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Based on the results of a quantum chemical consideration in the framework of DFT OPBE/TZVP and B3PW91/TZVP methods, the possibility of the self-existence of a chromium heteroligand complex with (NNNN)-donor macrocyclic ligand – tetra[benzo]porphyrazine and two oxoligands where chromium oxidation degree is (+6), have been shown. The data on the key structural parameters and also, on multiplicity of the ground state of the given macrocyclic metal complex have also been presented.

Using the density functional method (DFT) in the OPBE/TZVP//QZP approximation and the Gaussian09 program, geometric parameters and total energies of molecular structures of the Mo(II), Tc(II), Ru(II), Rh(II), Pd(II), Ag(II) and Cd(II) macrotricyclic complexes with (NSSN)- and (NNNN)-coordinations of the ligand donor centers to the complex, arising as a result of complexing between M(II) indicated above, dithiooxamide H 2 N–C(= S)–C(= S)–NH 2 and glyoxal HC(=O)–CH (=O), were calculated. Based on the data of this calculation, it is shown that in the case of Mo(II), Tc(II), Ru(II), Rh(II) and Pd (II) complexes with (NSSN)-coordination of ligand are more stable, whereas in the case of Ag(II) and Cd(II), with (NNNN)-coordination; in addition, for the Mo(II) and Ru(II) complexes, a pseudo-tetrahedral environment of the central metal ion takes place by donor atoms, while for the complexes Tc(II), Rh(II), Pd(II), Ag(II), and Cd(II) are planar ones. The bond lengths and bond angles in the indicated coordination compounds are given and it is noted that the Ag(II) and Cd(II) complexes are almost flat, the Tc(II), Rh(II), and Pd(II) complexes are small, while the Ru(II), a fairly significant deviation from coplanarity. The five-membered metal chelate cycles formed as a result of complexing, in most of these complexes are either practically flat, or exhibit a slight (within 5°) deviation from coplanarity; the only exceptions are the Mo(II) and Ru(II) complexes.

Using the quantum-chemical calculation methods QCISD and G3, the possibility of the existence of nitrogen molecules with the composition N4, N6, N8 and N10 has been discussed. On the basis of the data obtained, the conclusion about possibility of existence of three novel polymorphic modifications of elemental nitrogen with an even number of atoms in molecules, namely N4 with rectangular and regular tetrahedron shapes, and N6 in a form remotely resembling an "open book", has been made. The values of bond lengths, valence and torsion angles, and oscillations frequencies in each of the above-mentioned forms of elemental nitrogen have been presented.

Basic parameters of molecular structures of Al2Ti3 and Al2V3 metal clusters (bond lengths, bond angles, and torsion (dihedral) angles), have been calculated using DFT method at the OPBE/QZVP level. It has been shown that the Al2Ti3 cluster may exist in 14 modifications and Al2V3 in 11 ones, differing noticeably in their total energy. Besides, the molecular structures of these metal clusters differ significantly in terms of geometric parameters as well as in external form. Moreover, the most energetically stable modifications of Al2Ti3 and Al2V3 clusters differ each other considerably in geometric form also.