Conversion constants for redox potentials measured versus different reference electrodes in acetonitrile solutions at 25°C

Metallophthalocyanines as catalysts in electrochemical reactions

A zinc phthalocyanine with tyrosine substituents (ZnPcTyr), modified for efficient far-red/near-IR performance in dye-sensitized nanostructured TiO(2) solar cells, and its reference, glycine-substituted zinc phthalocyanine (ZnPcGly), were synthesized and characterized. The compounds were studied spectroscopically, electrochemically, and photoelectrochemically. Incorporating tyrosine groups into phthalocyanine makes the dye ethanol-soluble and reduces surface aggregation as a result of steric effects. The performance of a solar cell based on ZnPcTyr is much better than that based on ZnPcGly. Addition of 3alpha,7alpha-dihydroxy-5beta-cholic acid (cheno) and 4-tert-butylpyridine (TBP) to the dye solution when preparing a dye-sensitized TiO(2) electrode diminishes significantly the surface aggregation and, therefore, improves the performance of solar cells based on these phthalocyanines. The highest monochromatic incident photo-to-current conversion efficiency (IPCE) of approximately 24% at 690 nm and an overall conversion efficiency (eta) of 0.54% were achieved for a cell based on a ZnPcTyr-sensitized TiO(2) electrode. Addition of TBP in the electrolyte decreases the IPCE and eta considerably, although it increases the open-circuit photovoltage. Time-resolved transient absorption measurements of interfacial electron-transfer kinetics in a ZnPcTyr-sensitized nanostructured TiO(2) thin film show that electron injection from the excited state of the dye into the conduction band of TiO(2) is completed in approximately 500 fs and that more than half of the injected electrons recombines with the oxidized dye molecules in approximately 300 ps. In addition to surface aggregation, the very fast electron recombination is most likely responsible for the low performance of the solar cell based on ZnPcTyr.

Modified phthalocyanines for efficient near-IR sensitization of nanostructured TiO(2) electrode.

This article reviews recent work in the area of non-innocent behaviour in polynuclear metal complexes Non-innocence, which occurs when metal-based and ligand-based redox orbitals are similar in energy, has been known since the first dithiolene complexes of the Ni triad Our recent work in this field is with complexes of two distinct types: polynuclear complexes of Ru(II) with dioxolene-type bridging ligands; and dinuclear complexes based on tris(pyrazolyl)borato-Mo(V) or -Mo(I) units linked by bis-phenolate or bis-pyridyl bridging ligands Detailed redox and UV/Vis/NIR spectroelectrochemical studies on these complexes have been carried out An important point which emerges is that non-innocent behaviour in dinuclear complexes is an essential prerequisite for strong metal–metal electronic coupling across extended bridging ligands Many of the complexes studied show intense charge-transfer transitions in the near-IR region of the
spectrum, and the use of these in prototypical optical devices is briefly discussed

Non-innocent behaviour in mononuclear and polynuclear complexes: consequences for redox and electronic spectroscopic properties

Transition metal complexes with bulky 4,6-di-tert-butyl-N-aryl(alkyl)-o-iminobenzoquinonato ligands: Structure, EPR and magnetism

: The electrochemistry of 9, 16, 23-TETRA(NEOPENTOXY)PHTHALOCYANATO cobalt, and some binuclear analogs, has been studied in dichlorobenzene and in dimethylformamide. The redox mechanisms and species on the electrode are discussed. Using an optically thin electrode, the electronic spectra of seven different oxidation states of the mononuclear derivative are reported. Data for a selection of oxidation states of several binuclear species are also presented.

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Electrochemistry and spectroelectrochemistry of mononuclear and binuclear cobalt phthalocyanines

Preparation des complexes [Ru(bpy)(dioxolene) 2 ] u+ par electrolyse a potentiel controle des especes meres. Donnees IR, Raman, RMN, RPE

Bis(dioxolene)(bipyridine)ruthenium redox series

Using pentaerythritol as a framework, it has been possible to synthesize a tetranuclear phthalocyanine with a spiro type linkage. Electrochemical and spectroelectrochemical data are presented for the cobalt complex in the Co/sup III/Pc(-2), Co/sup II/Pc(-2), Co/sup I/Pc(-2), Co/sup III/Pc(-1), Co/sup II/Pc(-1), and Co/sup I/Pc(-3) oxidation levels. The Co(II) species aggregates very strongly, dimerizing with an aggregation constant in o-dichlorobenzene of 2.4 x 10/sup 5/ M/sup -1/, 2 orders of magnitude greater than for the parent Co/sup II/TNPc. Monolayers of the cobalt(II) species laid upon an ordinary pyrolytic graphite electrode are shown to electrocatalytically reduce oxygen more efficiently than previously described analogous mononuclear and binuclear phthalocyanines. The Co(II) tetranuclear species disproportionates into a 1:1 mixture of Co(I) and Co(III) species upon reaction with hydroxide ion in a nondonating or weakly donating solvent. A film containing (Co/sup I/TrNPc(-2))/sub 4//sup 4 -/ reduces nitrite ion in NaOH slowly, with oxidation to the Co(II) tetranuclear species. 60 references, 8 figures, 5 tables.

Synthesis, aggregation, electrocatalytic activity, and redox properties of a tetranuclear cobalt phthalocyanine

: Complexes of the general formula (Ru(bpy)(dioxolene)2)n+ have been prepared where (bpy) is 2,2'-bipyridine, and n = 1, 0, +1. The dioxolene ligand is 1,2-dihydroxybenzene (catechol), 3,5-di-t-butyl- or 3,4,5,6-tetrachloro-1,2-dihydroxybenzene which may formally exist in the catecholate, semiquinone or quinone oxidation state. Redox series of up to five members have been prepared by controlled potential electrolysis of the parent species or, in some cases, by chemical oxidation or reduction. Electrochemistry, magnetism, X-ray structural data and ultraviolet, visible and near infrared electronic, resonance Raman, vibrational (FTIR), nuclear magnetic resonance, electron spin resonance and photoelectron spectra, for various members of the redox series, are discussed in terms of the electronic structures (effective oxidation states, delocalization) of the complexes. Apparent conflicts between results obtained using different techniques are resolved using a simple, qualitative MO model. Keywords: Quinone, Ruthenium, Delocalization, Redox series.

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Bis(dioxolene)bis(pyridine)ruthenium redox series

The aggregation of mononuclear [2,9,16,23-tetra(neopentoxy)phthalocyanato]cobalt(II) and of some related binuclear cobalt(II) phthalocyanine derivatives, in o-dichlorobenzene, has been studied by electronic absorption spectroscopy. Dimerisation constants and the calculated aggregate dimer spectra are reported.

Wei Liu

Papers

Electrochemistry and spectroelectrochemistry of mononuclear and binuclear cobalt phthalocyanines

Bis(dioxolene)(bipyridine)ruthenium redox series

Synthesis, aggregation, electrocatalytic activity, and redox properties of a tetranuclear cobalt phthalocyanine

Bis(dioxolene)bis(pyridine)ruthenium redox series

Dimerisation of mononuclear and binuclear cobalt phthalocyanines