Photophysical characteristics of some 2-styrylindolium dyes

Abstract The absorption and fluorescence characteristics of some 2-styrylindolium dyes are reported. Depending on the nature of the substituent, a change from a polyene-type structure to a polymethine type is observed. This is accompanied by a significant change of colour, and a considerable decrease of the half-bandwidth of the longest-wavelength absorption maximum and Stokes' shift Δvst. Quantum-chemical calculations by the PPP (SCF-CI) method support the conclusions concerning the bond alternation change of the central styryl fragment. The spectral data suggest that the preferred configuration in the compounds studied is s-trans. By incorporating the dyes into a polymeric PVC film a strong enhancement of the fluorescent intensity is observed.