Spectral, structural, and theoretical elucidation of a novel adenine-based crystalline salt: Insights from NMR, XRD, DFT, NBO and NLO studies

Abstract

This study investigates the novel proton-transfer system, Adeninium 2,3 pyridine dicarboxylate (ADH⁺PD^-) derived from Adenine and 2,3 pyridine dicarboxylic acid. We determined its structural properties using SCXRD with a space group P1 n1. Frontier molecular orbital reveals distinct localization of HOMO and LUMO, indicating potential intermolecular charge transfers, and provides insights into regions of electron density. The atomic charge analysis results supported the SCXRD and HSA results, showing the formation of noncovalent interactions in organic crystalline salt. The results of the natural bond orbital (NBO) analysis confirmed the existence of (relatively weak) noncovalent interactions between the cation and anion moieties of the organic crystalline salt. UV–visible spectral studies were conducted to assess the suitability of the single crystal for various optical applications, revealing its excellence in linear optical transparency. Furthermore, Electron localization function (ELF), local orbital locator (LOL), and Reduced Density Gradient Analysis (RDG) were studied.