Encapsulation of phthalocyanine supramolecular stacks into virus-like particles

We report herein the encapsulation of a water-soluble phthalocyanine (Pc) into virus-like particles (VLPs) of two different sizes, depending on the conditions. At neutral pH, the cooperative encapsulation/templated assembly of the particles induces the formation of Pc stacks instead of Pc dimers, due to an increased confinement concentration. The Pc-containing VLPs may potentially be used as photosensitizer/vehicle systems for biomedical applications such as photodynamic therapy.     

Encapsulation of zinc phthalocyanine into bovine serum albumin aggregates

Artificial hybridization of molecules with proteins is beneficial for biomedical applications. Herein, we describe a novel method for encapsulation of zinc phthalocyanine (ZnPc) aggregates into bovine serum albumin (BSA) aggregates, but not monomeric BSA. This property is potentially useful for not only photodynamic or photothermal therapy but also development of a novel delivery system for hydrophobic drug molecules.     

Self-association of sulfo derivatives of cobalt phthalocyanine in aqueous solution

Sulfo derivatives of cobalt phthalocyanine containing naphthalene fragments have been synthesized, and their self-association and molecular complexation with pyridine in aqueous solution have been studied by spectrophotometry. The dissociation constants of the dimeric associates have been determined. The effects of the number of functional groups in the peripheral substituents and of the axial ligand on the phthalocyanine dimerization process have been revealed.     

Electrocatalytic activity of cobalt phthalocyanine stabilized by different matrixes

The behavior of cobalt phthalocyanine complexes incorporated inside an hydrotalcite-like clay (HT) or a sonogel-carbon composite has been investigated in order to develop chemically modified electrodes suitable for use as amperometric detectors. The electrocatalytic oxidation process of cysteine at this new electrode has been studied by cyclic voltammetry. For comparison, the oxidation of cysteine catalyzed by the cobalt phthalocyanine complex as a redox mediator, either dissolved in solution or entrapped inside the HT structure, has been followed by polarography. The sonogel-carbon composite electrode is stable and its response is repeatable. Cysteine oxidation is actually induced by the electrogenerated Co(III) complex, and the relevant anodic peak current varies linearly with cysteine concentration within the range 9.0x10(-4) to 1.0x10(-2) mol L(-1).     

Quantification of N-acetylcysteine in pharmaceuticals using cobalt phthalocyanine modified graphite electrodes

Flow injection analysis (FIA) with amperometric detection was employed for the quantification of N-acetylcysteine (NAC) in pharmaceutical formulations, utilizing an ordinary pyrolytic graphite (OPG) electrode modified with cobalt phthalocyanine (CoPc). Cyclic voltammetry was used in preliminary studies to establish the best conditions for NAC analysis. In FIA-amperometric experiments the OPG-CoPc electrode exhibited sharp and reproducible current peaks over a wide linear working range (5.0 × 10⁻⁵-1.0 × 10⁻³ mol L⁻¹) in 0.1 mol L⁻¹ NaOH solution. High sensitivity (130 mA mol⁻¹ cm²) and a low detection limit (9.0 × 10⁻⁷ mol L⁻¹) were achieved using the sensor. The repeatability (R.S.D.%) for 13 successive flow injections of a solution containing 5.0 × 10⁻⁴ mol L⁻¹ NAC was 1.1%. The new procedure was applied in analyses of commercial pharmaceutical products and the results were in excellent agreement with those obtained using the official titrimetric method. The proposed amperometric method is highly suitable for quality control analyses of NAC in pharmaceuticals since it is rapid, precise and requires much less work than the recommended titrimetric method.     

Electrode independent chemoresistive response for cobalt phthalocyanine in the space charge limited conductivity regime

The electrical properties of 50 nm thick metallophthalocyanine films, prepared by organic molecular beam epitaxy (OMBE) on interdigitated electrodes, were studied with DC current-voltage measurements and impedance spectroscopy. The transition from Ohmic behavior at low voltages to space-charge-limited conductivity (SCLC) at higher voltages depends on the metal electrode (Pt, Pd, and Au), but does not correlate with the work function of the electrode. Impedance spectroscopy studies show the coexistence of low- and high-frequency traps in the thin film devices, and the contribution of low-frequency traps associated with Ohmic behavior diminishes at higher bias. Although device resistances are strongly influenced by the electrode material, and vary by a factor of over 300, the relative chemical sensor responses on exposure to dimethyl methylphosphonate (DMMP), methanol, water, or toluene vapors are similar for CoPc on Pt, Pd, and Au electrodes when these devices are operated in the SCLC regime at room temperature. When the devices are operated at voltages where the low-frequency interfacial traps are filled, the sensor response to analyte becomes uniform and reliable regardless of the specific interfacial electrode contact.     

Raman spectroscopy of cobalt phthalocyanine adsorbed on a silver electrode

Raman spectra of cobalt tetrasulfonated phthalocyanine adsorbed on a silver electrode in aqueous electrolytes have been recorded in situ. It is shown that the entensity of the Raman bands is directly related to the amount of charge transfered during the electrochemical activation of the silver. The strong potential dependence of distinct Raman bands is discussed with respect to the resonance properties of the adsorbate, taking into account the orientation of the molecule on the surface.     

Gas sensing mechanism in chemiresistive cobalt and metal-free phthalocyanine thin films

The gas sensing behaviors of cobalt phthalocyanine (CoPc) and metal-free phthalocyanine (H2Pc) thin films were investigated with respect to analyte basicity. Chemiresistive sensors were fabricated by deposition of 50 nm thick films on interdigitated gold electrodes via organic molecular beam epitaxy (OMBE). Time-dependent current responses of the films were measured at constant voltage during exposure to analyte vapor doses. The analytes spanned a range of electron donor and hydrogen-bonding strengths. It was found that, when the analyte exceeded a critical base strength, the device responses for CoPc correlated with Lewis basicity, and device responses for H2Pc correlated with hydrogen-bond basicity. This suggests that the analyte-phthalocyanine interaction is dominated by binding to the central cavity of the phthalocyanine with analyte coordination strength governing CoPc sensor responses and analyte hydrogen-bonding ability governing H2Pc sensor responses. The interactions between the phthalocyanine films and analytes were found to follow first-order kinetics. The influence of O2 on the film response was found to significantly affect sensor response and recovery. The increase of resistance generally observed for analyte binding can be attributed to hole destruction in the semiconductor film by oxygen displacement, as well as hole trapping by electron donor ligands.     

Click chemistry electrode modification using 4-ethynylbenzyl substituted cobalt phthalocyanine for applications in electrocatalysis

In this work, we report on the synthesis and applications of a new cobalt tetrakis 4-((4-ethynylbenzyl) oxy) phthalocyanine (3) for the detection of hydrazine. The glassy carbon electrode (GCE) was first grafted through diazotization, providing the GCE surface layer with azide groups. Thereafter, the 1,3-dipolar cycloaddition reaction, catalyzed by a copper(I) catalyst was used to “click” complex 3 to the grafted surface of GCE. The new platform was then characterized using cyclic voltammetry (CV), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). This work shows that 3 is an effective sensor with sensitivity of 91.5 μA mM^?1 and limit of detection of 3.28 μM which is a great improvement compared to other reported sensors for this analyte.     

Solid-contact potentiometric sensor for ascorbic acid based on cobalt phthalocyanine nanoparticles as ionophore

A novel solid-contact potentiometric sensor for ascorbic acid based on cobalt phthalocyanine nanoparticles (NanoCoPc) as ionophore was fabricated without any need of auxiliary materials (such as membrane matrix, plasticizer, and other additives). The electrode was prepared by simple drop-coating NanoCoPc colloid on the surface of a glassy carbon electrode. A smooth, bright and blue thin film was strongly attached on the surface of the glassy carbon electrode. The electrode showed high selectivity for ascorbic acid, as compared with many common anions. The influences of the amount of NanoCoPc at the electrode surface and pH on the response characteristics of the electrode were investigated. To overcome the instability of the formal potential of the coated wire electrode, a novel electrochemical pretreatment method was proposed for the potentiometric sensor based on redox mechanism. This resulting sensor demonstrates potentiometric response over a wide linear range of ascorbic acid concentration (5.5 × 10⁻⁷ to 5.5 × 10⁻² M) with a fast response (<15 s), lower detection limit (ca. 1.0 × 10⁻⁷ M), and a long-term stability. Furthermore, microsensors based on different conductors (carbon fiber and Cu wire) were also successfully fabricated for the determination of practical samples.     

Determination of diethylstilbestrol by enhancement of luminol-hydrogen peroxide-tetrasulfonated cobalt phthalocyanine chemiluminescence

The ability of diethylstilbestrol to enhance the chemiluminescence reaction of luminol-H₂O₂, catalyzed by tetrasulfonated cobalt phthalocyanine in an alkaline medium, has been exploited to develop a new flow injection chemiluminescence method for the determination of diethylstilbestrol. Under the optimum conditions, the linearity of the calibration graph for the determination of diethylstilbestrol was in the range from 1.00×10⁻⁷ to 4.00×10⁻⁶ mol/l. The assay was sensitive (the detection limit was 6.42×10⁻⁸ mol/l, S/N=3), reproducible (the relative standard deviation was 2.6%, n=11), and accurate (recovery up to 92%). The method has been successfully applied to the determination of diethylstilbestrol in the pharmaceutical formulations. Dienestrol and hexestrol were specifically alkylphenols, which are similar to diethylstilbestrol, could be detected by this method. Furthermore, the enhanced mechanism of estrogen-like compounds was also discussed in this paper.     

Catalytic properties of cobalt complexes with tetrapyrazino porphyrazine and phthalocyanine derivatives

The catalytic activity of cobalt complexes with octaphenyltetrapyrazinoporphyrazine and phthalocyanine derivatives containing branched peripheral substituents is studied in heterogeneous catalysis of the oxidation of sodium diethyldithiocarbamate (SDC) with atmospheric oxygen. Cobalt phthalocyanines are shown to display higher catalytic activity than cobalt complexes with octaphenyltetrapyrazinoporphyrazine. The highest efficiency of heterogeneous catalysts is attained at temperatures of 298–303 K.     

Proton-coupled electron-transfer reduction of dioxygen catalyzed by a saddle-distorted cobalt phthalocyanine

Proton-coupled electron-transfer reduction of dioxygen (O(2)) to afford hydrogen peroxide (H(2)O(2)) was investigated by using ferrocene derivatives as reductants and saddle-distorted (α-octaphenylphthalocyaninato)cobalt(II) (Co(II)(Ph(8)Pc)) as a catalyst under acidic conditions. The selective two-electron reduction of O(2) by dimethylferrocene (Me(2)Fc) and decamethylferrocene (Me(10)Fc) occurs to yield H(2)O(2) and the corresponding ferrocenium ions (Me(2)Fc(+) and Me(10)Fc(+), respectively). Mechanisms of the catalytic reduction of O(2) are discussed on the basis of detailed kinetics studies on the overall catalytic reactions as well as on each redox reaction in the catalytic cycle. The active species to react with O(2) in the catalytic reaction is switched from Co(II)(Ph(8)Pc) to protonated Co(I)(Ph(8)PcH), depending on the reducing ability of ferrocene derivatives employed. The protonation of Co(II)(Ph(8)Pc) inhibits the direct reduction of O(2); however, the proton-coupled electron transfer from Me(10)Fc to Co(II)(Ph(8)Pc) and the protonated [Co(II)(Ph(8)PcH)](+) occurs to produce Co(I)(Ph(8)PcH) and [Co(I)(Ph(8)PcH(2))](+), respectively, which react immediately with O(2). The rate-determining step is a proton-coupled electron-transfer reduction of O(2) by Co(II)(Ph(8)Pc) in the Co(II)(Ph(8)Pc)-catalyzed cycle with Me(2)Fc, whereas it is changed to the electron-transfer reduction of [Co(II)(Ph(8)PcH)](+) by Me(10)Fc in the Co(I)(Ph(8)PcH)-catalyzed cycle with Me(10)Fc. A single crystal of monoprotonated [Co(III)(Ph(8)Pc)](+), [Co(III)Cl(2)(Ph(8)PcH)], produced by the proton-coupled electron-transfer reduction of O(2) by Co(II)(Ph(8)Pc) with HCl, was obtained, and the crystal structure was determined in comparison with that of Co(II)(Ph(8)Pc).     

Recoil behaviour of central metal atoms in cobalt and zinc phthalocyanine mixed crystals

The retentions of cobalt, copper and zinc recoils were studied in the mixed crystal system of -cobalt phthalocyanine and -zinc phthalocyanine. It was suggested that a part of the retentions of cobalt and zinc recoils was due to a competitive process. The relationship between the retentions of the zinc recoils and their recoil energy in different matrices was discussed.     

Spectroscopic evidence of monomeric aluminium phthalocyanine tetrasulphonate in aqueous solutions

Aqueous solutions of aluminium phthalocyanine tetrasulphonate (AlPcS(4)) were investigated by means of absorption and fluorescence spectroscopy. The absorption spectrum of AlPcS(4) is independent of concentration in a wide range (from 10(-8) to 10(-4) M). The fluorescence spectrum measured with a standard setup is strongly dependent on AlPcS(4) concentration, and the fluorescence maximum is gradually red-shifted with increasing concentration. Calculations that take into account reabsorption of fluorescence (inner-filter effect) fit the experimental observations at low concentrations (up to 10(-6) M). Disagreement between the calculations and spectra recorded at higher concentrations (above 10(-5) M) shows that the reabsorbed light may be reemitted as fluorescence. The influence of inner-filter effects on the spectral shape was demonstrated by the experiments where a fibre-optic front-face fluorescence setup was applied: Under such conditions the shape of the fluorescence spectra for a high concentration (10(-3) M) coincided with that of a low concentration (10(-8) M). In conclusion, the present spectroscopic results show that AlPcS(4) does not form aggregates and is a very stable compound in aqueous solutions.     

四羧基酞菁钴配合物的合成及其与牛血清蛋白的相互作用

在诸多治疗癌症的方法中,光动力治疗(photodynamin therapy)因其独特的优点而日益受到重视,成为近年来研究的热点之一.动力学治疗所使用的光敏剂称为抗癌光敏剂,是PDT疗法的关键.     

酞菁钴修饰碳糊电极对微量苯酚的测定

研究了苯酚在酞菁钴修饰碳糊电极上的电化学行为,提出了催化反应的机理,并以此为依据,用伏安法以酞菁钴修饰碳糊电极为工作电极测定了微量苯酚.在pH 8.7的磷酸盐缓冲溶液(PBS)中,苯酚在0.61 V(对SCE)出现一氧化峰,该峰电流与苯酚的浓度在5.0×10-7～1.0×10-4 mol/L之间呈线性关系,检出限为1.0×10-7 mol/L.此法可用于工业废水中苯酚的测定.     

Structures and orientations of cobalt phthalocyanine adsorbed on Sb(111)

The structures and orientations of cobalt phthalocyanine (CoPc) adsorbed on Sb(111) were investigated by low-temperature scanning tunneling microscope. We found that at the initial coverage molecular domains formed both on the terraces and at the vicinity of step edges that were saturated by molecular chains in advance. With the increasing of molecular coverage, the alternately arranged molecular rows of CoPc adsorbed on the bridge sites of Sb(111) and the orientations of them were rotated by 14° ± 2° with respect to the [-101] direction. At the coverage above one monolayer, the molecules of the second layer were assembled along the directions of the underlying molecular rows and showed similar configurations. Consequently, the second-layer CoPc molecules interacted with neighboring molecules via π orbitals, resulting in the observation of overlapped molecular orbitals.     

Experimental evidence for cobalt(III)-carbene radicals: key intermediates in cobalt(II)-based metalloradical cyclopropanation

New and conclusive evidence has been obtained for the existence of cobalt(III)-carbene radicals that have been previously proposed as the key intermediates in the underlying mechanism of metalloradical cyclopropanation by cobalt(II) complexes of porphyrins. In the absence of olefin substrates, reaction of [Co(TPP)] with ethyl styryldiazoacetate was found to generate the corresponding cobalt(III)-vinylcarbene radical that subsequently dimerizes via its γ-radical allylic resonance form to afford a dinuclear cobalt(III) porphyrin complex. X-ray structural analysis reveals a highly compact dimeric structure wherein the two metalloporphyrin units are arranged in a face-to-face fashion through a tetrasubstituted 1,5-hexadiene C(6)-bridge between the two Co(III) centers. The γ-radical allylic resonance form of the cobalt(III)-vinylcarbene radical intermediate could be effectively trapped by TEMPO via C-O bond formation to give a mononuclear cobalt(III) complex instead of the dimeric product. The allylic radical nature and related reactivity profile of the cobalt(III)-carbene radical, including its inability to abstract hydrogen atoms from toluene solvent, were established by DFT calculations.