New cadmium(II) porphyrin-based coordination dimer: Experimental and theoretic studies

Abstract

We report the synthesis, the experimental and the theoretical studies of the first reported cadmium(II) metalloporphyrin dimer. This new porphyrinic species was prepared by reacting the meso-tetra(p-chlorophenyl)porphyrinate)cadmium(II) ([Cd(TClPP)]) with an excess of pyrazine in dichloromethane. This synthesized compound with the formula [{Cd(TClPP)}2(μ2-pipz–CH2–pipz)]•CH2Cl2 (I) (pipz–CH2–pipz ​= ​4,4′-methylenebispiperazin) was characterized by physicochemical and spectroscopic techniques. The experimental and TD-DFT predicted UV/Vis absorption spectra have been carried out. Single-crystal X-ray analysis was accomplished to ensure the molecular structure of the complex. The Hirshfeld Surface analysis has been computed to elucidate the types of the bonding interactions between the 4,4′-methylenebispiperazin axial ligand and the two [Cd(TClPP)] moieties of complex I. The optimized structure, HOMO-LUMO iso-surfaces, and the molecular electrostatic potential surface (MEP) have been deeply interpreted to understand the stability of I and the charge transfer phenomenon. The intramolecular charge transfer (ICT) occurring between the 4,4′-methylenebispiperazin bridging ligand and the [Cd(TClPP)] moieties enhances the stability of complex I. QTAIM topological analysis has been performed. Accordingly, the interactions between the pipz–CH2–pipz bridging ligand and the two [Cd(TClPP)] moieties of complex I are of covalent and ionic types.