Charge density studies of an inorganic-organic hybrid p-phenylenediammonium tetrachlorocuprate

Abstract

High quality single crystals of an inorganic-organic hybrid, p-phenylenediammonium tetrachlorocuprate (pPDA:CuCl4), suitable for high-resolution X-ray data collection, have been crystallized. pPDA:CuCl4 crystallizes at special positions in the P21/c space group of the monoclinic crystal system with only halves of the moieties in the asymmetric part of the unit cell. This compound forms a hybrid structure consisting of separate inorganic anion and organic cation layers linked by weak N-HCl hydrogen bonds. The Cu atoms are located at the centers of symmetry and each of them is surrounded by six chlorine atoms thus forming a tetragonal bipyramid. Two pairs of the chlorine atoms form short Cu-Cl bonds (2.27964(4) and 2.29765(4) Å), whereas the third pair forms the longest Cu-Cl bond (2.90452(4) Å). Experimental and theoretical electron density distributions have been established. There is an excellent agreement between theoretical and experimental properties at bond critical points. The total charge of the organic cation is equal to +1.64 e− and is neutralized by the charge of the inorganic anion. The orbital population analysis of the copper 3d electrons and analysis of geometry of the tetrachlorocuprate have been performed and they clearly show presence of the Jahn-Teller effect. Comparison of some experimentally derived parameters such as area and linear density distribution with those calculated on the base of relations derived from literature shows that a longer series of experimental charge density investigations of the hybrid structures should be measured. It should allow for obtaining more reliable relations among different parameters for the hybrid structures with a strong predictive power of such relations. Analysis of residuals of measured intensities of reflections and those resulting from the refined model shows a serious underestimation of esds of measured reflections used in the refinement.