Laboratory for the Theoretical Modelling of Multifunctional Materials

Scientific results:

1. Using computer modeling with application of boundary conditions, we have studied the geometric and electron composition of a new allotrope of aluminum – crystalline supertetrahedral aluminum built on the basis of a diamond lattice in which carbon atoms are replaced with Al4 tetrahedrons. Computations of the electron zone structure of supertetrahedral aluminum demonstrated the possibility of the existing material manifesting good electrical conductivity and plasticity, which allows to classify it as a semimetal. The predicted phonon spectrum indicates the dynamic stability of this supertetrahedral structure of aluminum. Supertetrahedral aluminum, according to computations, has a density equal to 0.61 g/cm³, which is significantly lower than the density of water and of pure aluminum, which amounts to 2.7 g/cm³. The computed values of the Hooke’s constant and the shear modulus of this material indicates its high plasticity. An article devoted to these results has been published.
2. We have studied a new form of supertetrahedral aluminum relying on the  diamond crystal lattice, in which pairs of adjacent carbon atoms are replaced with supertetrahedral aluminum covalently bonded with a Х Al₄-X (X=B, C, Al, Si) atom. The crystal structures cF-Al₄C and cF-Al₄Si, which are metastable phases of these substances, are indirect-band-gap semiconductors, possess a significantly high hardness and plasticity. The crystal structures cF-Al₄B and cF-Al₄Al are dynamically unstable and are of no interest from the practical standpoint. The results have been published.
3. Using quantum chemical computations in the solid body approximation, we have predicted a new allotropic form of gallium constructed on the basis of a diamond crystal lattice in which each carbon atom is replaced with a Ga₄ tetrahedron. The new material is a conductor, has a low density (1.74 g/cm³) as well as a high plasticity, its melting temperature is about 273 К. The material produced on the basis of this allotropic form can find applications as a low-density metal. The results have been published.
4. Using quantum chemical computations in the solid body approximation, we have modeled a new ferromagnetic superoctahedral two-dimensional boron material. The result of a computation of the phonon spectrum and the molecular dynamics indicated that a 2D-B6 monolayer is dynamically and thermally stable. Moreover, it possesses considerable magnetic properties and has a metal electron structure. The predicted material is a second example of a magnetic 2D sheet and a first example of a ferromagnetic metal 2D sheet formed from pure boron. Therefore, this material is of great interest for the modern materials science, and its thermal and mechanical stability promise a wide range of applications. The results have been published.
5. With the help of computer modeling with application of periodic boundary conditions, we have demonstrated that the new material difluorophosphorane should have a flat structure, in which fluorine atoms are located over and under the plane of phosphorus atoms. Such a structure is dynamically stable and acts as a semiconductor, it is also promising for use in nanoelectronics. The results have been published.
6. Using quantum chemistry methods, we modeled a number of non-metallic two-dimensional materials with unpaired р electrons, among which we found a new two- dimensional material with the composition SiN that has ferromagnetic properties. Computations of the phonon spectrum and the molecular dynamics demonstrated that a 2D-SiN monolayer is dynamically and thermally stable, which makes it a potential candidate for experimental implementation. The results have been published. 
7. We have conducted quantum chemical computations of extended non-metallic chains with a general formula of P_nX_{3n + 2} (X = F, Cl) and infinite –(PX₃–PX₃)_∞– chains corresponding to them. It was demonstrated that all the highly symmetrical P_nX_{3n + 2} (n = 2–9) structures satisfy the energy minimums, while  structures in which the P–X bond is in the equatorial position have higher stability. Rotation around the P–P bond for fluorine derivatives is a low-barrier process, in the case of chlorine derivatives it is accompanied by the dissociation of the molecule is accompanied by a dissociation of the molecule. Computations with application of periodic boundary conditions that model an infinite linear –(PX₃–PX₃)_∞– chain demonstrated that both researched systems are dynamically stable and are wide-band-gap semiconductors with a direct band gap. The results have been published. 
8. From the results of computations we have proposed a new type of catalysts, MgO, with periodic surface defects that have a high catalytic activity. It was demonstrated that magnesium oxide with periodic surface defects has doubly occupied multicenter bonds inside each defect in which the oxygen atom is missing. It turned out that these structures are stable at up to 1500 К, which opens a possibility for their application in extreme conditions. In this work we reviewed both multiple and rare defects that are potential catalysts with one defect. The results have been published. 
9. Using methods of density functional theory, we studied the structures and properties of binuclear coordination compounds of transition metals with o-quinone ligands based on polyacenes. It was demonstrated that increasing the number of condensed rings leads to a stabilization of the biradicoloid state of acenes and a switch in the nature of exchange interactions between semiquinone forms of redox-active fragments from antiferromagnetic to ferromagnetic. The proposed cobalt(II) diketonate adducts with acenes functionalized with quinone fragments are able to undergo one- and two-step spin transitions caused by intramolecular electron transfers between metal ions and the ligand system. The unusual magnetic properties predicted by computations, which are caused by migration of paramagnetic centers, allow to view these complexes as promising candidates for the development of molecular electronics and spintronics devices. The results have been published.
10. Using methods of density functional theory, we studied a series of new magnetically active binuclear cobalt diketonates with mixed ligands that contain acene linkers. The results have been published.
11. The results of a computer modeling demonstrated good prospects of cobalt(II) diketonate adducts with polycyclic triangulene hydrocarbons functionalized with о-benzoquinone groups. By rationally choosing substitutes in terminal ligands, we found molecules that are able to undergo thermally-induced valence tautomeric rearrangements. The expected transformations will be accompanied by changes in the magnetic properties in a wide range, which allows to view the studied mixed-ligand complexes as molecular switches and spin qubits. The inclusion of heteroatoms into the polycyclic triangulene fragment leads to an increase in the difference of energies between the main (low-spin) and the high-spin state of mononuclear metal complexes, which allows to expect spin transitions only in complexes with cobalt hexafluoroacetylacetonate. The results have been published.
12. Using methods of density functional theory, we have studied the structures and stability of a new family of metal carbonyls Cr(CO)₅, Fe(CO)₄, Ni(CO)₃, Ti(CO)₄, Ni(CO)₂, cyclooctatetraene and cyclodecapentaene derivatives. All the cyclooctatetraene derivatives, except for the derivative Ti(CO)₄, have a flat structure and are characterized by a pronounced antiaromaticity of the central ring. In the case of cyclopentadecaene complexes flat structures are formed only for derivatives of Fe(CO)₄ and Ni(CO)₃. The stabilization of non-standard flat forms is caused by sterically enforced flattening of the central ring and its π-interactions with metal carbonyl fragments. The results have been published.
13. By performing a quantum chemical modeling of the structure and the magnetic properties of a series of neutral polycyclic aromatic hydrocarbons functionalized with radical groups, established the dependence of the nature and force of volume interactions between the paramagnetic centers on the size of the triangulene fragment, the presence of heteroatoms in it, the type of radical substitutes and their spatial location. We proposed molecules that have a high-spin main electron state and manifest ferromagnetic exchange interactions that allow to view such systems as promising building blocks for organic spintronics devices. The results have been published.
14. We have conducted a quantum chemical research of the possibility of stabilizing the aromatic molecule N₃P₃ with a flat hexagonal structure. This isomer is characterized  by thermodynamic instability against dissociation into a van-der-Waals complex of a distorted NP₃ tetrahedron and an N₂ molecule, but is kinetically stable, characterized by high energy barriers of possible isomerizations, which allows to expect its existence in thermal conditions.  The results have been published.
15. Our researchers have published a review devoted to the concept of σ-aromaticity and σ-antiaromaticity. We considered the examples of clusters, molecules and solid bodies, in which this concept helps to understand the chemical bond. It was shown that for σ-aromaticity and σ-antiaromaticity the bonding principles are similar to those for π-aromaticity and π-antiaromaticity.
16. For the first tie we have synthetically produced and completely characterized a new complex, [K([2.2.2]crypt)]₄[In₈Bi₁₃], which consists of two clusters: [Bi@In₈Bi₁₂]^3- of T_h-symmetry and [Bi@In₈Bi₁₂]^5- of C_s-symmetry. These are the largest of the currently known In/Bi clusters. Quantum chemical computations of (AdNDP, ELF, NICS) demonstrated that in clusters spherical aromaticity is implemented, which explains the high stability and magnetic properties of these compounds. The results have been published.
17. Using quantum chemical computations, we have predicted a new structure of two-dimensional phosphorane, 2D-B₄P₂. The results of molecular dynamics computations indicated a good thermal stability of two-dimensional phosphoborane, which allows to expect it to be possible to experimentally produce this material. According to the computations, the two-dimensional phosphoborane is a semiconductor with almost equal values of energies of direct and indirect band gaps. Such a material will have a low absorption coefficient comparable to that of borophene. Sheet 2D-B₄P₂ is quite a soft material, comparable in its characteristics to two-dimensional MoS₂. 2D-B₄P₂ can find potential applications in the production of displays and flexible electronics. The results have been published.
18. We have conducted a review of unusual structural manifestations of boron, analyzed more than 140 literature sources. In the review we presented the results of recent research of uncommon forms of boron derivatives, including flat hexagonal boron, boron fullerenes, supertetrahedral boron, superoctahedral boron. We analyzed approaches to creating such systems based on a combination of stable structural units, as well as methods aimed at compensating the electron deficit of non-standard boron structures. The results have been published.
19. The Laboratory has synthesized and completely characterized a (silatrigerma)cyclobutenyl cation salt. The homoaromaticity of this ion was established by crystallographic analysis as well as confirmed by quantum chemical computations. Using potassium graphite, a (silatrigerma)cyclobutenyl cation can transform into a (silatrigerma)cyclobutenyl radical, it has an allyl structure confirmed by X-ray structural analysis. The cation and the radical can easily transform into one another, therefore being a fully reversible redox couple. The results have been published.
20. We have been continuing our research of a series of supertetrahedral structures and studied materials based on cF-Ga₄X (X = C, Si) that are built upon a diamond crystal lattice in which each pair of adjacent carbon atoms is replaced with Ga₄X, where G₄ is a tetrahedroon of gallium atoms. It was found that in terms of its elastic properties, cF-Ga4C should be close to samarium and bismouth. The material remains in the solid state at up to 600 К, while its homogeneous melting temperature lies in the range from 600 to 700 К. In terms of their elastic properties, cF-Ga₄Si is similar to thallium and lead. The material remains in the solid state at up to 400 К, while its homogeneous melting temperature is in the range from 400 to 500 К. According to computations, both materials are indirect-band-gap semiconductors. The results have been published.
21. The Laboratory has studied two-dimensional octahedral boranes of the B₄X₂ (X = N, P, As, Sb) family. Successive N → Sb replacements allowed to determine the trend of narrowing of the band gap. It turned out that the most stable compounds are two-dimensional phosphorus (B₄P₂) and arsenic borane (B₄As₂). The stability, thinness and softness of B₄P₂ and B₄As₂ make them potentially suitable for flexible electronics and displays. The almost zero flaking energy opens paths to possible synthesis. The results have been published.
22. Using quantum chemical computations, we have researched two 18-electron titanium germylene complexes Cp₂Ti(L)=Ge[Si₃(SiMe^tBu₂)₄] (L = Me₃P and XylNC). We computed the supposed mechanism of the formation of these complexes. Both compounds were classified according to the type of Schrock complexes. Similar germylene molybdenum and wolfram complexes are described as Fischer complexes. The almost zero flaking energy for opens paths to possible synthesis. The results have been published.
23. We have studied a new transformation of Si₃S-bicyclo[1.1.0]butane into the corresponding Si₃S-cyclobutene. The impossibility of its isomerization into substituted cyclopropene (cyclo trixylene) was demonstrated. The results have been published.
24. The Laboratory has studied a new metal-organic cluster, 1-phospha-2,3,4,5-tetrasilatricyclo[2.1.0.0^2,5]pentane. We reviewed its isomers and ways of its formation. The results have been published.
25. We have researched a group of bis-atranes RX(YCH₂CH₂)₃Z(CH₂CH₂Y)₃XR (X = C, Si, Ge, Sn, Pb; Z = N, P; Y = O, S; R = H, F). We found a mutual transformation of two various types of multicenter bonds. For systems with Z=N the computed barriers of this mutual transformation do not exceed 1 kcal/mol, for systems with Z=P it does not exceed 14 kcal/mol. The results have been published.
26. We have researched a number of spiropyran isomers of the indoline series that contain a cation 3H-indoline substitute that is a potential molecular switch. Their geometrical and energy characteristics were computed. We demonstrated the effect of the perchlorate anion on the energy characteristics of the studied compounds. The equilibrium between various forms for one of the compounds in the solution and the crystallization of its trans-isomer of the merocyanine form observed in the experiment can be caused by a less energetically hindered transition for the spirocyclic into the cis-form and a higher relative stability of the trans-form. The results have been published.
27. Using computations with the method of density functional theory, we have demonstrated that 3-allyl-3-methyl-1,2-diphenyl cyclopropane and 3-allyl-2-methyl-1,3-diphenyl cyclopropane mutually transform with energy barriers of 35.6 and 31.9 kcal/mol by Cope rearrangement  with the formation of an intermediate that is able to transform into stable 1,2-diphenyl-6-methyltricyclo[2.2.0.0]hexane with a barrier of 11.8 kcal/mol by synchronous processes of the inversion of 5-membered ring and ring closure. The results have been published.
28. Computations relying on methods of density functional theory, we determined the molecular structures and relative stability of hexa-, penta- and tetracoordinated stereoisomers of bischelate complexes of Co^II and Ni^II with (N,O,O)-tridentate azomethine ligands that form MN₂O₂O₂, MN₂O₂O and MN₂O₂ coordination nodes. By modeling the mechanism of the reaction of the synthesis of ML₂ with polydentate ligands, we determined preferable hexacoordinated configurations of the molecular structure of Co^II and Ni^II complexes based on (N,O,O)-tridentate azomethine. The results have been published.
29. Using quantum chemical computations, we have demonstrated that a complex of gold(I) with the pentamethoxycarbonylcyclopentadienyl ligand Ph₃PAu[C₅(CO₂Me)₅] in which the gold atom is bound with sp³-hybridized carbon of the cyclopentadiene ring and is additionally coordinated with two neighboring carbon atoms of the ring, exhibits fluctuating behavior due to fast 1,5-sigmatropic shift of the AuPPh₃ group along the perimeter of the five-member ring. To the contrary, complexes of gold(I) with the Ph₃PAu[N(Ar)C(Ar´)N(Ar)C₅(CO₂Me)₄] polydentate amidinyltetrametoxycarbonylcyclopentadienyl ligands are the most stable in the form of an ylide isomer in which the gold atom is bound with the terminal nitrogen atom of the amidinium fragment and additionally coordinated with the π-system of the cyclopentadiene ring. Alternative isomers in which the gold atom is bound with the carbon atom of the ring of cyclopentadiene or the oxygen atom of the methoxycarbonyl substitute are significantly less stable. The results have been published.
30. During our research, we have synthesized a representative of stable alumels with chlorine substitutes near the aluminum atom by combining a derivative of a cyclobutadiene dianion and aluminum trichloride. Using X-ray structural analysis, we established the structure of the alumel and demonstrated that it exists in the form of a monomer. The aluminum atom is tetracoordinated with the fourth coordination center occupied with a tetrahydrofuran molecule, which reduces the internal high Lewis acidity of the aluminum center, thus stabilizing the alumel molecule. The results have been published.
31. By means of molecular dynamics modeling, we have demonstrated that supertetrahedral aluminum, the research of which started in our Laboratory in 2017, is a structurally stable material at a temperature of 200 K and lower. Being heating up to 225 K, supertetrahedral aluminum melts, which is followed by a phase transition and formation of face-centered cubic structure. According to the computations, this process is accompanied by the emission of 4260 kJ/kg of energy. Based on the results of the research of transformations of chemical bonds during a phase transition, we formulated a hypothesis on the cause of the emission of a considerable amount of energy. Taking into account the temperature range within which tetrahedral aluminum preserves stability, it is possible to conclude that, this material will not float in water due to its solid state at such temperatures. However, this material, if synthesized, will float in liquid nitrogen. The results have been published. 

Education and career development:

• The Laboratory has created the training module «Current state of the theory of chemical bonding», which is part of the professional discipline «Methods of the synthesis of   materials» of the basic study plan «Polyfunctional materials».
• Internship has been conducted for undergraduate and postgraduate students and young researchers in the courses «SUSE Linux Enterprise Server 12 Advanced Administration», «Data visualization using Microsoft Excel 2013 and Microsoft Power Point 2013».
• An employee of the Laboratory completed training in supercomputer technologies in the direction «Quantum informatics»at Moscow State University.
• Employees of the Laboratory have completed training in the course «Theoretical and practical issues of quantum chemical research using the Gaussian 16 software package», conducted by Gaussian, Inc. at Ulm University (Germany).
• The following training programs have been developed and launched:
• program of the training module «Quantum chemistry of organic, element-organic and coordination compounds» for master’s degree students majoring in Chemistry (name of the program «Polyfunctional materials»);
• program of the discipline «Workshop on computer modeling of polyfunctional materials» for master’s degree students majoring in Chemistry (name of the program «Polyfunctional materials»);
• program of the discipline «Forecasting the structure and properties of materials» for postgraduate students in the domain of training «Chemistry».

Collaborations:

Department of Chemistry and Biochemistry of Utah State University (USA), Professor Alexey I. Boldyrev, Doctor of Sciences in Physics and Mathematics. Joint research and publications. Two articles are currently under review by the editorial boards of foreign journals.

Department of Chemistry of the University of Tsukuba (Japan), Professor Vladimir Ya. Lee. Joint research and publication. Vladimir Ya. Lee, Sakai R., Kazunori Takanashi., Olga A, Gapurenko, Ruslan M. Minyaev, Heinz Gornitzka, Akira Sekiguchi . Titanium Germylidenes // Angewandte Chemie-International Edition – 2021. – Vol. 60, N. 8. – P. 3951-3955.