Supramolecular assembly of guanidinium benzilate and benzylammonium benzilate: structural and spectroscopic (FT-IR, UV–Vis and photoluminescence) analyses

Abstract

Guanidinium benzilate (GBA) and benzylammonium benzilate (BABA) have been prepared from guanidinium carbonate and benzylamine/benzilic acid (BA). GBA has inter-ionic, intraionic and intermolecular hydrogen bondings giving a three-dimensional supramolecular assembly. The carboxylate ion is present in the resonance form with C–O distances of 1.242 and 1.246 Å in GBA, whereas the C–O distances being 1.262 and 1.245 Å in BABA. In BABA, an inverted dimer with inter-ionic hydrogen bonding exist as a dimer with supramolecular assembly due to intermolecular hydrogen bonding between the ion pairs. So the counter cation decides the resonance form of the carboxylate ion, hydrogen-bonding network and the disposition of the phenyl rings in the benzilate and benzyl moiety. The IR, ¹H NMR and ¹³C NMR spectral data have been interpreted using the crystal structure data and by the comparison between the two similar derivatives. Both the compounds show the formation of the ammonium benzilate or methylammonium benzilate moiety which decompose leaving no residue. Both the compounds exhibit the emission at 442 nm (blue) and 547.2 nm (green) on excitation at 257 nm. Chromaticity indicated excellent emission characteristics of both GBA and BABA which is necessary for OLED applications.

Graphical abstract