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 III (HL 1 ) 2 (N 3 ) 2 ]ClO 4 (1), [Co III (L 2 )(HL 2 )(N 3 )]ClO 4 ·1.5H 2 O (2), and [Co III (L 3 )(HL 3 )(NCS)] 2 [Co II Cl 2 (NCS) 2 ] (3), where HL 1 = 2-(3-(dimethylamino)propyliminomethyl)-6-methoxyphenol, HL 2 = 2-(2-(dimethylamino)ethyliminomethyl)-4,6-dichlorophenol, and HL 3 = 2-(2-(dimethylamino)ethyliminomethyl)-6-methoxyphenol, as potential tridentate N 2 O-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 Pbcn , whereas both complexes 2 and 3 crystallize in triclinic space groups, P 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.