X-ray and DFT studies of the structure and spectral property of 2-[2-(4-dimethylaminophenyl)ethenyl]-1-methyl-pyridinium iodide

A hemicyanine dye: 2-[2-(4-dimethylaminophenyl)ethenyl]-1-methyl-pyridinium iodide (1) was synthesized and characterized by X-ray diffraction, 1H NMR, MS, IR, UV–Vis spectra and elemental analysis. The crystals are monoclinic, space group P21/c, with a = 7.1231(8), b = 20.672(2), c = 10.9642(12) Å, V = 1605.7(3) Å3, and Z = 4 (at 298(2) K). Crystal stacking scheme indicates the hydrogen bonds and intermolecular π⋯π interactions; the molecular planes arrange in a head-to-tail fashion along the ab plane due to the strong ‘push-pull’ electron system. Molecular geometries, frequencies and absorption properties were calculated at DFT/TD-DFT level using two hybrid exchange-correlation functionals, B3LYP and PBE1PBE. These calculations on (1) provide deep insight into its electronic structure and property.