Localized excitation effects in (E,E)-2,5-bis[2-(4-N,N-dipropylaminophenyl) ethylenyl]-3,6-dimethylpyrazine and generation of its different forms in solution

• Published in: Journal of applied spectroscopy 2012, Vol.78 (6), p.787-793
• Main Authors: Nemkovich, N. A., Detert, H., Sobchuk, A. N.
• Format: Article
• Language: English
• Subjects: Analytical Chemistry; Atomic/Molecular Structure and Spectra; Physics; Physics and Astronomy
• ISSN: 0021-9037; 1573-8647
• DOI: 10.1007/s10812-012-9534-1

Dipole moments of (E,E)-2,5- bis [2-(4-N,N-dipropylaminophenyl)ethylenyl]-3,6-dimethylpyrazine (VS365) quadrupolar dye in 1,4-dioxane and cyclohexane in addition to its instantaneous fluorescence spectra and fluorescence lifetimes in dichloromethane (pure and with added trifluoroacetic acid) were measured. Quantumchemical calculations show that the π − π conjugated system is localized in the flattest part of the molecule due to disorder in the ground-state geometry of the dye molecule and that this part is the one responsible for light absorption. The effect of localized excitation of the dye causes a considerable change in its dipole moment Δ a μ. Various fluorescent forms of the dye that feature considerably spaced emission spectra and different fluorescence lifetimes originate by adding trifluoroacetic acid to the solution of oligophenylenevinylene in dichloromethane.