X-ray, Hirshfeld surfaces analyses, DSC-TGA thermal stability, infrared, and optical properties studies of phenylammonium tetrachlorozincate hydrate (C6H5NH3)2ZnCl4.H2O

Abstract

This paper reports the synthesis, crystal structure reinvestigation at 296 ​K, Hirshfeld surfaces, DSC, TG-dTG, Infrared, and UV studies of (C6H5NH3)2ZnCl4.H2O, which crystalized in the triclinic space group P-1 [Z ​= ​2, a ​= ​7.575(3) Å, b ​= ​9.894(3) Å, c ​= ​13.101(4) Å, α ​= ​95.903(13)°, β ​= ​102.408(14)° and γ ​= ​111.659(13)°]. The crystal structure consists of two cations C6H5NH3+ linked to a distorted ZnCl42− tetrahedron anion, together linked to the water molecule via hydrogen bonds of N-H⋯Cl, N-H⋯O and O-HW···Cl types. The ZnCl42− tetrahedra and H2O molecules form an infinite two-dimensional layer parallel to (0 0 2) plan between the organic sheets. The powder and single-crystal X-ray analyses confirm the pure phase of the synthetized compound. The Hirshfeld surfaces and fingerprint plots, used to analyse quantitatively the interactions in the crystal structure, showed that Cl⋯H/H⋯Cl contacts due to O-H⋯Cl and N-H⋯Cl hydrogen bonding are the major contributor in the total crystal packing surface of (C6H5NH3)2ZnCl4.H2O. The DSC-TGA analyses showed that the compound dehydration made at around 80 ​°C, gives an anhydrous compound thermally stable between 80 ​°C and 120 ​°C. The anhydrous compound decomposition process is predicted, and confirmed by Infrared spectra at various temperatures. The observed bands are assigned and discussed based on the theoretical analyses; the non-fundamental bands resulted in the formation of hydrogen bonding are assigned. The photoluminescence spectra investigated at room temperature showed a red emission line at 2.60 ​eV, which may be associated with radiative recombination of exciton confined within the ZnCl42−. This suggests potential applications for this compound as UV detection and optical materials.