Using DFT model chemistries, M06/def2TZVP and B3PW91/TZVP in combination with the D3 Grimme dispersion, the molecular structures of the coordination compounds of Si(II) and Ge(II) with the doubly deprotonated form of porphyrazine (H2P) having [SiP] and [GeP] composition, respectively, were calculated. The values of the most important bond lengths, valence and non-valence angles in these compounds, as well as the data of the NBO analysis, are presented. A very significant difference between their structures is noted: in the compound [SiP], both the chelate node MN4 and the group of four nitrogen atoms that make up it exhibit a rather noticeable deviation from coplanarity, whereas in the analogous compound [GeP], both are strictly planar. Based on the NBO analysis data, a conclusion has been drawn about a fairly high degree of delocalization of the electron density in these compounds and about the decisive role of p-orbitals in the formation of Si-N and Ge-N bonds. Standard enthalpy Delta fH0, entropy Sf 0, and Gibbs energy Delta fH0 of formation of these compounds were also calculated; all were found to be positive and quite significant in magnitude. Good agreement was also noted between the calculated data obtained using the two aforementioned DFT model chemistries.

Using the DFT OPBE/TZVP and DFT B3PW91/TZVP model chemistries, the standard thermodynamic parameters of formation (enthalpy Delta Hf,2980, entropy Sf,2980, and Gibbs energy Delta Gf,2980) and the energies of the M - nitrido ligand bond for heteroligand complexes of the general formula [M L(N)] (L2- is a doubly deprotonated form of porphyrazine, M - 3d-element) were calculated. Based on these data, it was concluded that the most stable of them are complexes V, and upon passing from M = V to M = Cr, their stability decreases, from M = Cr to M = Mn, it increases, and from M = Mn to M = Fe, it decreases again. At the same time, it was noted that compounds with [M L(N)] composition, where M = Sc, Ti, Co, Ni, Cu, Zn, cannot exist. The key parameters of molecular structures of [V L(N)], [Cr L(N)], [Mn L(N)], and [Fe L(N)], namely bond lengths and bond angles, were calculated from these coordination compounds. It was noted that in each of them, the MN4 chelate node has a square-pyramidal structure with the nitrogen atoms in a planar orientation. Moreover, the 5-membered and 6-membered non-chelate rings have a strictly planar structure, while the 6-membered chelate rings are non-coplanar, with the sum of the internal bond angles deviating from the sum of the internal angles in a planar hexagon by no more than 10 degrees. NBO analysis of these compounds was performed, and based on its data, a high degree of delocalization of the electron density in them was concluded. Good agreement was also observed among the structural parameters obtained using the above-mentioned alternative DFT model chemistries.

Using density functional theory (DFT) with the M06 functional and the def2TZVP basis set, combining D3 version of Grimme's dispersion, the molecular structures of 10 structural isomers of corrole - [18]corrole(1.1.1.0) (A), [18]corrole(1.1.1.0) (B), [[18]corrole(2.0.1.0) (A), [18]corrole(2.0.1.0) (B), [18]corrole(1.0.0.2) (A), [18]corrole(1.0.0.2) (B), [18]corrole(1.0.0.2) (C), [18]corrole(1.0.0.2) (D), [18]corrole(3.0.0.0) (A), and [18]corrole(3.0.0.0) (B), were calculated. Calculations indicate that the [18]corrole(1.1.1.0)(A) is the most stable isomer, although the difference in total energy values is very small (< 2 kJ/mol), the least stable isomer is [18]corrole(3.0.0.0)(A). whose total energy is almost 200 kJ/mol higher. The standard enthalpy Delta H-f(0), entropy S(f )(0,)and Gibbs energy Delta(f)G(0) of formation of these compounds were also calculated. The values of the most important bond lengths, bond and non-bond angles in these compounds are presented. It was noted that in almost all of these isomers, both the groupings of four nitrogen atoms and the 15-membered macrocycles containing them are non-planar, and in some cases exhibit a very significant deviation from coplanarity. All four interatomic distances between neighboring nitrogen atoms in all these compounds are different; the same applies to the non-valent angles between these atoms. NBO analysis of all the above isomers was carried out. On the basis of its data, a high degree of delocalization of the electron density in these compounds was stated.

Establishing the fundamental possibility of the existence of the heteroligand macrotetracyclic complexes of vanadium, chromium, manganese, and iron-containing in the inner coordination sphere phthalocyanine, oxygen (O2-) and fluorine (F-) ions and having general [MPc(O)F] formula (M= V, Cr, Mn, Fe), by using of quantum-chemical calculation of parameters of their molecular/electronic structures and thermodynamical characteristics. The molecular and electronic structures of the above-mentioned heteroligand macrotetracyclic chelates of 3d elements (M) of the type [MPc(O)F] (M= V, Cr, Mn, Fe) which are unknown at present, were theoretically investigated. Standard thermodynamic parameters of formation (standard enthalpy DH0f, 298, entropy S0f, 298, and Gibbs's energy DG0f, 298) for these macrocyclic compounds were calculated, too. Identifying details of molecular and electronic structures of compounds indicated above. Density functional theory (DFT) model chemistries (B3PW91/TZVP and OPBE/TZVP) with a combination of the D3 version of Grimme's dispersion. The data on the geometric parameters of the molecular structure of these complexes are presented; it was shown that MN4 chelate nodes, all metal-chelate and 6-membered non-chelate rings in each of these macrocyclic coordination compounds, are practically planar with a small deviation from coplanarity (not more 3o); nonetheless, N4 grouping from donor nitrogen atoms and 5-membered non-chelate rings are strictly planar. Wherein, the bond angles between two donor nitrogen atoms and M atom are not equal to 90o; a similar situation occurs for the bond angles between donor atoms N, M, and O or F (notwithstanding the bond angles formed by M, O, and F atoms are exactly 180 degrees). Also, NBO analysis data and the values of the standard enthalpy, entropy, and Gibbs energy of the formation of these compounds were presented. Specific features of DFT calculated molecular and electronic structures of the heteroligand metal macrocyclic compounds have been discussed. It has been shown that good agreement between the parameters of molecular structures obtained by two various DFT model chemistries takes place. Also, it has been noted that predicting the possibility of the existence of exotic coordination compounds and modeling their molecular/electronic structures using modern quantum chemical calculations (and, in particular, using DFT of various levels) is a very useful tool for solving problems associated with such synthesis.

By using density functional theory with (DFT) with functional M06 and the def2TZVP basis set, combining D3 version of Grimme’s dispersion, the molecular structures of [18]porphyrin-(1.1.1.1) (porphyrin) and five its structural isomers, namely [18]porphyrin-(2.0.2.0) (porphycene), [18]-porphyrin-(2.1.0.1) (corphycene), [18]porphyrin-(2.1.1.0) (hemiporphycene), [18]porphyrin-(3.0.1.0) (isoporphycene), and “N-confused” porphyrin, were calculated. The values of the most important bond lengths, bond and non-bond angles in these compounds, and NBO analysis data are presented. It was noted that In almost all of these isomers, both the groups of four nitrogen atoms and the 16-membered macrocycles that contain these atoms are coplanar; the only exception is N-confused porphyrin, which has a small deviation from coplanarity (0.8[Formula: see text] and 5.1[Formula: see text], respectively). The interatomic distances between adjacent nitrogen atoms in porphyrin are identical, in porphycene, they are equal in pairs, in corphycene, two are equal to each other; the rest are different, and in the remaining isomers, all four are different. NBO analysis of all the above isomers was carried out, and based on the data, a high degree of delocalization of the electron density in these compounds was stated. The values of the standard enthalpy [Formula: see text], entropy [Formula: see text] and Gibbs energy [Formula: see text] of formation, and the total energies of these compounds were also calculated. Based on these data, it was concluded that the most stable isomer is porphyrin, Porphycene is slightly less stable, while the stability of the other isomers is significantly lower, and isoporphycene has the lowest stability (and, accordingly, the highest values of [Formula: see text] and relative total energy [Formula: see text].

Using quantum chemical design within the framework of density functional theory in three versions, namely DFT M06/TZVP, DFT B3PW91/TZVP, and DFT OPBE/TZVP, the possibility of the existence of a new "nitrogen-rich" zinc chemical compound-dodecaazacyclododecatetraene-1,4,7,10, which contains the currently maximum number of nitrogen atoms per one zinc atom, equal to 12, was shown. Data on the structural parameters of this unusual compound and the macrocyclic ligand H4(N12), of which this compound is a derivative are presented. It was noted that the group of four nitrogen atoms bonded with a zinc atom, and group containing the same atoms in the H4N12 molecule, are non-coplanar with a relatively small amount in the case of ZnN12 (no more than 6 degrees) and at the same time quite noticeable in the case of H4(N12) (about 23 degrees) deviation from the plane; , . The nitrogen atoms forming a 12-membered macrocycle are generally not equivalent to each other; it has rather considerable deviation of N12 group from coplanarity (more than 60 degrees). Good agreement was noted between the parameters of molecular structures of ZnN12 and H4N12 calculated using these various DFT versions. Standard thermodynamic parameters, NBO analysis data, and HOMO/LUMO images for this compound are also presented.

Using two variants of DFT model chemistries, specifically M06/def2TZVP and B3PW91/TZVP combined with D3 Grimme dispersion, the molecular structures of hydrogenated porphyrazine and its octafluoro-substituted derivatives, namely (22H,24H)-5,10,15,20-tetraazaporphin and perfluoro-(22H,24H)-5,10,15,20-tetraazaporphin, were calculated. The key bond lengths, valence and non-bonded angles in these compounds, along with NBO analysis data, are presented. It is observed that each of these compounds features groups of four nitrogen atoms that are strictly planar; additionally, the four nitrogen atoms not bonded to hydrogen are positioned at the vertices of a square, while those forming N-H bonds are at the vertices of a rhombus. The 16-membered macrocycles in all these compounds are non-planar, although their deviation from coplanarity generally does not exceed 10 degrees. According to NBO analysis, there is a high degree of electron density delocalization within these compounds. The standard enthalpy of formation (Delta H-f degrees), standard entropy (S-f degrees), and standard Gibbs free energy (Delta(f)G degrees) were also calculated. It was found that in perfluoro-(22H,24H)-5,10,15,20-tetraazaporphin, unlike (22H,24H)-5,10,15,20-tetraazaporphin, the values of Delta H-f degrees and Delta(f)G degrees are negative, indicating significantly greater thermodynamic stability compared to *(22H,24H)*porphyrazine. Good agreement was noted between the data derived from the two DFT model chemistry methods.

Using the density functional theory (DFT) with the M06 functional and the def2TZVP basis set, which combines the D3 version of the Grimme dispersion, the parameters of the molecular structures (the values of the most essential bond lengths, valence and non-valence angles) and the thermodynamic characteristics (standard enthalpy Delta H-f(0), entropy S-f(0) and Gibbs energy Delta(f)G(0) of formation) were calculated for four "N-confused" structural isomers of porphyrazine, which differ from each other in the location of the nitrogen atom on the outer "rim" (3N-, 7N-, 8N- and 12N-) in these macrocyclic compounds. It is noted that, contrary to expectations, the most stable of these isomers is not the "3N-confused" porphyrazine, but rather the "12N-confused" porphyrazine; the least stable is the "SN-confused" porphyrazine. The difference in the total energy values between the least and most stable structural isomers of "N-confused" porphyrazine is only 11.0kJ/mol, which, taking into account the highly probable kinetic inertness of these compounds, allows us to hope for the existence of each of these four isomers. It is noted that in all of these isomers, both the groups of four nitrogen atoms and the 16-membered macrocycles that include these atoms are not strictly coplanar, and for each of them, at least a slight deviation from coplanarity is observed, lying in the ranges of (0.5-0.7)degrees and (0.5-2.0)degrees, respectively. The molecular structures of all of these compounds lack any symmetry elements, so that each of them belongs to the symmetry group Cl; however, their electric dipole moments (1) are not very significant for such a low level of symmetry and are in the range of (2.5-4.0) Debye units. NBO analysis of all the above-mentioned isomers was also carried out, based on the data of which a high degree of delocalization of electron density in these compounds was established.

Using quantum chemical calculation data obtained by the DFT method with the B3PW91/TZVP and M062X/def2TZVP theory levels, the possibility of the existence of four Be(II) coordination compounds, each of which contains in the inner coordination sphere and the double deprotonated forms of subporphyrazine (H2SP), mono[benzo]subporphyrazine (H2MBSP), di[benzo]subporphyrazine (H2DBSP), and tri[benzo]subporphyrazine (subphthalocyanine) (H2TBSP) with a ratio Be(II) ion/ligand = 1:1, were examined Selected geometric parameters of the molecular structures of these (666)macrotricyclic complexes with closed contours are given; it was noted that BeN3 chelate nodes have a trigonal–pyramidal structure and exhibit a very significant (almost 30°) deviation from coplanarity; however, all three 6-membered metal-chelate and three 5-membered non-chelate rings in each of these compounds are practically planar and deviate from coplanarity by no more than 2.5°. The bond angles between two nitrogen atoms and a Be atom are equal to 60° (in the [BeSP] and [BeTBSP]) or less by no more than 0.5° (in the [BeMBSP] and [BeDBSP]). The presence of annulated benzo groups has little effect on the parameters of the molecular structures of these complexes. Good agreement between the structural data obtained using the above two versions of the DFT method was noticed. NBO analysis data for these complexes are presented; it was noted that, according to both DFT methods used, the ground state of the each of complexes under study is a spin singlet. Standard thermodynamic parameters of formation (standard enthalpy ΔfH0, entropy S0, and Gibbs free energy ΔfG0) for the above-mentioned macrocyclic compounds were calculated.

Conformational analysis of N,N-dialkylamides of diphenylphosphorylacetic acid has been carried out using the methods of dipole moments, IR spectroscopy, and quantum chemistry DFT B3PW91/6-311++G(df,p), including the CPCM model. In solution, N,N-diethyl-, N,N-dibutyl- and N,N-dioctylamides exist as equilibrium mixture of conformers, in which forms with cis-orientation of phenyl rings and synclinal orientation of the Csp3‒Csp2(C=O) bond relative to the phosphoryl group predominate, the carbonyl group and P‒Csp3 bond being anticlinal. The stabilization of the preferred conformers is facilitated by intramolecular hydrogen contacts and the possible presence of the p,π-conjugation between the phosphoryl group and the phenyl ring in their molecules.

The reaction of quinopimaric acid with P–H-phosphonium salts yielded quaternary phosphonium salts containing enol moiety at the phosphorus atom. The reaction proceeded with high regioselectivity. The structures of the resulting compounds were confirmed by NMR and IR spectroscopy, mass spectrometry, and single-crystal X-ray diffraction.

The existence of macrotricyclic complexes containing M(ii) ion (M = Ti–Zn) and double deprotonated form of subporphyrazine that is unknown for these 3d-elements, was shown by quantum-chemical calculation using three various DFT methods.

By using three independent of density functional theory (DFT) model chemistries with functionals B3PW91, M06 and OPBE, and the TZVP basis set, combining the D3 version of Grimme's dispersion with the original D3 damping function, the molecular structures of three types of 3d element (M) macrocyclic coordination compounds - homoligand with porphyrazine (H(2)L1), heteroligand with porphyrazine and two axially oriented fluoro ligands and heteroligand with perfluoroporphyrazine (H(2)L1) and two axially oriented fluoro ligands having [ML1], [ML1(F)(2)] and [ML2(F)(2)] compositions, respectively, were calculated. The values of the most important bond lengths, bond and non-bond angles in the resulting metal complexes, and NBO analysis data are presented. It was noted that almost each of these complexes contains a coplanar MN4 chelate unit and a group of N4 atoms, as well as coplanar 5- and 6-membered rings; moreover, both of them are pairwise identical to each other in terms of the sums of bond angles (540 degrees and 720 degrees, respectively) and their assortments. Bond angles formed by M atoms and two fluorine atoms are 180 degrees; bond angles formed by fluorine, M and nitrogen atoms are 90 degrees. NBO analysis of all the above 3d-metal chelates was carried out, and based on the data, a high degree of delocalization of the electron density in these coordination compounds was stated. The values of the standard enthalpy Delta H-f(0), entropy S-f(0) and Gibbs energy Delta(f)G(0)of formation of these compounds were also calculated. Particular attention was paid to the fact that according to these data, for the ([ML1]) and ([ML1(F)(2)]) complexes the values of Delta H-f(0) and Delta(f)G(0 )are positive, whereas for ([ML2(F)(2)]) complexes they are negative, and in the series [ML1] - [ML1(F)(2)] - [ML2(F)(2)] there is an increase in the thermodynamic stability of the complexes, which is undoubtedly due to the presence of peripheral fluorine substituents in the [ML2(F)(2)] structure. There was also good agreement between similar parameters calculated by different DFT methods, both qualitatively and quantitatively.

The reaction of alantolactone, a sesquiterpene α,β-unsaturated lactone, with H-phosphonium or H-arsonium triflates proceeds as P–H or As–H addition at the terminal =CH2 moiety to afford novel triphenyl(sesquiterpenyl)phosponium or -arsonium triflates. Their diastereoisomerism at the formed C11 chiral center has been simulated by quantum chemical calculations.

The conformational analysis of bis[ N -alkyl- N -(2-diphenylphosphorylethyl)]amides of diglycolic acid has been carried out using the methods of dipole moments, IR spectroscopy, and quantum-chemical DFT B3PW91/6-311++G(df,p) simulation. In solution, N , N -dimethyl-, N , N -dibutyl-, and N , N -dioctyl-substituted diamides of diglycolic acid exist as an equilibrium mixture of two groups of symmetrical or nonsymmetrical conformers, in some of which intramolecular contacts involving hydrogen atoms of the alkyl substituents and oxygen atoms of the ether bridge or carbonyl groups are possible.

By using quantum chemical calculation data obtained by the DFT method with the B3PW91/TZVP and OPBE/TZVP levels, the possibility of the existence of three Fe(V) complexes, each of which contains in the inner coordination sphere porphyrazine/trans-di[benzo]porphyrazine/tetra[benzo]porphyrazine (phthalocyanine), oxygen (O2−) and fluorine (F−) ions, was shown. Key geometric parameters of the molecular structure of these heteroligand complexes are given; it is noted that FeN4 chelate nodes, and all metal-chelate and non-chelate cycles in each of these compounds, are practically planar with the deviation from coplanarity, as a rule, by no more than 0.5°. Furthermore, the bond angles between two nitrogen atoms and an Fe atom are equal to 90°, or less than this by no more than 0.1°, while the bond angles between donor atoms N, Fe, and O or F, in most cases, albeit insignificantly, differ from this value. Nevertheless, the bond angles formed by Fe, O and F atoms are exactly 180°. It is shown that good agreement occurs between the structural data obtained using the above two versions of the DFT method. NBO analysis data for these complexes are presented; it is noted that, according to both DFT methods used, the ground state of the each of three complexes under consideration may be a spin quartet or spin doublet. Additionally, standard thermodynamic parameters of formation (standard enthalpy ∆fH0, entropy S0 and Gibbs’s energy ∆fG0) for the macrocyclic compounds under consideration are calculated.

The mechanism of formation of N-methyl-2-(diphenylphosphoryl)acetamide was studied by DFT. The first stage, the reaction of trichlorophosphine with 2-(diphenylphosphoryl)acetic acid, involves three elementary steps, and the explicit inclusion of solvent makes it possible to reduce the activation energy of each of them. The second stage, the reaction of 2-(diphenylphosphoryl)acetyl chloride with a phosphoryl-substituted amine, involves one elementary step.

Based on the results of a quantum chemical calculation using the DFT method in the B3PW91/TZVP, OPBE/TZVP, M06/TZVP, and M062/Def2TZVP levels, the possibility of the existence of M(N13) chemical compounds (M = Mn, Fe) that are unknown for these elements has been predicted. Data on the structural parameters, the multiplicity of the ground state, APT and NBO analysis, and standard thermodynamic parameters of formation (standard enthalpy ΔfH0, entropy S0, and Gibbs’s energy ΔfG0) for these compounds are presented.

The history of quantum chemistry dates back to 1926, when the German physicist Erwin Schrödinger, in his classical works [...].