Styrylpyridinium dyes

Fig. 2 Examples of the structures of a few fast-response electric filed sensitive dyes N-(4-sulpho-butyl)-4-(4-(4-(dipentylamino)phenyl)butadienyl)pyridinium inner salt (RH421, a styrylpyridinium dye), ANNINE 5 (an annellated hemicyanine dye), merocyanine 540, and N-[(4 -dimethylamino)-3-hydroxy-6-flavonyl mcthyl-N,N-trimcthyl ammonium (F4N1, a 3-hydroxychromone dye)...

Fig. 3 Excited state charge transfer in styrylpyridinium dyes...

Pham THN, Clarke RJ (2008) Solvent dependence of the photochemistry of the styrylpyridinium dye RH421. J Phys Chem B 112 6513-6520... 

Mishra, A., PateL S., Behera, R.K., Mishra, B.K., Behera, G.B. Dye-surfactant interaction role of an alkyl chain in the localization of styrylpyridinium dyes in a hydrophobic force field of a cationic surfactant (CTAB). Bull. Chem Soc. Jpn. 1997, 70(12), 2913-2918. 

Fast-response probes (response times less than milliseconds) styrylpyridinium and annellated hemicyanine dyes, merocyanine dyes, and 3-hydroxychromone dyes... 

Slow dyes that respond via a redistribution across the entire membrane (sometimes called Nemstain dyes) do so because of a change in the transmembrane electrical potential. As such, they can only be used as probes of the transmembrane potential and not as probes of the surface potential or the dipole potential. Dyes whose electric field sensing mechanism involves a movement between the aqueous medium and its adjacent membrane interface on one side of the membrane can, in principle, respond to changes in both the transmembrane electrical potential and the surface potential. Fast dyes that remain totally in the membrane phase (e.g., styrylpyridinium, annellated hemicyanine, and 3-hydroxyflavone dyes) respond to their local electric field strength, whatever its origin. Therefore, these dyes can, in principle, be used as probes of the transmembrane electrical potential, the surface potential, or the dipole potential. 

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