Aggregation behavior and UV-vis spectra of tetra- and octaglycosylated zinc phthalocyanines

Abstract

Several tetra- and octaglycosylated PcZn 's 1a, 2a–2d, 3a-b and 4 were investigated for their aggregation behavior using different concentrations of the PcZn -species in pure DMSO, water and in various DMSO/water mixtures by comparing their UV-vis spectra. The PcZn 's 1–4 are independent of the concentration in pure DMSO and in up to 25 vol.% water/DMSO mixtures are non aggregated. Increasing amounts of water leads to higher aggregation ratios. The aggregation behavior is influenced by the nature and the position of the sugar substituents on the Pc-ring. PcZn 4 was found the least aggregated compound even in pure water.

Synthesis and photophysics of an octathioglycosylated zinc(II) phthalocyanine

“…Notably, the spectrum in DMSO shows defined peaks and no apparent aggregation, but the marked decrease and broadening of the Q-band at 727 nm in both less polar solvents and phosphate buffered saline (PBS) indicates significant aggregation of this compound. 25 Similarly, there is a gradual decrease and broadening of this Q band with increasing amounts of water in the DMSO solution. The nearly 60 nm blue shift of both the Q bands and somewhat smaller blue shift in the B bands in the optical spectra in these solvents indicates the ZnPcGlc 8 aggregates are generally in a cofacial arrangement (H-aggregates).…”

Synthesis and Isolation of 2,9,17,23-Tetrakis[(3,5-dimethyl-1H-pyrazol-1-yl)phenoxy]phthalocyanine and Its Magnesium(II) and Zinc(II) Complexes

“…For generation of singlet oxygen from the phthalocyanines their aggregation behavior in different solvents therefore is an important issue. [53] Aggregation is usually depicted as a coplanar association of phthalocyanine rings progressing from monomer to dimer and higher order complexes. It is dependent on concentration, nature of the solvent, nature of the substituents, complexed metal ions and temperature.…”

“…However, Lambert-Beer's law is obeyed in the concentration ranging only from 0 to 5•10 -6 M. This phenomenon can be caused by the fact that DMF, being a coordinating solvent also as DMSO, binds axially to the central metal of metal phthalocyanines reducing their aggregation tendency. [53] …”

Photophysical and Photochemical Properties and Aggregation Behavior of Phthalocyanine and Naphthalocyanine Derivatives

“…This aggregation influences their photophysical and photochemical properties leading to disadvantages such as fluorescence quenching, lesser generation of singlet oxygen and loss of catalytic activity. 8,9 Several works demonstrated that the aggregation behavior is influenced by many factors, e.g. strong π-π electron interactions, coulombic forces, central metal, position and size of the substituents, axial substituents on the central metal, temperature and solvent.…”