Synthesis, X-ray molecular structure and QTAIM and NCI-RDG theoretic studies of a new cadmium (II) (4′4 diaminodiphenylmethane) (meso-arylporphyrin) coordination compound

Abstract In this study, a new five-coordinated cadmium porphyrin complex axially ligated with 4,4′-diaminodiphenylmethane (4,4′-mda) with the formula [Cd(TClPP)(4,4′-mda)]•CHCl3•(4,4′-mda)•2H2O (complex (1)) where TClPP is the meso-tetra(para-chlorophenyl)porphyrinate was prepared and characterized by FT-IR, 1H NMR, and UV/Vis spectroscopy. The crystal structure was determined using single crystal X-ray diffraction. This complex crystallizes in the monoclinic crystal system with the space group P-1. The coordination sphere around the cadmium center is shown as a distorted square pyramidal coordination environment and the porphyrin core presents a dome-type deformation due to the large size of the central cadmium(II) ion. The crystal lattice of (1) is mainly stabilized by classic and non-conventional hydrogen bonds as indicated by the experimental data explored by the PLATON program. To obtain an insight into the physical nature of these intermolecular bonds, we extensively used Bader's quantum theory of atoms-in-molecules (QTAIM). This analysis proved that the coordinated 4,4′-mda (ligand I) stabilizes the structure of (1) by the formation of Van der Waals (VdW) type interactions. Additionally, the non-covalent interaction via the reduced density gradient (NCI-RDG) analysis established nicely the presence of such intermolecular interactions type hydrogen bonding interactions between ligands I and II, from one side, and (iii) hydrogen bonding and Van der Waal interactions, from the other side, with involving [Cd(TClPP)(4,4′-mda)], ligand I and II and the neighboring [Cd(TClPP)(4,4′-mda)] molecules.