A cobalt(II) phthalocyanine with indole substituents: formation,characterization and electrocatalytic studies

Herein, we report the formation of a new cobalt(II) phthalocyanine (CoPc) containing peripheral tetra-substituted indole (CoPc-ind, 2) moieties. The derivatized phthalonitrile, 4-(indole-4-oxy)phthalonitrile (1) as well its corresponding metal complex was characterized by NMR (for 1), IR– and UV–Vis spectroscopy as well as TOF mass spectrometry and elemental analysis (for 2). The electrochemical properties of the N₄-macrocyclic metal complex were investigated using cyclic- and square-wave voltammetry as well as corroborated by UV–Vis spectroelectrochemistry. The CoPc was electrodeposited onto the surface of a Pt working electrode followed by the immobilization of multiwalled carbon nanotubes (MWCNTs) onto the modified working electrode surface. The electrocatalytic activity of the resultant modified electrode toward dopamine revealed a lower ΔE value of 80?mV versus Ag|AgCl for the modified (2-MWCNTs) Pt electrode compared to the bare Pt electrode (ΔE?=?280?mV vs. Ag|AgCl). The diffusion- and convection-controlled electron-transfer kinetics of the chemically modified electrode were evaluated by chronoamperometry and rotating disk electrode techniques. Electrochemical impedance spectroscopic studies revealed that the 2-MWCNTs Pt electrode had a lower charge-transfer resistance and a higher apparent electron-transfer rate constant.     

Synthesis and electrochemical behavior of novel peripherally and non-peripherally substituted ball-type cobalt phthalocyanine complexes

The syntheses of new ball-type Co(II) phthalocyanines containing 4,4′-(9H-fluorene-9,9-diyl)diphenol substituents at non-peripheral (complex 6) and peripheral (complex 7) positions are presented. These complexes were characterized by UV-Vis, FT-IR, mass spectroscopy and electrochemical methods. Both complexes exhibit metal and ring based redox processes, typical of cobalt phthalocyanine complexes. For 6, the metal based reduction was observed at −0.46 V followed by a ring based reduction at −1.40 V. The metal oxidation for 6 was observed at +0.16 V and the ring based oxidation at +1.05 V. For 7, reductions are easier but the oxidations are more difficult. The metal based reduction for 7 was observed at −0.38 V followed by a ring based reduction at −1.03 V. The metal oxidation for 7 was observed at +0.20 V and the ring based oxidation at +1.35 V.     

Theoretical insights and design of Ru(II)-based complexes with DNA-photocleavage properties

A theoretical research on the properties of Ru(II)-based complexes 1–5 with polypyridyl ligands damaging DNA with the help of light has been carried out. Firstly, the redox potential, electrons-transfer (ET) activation energy, and intra-molecular reorganization energy were computed using DFT (density functional theory), and the results can be used to explain the DNA-photocleavage efficiencies of complexes. Secondly, the effect of ligands on the reduction potentials of complexes in the excited state was elucidated, and the reason of complexes cleaving DNA by the oxidation-reduction reaction and the produced singlet oxygen was explained. Finally, the frontier orbitals of complexes were computed, which was used to qualitatively explain the reason of complexes with high reduction potentials in the excited state.     

Energy transfer followed by electron transfer(ETET) endows a TPE-NBD dyad with enhanced environmental sensitivity

Energy transfer and electron transfer are both fundamental mechanisms enabling numerous functional materials and applications. While most materials systems employ either energy transfer or electron transfer, the combined effect of energy and electron transfer processes in a single donor/acceptor system remains largely unexplored. Herein, we demonstrated the energy transfer followed by electron transfer(ETET) process in a molecular dyad TPE-NBD. Due to energy transfer, the fluorescence of TPE-NBD was greatly enhanced in non-polar solvents. In contrast, polar solvents activated subsequent electron transfer and markedly quenched the emission of TPE-NBD. Consequently, ETET endows TPE-NBD with significant polarity sensitivities. We expect that employing ETET could generate many functional materials with unprecedented properties, i.e., for single laser powered multicolor fluorescence imaging and sensing.     

The syntheses and photophysical properties of 4,4′-isopropylidendioxydiphenyl substituted ball-type dinuclear Mg(II) and Zn(II) phthalocyanines

The syntheses of ball-type dinuclear Zn(II) and Mg(II) phthalocyanines containing four 4,4′-isopropylidendioxydiphenyl substituents at the peripheral and non-peripheral positions are presented. The structures of the synthesized compounds were characterized using elemental analyses, and UV-Vis, FT-IR, ¹H NMR and mass spectroscopies. The Φ_F values were 0.14, 0.11, 0.22, 0.15 and Φ_T values were 0.84, 0.88, 0.62, 0.74, for 6-9, respectively. The largest triplet yields were observed for the non-peripherally substituted complexes 6 and 7, showing that non-peripheral substitution favors increased population of the triplet state. All complexes showed reasonably long triplet lifetimes with τ_T 510, 310, 910 and 350 μs in DMSO, respectively.     

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.     

Theoretical study of the binding nature of glassy carbon with nickel(II) phthalocyanine complexes

A theoretical study at the semiempirical RHF/PM3(tm) level (tm: transition metal) of the binding nature between a glassy carbon (GC) cluster and a nickel(II) complex (nickel(II) phthalocyanine NiPc, nickel(II) tetrasulphophthalocyanine NiTSPc) was performed. Three types of interactions for GC?NiPc (NiTSPc) were studied: (a) through an oxo (O) bridge, (b) through an hydroxo (OH) bridge, and (c) non-bridge. One layer (NiPc, NiTSPc) and two layers (NiPc?NiPc) of complex were considered. The binding energy calculated showed that in both cases NiPc and NiTSPc, the oxo structures are more stable than the hydroxo ones, and than the non-bridge systems. Charge analysis (NAO) predicted that GC gained more electrons in an oxo structure than in the analogues hydroxo. The theoretical results showed an agreement with the experimental data available, an oxo binding between GC and a nickel complex (NiPc, NiTSPc) in aqueous alkaline solutions is formed.     

Degradation of substituted phenols with different oxygen sources catalyzed by Co(II) and Cu(II) phthalocyanine complexes

Research on substituted phenol degradations has received substantial attention. In this work, effective Co(II) and Cu(II) phthalocyanine complexes as catalysts were studied to degrade toxic phenols to harmless products. The effect of various process parameters, such as initial concentration of phenol, catalyst, oxygen sources, and temperature on the degradation reaction was investigated to achieve maximum degradation efficiency. The catalytic activities of Co(II) and Cu(II) phthalocyanines were evaluated for oxidation of phenolic compounds such as p-nitrophenol, o-chlorophenol, 2,3-dichlorophenol, and m-methoxyphenol. Co(II) phthalocyanine displayed good catalytic performance in degradation of 2,3-dichlorophenol to 2,3-dichlorobenzaldehyde and 2,3-dichloro-1,4-benzoquinone with the highest TON and TOF values within 3?h at 50?°C. The fate of catalyst during the degradation process was followed by UV–Vis spectroscopy.     

Synthesis,characterization, pyrolysis kinetics and conductivity studies of chloro substituted cobalt phthalocyanines

Cobalt(II) phthalocyanine (CoPc), cobalt(II) tetrachloro phthalocyanine (CoPcCl₄), cobalt(II) octachloro phthalocyanine (CoPcCl₈) and cobalt(II) hexadecachloro phthalocyanine (CoPcCl₁₆) are synthesized pure and characterized using elemental analysis, UV-visible, IR-spectroscopy, magnetic susceptibility, X-ray crystallography, and thermogravimetry. All four complexes have monoclinic structure with different crystal lattice constants. Broido's, Coats-Redfern and Horowitz-Metzger relations were employed to calculate the kinetic and activation parameters associated with thermal decomposition of the above complexes. The compounds are analyzed for kinetic parameters, activation energies for decomposition and the Arrhenious pre-exponential factors, in their pyrolysis. Using these factors and standard equations, thermodynamic parameters such as enthalpy, entropy and free energies are calculated. The activation energies are evaluated based on their electrical conductivity conducted over the temperature range 30–200°C. The electrical conductivities observed at 30°C are in the order CoPcCl₁₆?>?CoPcCl₄?>?CoPcCl₈?>?CoPc. The relevant electrical conductivity data are reported.     

Correlation of reactivity with structural factors in a series of Fe(II) substituted cobalt ferrites

A series of powdered cobalt ferrites, Co_xFe_3−xO₄ with 0.66?x<1.00 containing different amounts of Fe^II, were synthesized by a mild procedure, and their Fe and Co site occupancies and structural characteristics were explored using X-ray anomalous scattering and the Rietveld refinement method. The dissolution kinetics, measured in 0.1 M oxalic acid aqueous solution at 70 °C, indicate in all cases the operation of a contracting volume rate law. The specific rates increased with the Fe^II content following approximately a second-order polynomial expression. This result suggests that the transfer of Fe^III controls the dissolution rate, and that the leaching of a first layer of ions Co^II and Fe^II leaves exposed a surface enriched in slower dissolving octahedral Fe^III ions. Within this model, inner vicinal lattice Fe^II accelerates the rate of Fe^III transfer via internal electron hopping. A chain mechanism, involving successive electron transfers, fits the data very well.     

Synthesis and electrochemical properties of new cobalt and manganese phthalocyanine complexes tetra-substituted with 3,4-(methylendioxy)-phenoxy

The synthesis and electrochemical properties of new cobalt and manganese phthalocyanine complexes, tetra-substituted with 3,4-(methylendioxy)-phenoxy at the peripheral (complexes 3 and 5) and non-peripheral (complexes 4 and 6) positions, are reported. Complexes 3 and 4 showed Q-band absorption, in DMF, at 668 and 686 nm, respectively while Q-band due to complexes 5 and 6 appeared at 732 and 760 nm, respectively in CHCl₃. All the complexes showed well resolved redox processes attributed to both metal and ring based processes. Complexes 3 and 4 showed four redox processes, labeled I, II, III and IV. For complex 3, process I (Co^IPc⁻²/Co^IPc⁻³) was observed at −1.45 V, II (Co^IIPc⁻²/Co^IPc⁻²) at −0.38 V, III (Co^IIIPc⁻²/Co^IIPc⁻²) at +0.49 V and IV (Co^IIIPc⁻¹/Co^IIIPc⁻²) at +0.97 V versus Ag|AgCl. Similar processes were observed for complex 4 at −1.36 V, −0.27 V, +0.56 V, +1.03 V versus Ag|AgCl, respectively. Complexes 5 and 6 showed two redox processes (I and II). For complex 5, these processes appeared at −0.79 V (Mn^IIPc⁻²/Mn^IIPc⁻³, I) and −0.07 V versus Ag|AgCl (Mn^IIIPc⁻²/Mn^IIPc⁻², II), while for complex 6, they were observed at −0.86 V and −0.04 V versus Ag|AgCl. Spectroelectrochemistry was used to probe and confirm the origin of these processes.     

2,9,16,23-四-(2,6-二甲基苯氧基)酞菁钴(Ⅱ)的合成、表征及性质

用4-(2,6-二甲基苯氧基)邻苯二腈和金属盐在熔融状态下合成了2,9,16,23-四-(2,6-二甲基苯氧基)酞菁钴配合物,对产物进行了IR、UV-vis光谱、元素分析、热重分析等测定和表征.     

Interaction of nitric oxide with cobalt(II) phthalocyanine: kinetics, equilibria and electrocatalytic studies

The coordination of nitric oxide (NO) to cobalt(II) phthalocyanine (CoPc) in dimethyl sulphoxide (DMSO) has been studied. CoPc coordinates with NO in a 1:1 ratio, forming a CoPc(NO) species. The IR band observed at 1680 cm⁻¹ is assigned to the coordinated NO. In the presence of excess NO, pseudo first order kinetics were followed. The observed rate constant, k_f, was determined to be 15.0±0.3 dm⁻³ mol⁻¹ s⁻¹ and the equilibrium constant was K=5.4±0.4×10⁴dm³ mol⁻¹. Solution or adsorbed CoPc catalyses the reduction of NO. The products of reduction include NH₃ and NH₂OH.     

Syntheses and investigation of the effects of position and nature of substituent on the spectral,electrochemical and spectroelectrochemical properties of new cobalt phthalocyanine complexes

The syntheses of new cobalt phthalocyanine (CoPc) complexes, tetra-substituted with diethylaminoethanethio at the peripheral (complex 3a) and non-peripheral (complex 3b) positions, and with benzylmercapto at the non-peripheral position (complex 5), are reported. The effects of the nature and position of substituent on the spectral, electrochemical and spectroelectrochemical properties of these complexes are investigated. Solution electrochemistry of complex 3a showed three distinctly resolved redox processes attributed to Co^IIIPc⁻²/Co^IIPc⁻² (E_½ = +0.64 V versus Ag|AgCl), Co^IIPc⁻²/Co^IPc⁻² (E_½ = −0.24 V versus Ag|AgCl) and Co^IPc⁻²/Co^IPc⁻³ (E_½ = −1.26 V versus Ag|AgCl) species. No ring oxidation was observed in complex 3a. Complex 3b showed both ring-based oxidation, attributed to Co^IIIPc⁻¹/Co^IIIPc⁻² species (E_p = +0.86 V versus Ag|AgCl), and ring-based reduction associated with Co^IPc⁻²/Co^IPc⁻³ species (E_½ = −1.46 V versus Ag|AgCl), with the normal metal-based redox processes in CoPc complexes: Co^IIIPc⁻²/Co^IIPc⁻² (E_p = +0.41 V versus Ag|AgCl) and Co^IIPc⁻²/Co^IPc⁻² (E_½ = −0.38 V versus Ag|AgCl). Solution electrochemistry of complex 5 showed the same type and number of species observed in complex 3a: Co^IIIPc⁻²/Co^IIPc⁻² (E_p = +0.59 V versus Ag|AgCl), Co^IIPc⁻²/Co^IPc⁻² (E_½ = −0.26 V versus Ag|AgCl) and Co^IPc⁻²/Co^IPc⁻³ (E_½ = −1.39 V versus Ag|AgCl) species. These processes were confirmed using spectroelectrochemistry.     

Through-space and through-bond mixed charge transfer mechanisms on the hydrazine oxidation by cobalt(II) phthalocyanine in the gas phase

Two quantum chemistry theoretical models in the gas phase at the density functional theory B3LYP/LACVP(d) level of calculation are proposed to rationalize the hydrazine oxidation by cobalt(II) phthalocyanine (Co(II)Pc). This oxidation reaction involves the net transfer of four electrons. These theoretical models that are described in terms of energy profiles include a through-space mechanism for the transfer of the first electron of the hydrazine and a through-bond mechanism proposed for the transfer of the three electrons remaining. The main difference between both models arises from a one-electron and one-proton alternate transfer for model 1 and a two-electron and two-proton alternate transfer for model 2. The main problem for experimental studies is to determine if the first transfer corresponds to an electron or a chemical transfer. Under this point of view, we proposed two models which deal with this problem. We conclude that model 1 is more reasonable than model 2 because the whole oxidation process is always exergonic.     

Theoretical study of long range electron transfer in Phthalimide–Peptide–Methyl Aminoacetate Model molecules

Long-range electron transfer (ET) matrix elements (V_PS), rate constants (k_ET) and reorganization energies for ET from phthalimide radical (pha) moiety to methyl aminoacetate radical (aa) moiety in pa–(gly)_n = 0–6–aa (pa = C₆H₄(CO)₂N–(CH₂CO), gly = glycine, aa = HNCH₂COOCH₃) ionic molecules have been investigated using two-state variational method (TSVM) and classical rate model. Calculations on V_PS reveal that the overlap between the frontier orbitals of two diabatic states is quite small, which leads to a small value of V_PS. k_ET has a minimum at the range n = 1–3 for β-strand conformation, but linearly increases as the peptide chain length (n) increases for pro II-helix conformation. These results are in good agreement with the experimental predictions. Relevant ET mechanisms are elucidated. The transition energies for charge transfer in such systems are also calculated to test the influences of local dipoles on the potentials of the donor and acceptor. For comparison electron couplings in [pa–(gly)_n = 1,3–aa]⁺ cations are calculated and the effects of electron correlation on inner reorganization energies in pha + pha^−/+ self-exchange reactions are examined at different levels of theory respectively. Calculated results are discussed also.     

Kinetics of the reaction of cobalt(II) phthalocyanine complexes with functionalized organosilicas

The kinetics of the reaction of cobalt(II) phthalocyanine complexes with functionalized aminoorganosilicas was studied. Comparison of the kinetic parameters of the reactions studied provided additional information on the reaction mechanism and structure of the supported metal complexes, permitting delineation between the diffusion and kinetic regions of the reaction.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 31, No. 5, pp. 303–307, September–October, 1995.     

Micellar effect on the electron transfer reaction of chromium(V) ion with organic sulfides

The rate of electron transfer from organic sulfides to [Cr^V(ehba)₂]⁻ (ehba-2-ethyl-2-hydroxy butyric acid) decreases with a decrease in the polarity of the medium. The anionic surfactant, SDS and the cationic surfactant, CTAB have different effects on the kinetics of this reaction. The micellar inhibition observed in the presence of SDS is probably due to the decrease in the polarity and the electrostatic repulsion faced by the anionic oxidant from the anionic micelle and the partition of the hydrophobic substrate between the aqueous and micellar phases. The micellar catalysis in the presence of CTAB is attributed to the increase in the concentration of both reactants in the micellar phase. This micellar catalysis is observed to offset the retarding effects of the less polar micellar medium and the unfavorable charge-charge interaction between the + charge developed on S center in the transition state and the cationic micelle. This catalysis is contrary to the enormous micellar inhibition observed with IO₄⁻, HSO₅⁻ and HCO₄⁻ oxidation of organic sulfides.     

Electron transfer. 153. Internal electron transfer to bound cobalt(III) induced by hydroxyl radical

Hydroxyl radicals, generated in aqueous solution from Fe²⁺ and H₂O₂, react with the formato, glycolato, lactato and mandelato complexes of (NH₃)₅Co^III, extracting H·, releasing CO₂ and inducing the internal reduction of Co^III to Co²⁺; decomposition of peroxynitrous acid (O=N—OOH) in the presence of these complexes also yields Co²⁺, indicating partial utilization (15% at 22°C and pH 1) of a path involving OH·.