Solid-state synthesis, characterisation, crystal structure and computational studies of a novel proton transfer compound: 8-Hydroxyquinoliniumphthalate-an optical limiting crystal

This paper reports the synthesis, characterisation and single-crystal X-ray diffraction studies of 8-hydroxyquinolinium phthalate (OXPH), a novel proton transfer compound. The title compound crystallises in monoclinic P2(1)/n space group. DFT calculations with B3LYP/6-311G ++(d,p) basis set have been carried out to supplement the experimental results. The nature of anion-cation interactions are explored using Hirshfeld surface analysis and the associated fingerprint plots. The hyperconjugative interactions and charge delocalisation leading to the stability of the molecule have been analysed using natural bond orbital (NBO) analysis. Theoretical analysis of HOMO and LUMO confirms the charge transfer taking place in the molecule. Open- and closed-aperture Z-scan studies show the reverse saturable absorption behaviour and negative nonlinear refractive property which suggests that the compound may be used in optical limiting applications.