Luminescence spectrum of dyes based on zinc phthalocyanine with galactopyranosyl radicals

The results of investigations of luminescence spectra of solutions of newly synthesized phthalocyanines dyes in dimethylsulfoxide (DMSO) in dependence on excitation wavelengths are presented. These dyes are compounds of zinc phthalocyanine (ZnPc) with D-galactopyranosyl radicals (Gal) located in the peripheral (p-GalZnPc) and nonperipheral (n-GalZnPc) positions with respect to the ZnPc macrocycles.
Excitation luminescence in dye solutions of ZnPc, n-GalZnPc and p-GalZnPc in DMSO and DMSO alone in ultraviolet (UV) light radiation leads to the observing of two wavelengths peaks in the luminescence spectral-respectively in 325-550 nm and 650-750 nm wavelength ranges. "Red" luminescence band in the wavelength range 650-750 nm observed at DMSO disappear when the excitation wavelength is more than 360 nm.
The luminescence spectra of dye solutions of n-GalZnPc and p-GalZnPc in DMSO are markedly different from one another and have a complex dependence on the wavelength of the exciting light.
It was shown that the peaks of luminescence spectra of solutions of dyes ZnPc, n-GalZnPc and p-GalZnPc in DMSO are shifted relative to the solvent luminescence peak in the UV-wavelengths range at the same excitation wavelength.
It was found that at increasing of excitation wavelength in the range near a wavelength of 320 nm there is an abrupt change in the position of peak of "red" luminescence band of p-GalZnPc and n-GalZnPc dyes - with 15 and 41 nm red shifts, respectively.
In the red region of the luminescence spectra of dye solutions of investigated compounds in DMSO, stepwise changes of positions and widths of the luminescence peaks lines was observed by increasing the excitation wavelength in the range 300-320 nm. The observed effect is more pronounced for n-GalZnPc dye solution in DMSO.
The complex dependence of the luminescence spectra of solutions of dyes p-GalZnPc and n-GalZnPc in DMSO may be caused by the intersystem interaction of the energy levels of compounds and the solvent dye in solution, that require further research.