Structural, spectral and thermal properties of a supramolecular assembly based on p-phenylenediamine and trichloroacetic acid: A combined experimental and computational study

Single-crystals of the p-phenylenediammonium bis(trichloroacetate) sesquihydrate compound (I) have been grown by slow evaporation method. XRD study showed the presence of two symmetrically independent water sites; one water site is fully occupied while the other one shows partial occupancy (0.5). The new compound has been characterized by FT-IR, Raman and UV-visible spectroscopies. Thermal behavior of (I) has been studied by TGA/DSC analysis. In the structure of (I), the coherence of the 3-D supramolecular assembly is ensured by conventional hydrogen bonds (O-H center dot center dot center dot O and N-H center dot center dot center dot O) and C-Cl center dot center dot center dot pi interactions. Nature and contribution of the different intermolecular interactions that occur in compound (I) were probed through the 3-D Hirshfeld surface and the associated 2-D fingerprint plots. O center dot center dot center dot H/H center dot center dot center dot O interactions (related to the H-bonds) contribute by 30.5% to the total Hirshfeld surface; furthermore, contacts involving chlorine atoms represent ca. 54% of the total surface. Quantum chemical study performed with DFT (B3LYP and HSEH1PBE) methods at 6-311G(++)(d.p) level has permitted calculation of optimized geometry, modes of vibrations, atomic charges, thermodynamic parameters, FMOs and NBOs of the title molecule. The detailed vibrational interpretation has been evaluated by potential energy distribution (PED) analysis. The UV-Vis spectrum has been calculated by TD-DFT/B3LYP/6-311G(++)(d,p) method in two solvents (water and methanol). (C) 2020 Elsevier B.V. All rights reserved.