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 (I) was synthesized and characterized by H-1 NMR, C-13 NMR, IR, MS, UV-Vis spectroscopy and elemental analysis. The crystals of dye 1, obtained from slow evaporation of solvent acetone, crystallized in the tri-clinic space group P - 1 with a = 9.6501(16) angstrom, b = 10.2308(17) angstrom, c = 10.7341(17) angstrom, V= 887.2(3) angstrom(3), and Z = 2 (at 298(2) K), and it was stabilized by the hydrogen bonds and intermolecular face-to-face pi...pi aromatic stacking interactions. Crystallographic, IR, H-1 NMR and UV-Vis data of dye I were compared with the results of density functional theory (DFT) method, and the calculated molecular geometries, vibrational bands, H-1 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. (C) 2013 Elsevier B.V. All rights reserved.