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The specific use of a functionalized sapphyrin diol is presented, which yields stable water-suspendable nanotubes and also allows the formation of well-defined assemblies in ionic liquids. The findings reveal that water-suspendable nanotube-sapphyrin complexes are formed from the functionalized sapphyrin derivative.

The synthesis, characterization, and electrochemical studies of [beta],[beta]'-fused metallocenoporphyrins are described. The novel Pd(0) catalyzed [3@] cycloaddition reaction with porphyrins was studied, a series of [beta][beta]' fused monoruthenoceno metalloporphyrins and bismetalloporphyrins with different central metals were prepared and significant electronic interactions between the metallocene and metalloporphyrin were observed.

The spectroscopic study of three types of protonated corroles [[(Cor)[H.sub.4]].sup.}, [[(Cor)[H.sub.5]].sup.2}, [[(Cor)[H.sub.6]].sup.3} in acidic nonaqueous media is described. The three corroles with one or two meso pyridyl substituents underwent multiple protonation both at the central nitrogens and at the nitrogens of the pyridyl substituents and a relationship is observed between the pKa values and the oxidation potential for the fully protonated corroles.

A study characterized the electrochemistry and UV-vis spectral properties of neutral and electroreduced Al(III) phthalocyanine, (PC)AlCl in four different nonaqueous solvents (THF, DMSO, DMF and pyridine). The initial phthalocyanine added to solution is represented as (Pc)AlCl, but the actual electroactive form of the compound varied as a function of both the solvent and type or number of bond anionic axial ligands.

The electrochemistry and pyridine binding reactions of different porphyrin-crrole dyads are investigated by cyclic voltammetry and thin-layer spectroelecrochemistry in pyridine. Up to four pyridine ligands can be coordinated to each dyad, with the exact value depending upon the metal oxidation state and type of spacer.

The synthesis and characterization of cofacial copper biscorroles and porphyrin-corroles linked by a biphenylenyl or anthracenyl spacer are described. The comparative study of four cofacial copper bis-corrole) BC and porphyrin-corrole (PC) dyads and their related monomeric corrole and porphyrin units shows that electron interaction between the two face-to-face macrocycles of these cofacial derivatives depends critically on the type and size of rigid spacer.

The copper(II) binding properties of the macrobicyclic diamide 1,9,12,18,22-pentaazatricyclo[7.6.6.1(super 3,7)]docosa-3,5,7-(22)-triene-13,19-dione (L(super 1)) are investigated by spectroscopic, structural, thermodynamic and electrochemical methods. Cross-bridging the 1 and 8 position of 5,12-dioxocyclam with a 2,6-pyridyl group affords a hemispherical macrobicyclic ligand exhibiting a split personality.

The studies have shown that anion binding to an appropriately chosen expanded porphyrin, diprotonated [30]octaphyrin(0.0.0.0.0.0.0.0) (cyclo[8]pyrrole, C8), is used for creating a noncovalently linked dyad capable of electron transfer. The high energy charge separated (CS) state decays with a lifetime 300 [micro]s in order to give a long-lived triplet state.

The metal-centered and macrocycle-centered electron-transfer oxidations and reductions of silver(II) porphyrins are characterized in nonaqueous media by electrochemistry and density functional theory calculations. The introduction of quinoxaline groups fused to the Ag(II) porphyrin macrocycle has provided a unique androgynous character to Ag(II) quinoxalinoporphyrins that has enabled them to act as both electron donors and good electron acceptors.

The electronic communication observed due to interaction between the porphyrin and the quinoxaline is demonstrated. The electron transfer through a molecular wire is demonstrated by using bis-(quinoxalino) porphyrins in free-base form and their [Zn.sup.II], [Cu.sup.II], [Ni.sup.II], and [Pd.sup.II] derivatives.

Electrochemically studies of six tin(IV) prophyrins showed that changes in the oxidation/reduction mechanism and the site of electron transfer can differ with changes in the axial ligands and the macrocycle.

The nitro-substituted silver(III) corrole obtained by reaction of corrole with AgN[O.sub.2] is studied using cyclic voltammetry and spectroelectrochemistry.The [pi]-cation radical of the complex acts as the reaction intermediate which is attacked by the nitrite ion.

Calix[4]pyrrole is used as a scaffold for the concurrent complexation of five metal centers, namely, four Ru(II) cations and one Cu(II) ion. Tetrakisruthenocene calixpyrrole derivative and its copper(II) complex have exhibited reversible four-electron oxidations, which might be used for easy-to-synthesize electron reservoirs.

The synthesis and redox properties of a series of free-base and metal(II) quinoxalino(2,3-b']porphyrins and their use in an investigation of the substituent effects on the degree of communication between the porphyrin and its [beta],[beta]'-fused quinoxalino component are reported.

A uranyl complex is formed when cyclo[6]pyrrole is treated with the uranyl cation under aerobic conditions. Spectroscopic, spectroelectrochemical and electron spin resonance data of this species are consistent with the ligand in the complex being oxidized to an antiaromtic form.

Three face-to-face linked porphyrin-corrole dyads are investigated as to their electrochemistry, spectroelectrochemistry, and chloride-binding properties in dichloromethane or benzonitrile. An axial binding of one or two Cl(super -) ligands to the cobalt center of the corrole is observed for singly and doubly oxidized (PCY)H2Co, with the exact stoichiometry of the reaction depending upon the spacer size and the concentration of Cl(super -) added to solution.

The structural and physicochemical properties of the manganese-corrolazine (Cz) complexes (TBP8Cz)Mn(super V) equivalent to O and (TBP8Cz)Mn(super III) (where TBP=p-tert-butylphenyl) are determined. The improved synthesis of manganese(III) and manganese(V)-oxo corrolazine complexes is accomplished.

Three series of cobalt(III) corroles were tested as catalysts for the electroreduction of dioxygen to water. Cyclic voltammetry and rotating ring-disk electrode voltammetry were both used to examine the catalytic activity of the cobalt complexes in acid media.

Gold(III) porphyrins of the type (P-R)AuPF6 were investigated as to their electrochemistry and spectroelectrochemistry in nonaqueous media. The change in the site of electron transfer was examined by electrochemistry combined with thin-layer UV-vis spectroelectrochemistry and ESR spectroscopy of the singly reduced compound produced by chemical reduction.

The synthesis and physicochemical properties of new porphyrazine macrocyles having peripheral heterocyclic five-, six-, and seven-membered rings is investigated. One of the most important aspects of electrochemical and spectroelectrochemical study of macrocyles is the electron delocalization for the oxidized and reduced species allowed by a 1H-6H tautomerism taking place on the peripheral diazepine rings.

A report is presented which states the synthesis spectroscopic characterization and electro chemistry of five new phosphorus corroles. The investigated complexes contained alkyl,aryl,oxo, or hydrido axial ligands and were represented as (OEC)P(H)(sub 2),(OEC)P(CH(sub 3))(sub 2), (OEC)P(C(sub 6)H(sub 5))(sub 2),(OEC)P=O is the trianion of octaethylcorrole.

Cobalt porphyrins having 0-4 meso-substituted ferrocenyl groups were synthesized and examined as to their electrochemical properties in N,N'-dimethylformamide (DMF) containing 0.1 M tetra-n-butylammonium perchlorate as a supporting electrolyte. The examined compounds are represented as (Fc)n(CH3Ph)4-nPorCo, where Por is a dianion of the substituted porphyrin, Fc and CH3Ph represent ferrocenyl and/or p-CH3C6H4 groups linked at the four meso-positions of the macrocycle, and n varies from 0 to 4. Each porphyrin undergoes two reversible one-electron reductions and two to six one-electron oxidations in DMF, with the exact number depending upon the number of Fc groups on the compound. The first electron addition is metal-centered to generate a Co(I) porphyrin. The second is porphyrin ring-centered and leads to formation of a Co(I) π-anion radical. The first oxidation of each Co(II) porphyrin is metal-centered to generate a Co(III) derivative under the given solution conditions. Each ferrocenyl substituent can also be oxidized by one electron, and this occurs at more positive potentials. Each compound was investigated as a catalyst for the electoreduction of dioxygen when adsorbed on a graphite electrode in 1.0 M HClO4. The number of electrons transferred (n) during the catalytic reduction was 2.0 for the three ferrocenyl substituted compounds, consistent with only H2O2 being produced as a product of the reaction. Most monomeric cobalt porphyrins exhibit n values between 2.6 and 3.1 under the same solution conditions, giving a mixture of H2O and H2O2 as a reduction product, although some monomeric porphyrins can give an n value of 4.0. Our results in the current study indicate that appending ferrocene groups directly to the meso positions of a porphyrin macrocycle will increase the selectivity of the oxygen reduction, resulting in formation of only H2O2 as a reaction product. This selectivity of the electrocatalytic oxygen reduction reaction is explained on the basis of steric hindrance by the ferrocene substituents which prevent dimerization. [ABSTRACT FROM AUTHOR]

Open-chain pentapyrroles were isolated as side-products from the synthesis of triaryl-corroles and then converted to the corresponding sapphyrins by catalytic oxidation in acidic media. The investigated compounds were characterized by UV-vis and 1H NMR spectroscopy, mass spectrometry, electrochemistry, and spectroelectrochemistry and are represented as (Ar)4PPyH3 and (Ar)4SH3, where Ar is a F- or Cl- substituted phenyl group, PPy is a trianion of the open-chain pentapyrrole, and S is a trianion of the sapphyrin. Cyclic voltammetry and thin-layer UV-vis spectroelectrochemistry measurements were carried out in PhCN and CH2Cl2 containing 0.1 M tetra-n-butylammonium perchlorate. The open-chain pentapyrroles undergo two reversible one-electron reductions and two reversible one-electron oxidations to generate [(Ar)PPyH3]-, [(Ar)PPyH3]2-, [(Ar)PPyH3]+, and [(Ar)PPyH3]2+ which were spectroscopically characterized. The corresponding sapphyrins exhibit two or three reversible one-electron oxidations in PhCN, but the reductions of these compounds are irreversible because of coupled chemical reactions following electron transfer. Comparisons are made between redox potentials and spectral properties of the open-chain pentapyrroles, sapphyrins, and structurally related corroles. Protonation of the open-chain pentapyrroles and sapphyrins was also carried out in CH2Cl2, and equilibrium constants were calculated by monitoring the spectral changes during titrations with trifluoroacetic acid. The pentapyrroles undergo a simultaneous two-proton addition to generate [(Ar)4PPyH5]2+ while the sapphyrins undergo two stepwise single proton additions to give [(Ar)4SH4]+ and [(Ar)4SH5]2+, respectively. [ABSTRACT FROM AUTHOR]

Gold(III) porphyrins containing two, three, or four β,β'-fused quinoxalines were synthesized and examined as to their electrochemical properties in tetrahydrofuran (THF), pyridine, CH2Cl2, and CH2Cl2 containing added acid in the form of trifiuoroacetic acid (TFA). The investigated porphyrins are represented as Au(PQ2)PF6, Au(PQ3)PF6, and Au(PQ4)PF6, where P is the dianion of the 5,10,15,20-tetrakis(3,5-di-tert-butylphenyl)porphyrin and Q is a quinoxa-line group fused to a β,β'-pyrrolic position of the porphyrin macrocycle. In the absence of added acid, all three gold(III) porphyrins undergo a reversible one-electron oxidation and several reductions. The first reduction is characterized as a AuIII/AuII process which is followed by additional porphyrin- and quinoxaline-centered redox reactions at more negative potentials. However, when 3-5 equivalents of acid are added to the CH2Cl2 solution, the initial AuIII/AuII process is followed by a series of internal electron transfers and protonations, leading ultimately to triply reduced and doubly protonated AuII(PQ2H2) in the case of AuIIIPQ2)+, quadruply reduced and triply protonated AII(PQ3H3) in the case of AuIII(PQ3)+, and AuIII(PQ3)+ after addition of five electrons and four protons in the case of AuIII(PQ4)+. Under these solution conditions, the initial Au(PQ2)PF6 compound is shown to undergo a total of three AuIII/ AuII processes while Au(PQ3)PF6 and Au(PQ4)PF6 exhibit four and five metal-centered one-electron reductions, respectively, prior to the occurrence of additional reductions at the conjugated macrocycle and fused quinoxaline rings. Each redox reaction was monitored by cyclic voltammetry and thin-layer spectroelectrochemistry, and an overall mechanism for reduction in nonaqueous media with and without added acid is proposed. The effect of the number of Q groups on half-wave potentials for reduction and UV--visible spectra of the electroreduced species are analyzed using linear free energy relationships. [ABSTRACT FROM AUTHOR]

Five meso-substituted cobalt(III) corroles were examined as to their catalytic activity for the electoreduction of O2 when coated on an edge-plane pyrolytic graphite electrode in 1.0 M HClO4. The investigated compounds are represented as (TpRPCor)Co(PPh3), where TpRPCor is the trianion of a para-substituted triphenylcorrole and R = OMe, Me, H, F, or Cl. Three electrochemical techniques, cyclic voltammetry, linear sweep voltammetry with a rotating disk electrode (RDE), and voltammetry at a rotating ring disk electrode (RRDE), were utilized to evaluate the catalytic activity of the corroles in the reduction of O2. Cobalt corroles containing electron-withdrawing substituents were shown to be better catalysts than those having electron-donating groups on the three meso-phenyl rings of the triarylcorroles. [ABSTRACT FROM AUTHOR]

The electrochemistry of gold(III) mono- and bis-quinoxalinoporphyrins was examined in CH2Cl2 or PhCN containing 0.1 M tetra-n-butylammonium perchlorate (TBAP) before and after the addition of trifluoroacetic acid to solution. The investigated porphyrins are represented as Au(PQ)PF6 and Au(QPQ)PF6, where P is the dianion of the 5,10,15,20-tetrakis(3,5-di-tert-butylphenyl)porphyrin and Q is a quinoxaline group fused to a β,β′-pyrrolic position of the porphyrin macrocycle; in Au(QPQ)PF6 there is a linear arrangement where the quinoxalines are fused to pyrrolic positions that are opposite each other. The porphyrin without the fused quinoxaline groups, Au(P)PF6, was also investigated under the same solution conditions. In the absence of acid, all three gold(III) porphyrins undergo a single reversible AuIII/AuII process leading to the formation of a Au(II) porphyrin which can be further reduced at more negative potentials to give stepwise the Au(II) porphyrin π-anion radical and dianion, respectively. However, in the presence of acid, the initial AuIII/AuII processes of Au(PQ)PF6 and Au(QPQ)PF6 are followed by an internal electron transfer and protonation to regenerate new Au(III) porphyrins assigned as AuIII(PQH)+ and AuIII(QPQH)+. Both protonated gold(III) quinoxalinoporphyrins then undergo a second AuIII/AuII process at more negative potentials. The electrogenerated monoprotonated monoquinoxalinoporphyrin, AuII(PQH), is then further reduced to its π-anion radical and dianion forms, but this is not the case for the monoprotonated bis-quinoxalinoporphyrin, AuII(QPQH), which accepts a second proton and is rapidly converted to AuIII(HQPQH)+ before undergoing a third AuIII/AuII process to produce AuII(HQPQH) as a final product. Thus, Au(P)PF6 undergoes one metal-centered reduction while Au(PQ)PF6 and Au(QPQ)PF6 exhibit two and three AuIII/AuII processes, respectively. These unusual multistep sequential AuIII/AuII processes were monitored by thin-layer spectroelectrochemistry and a reduction/oxidation mechanism for Au(PQ)PF6 and Au(QPQ)PF6 in acidic media is proposed. [ABSTRACT FROM AUTHOR]

Protonated meso-substituted free-base macrocycles of the form [(Cor)H4]+, [(Cor)H5]2+, and [(Cor)H6]3+ where Cor is the trianion of a given corrole, were chemically generated from neutral (Cor)H3 in benzonitrile by addition of trifluoroacetic acid (TFA) and characterized as to their relative acidity, electrochemistry, and spectroelectrochemistry. Three types of protonated free-base corroles with different electron-donating or electron-withdrawing substituents at the meso positions of the macrocycle were investigated. One is protonated exclusively at the central nitrogens of the corrole forming [(Cor)H4]+ from (Cor)H3, while the second and third types of corroles undergo protonation at one or two meso pyridyl substituents prior to protonation of the central nitrogens and give as the final products [(Cor)H5]2+ and [(Cor)H6]3+, respectively. Altogether the relative deprotonation constants (pKa) for 10 different corroles were determined in benzonitrile and analyzed with respect to the molecular structure and/or type of substituents on the three meso positions of the macrocycle. Mechanisms for oxidation and reduction of the protonated corroles are proposed in light of the electrochemical and spectroelectrochemical data. [ABSTRACT FROM AUTHOR]