Bn− monoanions have been systematically investigated up to n = 30. However, B26− has remained elusive in this size range.•Here we present a joint photoelectron spectroscopy and first-principles study on the structures and bonding of this seemingly enigmatic cluster.•Extensive global minimum searches and high-level calculations reveal that isomer I dominates the experimental spectrum and represents the smallest 2D boron cluster with a hexagonal vacancy.•Isomer III is found to contribute to the measured PE spectrum as a minor species.•Chemical bonding analyses show that isomer I can be viewed as an all-boron analog of the polycyclic aromatic hydrocarbon C17H11+.Anionic boron clusters have been systematically investigated both experimentally and theoretically up to 30 atoms and have all been proved to be planar or quasi-planar (2D) in their global minima. However, the B26− cluster has remained elusive in this size range up to now, because of its complicated potential landscape. Here we present a joint photoelectron spectroscopy (PES) and first-principles study on the structures and bonding of this seemingly enigmatic cluster. Extensive global minimum searches, followed by high-level calculations and Gibbs free energy corrections, reveal that at least three 2D isomers, I (C1, 2A), II (C1, 2A), and III (C1, 2A), could contribute to the observed PE spectrum for the B26− cluster. Isomer I, which has the lowest free energy at finite temperatures, is found to dominate the experimental spectrum and represents the smallest 2D boron cluster with a hexagonal vacancy. Distinct spectral features are observed for isomer III, which has a pentagonal hole and is found to contribute to the measured PE spectrum as a minor species. Isomer II with a close-packed triangular 2D structure, which is the global minimum at 0 K, may also contribute to the observed spectrum as a minor species. Chemical bonding analyses show that the principal isomer I can be viewed as an all-boron analog of the polycyclic aromatic hydrocarbon C17H11+ in terms of the π bonds.Download high-res image (134KB)Download full-size image
Synthesis, crystal structures, and chemical bonding are reported for four binary phosphides with different degrees of phosphorus oligomerization, ranging from isolated P atoms to infinite phosphorus chains. Ba3P2 = Ba4P2.67□0.33 (□ = vacancy) crystallizes in the anti-Th3P4 structure type with the cubic space group I4̅3d (no. 220), Z = 6, a = 9.7520(7) Å. In the Ba3P2 crystal structure, isolated P3– anions form distorted octahedra around the Ba2+ cations. β-Ba5P4 crystallizes in the Eu5As4 structure type with the orthorhombic space group Cmce (no. 64), Z = 4, a = 16.521(2) Å, b = 8.3422(9) Å, c = 8.4216(9) Å. In the crystal structure of β-Ba5P4, one-half of the phosphorus atoms are condensed into P24– dumbbells. SrP2 and BaP2 are isostructural and crystallize in the monoclinic space group P21/c (no. 14), Z = 6, a = 6.120(2)/6.368(1) Å, b = 11.818(3)/12.133(2) Å, c = 7.441(2)/7.687(2) Å, β = 126.681(4)/126.766(2)° for SrP2/BaP2. In the crystal structures of SrP2 and BaP2, all phosphorus atoms are condensed into ∞1P1– cis–trans helical chains. Electronic structure calculations, chemical bonding analysis via the recently developed solid-state adaptive natural density partitioning (SSAdNDP) method, and UV–vis spectroscopy reveal that SrP2 and BaP2 are electron-balanced semiconductors.
Co-reporter:Li-Ming Yang, Ivan A. Popov, Thomas Frauenheim, Alexander I. Boldyrev, Thomas Heine, Vladimir Bačić and Eric Ganz
Physical Chemistry Chemical Physics 2015 vol. 17(Issue 39) pp:26043-26048
Publication Date(Web):08 Sep 2015
DOI:10.1039/C5CP04893A
We discover unusual chemical bonding in a novel planar hyper-coordinate Ni2Ge free-standing 2D monolayer, and also in a nearly planar slightly buckled Ni2Si monolayer. This unusual bonding is revealed by Solid State Adaptive Natural Density Partitioning analysis. This analysis shows that a new type of 2c-2e Ni–Si σ and 3c-2e Ni–Ge–Ni σ bonds stabilize these 2D crystals. This is completely different from any previously known 2D crystals. Both of these free-standing monolayers are global minima in two-dimensional space. Although their exotic structure has unprecedented chemical bonding, they show extraordinary stability as single layers. The stabilities of these frameworks are confirmed by phonon dispersion calculations and ab initio molecular dynamics calculations. For Ni2Si, the framework was maintained during short 10 ps molecular dynamics annealing up to 1500 K, while Ni2Ge survived 10 ps runs up to 900 K. Both systems are predicted to be non-magnetic and metallic. As these new 2D crystals contain hypercoordinated Group 14 atoms, they are examples of a new class of 2D crystals with unconventional chemical bonding and potentially exciting new properties. Interestingly, we find that the stabilities of Ni2Si and Ni2Ge are much higher than that of silicene and germanene. Thus, this work provides a novel way to stabilize 2D sheets of Group 14 elements.
Co-reporter:Ivan A. Popov, Xinxing Zhang, Bryan W. Eichhorn, Alexander I. Boldyrev and Kit H. Bowen
Physical Chemistry Chemical Physics 2015 vol. 17(Issue 39) pp:26079-26083
Publication Date(Web):03 Sep 2015
DOI:10.1039/C5CP04148A
Group 13 elements are very rarely observed to catenate into linear chains and experimental observation of such species is challenging. Herein we report unique results obtained via combined photoelectron spectroscopy and ab initio studies of the Li2Al3H8− cluster that confirm the formation of an Al chain surrounded by hydrogen atoms in a very particular manner. Comprehensive searches for the most stable structure of the Li2Al3H8− cluster have shown that the global minimum isomer I possesses a geometric structure, which resembles the structure of propane, similar to the experimentally known Zintl-phase Cs10H[Ga3H8]3 compound featuring the propane-like [Ga3H8]3− polyanions. Theoretical simulations of the photoelectron spectrum have demonstrated the presence of only one isomer (isomer I) in the molecular beam. Chemical bonding analysis of the Li2Al3H8− cluster has revealed two classical Al–Al σ bonds constituting the propane-like kernel.
Theoretical investigations to evaluate the viability of extended nonmetal atom chains on the basis of molecular models with the general formula MnF4n+2 (M=S and Se) and corresponding solid-state systems exhibiting direct SS or SeSe bonding were performed. The proposed high-symmetry molecules were found to be minima on the potential energy surface for all SnF4n+2 systems studied (n=2–9) and for selenium analogues up to n=6. Phonon calculations of periodic structures confirmed the dynamic stability of the -(SF4–SF4)∞- chain, whereas the analogous -(SeF4–SeF4)∞- chain was found to have a number of imaginary phonon frequencies. Chemical bonding analysis of the dynamically stable -(SF4–SF4)∞- structure revealed a multicenter character of the SS and SF bonds. A novel definition and abbreviation (ENAC) are proposed by analogy with extended metal atom chain (EMAC) complexes.
Co-reporter:J. Tyler Gish;Ivan A. Popov ; Alexer I. Boldyrev
Chemistry - A European Journal 2015 Volume 21( Issue 14) pp:
Publication Date(Web):
DOI:10.1002/chem.201500664
Abstract
Invited for the cover of this issue is Alexander I. Boldyrev and co-workers at Utah State University. The image depicts the magician who symbolizes a chemist synthesizing molecules of “aluminum homocatenated ethane and propane” based on the idea of electronic transmutation. Read the full text of the article at 10.1002/chem.201500298.
Co-reporter:J. Tyler Gish;Ivan A. Popov ; Alexer I. Boldyrev
Chemistry - A European Journal 2015 Volume 21( Issue 14) pp:5307-5310
Publication Date(Web):
DOI:10.1002/chem.201500298
Abstract
A new class of aluminum homocatenated compounds (LinAlnH2n+2) is proposed based on quantum chemical calculations. In these compounds, Al abstracts an electron from Li, becoming valence isoelectronic with C, Si, and Ge, thus mimicking respective structural features of Group 14 hydrides. Using the Coalescence Kick search program coupled with density functional theory calculations, we investigated the potential energy surfaces of Li2Al2H6 and Li3Al3H6. Then single-point-energy coupled-cluster calculations were performed for the lowest energy structures found. Indeed, the global minima established for Li2Al2H6 and Li3Al3H6 contain the Al2H62− and Al3H63− kernels, which are isostructural with ethane (C2H6), disilane (Si2H6), digermane (Ge2H6) and propane (C3H8), trisilane (Si3H8), trigermane (Ge3H8) molecules, respectively. Structural, energetic, and electronic characteristics of the Li2Al2H6 and Li3Al3H8 compounds are presented and the viability of their synthesis is discussed.
Co-reporter:Ivan A. Popov;Boris B. Averkiev;Alyona A. Starikova;Dr. Alexer I. Boldyrev;Dr. Ruslan M. Minyaev;Dr. Vladimir I. Minkin
Angewandte Chemie International Edition 2015 Volume 54( Issue 5) pp:1476-1480
Publication Date(Web):
DOI:10.1002/anie.201409418
Abstract
Theoretical investigations to evaluate the viability of extended nonmetal atom chains on the basis of molecular models with the general formula MnF4n+2 (M=S and Se) and corresponding solid-state systems exhibiting direct SS or SeSe bonding were performed. The proposed high-symmetry molecules were found to be minima on the potential energy surface for all SnF4n+2 systems studied (n=2–9) and for selenium analogues up to n=6. Phonon calculations of periodic structures confirmed the dynamic stability of the -(SF4–SF4)∞- chain, whereas the analogous -(SeF4–SeF4)∞- chain was found to have a number of imaginary phonon frequencies. Chemical bonding analysis of the dynamically stable -(SF4–SF4)∞- structure revealed a multicenter character of the SS and SF bonds. A novel definition and abbreviation (ENAC) are proposed by analogy with extended metal atom chain (EMAC) complexes.
Co-reporter:Alina P. Sergeeva, Ivan A. Popov, Zachary A. Piazza, Wei-Li Li, Constantin Romanescu, Lai-Sheng Wang, and Alexander I. Boldyrev
Accounts of Chemical Research 2014 Volume 47(Issue 4) pp:1349
Publication Date(Web):March 24, 2014
DOI:10.1021/ar400310g
Boron is an interesting element with unusual polymorphism. While three-dimensional (3D) structural motifs are prevalent in bulk boron, atomic boron clusters are found to have planar or quasi-planar structures, stabilized by localized two-center–two-electron (2c–2e) σ bonds on the periphery and delocalized multicenter–two-electron (nc–2e) bonds in both σ and π frameworks. Electron delocalization is a result of boron’s electron deficiency and leads to fluxional behavior, which has been observed in B13+ and B19–. A unique capability of the in-plane rotation of the inner atoms against the periphery of the cluster in a chosen direction by employing circularly polarized infrared radiation has been suggested. Such fluxional behaviors in boron clusters are interesting and have been proposed as molecular Wankel motors. The concepts of aromaticity and antiaromaticity have been extended beyond organic chemistry to planar boron clusters. The validity of these concepts in understanding the electronic structures of boron clusters is evident in the striking similarities of the π-systems of planar boron clusters to those of polycyclic aromatic hydrocarbons, such as benzene, naphthalene, coronene, anthracene, or phenanthrene. Chemical bonding models developed for boron clusters not only allowed the rationalization of the stability of boron clusters but also lead to the design of novel metal-centered boron wheels with a record-setting planar coordination number of 10. The unprecedented highly coordinated borometallic molecular wheels provide insights into the interactions between transition metals and boron and expand the frontier of boron chemistry. Another interesting feature discovered through cluster studies is boron transmutation. Even though it is well-known that B–, formed by adding one electron to boron, is isoelectronic to carbon, cluster studies have considerably expanded the possibilities of new structures and new materials using the B–/C analogy. It is believed that the electronic transmutation concept will be effective and valuable in aiding the design of new boride materials with predictable properties.The study of boron clusters with intermediate properties between those of individual atoms and bulk solids has given rise to a unique opportunity to broaden the frontier of boron chemistry. Understanding boron clusters has spurred experimentalists and theoreticians to find new boron-based nanomaterials, such as boron fullerenes, nanotubes, two-dimensional boron, and new compounds containing boron clusters as building blocks. Here, a brief and timely overview is presented addressing the recent progress made on boron clusters and the approaches used in the authors’ laboratories to determine the structure, stability, and chemical bonding of size-selected boron clusters by joint photoelectron spectroscopy and theoretical studies. Specifically, key findings on all-boron hydrocarbon analogues, metal-centered boron wheels, and electronic transmutation in boron clusters are summarized.
The adaptive natural density partitioning (AdNDP) method has been applied for the first time to porphyrinoids in order to describe their aromaticity. The analysis of π-electron system reveals that aromaticity of annulene originates from 6-π-electron delocalization, while aromaticity of porphyrin can be better described in terms of local aromaticities of the appended 6-π-electron pyrrolic heterocycles and 6-π-electron central fragment. The patterns of chemical bonding for porphyrinoids obtained by AdNDP are consistent with chemical intuition and lead to unique and compact graphic formulas.
Co-reporter:Alexer S. Ivanov;Dr. Alexer I. Boldyrev;Dr. Gernot Frenking
Chemistry - A European Journal 2014 Volume 20( Issue 9) pp:2431-2435
Publication Date(Web):
DOI:10.1002/chem.201304566
Abstract
A theoretical study of Li90P90, which possesses a circular double-helix structure that resembles the Watson–Crick DNA structure, is reported. This is a new bonding motif in inorganic chemistry. The calculations show that the molecule might become synthesized and that it could be a model for other inorganic species which possess a double-helix structure.
Co-reporter:Alexander S. Ivanov, Gernot Frenking, and Alexander I. Boldyrev
The Journal of Physical Chemistry A 2014 Volume 118(Issue 35) pp:7375-7384
Publication Date(Web):January 28, 2014
DOI:10.1021/jp4123997
Despite the confirmation of Cl––Cl– association in aqueous solution and crystalline state, there have been no reports about the existence of stable dichloride anion pair in the gas phase. In the current work we performed a systematic ab initio study of microsolvation of dichloride anion pair. The stepwise solvation mechanism observed for free gaseous [Cl2(H2O)n]2– (n = 2–10) clusters was found to be quite interesting. The lowest structure for dichloride hexahydrate closely resembles cubic water octamer W8 in which two water molecules in the corners of the cube are substituted by two chloride anions. We have also shown that Cl––Cl– pair may be completely stabilized by about 36 water molecules in the gas phase. Stabilization of the pair leads to the formation of cyclic H2O structures that bridge the Cl– ions. It has been predicted that the large clusters of [Cl2(H2O)36]2– and [Cl2(H2O)40]2– may exhibit properties analogous to bulk aqueous solutions, therefore they could become good molecular models for understanding complicated processes of solvation of Cl– in the bulk.
Co-reporter:Ivan A. Popov, Wei-Li Li, Zachary A. Piazza, Alexander I. Boldyrev, and Lai-Sheng Wang
The Journal of Physical Chemistry A 2014 Volume 118(Issue 37) pp:8098-8105
Publication Date(Web):January 15, 2014
DOI:10.1021/jp411867q
Small boron clusters are known to be planar, and may be used as ligands to form novel coordination complexes with transition metals. Here we report a combined photoelectron spectroscopy and ab initio study of CoB12– and RhB12–. Photoelectron spectra of the two doped-B12 clusters show similar spectral patterns, suggesting they have similar structures. Global minimum searches reveal that both CoB12– and RhB12– possess half-sandwich-type structures with the quasi-planar B12 moiety coordinating to the metal atom. The B12 ligand is found to have similar structure as the bare B12 cluster with C3v symmetry. Structures with Co or Rh inserted into the quasi-planar boron framework are found to be much higher in energy. Chemical bonding analyses of the two B12 half sandwiches reveal two sets of σ bonds on the boron unit: nine classical two-center–two-electron (2c–2e) σ bonds on the periphery of the B12 unit and four 3c–2e σ bonds within the boron unit. Both σ and π bonds are found between the metal and the B12 ligand: three M–B single σ bonds and one delocalized 4c–2e π bond. The exposed metal sites in these complexes can be further coordinated by other ligands or become reaction centers as model catalysts.
Co-reporter:Alexer S. Ivanov;Ivan A. Popov;Dr. Alexer I. Boldyrev;Dr. Viktor V. Zhdankin
Angewandte Chemie International Edition 2014 Volume 53( Issue 36) pp:9617-9621
Publication Date(Web):
DOI:10.1002/anie.201405142
Abstract
IX (X=O, N, C) bonding was analyzed in the related hypervalent iodine compounds based on the adaptive natural density partitioning (AdNDP) approach. The results confirm the presence of a IX σ dative bond, as opposed to the widely used IX notation. A clear formulation of the electronic structure of these hypervalent iodine compounds would be useful in establishing reaction mechanisms and electronic structures in bioinorganic problems of general applicability.
Co-reporter:Dr. Jared K. Olson;Alexer S. Ivanov ;Dr. Alexer I. Boldyrev
Chemistry - A European Journal 2014 Volume 20( Issue 22) pp:6636-6640
Publication Date(Web):
DOI:10.1002/chem.201402572
Abstract
A theoretical study of ozone isoelectronic Li3N3 species has been performed. Ab initio electronic structure calculations prove the viability of the ozone-like Li3N3 molecule that might become synthesized. The predicted Li3N3 species with a novel N33− molecular motif possess structural and chemical bonding features similar to that of O3 molecules and can thus be considered as an “all-nitrogen ozone”.
IX (X=O, N, C) bonding was analyzed in the related hypervalent iodine compounds based on the adaptive natural density partitioning (AdNDP) approach. The results confirm the presence of a IX σ dative bond, as opposed to the widely used IX notation. A clear formulation of the electronic structure of these hypervalent iodine compounds would be useful in establishing reaction mechanisms and electronic structures in bioinorganic problems of general applicability.
Co-reporter:Ivan A. Popov, Yafei Li, Zhongfang Chen and Alexander I. Boldyrev
Physical Chemistry Chemical Physics 2013 vol. 15(Issue 18) pp:6842-6848
Publication Date(Web):08 Mar 2013
DOI:10.1039/C3CP43921F
The chemical bonding analysis using the adaptive natural density partitioning method of the C4F fluorinated graphene sheet revealed a chemical bonding model explaining its particular stability. We proposed that the stability of the C4F fluorinated graphene is due to the so-called “benzation” of graphene. On the basis of our chemical bonding model we predicted that other high-symmetry structures of the C7F4, C3F2, C13F10, etc. stoichiometries, containing planar hexagons, which are separated from each other by 2, 3, 4, etc. C–F fragments could also possess additional stability. We also suggested that other functionalized graphene structures of the C4X and C7X4, C3X2, C13X10 stoichiometries, where X is a monovalent atom (H, F, Cl) or a monovalent group (CN, CCH etc.), could also have extra stability. We hope that the developed model, obtained for the functionalization of pristine graphene, will give an impetus for experimentalists to devise methods, which could serve as useful tools for producing this kind of materials with the tailored properties.
Co-reporter:Timur R. Galeev, Benjamin D. Dunnington, J. R. Schmidt and Alexander I. Boldyrev
Physical Chemistry Chemical Physics 2013 vol. 15(Issue 14) pp:5022-5029
Publication Date(Web):20 Feb 2013
DOI:10.1039/C3CP50350J
A new tool to elucidate chemical bonding in bulk solids, surfaces and nanostructures has been developed. Solid State Adaptive Natural Density Partitioning (SSAdNDP) is a method to interpret chemical bonding in terms of classical lone pairs and two-center bonds, as well as multi-center delocalized bonds. Here we extend the domain of AdNDP to bulk materials and interfaces, yielding SSAdNDP. We demonstrate the versatility of the method by applying it to several systems featuring both localized and many-center chemical bonding, and varying in structural complexity: boron α-sheet, magnesium diboride and the Na8BaSn6 Zintl phase.
The Journal of Physical Chemistry A 2013 Volume 117(Issue 7) pp:1614-1620
Publication Date(Web):January 18, 2013
DOI:10.1021/jp310162v
Potential energy surfaces of anionic B6Hy clusters were sampled using the coalescence kick method. We found that the planar to three-dimensional transition occurs in this system when y = 4. This is an important discovery because this transition suggests a major structural change as a function of dehydrogenation for the stoichiometric BnHn– polyhedral boranes. We also found that the B6H3– global minimum structure has an optical isomer. The chemical bonding patterns revealed by the adaptive natural density partitioning (AdNDP) analysis explain the geometric structure of all clusters presented here. From our chemical bonding analysis, we concluded that the 2D–3D transition occurs at B6H4– because the addition of one extra hydrogen atom further destroys the network of the peripheral 2c–2e B–B σ-bonding, making planar structures less stable, and because the distorted octahedral structure provides some occupation of all s- and p-AOs of boron, avoiding the presence of any empty atomic orbitals. Theoretical vertical electron detachment energies (VDEs) were calculated for comparison with future experimental work.
Co-reporter:Alina P. Sergeeva ; Zachary A. Piazza ; Constantin Romanescu ; Wei-Li Li ; Alexander I. Boldyrev ;Lai-Sheng Wang
Journal of the American Chemical Society 2012 Volume 134(Issue 43) pp:18065-18073
Publication Date(Web):October 3, 2012
DOI:10.1021/ja307605t
Clusters of boron atoms exhibit intriguing size-dependent structures and chemical bonding that are different from bulk boron and may lead to new boron-based nanostructures. We report a combined photoelectron spectroscopic and ab initio study of the 22- and 23-atom boron clusters. The joint experimental and theoretical investigation shows that B22– and B23– possess quasi-planar and planar structures, respectively. The quasi-planar B22– consists of fourteen peripheral atoms and eight interior atoms in a slightly buckled triangular lattice. Chemical bonding analyses of the closed-shell B222– species reveal seven delocalized π orbitals, which are similar to those in anthracene. B23– is a perfectly planar and heart-shaped cluster with a pentagonal cavity and a π-bonding pattern similar to that in phenanthrene. Thus, B22– and B23–, the largest negatively charged boron clusters that have been characterized experimentally to date, can be viewed as all-boron analogues of anthracene and phenanthrene, respectively. The current work shows not only that boron clusters are planar at very large sizes but also that they continue to yield surprises and novel chemical bonding analogous to specific polycyclic aromatic hydrocarbons.
Quantum chemical calculations of the CpMoE6MoCp (E = P, As, Sb) triple-decker sandwich complexes showed that E6 fragments in the central decks of the complexes are planar. Analysis of molecular orbitals involved in vibrational coupling demonstrated that filling the unoccupied molecular orbitals involved in vibronic coupling with electron pairs of Mo atoms suppresses the PJT effect in the CpMoE6MoCp (E = P, As, Sb) sandwich, with the E6 ring becoming planar (D6h) upon complex formation. The AdNDP analysis revealed that bonding between C5H5– units and Mo atoms has a significant ionic contribution, while bonding between Mo atoms and E6 fragment becomes appreciably covalent through the δ-type M → L back-donation mechanism.
Co-reporter:Alexander S. Ivanov, Konstantin V. Bozhenko, and Alexander I. Boldyrev
Journal of Chemical Theory and Computation 2012 Volume 8(Issue 1) pp:135-140
Publication Date(Web):November 17, 2011
DOI:10.1021/ct200727z
In the current work, we performed a systematic study of the CxHxP4–x (x = 0–4) series using an unbiased CK global minimum and low-lying isomers search for the singlet and triplet P4–C4H4 species at the B3LYP/6-31G** level of theory. The selected lowest isomers were recalculated at the CCSD(T)/CBS//B3LYP/6-311++G** level of theory. We found that the transition from a three-dimensional tetrahedron-like structure to a planar structure occurs at x = 3, where planar isomers become much more stable than the tetrahedral structures due to significantly stronger π bonds between carbon atoms in addition to increasing strain energy at the carbon atom in the tetrahedral environment.
Co-reporter:Alexander S. Ivanov and Alexander I. Boldyrev
Physical Chemistry Chemical Physics 2012 vol. 14(Issue 46) pp:15943-15952
Publication Date(Web):16 Oct 2012
DOI:10.1039/C2CP42877F
Quantum chemistry can today be employed to invent new molecules and investigate their properties and chemical bonding. However, the predicted species must be viable in order to be synthesized by experimentalists. In this perspective article we describe the technology of reliable theoretical predictions and show how understanding of chemical bonding in studied chemical systems could help to design new molecular structures. We also provide a short overview of successfully predicted and already produced (in some cases) planar hypercoordinate species to demonstrate that the consistent theoretical prediction of viable molecules with unusual structures and properties is now a reliable tool for exploring new, yet unknown molecules, clusters, nanomaterials and solids.
European Journal of Organic Chemistry 2012 Volume 2012( Issue 18) pp:3485-3491
Publication Date(Web):
DOI:10.1002/ejoc.201200256
Abstract
Chemical-bonding analysis in coronene, isocoronene, and circumcoronene has been performed by using the Adaptive Natural Density Partitioning (AdNDP) method. This analysis revealed that coronene and isocoronene have two globally delocalized concentric π-systems. Circumcoronene does not have globally delocalized π-systems; instead, it has seven local sextets and can be represented by a single Clar structure. Thus, today there are a few known polycyclic aromatic hydrocarbons with two concentric π-systems, but there are as yet no examples of such molecules with three or more concentric π-systems. The results revealed by the AdNDP analysis are consistent with the results obtained by the current-density maps, NICS and NICSZZ indices as well as MCI, PDI, Iring and δ indices.
Chemical Physics Letters 2012 Volume 523() pp:83-86
Publication Date(Web):27 January 2012
DOI:10.1016/j.cplett.2011.11.079
We propose a concept of electronic transmutation. According to this concept, elements, by acquiring an extra electron, begin to have the chemical bonding and geometric structure properties of compounds composed of neighboring elements. We demonstrate that boron, by acquiring an extra electron in boron–hydrogen compounds, forms molecular analogs of those of saturated hydrocarbons. We show by the means of quantum chemistry that the Li2B2H6 molecule in the most stable geometric form has the B2H62− kernel, which is isostructural to the C2H6 ethane molecule. We believe that this concept may have a significant effect on predicting new chemical compounds.Graphical abstractHighlights► We propose a concept of electronic transmutation. ► This concept may have a significant effect on predicting new chemical compounds. ► Another outcome of this concept will be the simplification of teaching chemistry. ► We conducted an unbiased search for global minimum structures of Li2B2H6. ► The Li2B2H6 molecule is isostructural to the C2H6 ethane molecule.
The Journal of Physical Chemistry C 2012 Volume 116(Issue 4) pp:3147-3152
Publication Date(Web):January 5, 2012
DOI:10.1021/jp210956w
The substitution of every fourth carbon atom in graphene by a boron atom preserves the honeycomb structure in the BC3 two-dimentional lattice, but as we found in our adaptive natural density partitioning analysis, it remarkably alters the chemical bonding. First, in the BC3 lattice, where boron atoms are surrounded by three carbon atoms, carbon forces boron to form two-center–two-electron B–C σ-bonds, while boron is known to participate only in multicenter (three-center–two-electron or four-center–two-electron) σ-bonding in the most stable two-dimensional form of the pure boron lattice, the α-sheet. Second, six-center–two-electron π-bonds found over every hexagon in graphene and in the α-sheet migrate in BC3 to hexagons composed out of carbon atoms only, making π-bonding in those hexagons more similar to the corresponding π-bonding in benzene rather then graphene, leaving hexagons formed by carbon and boron atoms in the BC3 lattice empty without π-bonding. We believe that chemical bonding elements found in our chemical bonding analysis of graphene, the α-sheet of boron, and the BC3 lattice will be useful tools for rationalizing chemical bonding in other two-dimensional boron–carbon materials.
Co-reporter:Edison Osorio;Dr. Jared K. Olson; William Tiznado; Alexer I. Boldyrev
Chemistry - A European Journal 2012 Volume 18( Issue 31) pp:9677-9681
Publication Date(Web):
DOI:10.1002/chem.201200506
Abstract
We performed global minimum searches for the BnHn+2 (n=2-5) series and found that classical structures composed of 2c–2e BH and BB bonds become progressively less stable along the series. Relative energies increase from 2.9 kcal mol−1 in B2H4 to 62.3 kcal mol−1 in B5H7. We believe this occurs because boron atoms in the studied molecules are trying to avoid sp2 hybridization and trigonal structure at the boron atoms, as in that case one 2p-AO is empty, which is highly unfavorable. This affinity of boron to have some electron density on all 2p-AOs and avoiding having one 2p-AO empty is a main reason why classical structures are not the most stable configurations and why multicenter bonding is so important for the studied boron–hydride clusters as well as for pure boron clusters and boron compounds in general.
Co-reporter:Alexander S. Ivanov and Alexander I. Boldyrev
The Journal of Physical Chemistry A 2012 Volume 116(Issue 38) pp:9591-9598
Publication Date(Web):September 4, 2012
DOI:10.1021/jp307722q
In the current work we studied a structural transition from nonplanar three-dimensional structures to planar benzene-like structures in the Si6–nCnH6 (n = 0–6) series. We performed unbiased Coalescence–Kick global minimum and low-lying isomers search for the Si6H6, Si5CH6, Si4C2H6, Si3C3H6, Si2C4H6, and SiC5H6 stoichiometries at the B3LYP/6-31G** level of theory. The lowest isomers were recalculated at the CCSD(T)/CBS//B3LYP/6-311++G** level of theory. It was shown that the pseudo-Jahn–Teller effect, which is responsible for the deformation of planar Si6H6, Si5CH6, and Si4C2H6 structures, is suppressed at n = 3 (the planar structure of 1,3,5-trisilabenzene). We also showed that the 3D–2D transition, which occurs only at n = 5, is due to the aromaticity of monosilabenzene (SiC5H6) along with other factors, such as stronger C–C σ bonds compared to weaker C–Si and Si–Si σ bonds.
We analyze the chemical bonding in graphene using a fragmental approach, the adaptive natural density partitioning method, electron sharing indices, and nucleus-independent chemical shift indices. We prove that graphene is aromatic, but its aromaticity is different from the aromaticity in benzene, coronene, or circumcoronene. Aromaticity in graphene is local with two π-electrons delocalized over every hexagon ring. We believe that the chemical bonding picture developed for graphene will be helpful for understanding chemical bonding in defects such as point defects, single-, double-, and multiple vacancies, carbon adatoms, foreign adatoms, substitutional impurities, and new materials that are derivatives of graphene.
Open image in new window
Co-reporter:Wei-Li Li ; Constantin Romanescu ; Timur R. Galeev ; Zachary A. Piazza ; Alexander I. Boldyrev ;Lai-Sheng Wang
Journal of the American Chemical Society 2011 Volume 134(Issue 1) pp:165-168
Publication Date(Web):December 13, 2011
DOI:10.1021/ja209808k
We report the observation of two transition-metal-centered nine-atom boron rings, RhⓒB9– and IrⓒB9–. These two doped-boron clusters are produced in a laser-vaporization supersonic molecular beam and characterized by photoelectron spectroscopy and ab initio calculations. Large HOMO–LUMO gaps are observed in the anion photoelectron spectra, suggesting that neutral RhⓒB9 and IrⓒB9 are highly stable, closed shell species. Theoretical calculations show that RhⓒB9 and IrⓒB9 are of D9h symmetry. Chemical bonding analyses reveal that these complexes are doubly aromatic, each with six completely delocalized π and σ electrons, which describe the bonding between the central metal atom and the boron ring. This work establishes firmly the metal-doped B rings as a new class of novel aromatic molecular wheels.
Co-reporter:Gerardo Martínez-Guajardo, Alina P. Sergeeva, Alexander I. Boldyrev, Thomas Heine, Jesus M. Ugalde and Gabriel Merino
Chemical Communications 2011 vol. 47(Issue 22) pp:6242-6244
Publication Date(Web):01 Apr 2011
DOI:10.1039/C1CC10821B
We describe and explain the fluxionality of B13+. The chemical bonding analysis shows that the inner triangle of B13+ is bound to the peripheral ring by delocalized bonds only, allowing a quasi-free rotation of the inner ring.
Co-reporter:Timur R. Galeev, Alexander S. Ivanov, Constantin Romanescu, Wei-Li Li, Konstantin V. Bozhenko, Lai-Sheng Wang and Alexander I. Boldyrev
Physical Chemistry Chemical Physics 2011 vol. 13(Issue 19) pp:8805-8810
Publication Date(Web):12 Apr 2011
DOI:10.1039/C1CP20359B
In this joint experimental and theoretical work we present a novel type of structural transition occurring in the series of CxB8−x− (x = 1–8) mixed clusters upon increase of the carbon content from x = 2 to x = 3. The wheel to ring transition is surprising because it is rather planar-to-linear type of transition to be expected in the series since B8, B8−, B82− and CB7− are known to possess wheel-type global minimum structures while C8 is linear.
Co-reporter:Timur R. Galeev and Alexander I. Boldyrev
Physical Chemistry Chemical Physics 2011 vol. 13(Issue 46) pp:20549-20556
Publication Date(Web):24 Aug 2011
DOI:10.1039/C1CP21959F
In this work we examine a structural transition from non-planar three-dimensional structures to planar benzene-like structures in the CxHxP6−x (x = 0–6) series. The global minima of P6, CHP5, and C2H2P4 species are benzvalene-like structures. The benzvalene and benzene-like structures of C3H3P3 are close in energy with the former being slightly more stable at our best level of theory. The transition occurs at x = 4 (C4H4P2), where the benzene-like structures become significantly more stable than the benzvalene-like structures. We show that the pseudo Jahn–Teller effect, which is responsible for the deformation of planar P6, CHP5, and C2H2P4 structures, is completely suppressed at x = 3 (benzene-like structures of C3H3P3). We present NICSzz values of all the benzene-like isomers in the series.
Co-reporter:Timur R. Galeev, Qiang Chen, Jin-Chang Guo, Hui Bai, Chang-Qing Miao, Hai-Gang Lu, Alina P. Sergeeva, Si-Dian Li and Alexander I. Boldyrev
Physical Chemistry Chemical Physics 2011 vol. 13(Issue 24) pp:11575-11578
Publication Date(Web):20 May 2011
DOI:10.1039/C1CP20439D
Boron could be the next element after carbon capable of forming 2D-materials similar to graphene. Theoretical calculations predict that the most stable planar all-boron structure is the so-called α-sheet. The mysterious structure of the α-sheet with peculiar distribution of filled and empty hexagons is rationalized in terms of chemical bonding. We show that the hexagon holes serve as scavengers of extra electrons from the filled hexagons. This work could advance rational design of all-boron nanomaterials.
Chemical Physics Letters 2011 Volume 517(1–3) pp:62-67
Publication Date(Web):28 November 2011
DOI:10.1016/j.cplett.2011.10.009
Abstract
Potential energy surfaces of neutral and anionic B4H5 clusters were sampled using the Coalescence Kick method. We found that the neutral B4H5 cluster has two optical isomers as either a global minimum structure, or as almost degenerate isomers with the global minimum structure. For the anion only the third lowest isomer forms a pair of optical isomers. The chemical bonding patterns revealed by the Adaptive Natural Density Partitioning (AdNDP) analysis can easily explain the geometric structure of even very exotic isomers and global minima. Theoretical vertical electron detachment energies (VDEs) were calculated for comparison with future experimental work.
Co-reporter:Wei-Li Li, Constantin Romanescu, Timur R. Galeev, Lai-Sheng Wang, and Alexander I. Boldyrev
The Journal of Physical Chemistry A 2011 Volume 115(Issue 38) pp:10391-10397
Publication Date(Web):August 1, 2011
DOI:10.1021/jp205873g
The structures and the electronic properties of two Al-doped boron clusters, AlB9– and AlB10–, were investigated via joint photoelectron spectroscopy and high-level ab initio study. The photoelectron spectra of both anions are relatively broad and have no vibrational structure. The geometrical structures were established by unbiased global minimum searches using the Coalescence Kick method and comparison between the experimental and calculated vertical electron detachment energies. The results show that both clusters have quasi-planar structures and that the Al atom is located at the periphery. Chemical bonding analysis revealed that the global minimum structures of both anions can be described as doubly (σ- and π-) aromatic systems. The nona-coordinated wheel-type structure of AlB9– was found to be a relatively high-lying isomer, while a similar structure for the neutral AlB9 cluster was previously shown to be either a global minimum or a low-lying isomer.
Journal of Cluster Science 2011 Volume 22( Issue 3) pp:321-329
Publication Date(Web):2011 September
DOI:10.1007/s10876-011-0386-2
We designed a series of small 3D gold clusters using a four-atomic tetrahedron with a four center–two electron (4c–2e) bond inside as a building block. The follow-up results of the unbiased global minimum searches proved that indeed the designed 3D structures containing small tetrahedral building blocks with a 4c–2e bond inside are either global minimum structures or low-lying isomers. We believe that the proposed way of building 3D clusters could be used for rational design of other 3D gold clusters.
Co-reporter:Nancy Perez-Peralta and Alexander I. Boldyrev
The Journal of Physical Chemistry A 2011 Volume 115(Issue 42) pp:11551-11558
Publication Date(Web):September 16, 2011
DOI:10.1021/jp2074754
The potential energy surfaces of the LinSi4– (n = 0–5) clusters were explored using the Kick Coalescence method. We found that, for those systems with n ≤ 2, the butterfly and parallelogram Si42– kernels prevail as building blocks; however, when n ≥ 3, the Si44– tetrahedral kernel, which is commonly found in heavier alkali monosilicides, MSi (M = Na, K, Rb, Cs), arises as the prevailing building block. In addition, by a natural population analysis (NPA) we found that the maximum charge transfer −4 from Li atoms to Si atoms is attained when n = 3. The addition of more Li atoms to the Si44– system does not increase the charge transfer, but keeps it almost constant at the maximum value. We also calculated theoretical vertical electron detachment energies (VDEs) for low-lying isomers of the LinSi4– (n = 0–4) clusters in order to facilitate their experimental identification.
Co-reporter:Lei-Ming Wang ; Boris B. Averkiev ; Jordan A. Ramilowski ; Wei Huang ; Lai-Sheng Wang
Journal of the American Chemical Society 2010 Volume 132(Issue 40) pp:14104-14112
Publication Date(Web):September 21, 2010
DOI:10.1021/ja103846q
Bulk carbon and boron form very different materials, which are also reflected in their clusters. Small carbon clusters form linear structures, whereas boron clusters are planar. For example, it is known that the B5− cluster possesses a C2v planar structure and C5− is a linear chain. Here we study B/C mixed clusters containing five atoms, CxB5−x− (x = 1−5), which are expected to exhibit a planar to linear structural transition as a function of the C content. The CxB5−x− (x = 1−5) clusters were produced and studied by photoelectron spectroscopy; their geometric and electronic structures were investigated using a variety of theoretical methods. We found that the planar-to-linear transition occurs between x = 2 and 3: the global minimum structures of the B-rich clusters, CB4− and C2B3−, are planar, similar to B5−, and those of the C-rich clusters, C3B2− and C4B−, are linear, similar to C5−.
Co-reporter:Alina P. Sergeeva and Alexander I. Boldyrev
Physical Chemistry Chemical Physics 2010 vol. 12(Issue 38) pp:12050-12054
Publication Date(Web):20 Aug 2010
DOI:10.1039/C0CP00475H
A remarkable triple-decker sandwich complex [Pd4(μ4-C9H9)(μ4-C8H8)][BArf4] (BArf4 = B{3,5-(CF3)2(C6H3)}4) composed of cyclononatetraenyl anion and cyclooctatetraene as “bread pieces” and square tetrapalladium dication as “meat” (Fig. 1a) has been synthesized recently [Murahashi et al., J. Am. Chem. Soc., 2009, 131, 9888]. This complex attracted our attention because of the presence of an almost perfect square sheet composed of four palladium atoms. Such a structure could be a sign of aromatic nature of chemical bonding as it was shown to be present in the square Al42− cluster [Li et al., Science, 2001, 291, 859]. In this work we show that according to our chemical bonding analysis the bonding in the Pd42+ unit of [Pd4(μ4-C9H9)(μ4-C8H8)]+ is of δ-character among four palladium atoms, making the triple-decker sandwich complex the first synthesized compound identified as having δ-bonding in its cyclic building block when it's in solution or in a crystalline state.
We report the theoretical prediction of flattening of the puckered Si5 ring by suppression of the pseudo-Jahn−Teller effect through coordination of two Mg2+ cations to the Si5H5− anion to make an inverse [Mg2+Si5H5−Mg2+] sandwich complex. The pseudo-Jahn−Teller (PJT) effect was suppressed through the OMO−UMO gaps increase in the resultant [Mg2+Si5H5−Mg2+] sandwich complex, as compared to the initial Si5H5− anion. It was the influence of two Mg2+ cations that caused the OMO−UMO gaps increase that made this type of PJT effect suppression work. In the three other complexes under the current computational study, namely, [Li+Si5H5−Li+], [Na+Si5H5−Na+], and [Be2+Si5H5−Be2+], the Si5H5− moiety remains nonplanar. We believe that if the Mg(Si5H5)2 solid compound were synthesized, it could have planar Si5H5− building blocks.
Co-reporter:Haopeng Wang, Yeon Jae Ko, and Kit H. Bowen, Alina P. Sergeeva, Boris B. Averkiev, and Alexander I. Boldyrev
The Journal of Physical Chemistry A 2010 Volume 114(Issue 42) pp:11070-11077
Publication Date(Web):April 7, 2010
DOI:10.1021/jp101419b
Anion photoelectron spectra of GaxNy− cluster anions, in which x = 4−12, y = 1 and x = 7−12, y = 2, were measured. Ab initio studies were conducted on GaxNy− cluster anions in which x = 4−7, y = 1 and Ga7N2−, providing their structures and electronic properties. The photoelectron spectra were interpreted in terms of the computational results. This allowed for identification of the isomers present in the beam experiments for specific GaxN− cluster anions (x = 4−7). The unexpected presence of GaxN2− species is also reported.
Co-reporter:Xue-Bin Wang ; Alina P. Sergeeva ; Xiao-Peng Xing ; Maria Massaouti ; Tatjana Karpuschkin ; Oliver Hampe ; Alexander I. Boldyrev ; Manfred M. Kappes ;Lai-Sheng Wang
Journal of the American Chemical Society 2009 Volume 131(Issue 28) pp:9836-9842
Publication Date(Web):June 24, 2009
DOI:10.1021/ja903615g
The strong intramolecular Coulomb repulsion in multiply charged anions (MCAs) creates a potential barrier that provides dynamic stability to MCAs and allows electronically metastable species to be observed. The 1-hydroxy-3,6,8-pyrene-trisulfonate {[Py(OH)(SO3)3]3− or HPTS3−} was recently observed as a long-lived metastable MCA with a large negative electron binding energy of −0.66 eV. Here we use Penning trap mass spectrometry to monitor the spontaneous decay of HPTS3− → HPTS•2− + e− and have determined the half-life of HPTS3− to be 0.1 s. To explore the limit of electronic metastability, we tried to make the related quadruply charged pyrene-1,3,6,8-tetrasulfonate {[Py(SO3)4]4−}. However, only its decay product, the triply charged radical anion [Py(SO3)4]•3−, as well as the triply charged ion-pairs [Py(SO3)4H]3− and [Py(SO3)4Na]3−, was observed, suggesting that the tremendous intramolecular Coulomb repulsion makes the [Py(SO3)4]4− anion extremely short-lived. Photoelectron spectroscopy data showed that [Py(SO3)4]•3− is an electronically stable species with electron binding energies of +0.5 eV, whereas [Py(SO3)4H]3− and [Py(SO3)4Na]3− possess electron binding energies of 0.0 and −0.1 eV, respectively. Ab initio calculations confirmed the stability of these triply charged species and further predicted a large negative electron binding energy (−2.78 eV) for [Py(SO3)4]4−, consistent with its short lifetime.
We sampled potential energy surfaces of neutral and anionic B3Hy clusters using the Gradient Embedded Genetic Algorithm (GEGA) program at the B3LYP/3-21G level of theory. The lowest energy isomers were recalculated at the B3LYP/6-311++G**, MP2/6-311++G**, and CCSD(T)/6-311++G** levels of theory. We found a diverse set of global minimum structures and low-lying isomers for the studied clusters. The Adaptive Natural Density Partitioning (AdNDP) method was then used for chemical bonding analysis for all global minimum structures and low-lying isomers. The chemical bonding patterns revealed by the AdNDP analysis can easily explain the geometric structure of even very exotic isomers and global minima.
Co-reporter:Boris B. Averkiev, Lei-Ming Wang, Wei Huang, Lai-Sheng Wang and Alexander I. Boldyrev
Physical Chemistry Chemical Physics 2009 vol. 11(Issue 42) pp:9840-9849
Publication Date(Web):09 Sep 2009
DOI:10.1039/B908973J
We demonstrated in our joint photoelectron spectroscopic and ab initio study that wheel-type structures with a boron ring are not appropriate for designing planar molecules with a hypercoordinate central carbon based on the example of CB8, and CB8−clusters. We presented a chemical bonding model, derived from the adaptive natural density partitioning analysis, capable of rationalizing and predicting planar structures either with a boron ring or with a carbon atom occupying the central hypercoordinate position. According to our chemical bonding model, in the wheel-type structures the central atom is involved in delocalized bonding, while peripheral atoms are involved in both delocalized bonding and two-center two-electron (2c–2e) σ-bonding. Since carbon is more electronegative than boron it favors peripheral positions where it can participate in 2c–2e σ-bonding. To design a chemical species with a central hypercoordinate carbon atom, one should consider electropositive ligands, which would have lone pairs instead of 2c–2e peripheral bonds. Using our extensive chemical bonding model that considers both σ- and π-bonding we also discuss why the AlB9 and FeB9− species with octacoordinate Al and Fe are the global minima or low-lying isomers, as well as why carbon atom fits well into the central cavity of CAl42− and CAl5+. This represents the first step toward rational design of nano- and subnano-structures with tailored properties.
Co-reporter:Xue-Bin Wang, Alina P. Sergeeva, Jie Yang, Xiao-Peng Xing, Alexander I. Boldyrev and Lai-Sheng Wang
The Journal of Physical Chemistry A 2009 Volume 113(Issue 19) pp:5567-5576
Publication Date(Web):April 22, 2009
DOI:10.1021/jp900682g
Sulfate is an important inorganic anion and its interactions with water are essential to understand its chemistry in aqueous solution. Studies of sulfate with well-controlled solvent numbers provide molecular-level information about the solute−solvent interactions and critical data to test theoretical methods for weakly bounded species. Here we report a low-temperature photoelectron spectroscopy study of hydrated sulfate clusters SO42−(H2O)n (n = 4−7) at 12 K and ab initio studies to understand the structures and dynamics of these unique solvated systems. A significant increase of electron binding energies was observed for the 12 K spectra relative to those at room temperature, suggesting different structural isomers were populated as a function of temperature. Theoretical calculations revealed a competition between isomers with optimal water−solute and water−water interactions. The global minimum isomers all possess higher electron binding energies due to their optimal water-solute interactions, giving rise to the binding energy shift in the 12 K spectra, whereas many additional low-lying isomers with less optimal solvent−solute interactions were populated at room temperature, resulting in a shift to lower electron binding energies in the observed spectra. The current work demonstrates and confirms the complexity of the water-sulfate potential energy landscape and the importance of temperature control in studying the solvent−solute systems and in comparing calculations with experiment.
Co-reporter:Dmitry Yu. Zubarev and Alexander I. Boldyrev
The Journal of Physical Chemistry A 2009 Volume 113(Issue 5) pp:866-868
Publication Date(Web):December 10, 2008
DOI:10.1021/jp808103t
The recently developed adaptive natural density partitioning (AdNDP) method has been applied to a series of golden clusters. The pattern of chemical bonding in Au20 revealed by AdNDP shows that 20 electrons form a four-center−two-electron (4c−2e) bond in each of 10 tetrahedral cavities of the Au20 cluster. This chemical bonding picture can readily explain the tetrahedral structure of the Au20 cluster. Furthermore, we demonstrate that the recovered 4c−2e bonds corresponding to independent structural fragments of the cluster provide important information about chemically relevant fragmentation of Au20. In fact, some of these bonds can be removed from the initial tetrahedral structure together with the associated atomic fragments, leading to the family of smaller gold clusters. Chemical bonding in the systems formed in such a manner is yet closely related to the bonding in the parental systems showing persistence of the 4c−2e bonding motif. Thus, the multicenter bonds in golden cages recovered by the AdNDP analysis correspond to the fragments that should be seen as building blocks of these chemical systems.
Co-reporter:Alexander S. Ivanov and Alexander I. Boldyrev
Physical Chemistry Chemical Physics 2012 - vol. 14(Issue 46) pp:NaN15952-15952
Publication Date(Web):2012/10/16
DOI:10.1039/C2CP42877F
Quantum chemistry can today be employed to invent new molecules and investigate their properties and chemical bonding. However, the predicted species must be viable in order to be synthesized by experimentalists. In this perspective article we describe the technology of reliable theoretical predictions and show how understanding of chemical bonding in studied chemical systems could help to design new molecular structures. We also provide a short overview of successfully predicted and already produced (in some cases) planar hypercoordinate species to demonstrate that the consistent theoretical prediction of viable molecules with unusual structures and properties is now a reliable tool for exploring new, yet unknown molecules, clusters, nanomaterials and solids.
Co-reporter:Timur R. Galeev, Benjamin D. Dunnington, J. R. Schmidt and Alexander I. Boldyrev
Physical Chemistry Chemical Physics 2013 - vol. 15(Issue 14) pp:NaN5029-5029
Publication Date(Web):2013/02/20
DOI:10.1039/C3CP50350J
A new tool to elucidate chemical bonding in bulk solids, surfaces and nanostructures has been developed. Solid State Adaptive Natural Density Partitioning (SSAdNDP) is a method to interpret chemical bonding in terms of classical lone pairs and two-center bonds, as well as multi-center delocalized bonds. Here we extend the domain of AdNDP to bulk materials and interfaces, yielding SSAdNDP. We demonstrate the versatility of the method by applying it to several systems featuring both localized and many-center chemical bonding, and varying in structural complexity: boron α-sheet, magnesium diboride and the Na8BaSn6 Zintl phase.
Co-reporter:Li-Ming Yang, Ivan A. Popov, Thomas Frauenheim, Alexander I. Boldyrev, Thomas Heine, Vladimir Bačić and Eric Ganz
Physical Chemistry Chemical Physics 2015 - vol. 17(Issue 39) pp:NaN26048-26048
Publication Date(Web):2015/09/08
DOI:10.1039/C5CP04893A
We discover unusual chemical bonding in a novel planar hyper-coordinate Ni2Ge free-standing 2D monolayer, and also in a nearly planar slightly buckled Ni2Si monolayer. This unusual bonding is revealed by Solid State Adaptive Natural Density Partitioning analysis. This analysis shows that a new type of 2c-2e Ni–Si σ and 3c-2e Ni–Ge–Ni σ bonds stabilize these 2D crystals. This is completely different from any previously known 2D crystals. Both of these free-standing monolayers are global minima in two-dimensional space. Although their exotic structure has unprecedented chemical bonding, they show extraordinary stability as single layers. The stabilities of these frameworks are confirmed by phonon dispersion calculations and ab initio molecular dynamics calculations. For Ni2Si, the framework was maintained during short 10 ps molecular dynamics annealing up to 1500 K, while Ni2Ge survived 10 ps runs up to 900 K. Both systems are predicted to be non-magnetic and metallic. As these new 2D crystals contain hypercoordinated Group 14 atoms, they are examples of a new class of 2D crystals with unconventional chemical bonding and potentially exciting new properties. Interestingly, we find that the stabilities of Ni2Si and Ni2Ge are much higher than that of silicene and germanene. Thus, this work provides a novel way to stabilize 2D sheets of Group 14 elements.
Co-reporter:Ivan A. Popov, Xinxing Zhang, Bryan W. Eichhorn, Alexander I. Boldyrev and Kit H. Bowen
Physical Chemistry Chemical Physics 2015 - vol. 17(Issue 39) pp:NaN26083-26083
Publication Date(Web):2015/09/03
DOI:10.1039/C5CP04148A
Group 13 elements are very rarely observed to catenate into linear chains and experimental observation of such species is challenging. Herein we report unique results obtained via combined photoelectron spectroscopy and ab initio studies of the Li2Al3H8− cluster that confirm the formation of an Al chain surrounded by hydrogen atoms in a very particular manner. Comprehensive searches for the most stable structure of the Li2Al3H8− cluster have shown that the global minimum isomer I possesses a geometric structure, which resembles the structure of propane, similar to the experimentally known Zintl-phase Cs10H[Ga3H8]3 compound featuring the propane-like [Ga3H8]3− polyanions. Theoretical simulations of the photoelectron spectrum have demonstrated the presence of only one isomer (isomer I) in the molecular beam. Chemical bonding analysis of the Li2Al3H8− cluster has revealed two classical Al–Al σ bonds constituting the propane-like kernel.
Co-reporter:Timur R. Galeev, Qiang Chen, Jin-Chang Guo, Hui Bai, Chang-Qing Miao, Hai-Gang Lu, Alina P. Sergeeva, Si-Dian Li and Alexander I. Boldyrev
Physical Chemistry Chemical Physics 2011 - vol. 13(Issue 24) pp:NaN11578-11578
Publication Date(Web):2011/05/20
DOI:10.1039/C1CP20439D
Boron could be the next element after carbon capable of forming 2D-materials similar to graphene. Theoretical calculations predict that the most stable planar all-boron structure is the so-called α-sheet. The mysterious structure of the α-sheet with peculiar distribution of filled and empty hexagons is rationalized in terms of chemical bonding. We show that the hexagon holes serve as scavengers of extra electrons from the filled hexagons. This work could advance rational design of all-boron nanomaterials.
Co-reporter:Boris B. Averkiev, Lei-Ming Wang, Wei Huang, Lai-Sheng Wang and Alexander I. Boldyrev
Physical Chemistry Chemical Physics 2009 - vol. 11(Issue 42) pp:NaN9849-9849
Publication Date(Web):2009/09/09
DOI:10.1039/B908973J
We demonstrated in our joint photoelectron spectroscopic and ab initio study that wheel-type structures with a boron ring are not appropriate for designing planar molecules with a hypercoordinate central carbon based on the example of CB8, and CB8−clusters. We presented a chemical bonding model, derived from the adaptive natural density partitioning analysis, capable of rationalizing and predicting planar structures either with a boron ring or with a carbon atom occupying the central hypercoordinate position. According to our chemical bonding model, in the wheel-type structures the central atom is involved in delocalized bonding, while peripheral atoms are involved in both delocalized bonding and two-center two-electron (2c–2e) σ-bonding. Since carbon is more electronegative than boron it favors peripheral positions where it can participate in 2c–2e σ-bonding. To design a chemical species with a central hypercoordinate carbon atom, one should consider electropositive ligands, which would have lone pairs instead of 2c–2e peripheral bonds. Using our extensive chemical bonding model that considers both σ- and π-bonding we also discuss why the AlB9 and FeB9− species with octacoordinate Al and Fe are the global minima or low-lying isomers, as well as why carbon atom fits well into the central cavity of CAl42− and CAl5+. This represents the first step toward rational design of nano- and subnano-structures with tailored properties.
Co-reporter:Gerardo Martínez-Guajardo, Alina P. Sergeeva, Alexander I. Boldyrev, Thomas Heine, Jesus M. Ugalde and Gabriel Merino
Chemical Communications 2011 - vol. 47(Issue 22) pp:NaN6244-6244
Publication Date(Web):2011/04/01
DOI:10.1039/C1CC10821B
We describe and explain the fluxionality of B13+. The chemical bonding analysis shows that the inner triangle of B13+ is bound to the peripheral ring by delocalized bonds only, allowing a quasi-free rotation of the inner ring.
Co-reporter:Timur R. Galeev and Alexander I. Boldyrev
Physical Chemistry Chemical Physics 2011 - vol. 13(Issue 46) pp:NaN20556-20556
Publication Date(Web):2011/08/24
DOI:10.1039/C1CP21959F
In this work we examine a structural transition from non-planar three-dimensional structures to planar benzene-like structures in the CxHxP6−x (x = 0–6) series. The global minima of P6, CHP5, and C2H2P4 species are benzvalene-like structures. The benzvalene and benzene-like structures of C3H3P3 are close in energy with the former being slightly more stable at our best level of theory. The transition occurs at x = 4 (C4H4P2), where the benzene-like structures become significantly more stable than the benzvalene-like structures. We show that the pseudo Jahn–Teller effect, which is responsible for the deformation of planar P6, CHP5, and C2H2P4 structures, is completely suppressed at x = 3 (benzene-like structures of C3H3P3). We present NICSzz values of all the benzene-like isomers in the series.
Co-reporter:Alina P. Sergeeva and Alexander I. Boldyrev
Physical Chemistry Chemical Physics 2010 - vol. 12(Issue 38) pp:NaN12054-12054
Publication Date(Web):2010/08/20
DOI:10.1039/C0CP00475H
A remarkable triple-decker sandwich complex [Pd4(μ4-C9H9)(μ4-C8H8)][BArf4] (BArf4 = B{3,5-(CF3)2(C6H3)}4) composed of cyclononatetraenyl anion and cyclooctatetraene as “bread pieces” and square tetrapalladium dication as “meat” (Fig. 1a) has been synthesized recently [Murahashi et al., J. Am. Chem. Soc., 2009, 131, 9888]. This complex attracted our attention because of the presence of an almost perfect square sheet composed of four palladium atoms. Such a structure could be a sign of aromatic nature of chemical bonding as it was shown to be present in the square Al42− cluster [Li et al., Science, 2001, 291, 859]. In this work we show that according to our chemical bonding analysis the bonding in the Pd42+ unit of [Pd4(μ4-C9H9)(μ4-C8H8)]+ is of δ-character among four palladium atoms, making the triple-decker sandwich complex the first synthesized compound identified as having δ-bonding in its cyclic building block when it's in solution or in a crystalline state.
Co-reporter:Ivan A. Popov, Yafei Li, Zhongfang Chen and Alexander I. Boldyrev
Physical Chemistry Chemical Physics 2013 - vol. 15(Issue 18) pp:NaN6848-6848
Publication Date(Web):2013/03/08
DOI:10.1039/C3CP43921F
The chemical bonding analysis using the adaptive natural density partitioning method of the C4F fluorinated graphene sheet revealed a chemical bonding model explaining its particular stability. We proposed that the stability of the C4F fluorinated graphene is due to the so-called “benzation” of graphene. On the basis of our chemical bonding model we predicted that other high-symmetry structures of the C7F4, C3F2, C13F10, etc. stoichiometries, containing planar hexagons, which are separated from each other by 2, 3, 4, etc. C–F fragments could also possess additional stability. We also suggested that other functionalized graphene structures of the C4X and C7X4, C3X2, C13X10 stoichiometries, where X is a monovalent atom (H, F, Cl) or a monovalent group (CN, CCH etc.), could also have extra stability. We hope that the developed model, obtained for the functionalization of pristine graphene, will give an impetus for experimentalists to devise methods, which could serve as useful tools for producing this kind of materials with the tailored properties.
Co-reporter:Timur R. Galeev, Alexander S. Ivanov, Constantin Romanescu, Wei-Li Li, Konstantin V. Bozhenko, Lai-Sheng Wang and Alexander I. Boldyrev
Physical Chemistry Chemical Physics 2011 - vol. 13(Issue 19) pp:NaN8810-8810
Publication Date(Web):2011/04/12
DOI:10.1039/C1CP20359B
In this joint experimental and theoretical work we present a novel type of structural transition occurring in the series of CxB8−x− (x = 1–8) mixed clusters upon increase of the carbon content from x = 2 to x = 3. The wheel to ring transition is surprising because it is rather planar-to-linear type of transition to be expected in the series since B8, B8−, B82− and CB7− are known to possess wheel-type global minimum structures while C8 is linear.
The adaptive natural density partitioning (AdNDP) method has been applied for the first time to porphyrinoids in order to describe their aromaticity. The analysis of π-electron system reveals that aromaticity of annulene originates from 6-π-electron delocalization, while aromaticity of porphyrin can be better described in terms of local aromaticities of the appended 6-π-electron pyrrolic heterocycles and 6-π-electron central fragment. The patterns of chemical bonding for porphyrinoids obtained by AdNDP are consistent with chemical intuition and lead to unique and compact graphic formulas.
![Tripyreno[2,1,10,9,8,7-defghij:2',1',10',9',8',7'-nopqrst:2'',1'',10'',9'',8'',7''-xyza b c d ]trinaphthylene](/data/chemimg/3730200/72210-95-8.png)
![Tripyreno[2,1,10,9,8,7-defghij:2',1',10',9',8',7'-nopqrst:2'',1'',10'',9'',8'',7''-xyza b c d ]trinaphthylene](/data/chemimg/3730200/72210-95-8_b.png)
![2-Phosphabicyclo[2.2.0]hexa-2,5-diene](http://img.cochemist.com/ccimg/340200/340142-32-7.png)
![2-Phosphabicyclo[2.2.0]hexa-2,5-diene](http://img.cochemist.com/ccimg/340200/340142-32-7_b.png)
![1-PHOSPHABICYCLO[2.2.0]HEXA-2,5-DIENE](http://img.cochemist.com/ccimg/340200/340142-31-6.png)
![1-PHOSPHABICYCLO[2.2.0]HEXA-2,5-DIENE](http://img.cochemist.com/ccimg/340200/340142-31-6_b.png)
![2-Phosphatricyclo[3.1.0.02,6]hex-3-ene](http://img.cochemist.com/ccimg/340200/340142-29-2.png)
![2-Phosphatricyclo[3.1.0.02,6]hex-3-ene](http://img.cochemist.com/ccimg/340200/340142-29-2_b.png)
![Tricyclohepta[cde,hij,mno]trindene](http://img.cochemist.com/ccimg/89200/89168-42-3.png)
![Tricyclohepta[cde,hij,mno]trindene](http://img.cochemist.com/ccimg/89200/89168-42-3_b.png)
![Bicyclo[2.2.0]hexa-2,5-diene](http://img.cochemist.com/ccimg/5700/5649-95-6.png)
![Bicyclo[2.2.0]hexa-2,5-diene](http://img.cochemist.com/ccimg/5700/5649-95-6_b.png)
![tricyclo[3.1.0.0~2,6~]hex-3-ene](http://img.cochemist.com/ccimg/700/659-85-8.png)
![tricyclo[3.1.0.0~2,6~]hex-3-ene](http://img.cochemist.com/ccimg/700/659-85-8_b.png)
![Tetracyclo[2.2.0.02,6.03,5]hexane](http://img.cochemist.com/ccimg/700/650-42-0.png)
![Tetracyclo[2.2.0.02,6.03,5]hexane](http://img.cochemist.com/ccimg/700/650-42-0_b.png)
