Abstract
The influence of albumin and amino acids (l-serine, glycine, l-histidine, l-tryptophan, l-cysteine) on the properties of aluminum octacarboxyphthalocyanine hydroxide (Al(OH)PcOC) was investigated in a phosphate buffer (pH 8.0). Particular attention was paid to the spectroscopic properties and photostability of Al(OH)PcOC. The effect of albumin or amino acids on the photodegradation of Al(OH)PcOC was examined in water using red light: 685 nm and daylight irradiation. Analysis of kinetic curves indicated that interaction with those molecules increases the photostability of Al(OH)PcOC. The molecular structure of Al(OH)PcOC complexes (in vacuum and in water) with axially or equatorially coordinated amino acids was studied by the B3LYP/6-31G* method, and the effects on molecular structure and electronic absorption spectrum were investigated on the basis of the density functional theory. The calculation results revealed that axial coordination significantly reduces the non-planarity of the phthalocyanine ring, and, thus, alters the electronic structure. On the other hand, hydrogen bonding of phthalocyanine side COOH groups with amino acids, in equatorial complexes, does not change the structure within the center of the phthalocyanine, and causes only a slight increase in UV–vis bands intensity, which is in perfect agreement with experimental data.Graphical abstractStructure of equatorial complex of Al(OH)PcOC with l-histidine calculated byB3LYP/6-31G(d) method. Dotted lines H-bonds
Highlights
Phthalocyanines (Pcs) are structural analogues of porphyrins, but, in contrast to the latter, they are not found in nature and are obtained solely by chemical synthesis [1]
Due to strong π–π interaction and the flatness of the aromatic cores, have a tendency to aggregate in solutions, which, for this type of complex, is a well-known feature widely described in the literature [12, 26,27,28,29]
In photodynamic therapy (PDT), association is a negative phenomenon, i.e., it has an unfavorable effect on the physicochemical features of photosensitizers and decreases efficiency of generating reactive oxygen species (ROS), which causes a meaningful weakness in the cytotoxicity of a potential drug [30,31,32]
Summary
Phthalocyanines (Pcs) are structural analogues of porphyrins, but, in contrast to the latter, they are not found in nature and are obtained solely by chemical synthesis [1]. Pcs compounds can form complexes with most elements [2]. Due to their spectroscopic and photoelectric properties, as well as excellent chemical and thermal stability in different environments, substituted Pcs have been studied extensively, especially in recent years [3]. The complexes of Pcs containing metals such as Al3+, Ga3+ and Zn2+ are interesting because these molecules have a high triplet quantum yield and long triplet lifetimes. These properties are necessary for high singlet oxygen quantum yields, and guarantee high cytotoxicity against
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