A Combined Experimental and Theoretical Investigation on Organic Cation Dichlorocopper (II): Structural Characterization, Hirshfeld Surface Analysis, Spectroscopic Properties and DFT Calculation

Abstract

The (ethylenediamine) dichlorocopper(II) complex, {[Cu(en)]Cl2}n(en:C2H8N2), was synthesized by hydrothermal technique. The X-ray structure of {[Cu(en)]Cl2}n shows that the compound crystallizes as a one dimensional chain with one chlorine that is non-bridging and the other chlorine which is triply bridging. It crystallizes at room temperature in the centrosymmetric space group P21/m. The structure of {Cu(en)Cl2}n was originally reported by Kumara et al. The surrounding copper is best described as distorted octahedral. The crystal structure was stabilized with an extensive network of N-H…Cl classical hydrogen bond interactions. The investigation on that close intermolecular interactions between the molecules via Hirshfeld surface analyses is presented to reveal subtle differences and similarities in the crystal structures. The decomposition of the fingerprint plot area provides a percentage of each intermolecular interaction, allowing for a quantified analysis of close contacts within the crystal. The optimized molecular structure and vibrational spectra were calculated by the Density Functional Theory (DFT) method using the B3LYP function with the LanL2DZ basis set. Good consistency is found between the calculated results and the experimental structure, FTIR, and FT-Raman spectra. The detailed interpretation of the vibrational modes was carried out. Optical transmission measurements performed on thin films of {[Cu(en)]Cl2}n revealed two absorption bands at 3.64 eV and 1.907 eV. The calculated HOMO-LUMO energies reveal that charge transfer occurs within the molecule.