Experimental and DFT characterization of the organic-inorganic monohydrated Co(II) complex with 2,6-diaminopyridine ligand, (C5H8N3)2[CoBr4]·H2O

Single crystals of the new organic-inorganic compound (C5H8N3)2[CoBr4]·H2O were grown by hydrothermal technique and characterized by X-ray diffraction, infrared absorption, raman spectroscopy scattering, optical absorption and thermal analysis. The title compound belongs to the triclinic space group P1¯ and in the crystal structure, the inorganic layers are built from tetrabromidocobaltate anions [CoBr4]2− and free water molecules, linked together by O-H⋯Br hydrogen bonds and halogen···halogen interactions. The organic cations are intercalated between the mineral layers via N-H⋯Br hydrogen bonds and form chains through π⋯π interactions. Theoretical calculations were performed using density functional theory with the B3LYP/LanL2DZ level for studying the molecular structure and vibrational spectra of the title compound. Good consistency is found between the calculated results and the experimental structure, IR and Raman spectra. The optical properties were investigated by optical absorption showing Ligand-to-Metal Charge-Transfer transitions in the visible region and organic related π−π* transitions in the UV region.