α,ω-Diphenylpolyenes Cabable of Exhibiting Twisted Intramolecular Charge Transfer Fluorescence: A Fluorescence and Fluorescence Probe Study of Nitro- and Nitrocyano-Substituted 1,4-Diphenylbutadienes

Abstract

cyano-1-p-nitrophenyl-4-phenylbuta-1Z,3E-diene (6), and 1-cyano-1-phenyl-4-pnitrophenylbuta-1Z,3E-diene (7), have been synthesized and their absorption and fluorescence properties in organic solvents, water-dioxane, and SDS, CTAB, and Triton-X-100 micelles have been investigated. The fluorescence behavior of these dienes has also been examined in ethanol-methanol (1:1) matrix at 298 and 77 K. The dienes with nitro substituents on the aromatic ring are capable of exhibiting dramatically redshifted fluorescence emission due to twisted intramolecular charge-transfer excited states. The fluorescence properties of nitro-substituted dienes 3, and 5-7 have been utilized to probe the microenvironment of SDS and CTAB micelles in terms of dielectric constant of water-micelle interface, location of the probe molecules in the micelles, and the cmc values. This study has brought out interesting features of the excited state structure and potential energy surface of diphenylpolyenes. It further provides new directions for the development of fluorescence probes as sensors and reporters of microenvironments of organized assemblies.

Donor-Acceptor Conjugated Linear Polyenes: A Study of Excited State Intramolecular Charge Transfer, Photoisomerization and Fluorescence Probe Properties

“…The excited state properties of several other substituted stilbenes have been examined in order to understand the role of electron withdrawing group in the formation of ICT state [43][44][45][46][47][48][49][50][51][52][53][54][55][56][57]. Our group has examined steady state fluorescence behavior of nitro-and amino-substituted trans-stilbene, substituted phenyl ethenylindoles, and substituted DPB (Fig.…”

“…Our group has examined steady state fluorescence behavior of nitro-and amino-substituted trans-stilbene, substituted phenyl ethenylindoles, and substituted DPB (Fig. 2) [47][48][49][50][51][52][53]. The ethenyl indole and DPB having a nitro substituent undergo ICT with highly fluorescent excited specie in non-polar and moderately polar solvent.…”

“…4), wherein blue-shifted fluorescence is observed in the solid state as compared to solution state [52,53]. Over all, it has been found that nitro-substituted arylethenylindoles [50][51][52][53] show fluorescence behavior similar to nitro-substituted-DPB [47][48][49] in which none of the chain single and double bonds have conformational restrictions. Further, such nitro compounds exhibit, a blue-shifted fluorescence maximum at low temperature (77 K), and in the solid state.…”

“…Hence, attempts have been made to design and develop neutral hydrophobic fluorescence probes. A few such probes include the DPB [39,47,48,100,101], ethenylindole [102][103][104], prodan [105], etc.…”

A fluorescence study of differently substituted 3‐styrylindoles and their interaction with bovine serum albumin

“…Diphenylpolyenes capable of fluorescing from their charge transfer excited states have been considered as useful and further employed to study the microenvironment of micelles and proteins (7)(8)(9)(10)(11)(12)(13)(14). 3-Styrylindoles with push-pull characteristics have also been found to exhibit solvent polarity-sensitive fluorescence emission from the ICTexcited state (15,16).…”