Effects of the degree of substitution on the physicochemical properties and photodynamic activity of zinc and aluminum phthalocyanine polycations

Effect of pH on Acid-Base and Photophysicochemical Properties of 2,3,9,10,16,17,23,24-Octacarboxyphthalocyanines in Aqueous Media

“…However, it is known that for cationic aluminum and zinc phthalocyanines, correspondingly, about four and six charged groups per molecule are needed for monomerization. [24] Increase of pH of MPc oc solutions results in progressive dissociation of carboxyl groups and accumulation of negative charge on the periphery of molecule and, when electrostatic repulsion becomes sufficient, dye monomerization. Since in MPc oc the adjacent carboxyl groups exert the most efficient acceptor impact at each other, and by analogy with o-phthalic acid (pK a are 2.95 and 5.41), [25] it is reasonable to simplify multi-step ionization of carboxyl groups in MPc oc to two-step process, with pK a of first four carboxyl groups (one on each of four benzene rings of macrocycle) ionization standing far apart from those of other four ones.…”

“…The selective excitation of differently ionized ZnPc oc in the Q absorption band resulted in disappearance of DPBF (example for ZnPc oc acid is given in Figure 5). The DPBF absorption at 416 nm was monitored and the decrease in absorbance was Octaanion (pH 7.4) 690 224000 700 0.18 (pH 10) [23] 0.57 (PBS, pH 7.4) [24] 1.0•10…”

The synthesis and photophysical properties of novel cationic tetra pyridiloxy substituted aluminium, silicon and titanium phthalocyanines in water

“…For example, for a series of zinc and aluminium phthalocyanines substituted with pyridiniomethyl groups, as the number of cation substituents increased, the aggregation ability of phthalocyanines were found to decrease in aqueous media, and the quantum yields of fluorescence and singlet oxygen generation increased as well as the photodynamic inactivation of bacteria [25,26]. The reason for such monomeric state of these complexes was attributed to strong electrostatic repulsive force of eight charges thereby preventing the formation of the aggregates [25].…”

Hybrid structures of polycationic aluminum phthalocyanines and quantum dots

“…In such clusters we observe fast nonradiative relaxation of excited states leading to the decrease in 3 PC* amount and ROS generation quantum yield. The incorporation of charged substitutes at the ring periphery decreases the clustering of PCs [18].…”

“…The absorption spectrum of polyanionic phthalocyanines in complex with QDs is almost equal to the sum absorption spectra of the individ ual substances; however, the interaction of QDs with polycationic phthalocyanines leads to a significant distur bance of the spectrum of the latter [38]. The number of charged substituents in phthalocyanine structures is known to influence their ability for aggregation, hence defining the photophysical and photochemical properties of these substances [18].…”