Synthesis, crystal structure, and spectroscopic properties of new stilbazolium salt with enlarged π-conjugated system

A new stilbazolium dye 4-{(E)-2-[4-(dimethylamino)naphthalen-1-yl]ethenyl}-1-methylquinolinium iodide monohydrate (DANSQI) having enlarged π-conjugated system was synthesized and characterized by X-ray diffraction, IR, Raman, UV-Vis, Fluorescence, (1)H- and (13)C NMR spectroscopy. Quantum chemical calculations were performed to obtain electronic structure and vibrational data, using DFT. The crystals are monoclinic, space group P21/n, with a=8.0751(14), b=25.839(4), c=10.9031(15) Å, V=2141.4(6) Å(3), and Z=4 (at 300(2) K). The unit cell contains four molecules of the dye, participating in weak intermolecular interactions. The cation is nearly flat with a deviation of the planarity of 5.08 (1)°. The dye investigated is the first stilbazolium iodide containing water molecule in the solid state therefore the N-dimethylamino group declines significantly from planarity, as indicated by C13N1C2C3 torsion angle of 16.08°. The dye studied shows solvatochromism of 84 nm in visible region and very large Stokes shift up to 253 nm. The intensity of fluorescence bands strongly depends on solvent polarity.