Photoprocesses of Bisthiacarbocyanine Dyes in the Presence of Cucurbit[7,8]urils in Water

Spectral, spectral–kinetic, and photochemical properties of bisthiacarbocyanine (bis-TCC) dyes, based on 3,3′-dimethylthiacarbocyanine perchlorate, in water have been studied. The existence of two bis-TCC forms absorbing in the long-wavelength (monomeric form) and short-wavelength (dimeric form) spectral regions has been revealed. The monomeric form of bis-TCC is capable of fluorescence, photoisomerization, and transition to the triplet state. The dimeric form is characterized by effective intersystem crossing, the almost complete absence of fluorescence, and photoisomerization. Both the monomeric and dimeric forms of bis-TCC undergo complexation with cucurbit[7,8]urils. Complex formation leads to an increase in the fluorescence intensity of the monomeric and dimeric forms and increases the yield of delayed fluorescence and the lifetime of the dimeric form in the triplet state and those of the photoisomer of the monomeric form. The dimeric form of bis-TCC in the triplet state is capable of entering into the photooxidation reaction with p-nitroacetophenone both in the absence and in the presence of cucurbit[7,8]urils.