Zinc(II), Palladium(II), and Metal-Free Phthalocyanines Bearing Nipagin-Functionalized Substituents against Candida auris and Selected Multidrug-Resistant Microbes

Due to the rapidly increasing problem of antibiotic resistance in recent years, the use of phthalocyanines as photosensitizers with their superior properties in photodynamic antimicrobial therapy (PACT) applications has become important. In this study, magnesium(II) 1,4,8,11,15,18,22,25-octakis(4-[4-butoxycarbonylphenoxy]butyloxy)phthalocyanine was used in the demetalation reaction in trifluoroacetic acid, and subsequently subjected to metalation reaction in dimethylformamide with zinc(II) acetate and bis(benzonitrile)palladium(II) chloride towards zinc(II) and palladium(II) derivatives. Three phthalocyanines, including a demetalated one as well as two metalated, in the core with zinc(II) and palladium(II) were characterized using 1D and 2D NMR spectroscopy and mass spectrometry. In addition, all macrocycles were subjected to absorption and emission studies as well as photostability tests. In a photochemical study, zinc(II) and palladium(II) phthalocyanine complexes appeared to be efficient singlet oxygen generators. There were noted quantum yields of singlet oxygen generation for zinc(II) phthalocyanine derivative in DMF and DMSO at 0.55 and 0.72, whereas for palladium(II) complex at 0.73 and 0.77, respectively. Liposomal formulations of phthalocyanine derivatives were prepared, and their activity was evaluated against a broad spectrum of antibiotic-resistant microorganisms, such as methicillin-resistant Staphylococcus aureus (MRSA), Escherichia coli (ESBL+), Candida albicans resistant to fluconazole, C. auris, and against dermatophytes. Phthalocyanine palladium(II) complex showed the highest bactericidal activity against all antibiotic-resistant microorganisms, including reducing C. auris growth at 3.54 log.

Nipagin-Functionalized Porphyrazine and Phthalocyanine-Synthesis, Physicochemical Characterization and Toxicity Study after Deposition on Titanium Dioxide Nanoparticles P25

Aza-porphyrinoids exhibit distinct spectral properties in UV-Vis, and they are studied in applications such as photosensitizers in medicine and catalysts in technology. The use of appropriate peripheral substituents allows the modulation of their physicochemical properties. Phthalocyanine and sulfanyl porphyrazine octa-substituted with 4-(butoxycarbonyl)phenyloxy moieties were synthesized and characterized using UV-Vis and NMR spectroscopy, as well as mass spectrometry. A comparison of porphyrazine with phthalocyanine aza-porphyrinoids revealed that phthalocyanine macrocycle exhibits higher singlet oxygen generation quantum yields, reaching the value of 0.29 in DMF. After both macrocycles had been deposited on titanium dioxide nanoparticles P25, the cytotoxicities and photocytotoxicities of the prepared materials were studied using a Microtox® acute toxicity test. The highest cytotoxicity occurred after irradiation with a red light for the material composed of phthalocyanine deposited on titania nanoparticles.

Lipid vesicle-loaded meso-substituted chlorins of high in vitro antimicrobial photodynamic activity

Photodynamic inactivation potential against bacteria of four chlorin derivatives with phenyl or fluorophenyl substituents was evaluated. The quantum yield values of singlet oxygen formation were in the range of 0.16-0.86. Compounds were characterized by high quantum yields of fluorescence (0.15-0.44) and moderate photostability in DMF solutions. Irradiation of chlorins in DMSO resulted in their phototransformation and then photodecomposition. Photodynamic inactivation of bacteria was performed after the compounds had been loaded into lipid vesicles. The following log reductions of growth values were obtained: Enterococcus faecalis >5.44; Staphylococcus aureus 2.74-5.34; Escherichia coli 0.01-2.14. No activity of meso-substituted chlorins was noticed against Pseudomonas aeruginosa and fungi Candida albicans and Trichophyton mentagrophytes.

Photodynamic inactivation of Enterococcus faecalis by non-peripherally substituted magnesium phthalocyanines entrapped in lipid vesicles

Photophysical properties and photodynamic antibacterial potential of magnesium phthalocyanines bearing 2-propoxy, benzyloxy, 3,5-bis(benzyloxy)benzyloxy substituents at non-peripheral positions were studied. The UV-Vis absorption spectra of researched phthalocyanine derivatives were found typical. Extension of peripheral substituent size from 2-propoxy to benzyloxy and finally 3,5-bis(benzyloxy)benzyloxy was accompanied by the rise of quantum yield of fluorescence up to 0.17 and 0.04 in DMF and DMSO, respectively. Similarly, the expansion of the phthalocyanine periphery from the 2-propoxy to benzyloxy and 3,5-bis(benzyloxy)benzyloxy groups resulted in a detectable increase of the singlet oxygen quantum yield values to 0.04, 0.12, 0.14 respectively, which was assessed following direct method of singlet oxygen phosphorescence measurement at 1270 nm. Studied phthalocyanines undergo photobleaching process with the quantum yields at the level of 10^-6 in DMSO and 10^-5 in DMF. The size of phthalocyanine impacted the process of liposomal formulation. Small liposome vesicles containing non-peripherally substituted phthalocyanines with 2-propoxy and benzyloxy substituents were obtained following extrusion method. The unification process of the liposomes loaded with 3,5-bis(benzyloxy)benzyloxy non-peripherally substituted phthalocyanines was not possible. In in vitro antimicrobial photodynamic inactivation study, log reduction values of bacterial (Enterococcus faecalis) growth at 3.61 and 2.99 were achieved for liposomal formulations containing phthalocyanines with 2-propoxy and benzyloxy substituents respectively, whereas phthalocyanine with 3,5-bis(benzyloxy)benzyloxy substituents was inactive. Phthalocyanine with 2-propoxy substituents exhibited relatively low toxicity in Vibrio fischeri bioluminescence test, whereas phthalocyanine with benzyloxy substituents revealed intense bioluminescence, which could be associated with hormesis phenomenon.

Synthesis and photophysicochemical studies of non-metal 2,3,9,10,16,17,23,24-octacarboxyphthalocyanine

A new method of preparation and the properties (solubility, aggregation, spectralluminescent properties, singlet oxygen and photobleaching quantum yields) of non-metal 2,3,9,10,16,17,23,24-octacarboxyphthalocyanine are reported. The influence of ionization state on photophysicochemical properties of this dye is also presented.

Synthesis and investigation on photophysical and photochemical properties of 7-oxy-3-methyl-4-phenylcoumarin bearing zinc phthalocyanines

The synthesis of peripherally and non-peripherally tetrakis-(7-oxy-3-methyl-4-phenylcoumarin) and peripherally octakis-[tetrachlorotetra-(7-oxy-3-methyl-4-phenyl coumarin)] substituted zinc(II) phthalocyanines are performed and characterized for the first time in this study. The new compounds show excellent solubility in organic solvents, which makes them candidates for use in different applications. Photophysical (fluorescence quantum yields and lifetimes) and photochemical (singlet oxygen generation and photodegradation under light irradiation) properties of these novel coumarino phthalocyanines are investigated in dimethylformamide (DMF). The effects of the positions (peripheral or nonperipheral) of the substituents on the photophysical and photochemical parameters of the coumarino zinc(II) phthalocyanines are reported. The fluorescence quenching behavior of the studied zinc(II) phthalocyanines by addition of 1,4-benzoquinone (BQ) are also described.

Synthesis and photophysical properties of covalent conjugates of aqua platinum(II) and octacarboxy-substituted zinc phthalocyanine

New covalent conjugates of aqua platinum(II) and octacarboxy-substituted zinc phthalocyanine, bearing one, two, three and four aqua platinum moieties on the periphery of the Pc ligand have been synthesized and characterized. The effect of the stepwise introduction of the aqua platinums on the photophysical and photochemical properties of these compounds has been investigated in dimethylsulfoxide solution. It has been found that aqua platinum moieties have only a limited effect on the dynamics of the singlet and triplet excited states, on the ability to sensitize singlet oxygen formation and on the photostability. Each conjugate has a high singlet oxygen quantum yield (ΦΔ 0.51–0.62) and thus retains potential for use as a dual action anticancer drugs by acting as a sensitizer for PDT in addition to the likely chemotherapeutic effects of the Pt(II) complexes.

Oxidative photobleaching of phthalocyanines in solution

Metallophthalocyanines form a very important class of commercial dyes and have achieved significant success in a variety of applications, in which their photostability is of fundamental importance. On this ground, considerable data on phthalocyanine photobleaching were published over recent years. We do not intend to give exhaustive compilation of the photobleaching quantum yields, which are known for wide circle of phthalocyanines in different solvents. This review begins by discussing pertinent background information about processes following phthalocyanine excitation. Then using selected examples of the recent literature, including authors' works, we survey a variety of photobleaching effects from the fundamental origins to specific for phthalocyanine chromophore. Finally, the mechanisms of phthalocyanine oxidative photobleaching are discussed.

New heterogeneous photosensitizers with phthalocyanine molecules covalently linked to aminopropyl silica gel

New heterogeneous photosensitizers were synthesized, in which phthalocyanines of zinc and aluminum, tetrasubstituted at non-peripheral positions with modified thiophenyl groups, were grafted to aminopropyl silica gel. The absorption and fluorescence spectra, and the quantum yields of fluorescence and photosensitized singlet oxygen generation were estimated for aqueous suspensions of these sensitizers. It is shown that upon photoexcitation, silica gel-bound phthalocyanines produce singlet oxygen and display photobactericidal activity against bacteria E. coli.