Phthalocyanine Dianion Research Articles

Metallophthalocyanine catalysed electroreduction of nitrate and nitrite ions in alkaline media

The electrochemical reduction of nitrite and nitrate in alkaline solution has been studied on glassy carbon electrodes modified with phthalocyanine complexes of Mn, Fe, Co, Ni, Cu and Zn (MnPc, FePc, CoPc, NiPc, CuPc and ZnPc, respectively, and Pc(-2) is phthalocyanine dianion). Voltammetry shows that the reduction of nitrite occurs at potentials slightly less negative than for nitrate reduction. The MPc complexes lower the overpotential for the reduction of nitrite and nitrate as follows: CuPc > FePc > NiPc > CoPc > MnPc > ZnPc > glassy carbon electrode. The main product for the reduction of nitrite and nitrate is ammonia, with high yields of ammonia being obtained, depending on the choices of the electrolysis potential and MPc complex.

The study of the interactions of cobalt(II) tetrasulfophthalocyanine with cysteine and histidine

Kinetics for the interaction of cobalt(II) tetrasulfophthalocyanine ([Co IITSPc] 4−, Pc(−2) = phthalocyanine dianion) with the amino acids, histidine and cysteine, in pH 7.2 phosphate buffer were studied. The rates were found to be first order in both the [Co IITSPc] 4− and the amino acid. The formation of the [Co IIITSPc] 3− species in the presence of histidine occurred with a rate constant of 0.16 dm 3 mol −s −1, whereas the formation of the [Co ITSPc] 5− species in the presence of cysteine gave a rate constant of 2.2 dm 3 mol −1.

Cyclic voltammetry and spectroelectrochemistry of osmium phthalocyanines in aqueous and non-aqueous solvents

Cyclic voltammetry of osmium phthalocyanine complexes, [(CN) 2Os IIPc] 2− and (py) 2OS IIPc (PC = phthalocyanine dianion), show two oxidation couples and two reduction couples in acetonitrile and dimethy1formamide. Oxidation and reduction in these complexes occur at the ring to form cation and anion radical species, respectively. The [(CN) 2Os IIPC] 2− complexes show a remarkable ease of ring oxidation with oxidation potentials that are much lower than is typical for metallophthalocyanines. Half-wave potentials of 0.25 and 0.67 V (versus saturated calomel electrode, SCE) were obtained for the first and second ring oxidations, respectively. The [(CN) 2OS IIPc] 2− complex is soluble in water at pHs greater than 4. This complex shows one oxidation couple in pH 9 buffer at −0.11 V versus SCE.

Electrocatalytic oxidation of cysteine by molybdenum(V) phthalocyanine complexes

Chemically modified electrodes, constructed by incorporating oxomolybdenum(V) phthalocyanine (OMo(V)(OH)Pc, Pc = phthalocyanine dianion) into graphite powder were used to catalyse the oxidation of cysteine. Solution catalysis of cysteine by oxomolybdenum(V) tetrasulfophthalocyanine, [OMo(V)(OH)TSPc] 4−, was also investigated. A considerable reduction in overpotential for cysteine oxidation was observed. Cysteine oxidation occurred at 0.26 and 0.28 V vs. Ag/vbAgCl for catalysis by Omo(V)(OH)Pc and [OMo(V)(OH)TSPc] 4− respectively as opposed to 0.77 V vs. Ag/vbAgCl observed on CoPc chemically modified electrodes. The anodic peak currents vary linearly with cysteine concentration in the range 0.02 to 0.08 mol dm −3 and 0.008 to 0.02 mol dm −3 for [OMo(V)(OH)TSPc] 4− and OMo(V)Pc respectively.

The reaction of cyanide with iron(II) hexadecachlorophthalocyanine

Kinetics and equilibria for the reaction between cyanide and iron(II) hexadecachlorophthalocyanine ((Cl) 16PcFe(DMSO) 2, where Pc(−2) = phthalocyanine dianion) in dimethyl sulphoxide (DMSO) are reported. Only the spectrophotometric changes due to the formation of the dicyano, [(Cl) 16PcFe(CN) 2] 2−, complex were observed. This complex is formed with the equilibrium constant, K 3 = 1.6 × 10 3 dm 3 mol −1 and a rate constant of k 3f = 4.2 × 10 −3 dm 3 mol −1 s −1. The K 2[(Cl) 16PcFe(CN) 2] complex dissolves in DMSO and dimethyl formamide (DMF) with ϵ = 110 000 and 92 000 dm 3 mol −1 cm −1, respectively.

Cyclic voltammetric studies of hafnium and zirconium phthalocyanines

Cyclic voltammograms of (OH) 2HfPc(Cl) and (OH) 2ZrPc(Cl) (Pc(-2) = phthalocyanine dianion) show one oxidation couple and two reduction couples in the presence of a variety of solvent-electrolyte systems. All redox processes are centred on the phthalocyanine ring rather than the metal. The first oxidation occurs at the phthalocyanine ligand to give [HfPc(-1)] ·+ and [ZrPc(-1)] ·+ π cation radical complexes. The two reduction couples correspond to the successive one-electron reductions of the phthalocyanine ligand to give MPc(-3) ·− and MPc(-4) 2− species. A third reduction couple, observed only for solutions (OH) 2HfPc(Cl) in dimethyl sulfoxide, is assigned to further reduction of the ring and the formation of the HfPc(-5) ·3− species.

Photoreduction of tin(IV) phthalocyanines

Photolysis of Sn(IV)Pc(OH) 2 (Pc = phthalocyanine dianion) and Sn(IV)Pc(Cl) 2 using a tungsten lamp, and in the presence of SnCl 2·2H 2O as an electron donor results in the reduction of these complexes of π anion radical species. The reduction shows second order dependence on the concentration of the Sn(IV)Pc complexes and a first order dependence on SnCl 2·H 2O.

Syntheses and Characterization of Bromo- and Chloro(phthalocyaninato)bismuth(III) Complexes

Abstract By the reactions of BiX3 (X = Cl−, Br−, I−, and NO3−) with Li2(pc) (pc = phthalocyaninate dianion, C32H16N82−) in dimethyl sulfoxide, N,N-dimethylformamide, acetonitrile, and acetone, [Bi(pc)X] complexes have been produced. These complexes were also produced by heating a mixture of BiX3 and phthalonitrile. Among them, [Bi(pc)Cl] and [Bi(pc)Br] were isolated for the first time as a phthalocyanine complex of group-15 elements and successfully characterized by elemental analyses, solution chemistry, electronic and IR spectroscopy. The latter two complexes were soluble in polar solvents, but were insoluble in nonpolar solvents. In solutions, bismuth(III) in [Bi(pc)X] was labile and was readily expelled from a pc ring by a trace amount of water, acids, and bases, and it was replaced by a divalent transition metal upon the addition of MSO4 (M = cobalt(II), nickel(II), copper(II), and zinc(II)) forming [M(pc)]. The electronic and IR spectra of the [Bi(pc)X]s were characteristic of the usual metallophthalocyanines, except that a hyper metal-to-ligand charge-transfer band appeared in their electronic spectra.

Cyclic voltammetry and spectroelectrochemistry of rhodium phthalocyanines

The electrochemistry of RhIII(pc)(pc = phthalocyanine dianion) complexes containing chloride, pyridine, dimethyl sulfoxide (dmso) and cyanide as axial ligands was investigated by cyclic voltammetry and UV/VIS spectroelectrochemistry. The compounds were K[Rh(pc)(CN)2], [Rh(pc)(Cl)(py)] and [Rh(pc)Cl(dmso)]. For all of these the first oxidation occurs at the phthalocyanine ligand with the formation of a π-cation radical species. The addition of one electron to the complexes leads to one of two different reduction products depending on the nature of the axial ligands. The first reduction of [Rh(pc)Cl(py)] and [Rh(pc)Cl(dmso)] occurs at the metal, followed by rapid dimerization of the reduced species. The first and subsequent reductions of K[Rh(pc)(CN)2] occur at the ring.

Cyclic voltammetry and photooxidation of molybdenum(V) phthalocyanine

Cyclic voltammetry of OMo V(OH)Pc in chloronaphthalene shows two quasi-reversible oxidation couples at 0.38 and 1.22 V and three quasi-reversible reduction couples at −0.74, −1.15 and −1.85 V vs S.C.E. Bulk electrolysis of OMo V(OH)Pc (Pc 2 = phthalocyanine dianion) shows that the first oxidation couple is due to the oxidation of the central Mo V metal to Mo VI and the first reduction couple due to reduction to OMo IVPc. Cyclic voltammetry and spectroelectrochemistry in DMSO also showed redox activity at the metal. Further reductions or oxidations in OMo VPc complexes occur at the phthalocyanine ring. OMo V(OH)Pc is readily photooxidized at the metal in the presence dichloromethane or dichlorobenzene, with the formation of OMo VIPc species.

Double-decker actinide porphyrins and phthalocyanines. Synthesis and spectroscopic characterization of neutral, oxidized, and reduced homo- and heteroleptic complexes

The synthesis, spectroscopic characterization, and electrochemistry of 26 different neutral and singly-oxidized homoleptic and heteroleptic actinide double-decker complexes are reported. The investigated compounds are represented as [M(P) 2 ] n , [M(P)(P')] n , [M(Pc) 2 ] n , and [M(P)(Pc)] n where n=0 or 1+, M=U or Th, Pc=the dianion of phthalocyanine, and P or P'=the dianions of octaethylporphyrin (OEP), tetraphenylporphyrin (TPP), or tetra-p-tolylporphyrin (TpTP). Each neutral compound was characterized by 1 H NMR, UV-visible, and IR spectroscopy and comparisons made to the cationic singly-oxidized double-decker derivatives which were chemically generated and isolated as a SbCl 6 - salt

Oxidizing properties of transition metal hexafluorides towards p-block elements and polymeric μ-fluoro(phthalocyanine)aluminium(III)

The behaviour of UF 6, MoF 6 and WF 6 towards the p-block elements Se, As, Sb and Bi has been studied using MeCN as solvent. The results obtained, together with previous work involving I 2, Br 2 and Te with MoF 6 and UF 6 [1], have enabled a detailed picture of p-block element redox chemistry in MeCN to be obtained. Complex cation, hexafluorometallates (V) have been isolated for all the elements examined and structures for the cations are proposed on the basis of spectroscopic studies. Oxidation of [Al(Pc)(μ-F)] n Pc = phthalocyanine dianion, by the hexafluorides which has been reported previously using microcrystalline material [2], occurs also in the presence of MeCN. Soluble products are obtained whose electronic spectra are very similar to those of [Al(Pc)(μ-F)] n dissolved in the protonic acids CF 3CO 2H, CF 3SO 3H and HSO 3F. Thin films of [Al(Pc)(μ-F)] n, grown by evaporation onto single crystal KCl or silica wafers, are also oxidised when exposed to UF 6, MoF 6 or WF 6 vapours. The oxidised films are stable in the absence of moisture unlike those obtained using I 2 as oxidant, where the redox reaction appears to be reversible. We thank the SERC for support of this work.

Synthesis and electrochemistry of acetylacetonatolanthanide(III)- phthalocyaninates

The synthesis and electrochemistry of acetylacetonatolanthanide(III)phthalocyaninates are reported. Two new kinds of lanthanide complexes Li[Pc]Ln(acac) 2] and (Pc)Ln(acac) were obtained where Ln is the trivalent ions of Eu, Gd, Dy, Tb, Ho, Er, Tm, Lu, and Pc is the dianion of phthalocyanine and acac is the acetylacetonate anion. These complexes were characterized by infrared and electronic absorption spectroscopy. An overall oxidation reduction mechanism at a platinum electrode in dimethyl sulfoxide is presented.

Photoreduction of methylviologen catalyzed by phthalocyanine complexes of yttrium(III) and lanthanoid(III) metals

The preparation of phthalocyanine complexes of yttrium, samarium, gadolinium, ytterbium, and lutetium is reported. The PcLnAcO complex (Pc = phthalocyanine dianion and AcO = acetate anion) was found to act as the sensitizer for the photoreduction of methylviologen chloride (MVCl{sub 2}) in a methanol solution upon irradiation with visible light. On the basis of data from visible spectrophotometric studies and laser flash-photolysis studies, the observation is made that the photoreduction of metalophthalocyanine complexes proceeds via an oxidative process, and a reaction scheme is proposed. 15 refs., 2 figs.

Carrier Properties of Porphyrinic Molecular Metals

Abstract A series of quasi one-dimensional molecular metals based on metallomacrocycle building blocks is compared. The group of compounds Ni(L)I, where L = dian-ion of phthalocyanine (PC), tetrabenzporphyrin (TBP), or triazatetrabenzporphyrin (TATBP), are isoionic and isostructural but the nature of the charge carrier is quite different in each material. Oxidation in Ni(PC)l is exclusively from ligand π-orbitals so that conduction is associated with delocalized π-orbitals. Ni(TBP)I and Ni(TATBP)I display epr spectra that demonstrate that oxidation has occurred from both ligand ir-orbitals and Ni d-orbitals so that these compounds display a novel, doubly mixed-valence state. The compounds Ni(PC)I, Ni(TMP)I, and Ni(OMTBP)I (TMP = tetramethylporphyrin, OMTBP = octamethyltetrabenzporphyrin) form an isoionic series where Coulomb correlations are of progressively greater importance.

Planar, pleated, and saddle-shaped structures of the phthalocyanine dianion in two novel multidentate oxygen-donor complexes of dipotassium phthalocyanine

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTPlanar, pleated, and saddle-shaped structures of the phthalocyanine dianion in two novel multidentate oxygen-donor complexes of dipotassium phthalocyanineR. F. Ziolo, W. H. H. Guenther, and J. M. TroupCite this: J. Am. Chem. Soc. 1981, 103, 15, 4629–4630Publication Date (Print):July 1, 1981Publication History Published online1 May 2002Published inissue 1 July 1981https://doi.org/10.1021/ja00405a078RIGHTS & PERMISSIONSArticle Views180Altmetric-Citations28LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (310 KB) Get e-AlertsSupporting Info (1)»Supporting Information Supporting Information Get e-Alerts

Evidence for the existence of the phthalocyanine dianion: the demetalation of dilithium phthalocyanine

Evidence for the existence of the phthalocyanine dianion: the demetalation of dilithium phthalocyanine