18-Crown-6 based supramolecular structure, hydrogen bonding behaviour and its nonlinear optical properties

Abstract

Abstract Self-assembled supramolecular cocrystals of (18-crown-6).2(5-amino-2,4,6-triiodoisophthalic acid).2(H2O) has been synthesised from 18-crown-6 (18C6) and 5-amino-2,4,6-triiodoisophthalic acid (5ATIPA) by slow evaporation solution growth technique. The cocrystal was characterized by IR, DRS and PL spectroscopy, single-crystal X-ray diffraction and z-scan technique. It crystallizes in a monoclinic system with centrosymmetric space group P21/c. Supramolecular assembly is constructed by N─H•••O and O─H•••O interactions. The inclusion of the water molecules is involved in bifurcated hydrogen bonds with the 18C6 molecule and the -NH2 group is involved in intramolecular hydrogen bonds with iodine atoms of the 5ATIPA molecule. The vibrational patterns in FT–IR is used to identify the functional groups. Direct band gap energies estimated by diffuse reflectance spectrum is, 3.13 eV. Fingerprint plots of Hirshfeld surfaces were used to locate and analyze the percentage of hydrogen bonding interactions. The z-scan technique indicates the suitability of cocrystal for third-order NLO applications.