Extremely Photostable Electron-Deficient Phthalocyanines that Generate High Levels of Singlet Oxygen

A robust lead-mediated synthetic procedure for the generation of phthalocyanines substituted with electron-withdrawing groups has been developed. The free-base phthalocyanine and various metal complexes were prepared without discernible degradation of the peripheral electron-withdrawing substituents. Upon irradiation with red light, some of the thus-obtained metal complexes generated high levels of singlet oxygen. In particular, a palladium complex exhibited attractive photostability upon exposure to singlet oxygen as a bleaching agent. The photostability of such complexes that may manifest concomitantly to the generation of high levels of singlet oxygen was attributed to the presence of the electron-withdrawing groups, which results in energetically low-lying highest occupied molecular orbitals.     

The Reactions of Carbon Monoxide and Phenols Promoted by Palladium Complexes

The reaction of phenols with carbon monoxide at atmospheric pressure and room temperature in the presence of palladium cholrode and tertiary amine produces diaryl carbonates and aryl salicylates. Only diaryl cabonates are produced when palladium carbonyl cholride is substituted for palladium chloride. Reaction pathways are proposed.     

Photosensitizing properties of a boronated phthalocyanine: studies at the molecular and cellular level.

A synthetic procedure has been developed for the preparation of a Zn-phthalocyanine peripherally substituted with a dodecaborane. The absorption spectrum of the derivative is typical of the phthalocyanine chromophore. Moreover, the boronated phthalocyanine exhibits a high photosensitizing efficiency against a model biological substrate, such as N-acetyl-L-tryptophanamide, and a singlet oxygen quantum yield of 0.53 in dimethylformamide. Even though the presence of the dodecaborane moiety appears to decrease the affinity of the phthalocyanine for HT-1080 transformed human fibroblasts, the boronated phthalocyanine causes an essentially complete loss of cell viability upon irradiation with 600-700 nm light under mild conditions (1 microM concentration, 5-min irradiation at 10 mW/cm(2)).     

A tightly coupled bis(zinc(II) phthalocyanine)-perylenediimide ensemble to yield long-lived radical ion pair states

A conjugated donor-acceptor array composed of two phthalocyanines connected to the bay region of a perylenediimide is assembled by using palladium chemistry. Excitation of the phthalocyanine produces a nanosecond lived charge-separated state.     

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 of novel unsymmetrical phthalocyanines substituted with crown ether and nitro groups

This work reports on the synthesis of new unsymmetrically substituted phthalocyanines (M = Zn, Cu, Co, Ni) bearing three benzo-15-crown-5 units through oxy bridges and a nitro group. Phthalocyanines were prepared by a statistical condensation of 4-nitro phthalonitrile and 1-{[(benzo-15-crown-5)-4′-yl]oxy}phthalonitrile in the presence of anhydrous metal salts. All the target unsymmetrical phthalocyanines were separated by column chromatography and characterized elemental analyses, ¹H NMR, IR, mass and UV–Vis spectral data. Electrochemical behaviors of Cu (II) phthalocyanine by cyclic voltammetry and differential pulse voltammetry techniques gave two common phthalocyanine ring reductions and one ring oxidation processes. Peak-to-peak separation of the processes II and III (388 mV) and the measure of gap (1.672 V) between the HOMO and LUMO for the complex, fits a phthalocyanine with electrochemically inactive metal center.     

Characterization of endoperoxide and hydroperoxide intermediates in the reaction of pyridoxine with singlet oxygen

The photosensitized oxidation of vitamin B6, pyridoxine, is investigated by product and kinetic analysis. Singlet oxygen quenching rates, measured by time-resolved laser flash generation of singlet oxygen followed by monitoring singlet oxygen phosphorescence decay, confirm previous observations that pyridoxine is a moderate quencher. The quenching rate for 3-methoxypyridine is 100 times slower than that for 3-hydroxypyridine, indicating the hydroxy moiety is required for efficient quenching. The chemical quenching rate constant, kr, was estimated by comparison with a known singlet oxygen reaction. Results indicate that the chemical quenching rate of pyridoxine dominates the total quenching. The major reaction product in methanol was isolated and characterized by NMR and MS. The data are consistent with a solvent adduct of the substituted 2,5-pyridinedione. At low temperature, two semistable intermediates were characterized by NMR. The data are consistent with a hydroperoxide and endoperoxide. These intermediates suggest initial attack of singlet oxygen para to the hydroxy group followed by either proton transfer to form the hydroperoxide or addition of the peroxide to the imine to form the endoperoxide. In the presence of protic solvents, the solvent adducts to the imine and elimination of water yield the observed 2,5-pyridinedione product.     

Synthesis,photophysics, and photochemistry of peripherally Schiff base-zinc complex substituted zinc phthalocyanine

The content of this work is based on the introduction of the salicylhydrazone-zinc complexes into the phthalocyanine core. The reaction of the salicylhydrazone substituted ZnPc (1) with the related zinc(II) salt in basic conditions in DMF yielded bis[bis(salicyhydrazone)phenoxy)zinc(II)] phthalocyaninato zinc(II) (5) in which two salicylhydrazone-Zn complexes are linked through oxygen bridges to the macrocyclic core as three-nuclear complex. The novel compound synthesized in this study was fully characterized by general spectroscopic techniques such as FT-IR, UV-vis, ¹H NMR, ¹³C NMR, elemental analysis and mass spectroscopy. In addition, spectral, photophysical (fluorescence quantum yields), and photochemical (generation of singlet oxygen and photo stability under light irradiation) properties of newly synthesized phthalocyanine (5) and the starting Pcs molecules used to obtain this molecule were investigated in DMSO solutions, comparatively.     

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.     

Three-component, stereoselective palladium-catalyzed synthesis of functionalized bicyclopentanoids

1,5-Cyclooctadiene can be stereoselectively transformed into a substituted bicyclo[3.3.0]octane ring system under palladium catalysis with concomitant formation of three carbon-carbon bonds. Reaction with an aryl iodide or triflate and malonate gives an exo-endo product, while the reaction with a malonate in the presence of oxygen affords a bis-endo adduct.     

Synthesis and Characterization of New Cross‐like Porphyrin–Naphthalocyanine and Porphyrin–Phthalocyanine Pentads

Synthesis and characterization of new cross‐like porphyrin–naphthalocyanine and porphyrin–phthalocyanine systems, where one naphthalocyanine and one phthalocyanine are the central moieties of the pentads, respectively, and in both cases substituted with four porphyrin units, in a cross‐shape structure. Porphyrin–naphthalonitrile and porphyrin–phthalonitrile adducts were prepared from the reaction of 5‐(p‐hydroxyphenyl)‐10,15,20‐triphenylporphyrin with the appropriate dihalogenated naphthalonitrile or phthalonitrile, respectively, to provide a straightforward cyclotetramerization in the presence of metallic magnesium, used as template. Spectroscopic characterization and initial photophysical assessment are also reported.     

Taming of Singlet Oxygen: Towards Artificial Oxygen Carriers Based on 1,4-Dialkylnaphthalenes

Naphthalene endoperoxides are known as convenient sources of singlet oxygen (O₂, ¹Δ_g), which is the major product of endoperoxide cycloreversion reaction. However, their potential as carriers of ground-state molecular oxygen (O₂, ³Σ_g) similar to artificial oxygen carriers remains largely unexplored. This is due to the extreme reactivity and cytotoxic effects of the released singlet oxygen. We now report that a compound with a bimodular design, which incorporates an endoperoxide and an efficient physical quencher of singlet oxygen, 1,4-diazabicyclo[2.2.2]octane (DABCO), produces exclusively ground-state molecular oxygen. This result, coupled with the fact that oxygen release rates from endoperoxides are highly amenable to fine-tuning in a very broad range, and open to targeting by ligand attachment, raises the potential of these compounds far above any comparable chemical, or even biochemical sources. In cell culture experiments, we showed that the addition of the endoperoxide-quencher conjugate can enhance and sustain cell proliferation.     

Selective preparation of non-symmetrically substituted divinylbenzenes by palladium-catalysed arylations of alkenes with bromobenzoic acid derivatives

Palladium-catalysed arylation of alkenes with the three bromobenzoic acids or their acyl chlorides provides an efficient and selective method for the preparation of non-symmetrically substituted divinylbenzene derivatives. In the presence of palladium acetate and a phosphorus ligand the free acids react as aryl bromides, with the exception of 2-bromobenzoic acid. If palladium acetate is used alone as catalyst, all three bromobenzoyl chlorides react only as aroyl chlorides. Using two different alkenes a given non-symmetrically substituted divinylbenzene can be prepared by four different routes, allowing for an optimum choice of synthesis path. Substituent effects in the aromatic derivatives and the reactivity of the alkenes in arylation are the principal features to be taken into account. The reaction pathway can generally be chosen to give excellent yields in short reaction times at low palladium concentrations.     

A Glutathione‐Activated Phthalocyanine‐Based Photosensitizer for Photodynamic Therapy

A zinc(II) phthalocyanine substituted with a 2,4‐dinitrobenzenesulfonate group has been prepared. Its fluorescence emission and reactive oxygen species generation can be greatly enhanced by glutathione in phosphate‐buffered saline and inside MCF‐7 cells. This compound thus functions as a highly efficient molecular‐based activatable photosensitizer.     

SUPPORTED METALATED PHTHALOCYANINE AS CATALYST FOR OXIDATION BY MOLECULAR OXYGEN. SYNTHESIS OF QUINONES AND CARBONYL COMPOUNDS

ABSTRACT

Supported metalated phthalocyanine on K10 or on lamellar zirconium phosphate catalyses the oxidation of hydroquinones (and phenols) into quinones. Some interesting natural napthoquinones were also prepared (Juglone, Menadione, Lawsone, Phthiocol). Supported metalated phthalocyanine was also used in re-oxidation by oxygen of palladium and ruthenium, in the Wacker oxidation of olefins into ketones, in the oxidation of cyclohexadiene and in oxidation of benzylic alcohols in aldehydes.     

钯、铱单取代十二钼磷酸盐的制备及性质的研究

本文报道了Pd 、Ir 　取代的十二钼磷酸四丁基铵盐 (α (n Bu4 N) 5[PMo11Pd(OH2 )O39]、α (n Bu4 N) 3[PMo11Ir(OH2 )O39])的制备方法。IR、UV及31P NMR证实产物仍保持Keggin结构 ,并有一个Mo 为Pd 、Ir 所取代。电化学上 ,Ir 取代化合物存在三个清晰的多酸骨架氧化 还原峰而Pd 取代化合物由于电极吸附作用使它的氧化 还原峰无法被观察到。在两个取代化合物的烯烃催化氧化中醇、酮为主要产物。　值得注意的是 ,Pd 取代化合物催化的反应中苯酚取代环己烯酮而成为主要产物     

Synthesis of indenes by the palladium-catalyzed carboannulation of internal alkynes

[reaction: see text] A number of highly substituted indenes have been prepared in good yields by treating functionally substituted aryl halides with various internal alkynes in the presence of a palladium catalyst. The reaction is believed to proceed by regioselective arylpalladation of the alkyne and subsequent nucleophilic displacement of the palladium in the resulting vinylpalladium intermediate.     

Synthesis of 5-arylhistidines via a Suzuki-Miyaura cross-coupling

Microwave irradiation efficiently promoted the Suzuki-Miyaura reaction of a 5-bromohistidine with various arylboronic acids in the presence of a palladium catalyst. This methodology allowed the synthesis of histidines substituted at position 5 of the imidazole ring with a phenyl, a substituted phenyl, a pyridyl or a thienyl ring. The corresponding 5-arylhistidines were obtained in moderate to good yields.     

Photooxidation and reproduction of pentacene derivatives substituted by aromatic groups

Pentacene derivatives substituted by aromatic groups at the 6,13-positions were prepared and investigated for their electronic properties and the photoaddition reaction with oxygen. The pentacene derivatives substituted by 2-thienyl and phenyl groups reacted with oxygen in solution under light and afforded their endoperoxides. These first-order kinetic constants were evaluated to be 1.5×10⁻³ s⁻¹ and 2.7×10⁻³ s⁻¹. The pentacene derivative with pentafluorophenyl groups was relatively stable in solution. The thermolysis and photolysis of the endoperoxide with 2-thienyl groups in solution afforded the pentacene derivative with yields of 30 and 44%, respectively. In addition, UV irradiation (254 nm) of the thin film of the endoperoxide was studied, which indicated the reproduction of the pentacene derivative.     

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.