Photophysics of representative ketocyanine dyes: Dependence on molecular structure

Spectral properties of a new fluorescent ketocyanine dye have been discussed. The energy of maximum absorption/fluorescence of the dye exhibits bathochromic shift with increasing polarity of the medium. Both dipolarity–polarisability and hydrogen bond donation interaction contribute to solvation of the dye. Study of fluorescence parameters points to existence of different emitting states of the dye for aprotic and protic solvents. While the emitting state is the 1(π, π*) state for aprotic solvents, fluorescence supposedly take place from a different emitting state involving H-bond formation in the excited state in protic solvents. Fluorescence parameters of the dye have been compared with those for a structurally similar symmetric ketocyanine dye. The faster decay of the dye relative to its symmetric counterpart has been explained as due to an increase of nonradiative decay.

Graphical abstractVariation of decay constant by non-radiative process of a ketocyanine dye as a function of solvent polarity.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Optical response of a new ketocyanine dye has been studied in various media. ► Photophysics of the dye in protic media differs from that in aprotic media. ► S1 state for the dye decays at a faster rate than the corresponding symmetric dye.