Twelve-Nitrogen-Atom Cyclic Structure Stabilized by 3d-Element Atoms: Quantum Chemical Modeling

Abstract

Using various versions of density functional theory (DFT), DFT M06/TZVP, DFT B3PW91/TZVP, DFT OPBE/TZVP, and, partially, the MP2 method, the possibility of the existence of 3d-element (M) compounds with nitrogen having unusual M: nitrogen ratio 1:12, unknown for these elements at the present, was shown. Structural parameter data were presented. It was shown that all MN4 groupings have tetragonal-pyramidal structure. It was noted that the bond lengths formed by nitrogen atoms and an M atom were equal to each other only in the case of M = Ti, V, Cr and Co, whereas for other Ms, they were slightly different; moreover, the bond angles formed by nitrogen atoms and an M atom were equal to 90.0°, or practically did not differ from this value. Thermodynamic parameters, NBO analysis data and HOMO/LUMO images for this compound were also presented. Good agreement between the calculated data obtained using the above three quantum chemical methods was also noted.

Coordination compounds with subporphyrazine may exist: DFT quantum chemical prediction for M(ii) complexes with a given macrocyclic ligand (M = Ti–Zn)

“…The calculations were carried out using the Gaussian09 program package. 48 As in our previous articles, in which the DFT method of calculation was used, [34][35][36][37] the correspondence of the found stationary points to the energy minima in all cases was proved by calculating the second derivatives of the energy to the coordinates of the atoms; herein, all equilibrium structures corresponding to the minimum points on the potential energy surfaces had only real (and, moreover, always positive) frequency values. Among the optimized structures for further consideration, the one with the lowest total energy was selected.…”

“…The version of the DFT method, namely, DFT with the B3PW91 functional described in detail in, [30][31][32] which combines the standard extended split valence basis set TZVP 33 and has already been used before by us, in particular, in, [34][35][36][37] was also used in this work. The use of the given version of the DFT method in this case is because according to, [30][31][32] it allows one to obtain the most accurate (i.e., close to experimental) values of the geometric parameters of molecular structures as well as much more accurate values of thermodynamic and other physicochemical parameters in comparison with other variants of the DFT method.…”