Synthesis, characterization and comparative studies on the photophysical and photochemical properties of metal-free and zinc(II) phthalocyanines with phenyloxyacetic acid functionalities

The synthesis and characterization of new peripherally and non-peripherally tetra-substituted metal-free and zinc(II) phthalocyanines with 2-, 3- and 4-phenyloxyacetic acid functionalities are described for the first time in this study. The new compounds have been characterized by elemental analysis, FT-IR, UV-Vis, MALDI-TOF and ¹H-NMR spectra. Photodegradation, singlet oxygen and fluorescence quantum yields, and fluorescence lifetimes of these compounds are studied in dimethylformamide (DMF). The influence of the substituent position on the phthalocyanine framework (non-peripherally or peripherally), central metal ion (metal-free or zinc) and the position of the COOH group (2-, 3- or 4-position on the phenyloxyacetic acid) on the spectroscopic, photophysical and photochemical properties have been investigated. Non-peripherally zinc(II) phthalocyanines (1b and 2b) and peripherally zinc(II) phthalocyanine (4b) gave good singlet oxygen quantum yields (Φ_Δ) (0.37, 0.39 and 0.38, respectively) which indicate the potential of the complexes as photosensitizers in applications of PDT.     

Multi-electron transfer processes for molecular conversions

Multi-electron transfer plays an important role in many chemical reactions. A collection of examples, both of metal complexes that exhibit one-step, multi-electron transfer process, and of chemical reactions based on a multi-electron transfer system, is presented. Emphasis is placed on the role of multi-electron transfer process in a sense that some molecular conversion systems such as reduction of O₂ and oxidation of H₂O become feasible through multi-electron transfer. As an important example of molecular conversion, oxidative polymerization of sulfur-containing compounds through two-electron transfer, is also reviewed.     

Oxidation and photooxidation of sulfide and thiosulfate ions catalyzed by transition metal chalcogenides and phthalocyanine complexes

The catalytic and photocatalytic activities of supported cobalt or zinc phthalocyanine complexes, bulk MoS₂, MoS₂ deposited on Al₂O₃, potassium intercalated MoS₂ (K_0.33 H₂O_0.66 MoS₂), CdS and polycrystalline nickel phosphorus trisulfide (NiPS₃) have been investigated in the oxidation of sodium sulfide and Na₂S₂O₃. The phthalocyanine complexes and the metal chalcogenides do not catalyze, in the absence of light, the complete oxidation of the sulfide ion to sulfate ion. The final product of the catalytic oxidation is the formed thiosulfate. No oxidation of Na₂S₂O₃ has been registered in the dark in the presence of any of the catalytic samples. Their activity was enhanced upon irradiation with visible light. Thiosulfate appears to be the final product also of the photooxidation of the sulfide ion catalyzed by metal chalcogenides. They do not catalyze the further photooxidation of Na₂S₂O₃. The only photocatalysts which favour with their presence the oxidation of the sulfide and thiosulfate ions to sulfate ion, are the zinc phthalocyanine complexes. In this case, the photooxidation process involves singlet oxygen.     

Phthalocyanines prepared from 4-chloro-/4-hexylthio-5-(4-phenyloxyacetic acid)phthalonitriles and functionalization of the related phthalocyanines with hydroxymethylferrocene

The phthalonitrile derivative chosen for the synthesis of substituted phthalocyanines [M: 2H, Zn(II), Co(II)] with four chloro and four phenyloxyacetic acid substituents on the periphery is 4-chloro-5-(4-phenyloxyacetic acid)phthalonitrile. The sodium salt of carboxyl substituted zinc phthalocyanine is good soluble in water. Further reactions of zinc and cobalt phthalocyanines bearing phenyloxyacetic acid with thionylchloride gave the corresponding acylchlorides. This functional group reacted with hydroxymethylferrocene in dry DMF to obtain ferrocenyl substituted phthalocyanines. Also chloro substituent in new phthalonitrile was substituted with hexylsulfanyl substituent and its cyclotetramerization in the presence of Zn(AcO)₂·2H₂O and 2-(dimethylamino)ethanol resulted with zinc phthalocyanine. The compounds have been characterized by elemental analysis, MALDI-TOF mass, FT-IR, ¹H NMR, UV-Vis and fluorescence data. Aggregations properties of phthalocyanines were investigated at different concentrations in tetrahydrofuran, dimethylformamide, dimethylsulfoxide, water, and water/ethanol mixture. Also fluorescence spectral properties are reported.     

Synthesis,Supramolecular Behavior,and In Vitro Photodynamic Activities of Novel Zinc(II) Phthalocyanines “Side‐strapped” with Crown Ether Bridges

Two new tetra‐ or di‐α‐substituted zinc(II) phthalocyanines 5 and 6 have been prepared through a “side‐strapped” method. In the molecules, the adjacent benzene rings of the phthalocyanine core are linked at α‐position through a triethylene glycol bridge to form a hybrid aza‐/oxa‐crown ether. The tetra‐α‐substituted phthalocyanine 5 shows an eclipsed self‐assembly property in CH₂Cl₂ and the effect on the di‐α‐substituted analogue 6 is significantly weakened. Furthermore, the crown ethers of these compounds can selectively complex with Fe³⁺ or Cu²⁺ ion in DMF, leading to formation of J‐aggregated nano‐assemblies, which can be disaggregated in the presence of some organic or inorganic ligands, such as triethylamine, tetramethylethylenediamine, CH₃COO^?, or OH^?. In addition, both compounds are efficient singlet oxygen generators with the singlet oxygen quantum yields (Φ_Δ) of 0.54‐0.74 in DMF relative to unsubstituted zinc(II) phthalocyanine (Φ_Δ=0.56). They exhibit photodynamic activities toward HepG2 human hepatocarcinoma cells, but the compound 6 , which has more than 40‐fold lower IC₅₀ value (0.08 μM ) compared to the analogue 5 (IC₅₀=3.31 μM ), shows remarkablely higher in vitro photocytotoxicity due to its significantly higher cellular uptake and singlet oxygen generation efficiency. The results suggest that these compounds can serve as promising multifunctional materials both in (opto)electronic field and photodynamic therapy.     

Phthalocyanines formed from several precursors: synthesis,characterization, and comparative fluorescence and quinone quenching

Abstract

We have synthesized a new phthalonitrile with different substituents in 4- and 5-positions (1). Cyclotetramerization of 1 yielded phthalocyanines with cobalt(II) (2), zinc(II) (3), gallium(III)chloride (4), and indium(III)chloride (5) containing diethylamino-phenoxy and hexylsulfanyl substituents on each benzene unit. Elemental analyses, Fourier transform infrared spectra, ¹H-nuclear magnetic resonance spectra, mass spectra, and ultraviolet-visible spectra were used for characterization of the phthalocyanines. The aggregation behavior of the zinc phthalocyanine derivative was studied in different concentrations. Also four chloro and four diethyllaminophenoxy substituted zinc phthalocyanine (6) and octa-diethylaminophenoxy substituted zinc phthalocyanine (7) were synthesized. These phthalocyanines (3, 6, and 7) were compared for electronic absorption spectra, fluorescence quantum yields, fluorescent lifetimes, and fluorescence quenching in the presence of benzoquinone. The fluorescence quantum yield gives the efficiency of the fluorescence process. The fluorescence lifetime is an important parameter for practical applications of fluorescence such as fluorescence resonance energy transfer and fluorescence-lifetime imaging microscopy.     

Synthesis, characterization, spectroscopic and electrochemical properties of phthalocyanines substituted with four 3-ferrocenyl-7-oxycoumarin moieties

The synthesis, spectroscopic and electrochemical properties of the tetra-(3-ferrocenyl-7-oxycoumarin)-substituted zinc (II) and cobalt (II) phthalocyanines (3 and 4) are reported for the first time. The synthesis of novel 3-ferrocenyl-7-hydroxycoumarin (1) was performed according to Perkin reaction, and the ligand, 7-(3,4-dicyanophenoxy)-3-ferrocenylcoumarin (2), was synthesized by the reaction of 3-ferrocenyl-7-hydroxycoumarin with 4-nitrophthalonitrile in the presence of K₂CO₃ as the base in dry dimethylformamide. The preparation of the corresponding zinc (II) and cobalt (II) metallo phthalocyanines (3 and 4) substituted with 3-ferrocenyl-7-oxycoumarin moieties at β-positions of the phthalocyanine ring was achieved by the cyclotetramerization of the coumarin ligand (2) with relevant metal(II) acetates in dry 2-dimethylaminoethanol. The new compounds have been characterized by elemental analyses, FT-IR, ¹H NMR, Mass and electronic spectroscopy. The fluorescence property of the zinc metallo phthalocyanine (3) is strongly affected by the presence of ferrocenyl moiety. The ferrocenyl moieties were very efficient in quenching the excited state of 3, which show very poor fluorescent intensity. The electrochemical properties of the complexes were also investigated by cyclic and differential pulse voltammetry techniques in non-aqueous medium. It was found that the redox-active ferrocene substituents are reduced concurrently at one potential.     

Comparing Singlet Oxygen Generation of Schiff Base Substituted Novel Silicon Phthalocyanines by Sonophotochemical and Photochemical Applications

Although the sonophotodynamic method has an effective therapeutic outcome for anticancer treatment compared with the photodynamic method, there are not enough related studies in the literature and this study aims to contribute to the development of sonophotodynamic studies. For this purpose, the Schiff base substituted silicon phthalocyanines were designed and synthesized as effective sensitizer candidates and the photophysicochemical and sonophotochemical features of the phthalocyanines were examined to increase singlet oxygen efficiency. The calculated Φ_Δ values indicate that the contribution of substituent groups improved the production of singlet oxygen compared with silicon (IV) phthalocyanine dichloride (SiPcCI₂) and also the sonophotochemical applications increased the singlet oxygen yields. The Φ_Δ values (Φ_Δ = 0.76 for axially bis-{4-[(E)-(pyridin-3-ylimino)methyl]phenol} substituted silicon (IV) phthalocyanine ( 2a ), 0.68 for axially bis-4-[(E)-{[(pyridin-3-yl)methyl]imino}methyl]phenol substituted silicon (IV) phthalocyanine ( 2b ) in photochemical study) reached to Φ_Δ = 0.98 for 2a , 0.94 for 2b in sonophotochemical study. This article will enrich the literature on increasing singlet oxygen yield.     

Synthesis,electrochemical, in situ spectroelectrochemical and in situ electrocolorimetric characterization of new phthalocyanines peripherally fused to four flexible crown ether moieties

Novel Ni(II), Zn(II), Co(II) and Cu(II) phthalocyanines with four peripheral 4-[methyleneoxy(18-crown-6)] groups have been synthesized via the cyclic tetramerization of 4-[{(18-crown-6)-yl}methyleneoxy]phthalonitrile and the corresponding metal salts (NiCl₂, Zn(CH₃COO)₂, CoCl₂ and CuCl₂). The thermal stabilities of the metal-free and metallophthalocyanine compounds were determined by thermogravimetric analysis. The structures of the target compounds were confirmed using elemental analysis, IR, ¹H-NMR, ¹³C-NMR, UV–Vis and MS spectral data. Voltammetric and in situ spectroelectrochemical measurements show that while the cobalt phthalocyanine complex gives both metal-based and ring-based redox processes, the metal-free, nickel, zinc and copper phthalocyanines show only ring-based reduction and oxidation processes. An in situ electrocolorimetric method has been applied to investigate the color of the electro-generated anionic and cationic forms of the complexes.     

Comparison between non-peripherally and peripherally tetra-substituted zinc (II) phthalocyanines as photosensitizers: Synthesis,spectroscopic, photochemical and photobiological properties

A series of zinc phthalocyanines tetra-α-substituted with 4-(butoxycarbonyl) phenoxy groups (1a) or 4-carboxylphenoxy groups (2a) or 4-(2-carboxyl-ethyl)phenoxy groups (3a), and the corresponding tetra-β-substituted (1–3b) analogues, have been synthesized and characterized. The effects of the position of substituents at the phthalocyanine skeleton on their spectroscopic, photochemical and photobiological properties have been revealed. When compared with the tetra-β-substituted phthalocyanines, the corresponding tetra-α-substituted analogues exhibit a less aggregating trend in the cellular growth medium, a slightly higher singlet oxygen quantum yield and higher photo-stability in DMF, and a comparable cellular uptake. As a result, the tetra-α-substituted zinc phthalocyanines exhibit a higher photocytotoxicity toward MGC803 human gastric carcinoma cells than the tetra-β-substituted counterparts. Among all these compounds, phthalocyanine 2a shows the highest photodynamic activity, which may mainly be due to its non-aggregated nature in cellular culture medium and high cellular uptake.     

Synthesis and characterization of functionalized silicon phthalocyanines for fabrication of self-assembled monolayers

Novel octasubstituted phthalocyanine derivatives XYSiPc(OR)₈ (X=alkyl, Y=alkoxy, R=alkane or alkene) were synthesized by reaction of alkoxy-substituted diiminoisoindolines with XSiCl₃ followed by quenching with an alcohol YOH. Three synthetic routes for adding anchoring groups to the phthalocyanines were explored: variation of the axial groups X and Y, or incorporation of vinyl groups around the periphery of the phthalocyanine ring. The latter approach yielded silicon and copper phthalocyanines with eight terminal vinyl groups, which reacted cleanly with thioacetic acid/AIBN to give products with eight protected terminal thiols.     

Highly soluble tetra lauryl alcohol substituted phthalocyanines; synthesis,electrochemistry, spectroelectrochemistry

The tetra peripherally β-substituted 2(3),9(10),16(17),23(24)-tetrakis undecyloxy phthalocyanine derivatives, M{Pc[O-(CH₂)₁₁CH₃)]₄} Pc: Phthalocyanine, [M: Zn(II)(2), Ga(III)(3), and Ti(IV)(4)], have been synthesized and characterized using FT-IR, ¹H, and ¹³CNMR, MS (MALDI-TOF), UV–vis, atomic force microscopy, electro and spectroelectro chemical and elemental analysis. The new synthesized complexes are soluble in both polar solvents and nonpolar solvents, such as THF, DMF, CHCl₃, CH₂Cl_2, benzene, and even hexane. Electrochemical and spectroelectrochemical measurements give common metal-based and/or Pc ring-based redox processes which support the proposed structures of the complexes. While titanium phthalocyanine exhibits metal- and Pc ring-based reduction and/or oxidation couples, gallium and zinc phthalocyanines give only Pc ring-based electron transfer processes.     

Synthesis, photophysical and photochemical properties of substituted zinc phthalocyanines

The synthesis, photophysical and photochemical properties of the 4-({3,4,5-tris-[2-(2-ethoxyethoxy)ethyloxy]benzyl}oxy) and 4-({3,4,5-tris-[2-(2-ethoxyethoxy)ethyloxy]benzyl}thio) zinc(ii) phthalocyanines are reported for the first time. The new compounds have been characterized by elemental analysis, IR, (1)H and (13)C NMR spectroscopy, electronic spectroscopy and mass spectra. General trends are described for photodegradation, singlet oxygen, fluorescence and triplet excited state quantum yields, and triplet state and fluorescence lifetimes of these compounds in dimethylsulfoxide (DMSO). The fluorescence of the complexes was quenched by benzoquinone (BQ). The effects of the substitution on the photophysical and photochemical parameters of the zinc(II) phthalocyanines (6, 7 and 8) are also reported. Photophysical and photochemical properties of phthalocyanine complexes are very useful for PDT applications. The substituted Zn(II) phthalocyanines showed high triplet and singlet oxygen quantum yields. High singlet oxygen quantum yields are very important for Type II mechanism. Thus, these complexes show potential as Type II photosensitizers.     

Photophysics of Zinc (II) Phthalocyanine Polymer and Gel Formulation

The photophysical properties of lipophilic phthalocyanines encapsulated into a polymer and two different gels were studied in order to predict their photosensitizing efficacy in vivo. Photophysical techniques for solid phase were adapted for light dispersing samples. Gel formulation of two tetrasubstituted phthalocyanines, tetra-t-butylphthalocyaninato zinc(II) ( 1 ), tetrakis(1,1-dimethyl-2-phthalimido)ethylphtalocyaninatozinc(II) ( 2 ) and two octasubstituted phthalocyanines, 2,3,9,10,16,17,23,24-octakis(decyloxy)phthalocyaninatozinc(II) ( 3 ) and 2,3,9,10,16,17,23,24-octakis[(N,N-dimethylamino)ethylsulfanyl]phthalocyaninatozinc(II) ( 4 ) were investigated for their possible use in photodynamic therapy for topical purposes. Supporting the fact that gel formulation improves the photophysical properties of phthalocyanines, singlet molecular oxygen quantum yield (Φ_Δ) values for 1 – 4 zinc(II) phthalocyaninates in Lutrol^® F 127-Cremophor^® RH 40 were 0.60, 0.60, 0.20 and 0.26, respectively. Permeation studies showed that no release of phthalocyanines occurs, thus indicating there should be no risk of generalized skin photosensitivity in areas other than the dye-deposition site.     

Photophysicochemical and fluorescence quenching studies of benzyloxyphenoxy-substituted zinc phthalocyanines

Photochemical and photophysical measurements were conducted on peripheral and non-peripheral tetrakis- and octakis(4-benzyloxyphenoxy)-substituted zinc phthalocyanines (1, 2 and 3). General trends are described for photodegradation, and fluorescence quantum yields, triplet lifetimes and triplet quantum yields as well as singlet oxygen quantum yields of these compounds in dimethylsulphoxide (DMSO) and toluene. The fluorescence of the complexes is quenched by benzoquinone (BQ), and fluorescence quenching properties are investigated in DMSO and toluene. The effects of the solvents on the photophysical and photochemical parameters of the zinc(II) phthalocyanines (1, 2 and 3) are also reported. Photophysical and photochemical properties of phthalocyanine complexes are very useful for PDT applications.     

Synthesis, photophysical and photochemical properties of poly(oxyethylene)-substituted zinc phthalocyanines

The synthesis, photophysical and photochemical properties of the tetra- and octa-poly(oxyethylene)substituted zinc (II) phthalocyanines are reported for the first time. The new compounds have been characterized by elemental analysis, IR, 1H and 13C NMR spectroscopy, electronic spectroscopy and mass spectra. General trends are described for photodegradation, singlet oxygen, triplet state and fluorescence quantum yields, and triplet and fluorescence lifetimes of these compounds in dimethylsulfoxide (DMSO). Photophysical and photochemical properties of phthalocyanine complexes are very useful for PDT applications. The effects of the substituents on the photophysical and photochemical parameters of the zinc(II) phthalocyanines (3a, 5a and 6a) are also reported. The singlet oxygen quantum yields (Phi(Delta)), which give an indication of the potential of the complexes as photosensitizers in applications where singlet oxygen is required (Type II mechanism) ranged from 0.60 to 0.72. Thus, these complexes show potential as Type II photosensitizers. The fluorescence of the complexes was quenched by benzoquinone (BQ).     

Novel nonperipheral octa-3-hydroxypropylthio substituted metallo-phthalocyanines: synthesis,characterization, and investigation of their electrochemical,photochemical and computational properties

The current study describes the synthesis, electrochemical, computational, and photochemical properties of octa (3-hydroxypropylthio) substituted cobalt (II) ( 4 ), copper (II) ( 5 ), nickel (II) ( 6 ) and zinc(II) ( 7 ) phthalocyanine derivatives. These novel compounds were characterized by elemental analysis,¹H,¹³C NMR, FT-IR, UV-Vis, and MS. The redox behaviors of these metallo-phthalocyanines were investigated by the cyclic voltammetric method. The optimized molecular structure and gauge-including atomic orbital (GIAO)¹H and¹³C NMR chemical shift values of these phthalocyanines in the ground state had been calculated by using B3LYP/6–31G(d,p) basis set. The outcomes of the optimized molecular structure were given and compared with the experimental NMR values. The photochemical properties including photodegradation and singlet oxygen generation of zinc(II) phthalocyanine were studied in DMSO solution for the determination of its photosensitizer behaviors.     

Oxidation of benzyl alcohol by novel peripherally and non-peripherally modular C2-symmetric diol substituted cobalt (II) phthalocyanines

In this study, a modular ligand structure was designed by altering the binding position of the phenyl group at backbone of hydrobenzoin. A series of regio isomeric substituted phthalonitriles derived from this modular C₂-symmetric ligand was synthesized and characterized. Then, eight cobalt (II) phthalocyanines (CoPc) were obtained from the reaction of phthalonitrile derivatives with cobalt (II) chloride. The catalytic activities of synthesized cobalt (II) phthalocyanines were tested for benzyl alcohol oxidation in acetonitrile using tert-butylhydroperoxide as the oxygen source and in the presence of N-bromosuccinimide as an additive at 80 °C for 5 hr of the reaction. In this sense, the effect of substrate to catalyst ratio and oxidant to catalyst ratio have been studied in detail for getting the highest benzaldehyde selectivity (up to 83%). The effect of structural design of substituents at peripheral or non-peripheral positions of phthalocyanine skeleton on the catalytic activity performance of cobalt (II) phthalocyanines in benzyl alcohol oxidation was also clarified. All newly synthesized compounds are characterized by FT-IR, ¹H NMR, IR, UV–Vis and MALDI-TOF MS spectral data.     

Benzophenone and zinc(II) phthalocyanine dichromophores-labeled poly (aryl ether) dendrimer: synthesis,characterization and photoinduced energy transfer

A series of benzophenone chromospheres and zinc(II) phthalocyanine dichromophores labeled poly (aryl benzyl ether) dendrimer (G_n-DZnPc(BP)_8n, n = 1?2) were synthesized. Their structures were characterized by elemental analysis, ¹H NMR, IR, UV–vis and matrix-assisted laser desorption/ionization time-of-flight spectrometry (MALDI-TOF MS). Their photophysical properties were examined by steady-state and time-resolved fluorescence methods. Both the poly (aryl benzyl ether) dendrimer and BP terminal chromophores had a significant effect on photophysical properties of the zinc(II) phthalocyanine core. Time-resolved spectroscopic measurements indicated that the lifetime of benzophenone (donor) chromophore was longer than that of the zinc(II) phthalocyanine (acceptor). The fluorescence of the peripheral benzophenone chromophores was quenched by the phthalocyanine group attached to the focal point. All of these observations suggest that an intramolecular singlet energy transfer occurs in G_n-DZnPc(BP)_8n molecules. The light-harvesting abilities of these molecules increased with generations due to an increase in the number of benzophenone chromophores. The energy transfer efficiencies were ca. 0.49 and 0.68 for generations 1 and 2, respectively, and the rate constants of the singlet-singlet energy transfer were ca. 10⁸ s^?1. The rate constants changed inconspicuously with increase of dendron generations. The intramolecular singlet-singlet energy transfer is proposed to proceed mainly via a Förster-type interaction mechanism involving the dendrimer backbone as a scaffold to hold the peripheral benzophenone chromophores and the phthalocyanine core together. This dendrimer was an effective new energy transmission complex with high efficiency and could be used as a potential light-harvesting system.     

Synthesis,electrochemical, in situ spectroelectrochemical and in situ electrocolorimetric characterization of new metal-free and metallophthalocyanines substituted with 4-{2-[2-(1-naphthyloxy)ethoxy]ethoxy} groups

The synthesis of novel metal-free and metallophthalocyanines [Ni(II), Zn(II), Co(II), Cu(II)] were prepared by cyclotetramerization of a novel 4-{2-[2-(1-naphthyloxy)ethoxy]ethoxy}phthalonitrile and the corresponding metal salts (NiCl₂, Zn(CH₃COO)₂, CoCl₂ and CuCl₂). The structures of the target compounds were confirmed using elemental analysis, IR, ¹H NMR, ¹³C NMR, UV–Vis and MS spectral data. Voltammetric and in situ spectroelectrochemical measurements show that while cobalt phthalocyanine complex gives both metal-based and ring-based redox processes, metal-free, and zinc phthalocyanines show only ring-based reduction and oxidation processes. All complexes decomposed and coated on the electrode as nonconductive film at positive potential window of the electrolyte. An in situ electrocolorimetric method has been applied to investigate color of the electro-generated anionic and cationic forms of the complexes.