Synthesis, structural, photoluminescence, vibrational and DFT investigation of the bis (4-aminopyridinium) tetrachloridocuprate(II) monohydrate

The crystals of the family of alkylammonuim tetrachloridocuprate (II), (C5H7N2)2CuCl4H2O, have been grown, structurally characterized and their vibrational as well as optical properties been studied. A preliminary single crystal X-ray diffraction structural analysis has revealed that the title compound belongs to the monoclinic system with space group C2/c. Its unit cell dimensions are: a=8.454 (2) Å, b=14.279 (2) Å, c=14.363 (3) Å, β=95.813 (4)°, with Z=4 and its crystal structure was determined and refined down to R1=0.029 and wR2=0.080. The crystal lattice is composed of discrete [CuCl4]2− tetrahedra surrounded by 4-aminopyridinium cations and water molecules which are interconnected by means of hydrogen bonding contacts [N-H…Cl, O-H…Cl and N-H…O]. Furthermore, the room temperature IR and Raman spectra of the title compound were recorded and analyzed. The optimized molecular structure and the vibrational spectra were calculated by the density functional theory (DFT) method using the B3LYP function. The organic-inorganic hybrid crystal thin film can be easily prepared by spin-coating method from the ethanol solution of the (C5H7N2)2CuCl4H2O perovskite and it showed characteristic absorptions of CuCl-based layered perovskite centered at 288 and 400 nm, as well as the photoluminescence peak at around 443 nm. The unaided-eye-detectable blue luminescence emission comes from the excitonic transition in the CuCl4 anions.