Excited states 1,6-diphenyl-1,3,5-hexatriene

Similar aggregation to form nanotubes, see flgure 5, was observed with / - and y-CD linked by strings of all trans l,6-diphenyl-l,3,5-hexatriene (DPH). The formation of such aggregates, containing 20 -CD or 20-35 y-CD, is characterized by red shift in absorption and fluorescence emission spectra of DPH and by an anisotropy value indicating scarce reorientation of DPH during the life of the excited state [135]. 

Similarly, l-anilinonaphthalene-8-sulfonic acid (ANS) only emits in a hydrophobic environment, being almost completely quenched in aqueous solution. ANS and some other dyes, including 6-(p-toluidinyl)naphthalene-2-sulfo-nate, pyrene, l,6-diphenyl-l,3,5-hexatriene, fluorescein, and rhodamine derivatives attached to long acyl chains or to fatty acids that localize in the cellular membranes were used as probes for hydrophobic sites in proteins, protein folding, imaging of membranes of the cell, and solvent polarity. Pyrene-labeled fatty acids were used to detect the fusion of two membranes. When present in a membrane at sufficiently high concentrations, pyrene excimers (excited-state dimers) are formed that emit at 470 nm. Upon fusion with other membranes, probe concentration decreases, and excimer fluorescence is replaced by monomer fluorescence at 400 nm. This process can be monitored by ratiometric detection of pyrene labels. 

Hilinski, E.F., McGowan, W.M., Sears, D.F., Jr., and Saltiel, J., Evolutions of singlet excited-state absorption and fluorescence of all-frflns-l,6-diphenyl-l,3,5-hexatriene in the picosecond time domain,/. Phys. Chem., 100, 3308-3311, 1996. 

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