Synthesis, structure and Hirshfeld surface analysis, vibrational and DFT investigation of (4-pyridine carboxylic acid) tetrachlorocuprate (II) monohydrate

Abstract

The new organic–inorganic hybrid compound [C₆H₆NO₂]₂CuCl₄⋅H₂O has been grown from an aqueous mixture by the solvent evaporation method. X-ray diffraction, Hirshfeld surface analysis, FT-IR and FT-Raman spectroscopy were applied to characterize the composition and crystal structure of the complex. It is crystallized in a triclinic system (${P}\bar {{1}}$ space group). The structure of this compound might be described as layered with two parallel anionic and cationic layers. The first layer is composed of isolated square planar [CuCl₄]²⁻ and the second layer of [C₆H₆NO₂]²⁺. The water molecule is placed between the layers formed by organic cations along the b axis. Network hydrogen-bonding and π–π interactions lead to the formation of a three-dimensional architecture. Hirshfeld surface analysis for visually analysing intermolecular interactions in crystal structures employing molecular surface contours and 2D fingerprint plots has been used to scrutinize molecular shapes. The vibration properties of this structure were studied by IR spectroscopy and Raman scattering. Vibration spectra were also calculated theoretically by means of Gaussian 03 package of programs within the density functional theory (DFT) framework using the B3LYP/LanL2DZ level of theory. To sum up, good consistency is found between the calculated results on one hand and the IR and Raman spectra and experimental structure on the other. This study confirms the presence of the organic cations [C₆H₆NO₂]²⁺, the inorganic anions [CuCl₄]²⁻ and H₂O.