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

Abstract

Using quantum chemical calculation data obtained via the DFT method with B3PW91/TZVP, M06/TZVP, and OPBE/TZVP levels, the possibility of the existence of 3d-element coordination compounds, each of which contain an inner coordination sphere, the double deprotonated form of subporphyrazine (H₂SP) with a 3d-element M(II) ion : ligand ratio of 1 : 1 was investigated. The key geometric parameters of the molecular structures of these (666) macrotricyclic complexes with a closed contour are given; it was noted that BeN3 chelate nodes have a trigonal-pyramidal structure and exhibit a very significant (in most cases, more than 80°) deviation from coplanarity. Six-membered metal-chelate and five-membered non-chelate rings were also not flat, but their deviation from coplanarity was much smaller and did not exceed 20° and 4°, respectively. It was noted that all these complexes can be divided into two groups: in the first (M = Ti, V, Mn, Co, Ni, Zn) all M–N bond lengths, bond angles (NMN) at the MN3 chelate site, and non-bonded angles between nitrogen atoms entering the chelate site are almost the same, while in the second group (M = Cr, Fe, Cu), they are different from each other. Good agreement between the structural data obtained using the above three versions of the DFT method was noticed. NBO analysis data for these complexes are presented; it was noted that according to each of the DFT methods used, the ground state of each complex under examination has the same spin multiplicity as the ground state of the corresponding M(II) central ion. The standard thermodynamic parameters of formation (standard enthalpy Δ_fH⁰, entropy S_f⁰, and Gibbs energy Δ_fG⁰) for the above-mentioned macrocyclic compounds were also calculated.