Isomerization and Properties of Isomers of Carbocyanine Dyes

Abstract

One of the important features of polymethine (cyanine) dyes is isomerization about one of C–C bonds of the polymethine chain. In this review, spectral properties of the isomers, photoisomer-ization and thermal back isomerization of carbocyanine dyes, mostly meso-substituted carbocy-anine dyes, are considered. meso-Alkyl-substituted thiacarbocyanine dyes are present in polar solvents mainly as cis isomers and, hence, exhibit no photoisomerization, whereas in nonpolar solvents, in which the dyes are in the trans form, photoisomerization takes place. In contrast, the meso-substituted dyes 3,3′-dimethyl-9-phenylthiacarbocyanine and 3,3′-diethyl-9-(2-hydroxy-4-methoxyphenyl)thiacarbocyanine occur as trans isomers and exhibit photoisomerization in both polar and nonpolar solvents. The behavior of these dyes may be ex-plained by the fact that the phenyl ring of the substituent in their molecules can be twisted at some angle, removing the substituent from the plane of the molecule and reducing its steric ef-fect on the conformation of the trans isomer. In some cases, photoisomerization of cis isomers of meso-substituted carbocyanine dyes is also observed (for some meso-alkyl-substituted dyes com-plexed with DNA and chondroitin-4-sulfate; for 3,3′-diethyl-9-methoxythiacarbocyanine in moderate polarity solvents). The cycle photoisomerization–thermal back isomerization of cya-nine dyes can be used in various systems of information storage and deserves further investiga-tion using modern research methods.

Characterization, Stability, and Antibrowning Effects of Oxyresveratrol Cyclodextrin Complexes Combined Use of Hydroxypropyl Methylcellulose

“…Approximately 60.01% of total Oxy remained after storage in HPMC solution. It is worth noting that almost no cis -Oxy was formed in the HPMC solution, which is very consistent with the earlier findings that viscosity is the main solvent property that affects the isomerization kinetics [ 52 ]. The Oxy–CD–HPMC ternary complex has the advantages of CD and HPMC.…”

Dynamics of Excitons in Conjugated Molecules and Organic Semiconductor Systems

“…Examples of photochromic molecules that demonstrate (a) isomerization and (b) cyclization upon photoexcitation. Whereas stilbenes, azobenzenes, and unsubstituted carbocyanines are able to undergo reversible photoisomerization, meso-substituted carbocyanine, styrene, rhodopsin, and bilirubin undergo irreversible photoisomerization with only one preferred isomer.…”

Co-assembling system that exhibits bright circularly polarized luminescence

“…4e). 20 Therefore, we conclude that exciton coupling occurred among the embedded NK-77 molecules without direct stacking, but with a distance between them. Embedding NK-77 in the tightly packed cavity is accompanied by restriction of the internal rotations, including photoisomerization to the cis form.…”

“…NK-77, which have a meso -methyl substituent, in polar ethanol should form the cis isomer with a higher intramolecular degree of freedom. 20 Restriction of the internal rotation of the embedded NK-77 molecules also resulted in increases in both absorbance and emission. The absorbance was 2.5 times higher than that of NK-77 in ethanol (Fig.…”