Experimental and theoretical investigations of a proton transfer supramolecular adduct, aminoguanidinium p-nitrophenolate: p-nitrophenol

Abstract

Single crystals of aminoguanidinium p-nitrophenolate: p-nitrophenol (AGPNP) were grown by slow-evaporation method and the crystal structure of AGPNP was confirmed by Single crystal X-ray diffraction analysis. Spectral analyses such as FT-IR, 1H NMR and 13C NMR were carried out in order to detect the functional groups and find out the different kinds of protons and carbons. Optical transmittance and band gap of AGPNP were investigated through both UV-NIR and Frontier Molecular Orbital analyses. The HOMO-LUMO energy gap was found to be 3.242 eV. A quantitative analysis of hydrogen bonding interactions as well as various atom...atom contacts was carried out using Hirshfeld surface analysis. It shows that the crystal surface was dominated by O⋯H/H⋯O interactions with high contribution of 38%.Optimized geometry shows that NH⋯O and OH⋯O hydrogen bonding interactions were responsible for charge delocalization within the moieties. The existence of various hyperconjugative interactions and charge delocalization were analysed using Natural Bond Orbital analysis. Mulliken charge analysis also reveals the occurrence of hydrogen bonds. Proton transfer mechanism was confirmed by molecular electrostatic potential analysis. It is found that the calculated first order hyperpolarizability of AGPNP is 43.6 times higher than that of urea at B3LYP/6-311 + G(d,p) level of theory.