Structure-directing role of CH⋯X (X = C, N, S, Cl) interactions in three ionic cobalt complexes: X-ray investigation and DFT study using QTAIM Vr predictor to eliminate the effect of pure Coulombic forces.

Three cobalt complexes, namely [Co(HL)(N)]ClO (1), [Co(L)(HL)(N)]ClO·1.5HO (2), and [Co(L)(HL)(NCS)] [CoCl(NCS)] (3), where HL = 2-(3-(dimethylamino)propyliminomethyl)-6-methoxyphenol, HL = 2-(2-(dimethylamino)ethyliminomethyl)-4,6-dichlorophenol, and HL = 2-(2-(dimethylamino)ethyliminomethyl)-6-methoxyphenol, as potential tridentate NO-donor Schiff base ligands, were synthesized and characterized using elemental analysis, IR and UV-vis spectroscopy, and single-crystal X-ray diffraction studies. All three were found to be monomeric ionic complexes. Complex 1 crystallizes in the orthorhombic space group , whereas both complexes 2 and 3 crystallize in triclinic space groups, 1̄. Further, 1 and 2 are cationic complexes of octahedral cobalt(iii) with perchlorate anions, whereas complex 3 contains a cationic part of octahedral cobalt(iii) and an anionic part of tetrahedral cobalt(ii). Hydrogen-bonding interactions involving aromatic and aliphatic CH bonds as H-bond donors and the pseudo-halide co-ligands as H-bond acceptors were established, which are important aspects governing the X-ray packing. These interactions were analyzed theoretically using the quantum theory of atoms in molecules (QTAIM) and non-covalent interaction plot (NCI plot) analyses. Moreover, energy decomposition analysis (EDA) was performed to analyze the stabilization of the complexes in terms of the electrostatic, dispersion, and correlation forces.