Synthesis, spectra, delivery and potentiometric responses of new styryl dyes with extended spectral ranges.

Styryl dyes have been among the most widely used probes for mapping membrane potential changes in excitable cells. However, their utility has been somewhat limited because their excitation wavelengths have been restricted to the 450-550 nm range. Longer wavelength probes can minimize interference from endogenous chromophores and, because of decreased light scattering, improve recording from deep within tissue. In this paper we report on our efforts to develop new potentiometric styryl dyes that have excitation wavelengths ranging above 700 nm and emission spectra out to 900 nm. We have prepared and characterized dyes based on 47 variants of the styryl chromophores. Voltage-dependent spectral changes have been recorded for these dyes in a model lipid bilayer and from lobster nerves. The voltage sensitivities of the fluorescence of many of these new potentiometric indicators are as good as those of the widely used ANEP series of probes. In addition, because some of the dyes are often poorly water soluble, we have developed cyclodextrin complexes of the dyes to serve as efficient delivery vehicles. These dyes promise to enable new experimental paradigms for in vivo imaging of membrane potential.

Novel Radical Cation Reactions of Bichromophoric Systems. Transannular Aryl Migrations; Mechanistic and Exploratory Organic Photochemistry(,)(1)(,)(2).

Eight aryl-substituted 1,4-pentadienes were subjected to photochemically induced electron transfer using dicyanonaphthalene and dicyanoanthracene. The radical-cations produced underwent a regioselective cyclization, wherein one electron-deficient aryl group of one diarylvinyl moiety bonds to the beta-carbon of the second diarylvinyl group. A pattern of regioselectivity and reactivity was encountered. As cyclization proceeds, the odd-electron density becomes localized in the benzhydryl side chain while the positive charge becomes localized in the second portion of the molecule. Substitution in one diarylvinyl branch designed to delocalize odd-electron density but destabilize electron deficiency led to higher reactivity than the unsubstituted parent 1,1,5,5-tetraphenyl-3,3-dimethyl-1,4-pentadiene. The benzhydryldihydronaphthalene photoproducts themselves proved photochemically reactive. On sensitization, the benzhydryldihydronaphthalene reacted with a transannular 1,5-migration of one aryl group of the benzhydryl moiety. Where the two benzhydryl aryl groups were different, the cyanophenyl group migrated in preference to phenyl, and both diastereomers led to the same product stereoisomer. Ab initio and semiempirical computations were in accord with the radical cation and triplet regioselectivity.