The influence of the N -Ammonioalkyl substituent length on the structure and spectra of styryl dye complexes with cucurbit[7]uril

Spectral properties of inclusion complexes of cucurbit[7]uril (CB[7]) with styryl dye dications containing N -ammonioalkyl substituents of various length (D1, D2, D3) in water have been studied. The optimized structures of these complexes calculated by DFT methods made it possible to correlate the observed effects with the position of the nitrogen atom of the pyridinum residue of styryl dyes with respect to the CB[7] cavity. The bathochromic shifts of long-wavelength absorption bands for the inclusion complexes of D1 and D2 and the absence of such a shift for D3 are caused by structural distinctions between the inclusion complexes.