Effect of cucurbit[8]uril on the spectral and luminescent properties of alkyl-substituted thiacarbocyanines

Abstract

In the presence of cucurbit[8]uril, polymethine dyes 3,3’-dimethylthiacarbocyanine (DMCy) and 3,3’-diethylthiacarbocyanine (DECy) in aqueous solution can form both nonfluorescing D@CB8 and fluorescing D@2CB8 dimer complexes. The D@2CB8 complexes with DMCy have a symmetrical narrow absorption band. The substitution of the СН₃ group in DMCy for the С₂Н₅ group in the DECy molecule results in a difference in the absorption spectra of the dimeric dye complexes. Quantum chemical calculations show a difference in structure between the dimeric complexes for DMCy and DECy. The enthalpies of dimerization of DMCy and DECy in water and of the formation of complexes D@CB8 and D@2CB8 are close.