Supramolecular assembly in 2-amino-5-bromo-3-methylpyridinium-2,4-dihydroxybenzoate monohydrate mediated by hydrogen bonding interactions: experimental and theoretical approach

A supramolecular assembly was successfully constructed by 2-amino-5-bromo-3-methylpyridine (ABMP) and 2,4-dihydroxybenzoic acid (DHB) through N + –H⋯O − , N–H⋯O and O–H⋯O hydrogen bonding interactions. The structure of molecular salt was determined by single-crystal X-ray crystallography. Further, the synthesized salt was elucidated by optical, Fourier transform infrared and nuclear magnetic resonance spectroscopic studies. UV–Vis–NIR transmittance spectrum reveals that the ABMP-DHB crystal exhibits a better transmittance in the region of entire visible window, and the lower cut-off wavelength is 358 nm. Thermal property was determined by TG/DTA analysis which indicates that the compound is thermally stable up to 210 °C. The molecular structure of ABMP-DHB crystal was optimized using density functional theory at the B3LYP level with 6-31g(d) basis set. The intermolecular interaction and charge delocalization were theoretically found by natural bond orbital analysis. The existence of various intermolecular contacts was identified through finger plot of Hirshfeld surface analysis. ABMP-DHB shows better scavenging activity against DPPH radical. Fukui functions calculation was applied to find out the reactive site in the crystal.