One trinucleus dimethine cyanine dye: Experimental and theoretical studies on molecular structure as well as absorption and fluorescence properties

A kind of trinucleus dimethine cyanine dye: 1-methyl-2,6-bis[2-(furan-2-yl)vinyl]pyridinium iodide (1) was synthesized and characterized by 1H NMR, 13C NMR, IR, MS, UV–Vis spectroscopy and elemental analysis. The crystals of dye 1, obtained from slow evaporation of solvent acetone, crystallized in the triclinic space group P − 1 with a = 9.6501(16) Å, b = 10.2308(17) Å, c = 10.7341(17) Å, V = 887.2(3) Å3, and Z = 2 (at 298(2) K), and it was stabilized by the hydrogen bonds and intermolecular face-to-face π⋯π aromatic stacking interactions. Crystallographic, IR, 1H NMR and UV–Vis data of dye 1 were compared with the results of density functional theory (DFT) method, and the calculated molecular geometries, vibrational bands, 1H NMR chemical shifts and UV–Vis maximum absorption were consistent with the experimental results. The fluorescence spectra were predicted in four different solvents with CIS/PCM methods. Compared with experimental values, the absolute deviations of emission maxima were −17.4 nm in chloroform, 6.3 nm in DMSO, 4.9 nm in methanol, and 6.8 nm in water, respectively. And the experimental fluorescence spectra were nicely reproduced by the simulated fluorescence spectra for each solvent.