Search

Twenty-one hybrid materials incorporating cobalt(III) corrole complexes were synthesized by a sol-gel process or by grafting the metallocorrole onto a mesostructured silica of the SBA-15 type. All the materials show an almost infinite selectivity for carbon monoxide with respect to dinitrogen and dioxygen in the low-pressure domain where the chemisorption phenomenon is predominant. This peculiar property is of prime importance for an application as a CO sensor. The selectivity slightly decreases at high pressures where nonselective physisorption phenomena mainly occur. The percentage of active sites for CO chemisorption ranges from 22 to 64 %. This low percentage may be attributable to interactions between the cobalt(III) corroles with silanol or siloxane groups remaining at the surface of the materials which prevent further coordination of the CO molecule. Notably, the most efficient materials are those prepared in the presence of a protecting ligand (pyridine) during the gelation or the grafting process. The removal of this ligand after the gelation process releases a cavity around the cobalt ion that favors the coordination of a carbon monoxide molecule. The CO adsorption properties of the SBA-15 hybrid were not affected over a period of several months thus indicating a high stability of the material. Conversely, the xerogel capacities slowly decrease owing to the evolution of the material structure.

The synthesis and characterization of a new series of relatively flexible cofacial donor-acceptor dyads for singlet-singlet energy transfer with the corrole or etio-porphyrin free base and zinc porphyrin is described, as the acceptor and donor. The results show that the presence of a bulky group located between the acceptor and the donor moiety influences the energy transfer rate.

The formation of a [pi]-complex of a free-base bisporphyrin (H4DPOx) with acridinium perchlorate (Ac[H.sup.}Cl[O4.sup.-]) and the photodynamics in benzonitrile (PhCN) is reported. Results reveal that a 1:1 [pi]-complex is formed between H4DPOx and Ac[H.sup.} in PhCN with a large binding constant.

The synthesis of bisporphyrins and estimation of the efficient surface of the chromophores for O(sub 2) interactions are presented. It is concluded that there is a diffusion mechanism of O(sub 2) towards the chromophore contrasting with a static mechanism and it is possible for the preparation of effective O(sub 2) sensing porphyrins at an extreme price.

A combination of potentiometric and absorption spectroscopic data allowed to characterize the formation and the dissociation mechanism of octacoordinated lead complexes of primary and tertiary tetrakiscarbamoylmethyl cyclam derivatives. In solution, the Pb(super 2+) cation is entrapped in a molecular cage constituted by the four macrocyclic nitrogen and the four amidic oxygen atoms.

The selectivity of the reaction of two linear tetraamines with pyruvic aldehyde, the cyclization of the bisaminal intermediates with biselectrophilic reagents, and the quaternization of the protected macrocycles are discussed. The structure of the compounds was solved by X-ray diffraction, and the unexpected results are rationalized according to the molecular modeling calculations.

The synthesis of a novel family of heterobinuclear cofacial biphenylene (B), anthracene (A), 9,9-dimethylxanthene (X) or dibenzofuran (O) bridged porphyrin-corrole complexes, (PCY)MCICoCl, is reported, M being either an iron(III) or manganese(III) ion. Each complex is characterized by electrochemistry, mass spectrometry, UV-vis, IR, and electron spin resonance spectroscopy.

A study was carried out on the free base and biszinc(II) complexes of 5,17-bis[5(2,8,13,28-tetramethy-porphyrin0]-25,26,27,28-tetrapropoxycalix[4]arene that was obtained in four and five steps respectively. Details of the photophysical data and variable-temperature (super 1)H NMR that shows an open geometry of the two porphyrin macrocyles at 298 K are discussed.

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.

Research has been conducted on the cofacial biscorroles and linked Co(II) porphyrins and Co(III) corroles. The synthesis and characterization of these compounds with the same face to face orientation are discussed.

Research has been conducted on the cyclam-based manganese(II) complexes. The electrochemical, EPR and variable-temperature magnetism data of [(tmc)MnCl]. X have been investigated and the results are reported.

Research has been conducted on the (BCA)Co (sub)2 and (BCB)Co (sub)2 where BCA and BCB are biscorroles linked by anthracenyl and biphenyl bridge. The synthesis, spectroscopic properties and electrochemistry of these compounds have been investigated, and the effect of the anthracenyl and biphenyl bridge on the ligand binding properties has been examined.

Research has been conducted on the alkyl- and aryl-substituted cobalt(III) corroles. The synthesis, spectroscopic properties and electrochemistry of these corroles have been investigated and the results of the ligand binding and electrochemical reactions are described.

Research describes synthesis of a new series of heterobimetallic cofacial diporphyrins containing luminescent Ga(III) centers. The reduction of dioxygen by cofacial cobalt(II) diporphyrins is studied by photophysical and spectroscopic methods.

Research has been conducted on the sigma-bounded organo-iron and -cobalt porphyrins. The examination of these porphyrins as a compound oxidation state function had been carried out.

A study was conducted to analyze homogeneous electron-transfer kinetics for the oxidation of different iron(III) porphyrins using three oxidants in deaerated acetonitrile. The reorganization energies of the rate-determining oxidation of iron(III) and iron(IV) were examined based on the Marcus theory of electron transfer. Results indicated that the size of the metal ion changes the degree of planarity of the porphyrin macrocycle.

Several iron porphyrins with sigma-bonded methyl, phenyl and substituted phenyl axial ligands were synthesized and characterized. Four new sigma-bonded aryl iron(III) porphycenes have been synthesized and characterized. They are represented as (EtioPc)Fe(R), with each compound characterized and compared to similar sigma-bonded aryl iron(III) complexes, having the octaethylporphyrin macrocycle. The reaction may or may not involve the metal center in the second reduction of the sigma-bonded porphyrins, and the second reduction of the sigma-bonded porphycenes only occurs at the macrocycle.

A systematic investigation of the redox properties of five sigma-bonded porphyrins in the OEP series under experimental conditions where a third oxidation might be observed at very positive potentials was conducted. The porphyrins were represented as (OEP)Fe(R), where R = C6H5, 3,4,5-C6F3H2,2,4,6-C6F3H2,C6F4H, or C6F5. Results demonstrate that neither the iron(III) spin state nor the ligand field strength of the sigma-bonded axial ligand are key factors in the occurrence of such reaction.

A five step procedure has successfully generated symmetrical cylindrical macrotricyclic ligands. Aromatic chains link cyclam subunits and nitrogen atoms. Binuclear species are formed with the ligand coordination of either divalent copper or divalent nickel. X-ray diffraction studies were undertaken to determine the crystal structure of these ligands. The cell unit dimensions are presented.

An experiment was conducted to examine the electrochemistry and ozonation reactions of manganese (III) dodecaphenylporphyrins compounds and their derivatives. Nuclear magnetic resonance (NMR) and UV-visible spectra were performed on the compounds using UV and NMR spectroscopy. Results showed that each (P)MnCl derivative can exist in five different oxidation states and that all compounds are stable in their neutral form and even during the addition of three electrons.

Chemical research has established the structure and spectral properties of bis(lutetium) derivatives of the anthracenyl-and biphenylenyl-bridged cofacial porphyrins [Lu(OH)]2.CH3OH and [Lu(OH)]2.CH3OH. X-ray analysis identifies dark blue crystals of 3' and 4' from the monoclinic system. The complexes have one or several metal-bonded bridging ligands.

Chemical research has established how to synthesize three rare earth metal lanthanide complexes consisting of Ce, Gd and Eu with 1,4,8,11-tetrakis-(2-carboxyethyl)-1,4,8,11-tetraazacyclotetradecane ligand (TETP). X-ray crystallography and molecular modelling analysis shows that a centrosymmetric TETP macrocyle with a [3434] conformation exists in the crystal structures of [Ce(H2TETP)]-(OH)(H2O).10H2O, [Gd(H3TETP)(OH)2(H2O)2.3H2O and [Eu(H3TETP)(OH)2(H2O)2.3H20. The chemical structures for each complex is given.

The electrochemistry of eight nickel porphycenes reveals the substituent dependency of the highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) separation of 2.25 V. The substituents are present on the pyrrole beta and/or the ethylenic carbons of the porphycene macrocycle. Moreover, substitutions at the ethylenic carbon have greater effect compared to those at pyrrole beta. The HOMO-LUMO energy gap value lowers as the conjugation of the porphycene ring is extended.

The synthesis and characterization are reported for a heterodinuclear complexes (DP)CoM(X), where DP(super 4-) is the tetraanion of the biphenylenylbisporphyrin and X = O, OAc, Cl, OH, or acac coordinated to M = Ti, Ga, In, Sc, or Lu. Mass spectrometry, UV-visible, IR, ESR, and NMR spectroscopies are used for characterizing these complexes. The electrochemical study in (DP)CoLn(X) (Ln = Lu, Sc) complexes show that the presence of two cobalt centers is unnecessary for a good catalytic behavior towards dioxygen.

UV-visible, 1H NMR, and IR spectroscopic studies of several neutral, oxidized heteroleptic phthalocyaninato and porphyrinato complexes of Zr(IV) and Hf(IV) indicate that these double-decker complexes undergo ring-centered reversible oxidation and reduction reactions. The nature of the porphyrin ring influences the half-wave potentials of both the reactions, which also depend on ion size during oxidation. A decrease in ionic radius facilitates easy oxidation.

A new method enables the synthesis of a novel family of heterobimetallic cofacial biphenylene-bridged or anthracene-bridged bisporphyrin, (DP)CuMnX. (DP- 1,8-bis(2,8,13,17-tetraethyl-3,7,12,18-tetramethylporphyrin-5-yl, B-Biphenylene, A-Anthracene)). Spectroscopic studies of the complexes reveal the metal-metal interactions and magnetic susceptibility studies suggest the interactions to be ferromagnetic. X-ray diffraction studies help determine the structure of (DPB)CuMnCl, which forms a reversible oxygen adduct at room temperatures.

Cyclic voltammetric studies help examine the redox properties of sigma-bonded metalloporphycenes, (EtioPc)M(C6H5) where M=Fe or In and EtioPc = dianion of 2,7,12,17-tetraethyl-3,6,13, 16-tetramethylporphycene in different mediums. (EtiOPc)Fe(C6H5) undergoes three one-electron oxidations generating an iron(IV) porphycene, an iron(IV)Pi cation radical and a dication respectively. Both sigma-bonded systems exhibit two one-electron reductions at the conjugated Pi ring system. Spectrochemical data and a comparative study with (EtiOPc)FeCl/and (EtioPC)In(C6H5) help assign electron transfer centers for oxidation and reduction of (EtioPc)Fe(C6H5).

An analysis of Fe(III) mu-oxo porphycene dimers reveals that they are stable under nine different cyclic voltammetric time scale-based oxidation states. Thin-cell layer-based reduction yields two stable reduced ((Pc)Fe)2O forms. Spectral data reveal that the dimer reduction occurs at the conjugated pi-ring system.

Addition of related Grignard reagents to the dication of dimetallodiporphyrins is used to synthesize various cofacial bisorganometallic diporphyrin complexes, M2III/IIIR2diporohyrinatobiphenyle (M = Ru, Os and R = methyl, p-tolyl, 3,5-bis(trifluoromethyl)phenyl). H NMR, cyclic voltammetry, UV-vis and mass spectrometry are used to characterize there paramagnetic compounds. Diamagnetic species, (M2II/IIR2DPB)2-, where DPB = diporohyrinatobiphenyle, is generated from quantitative two-electron chemical reduction of paramagnetic M2III/IIIR2DPB complexes.

Spectroelectrochemical and electrochemical methods reduced flurophenyl sigma-bonded iron(III) porphyrins, resulting in OH- and RH. The porphyrins involved in the process are (P)Fe(C6F4H) and (P)Fe(C6F5). The unreduced (P)Fe(R) has an axial flurophenyl ligand that is displaced by OH-, inducing a chain reaction that enables total conversion of the sigma-bonded porphyrin to monomeric (P)FeOH. Substoichiometric quantities of OCH3- or F-, when added to (P)Fe(R), yields identical Fe(III) prophyrin products.

The synthesis of a cofacial dirhodium(II) diporphyrin, Rh2DPB, and its reactivity with H2 in the presence of ancillary ligands were reported. The reaction of Rh2DPB with H2 in the presence of CO yields a result different from that of monomeric porphyrins. The H2 cleavage reaction seems to occur within the cavity of the cofacial diporphyrin, on the basis of the unusually high T1 values of the resultant dimeric hydrides.

A study is made on the isolation and comprehensive characterization of the stable superoxo complex of the cofacial diporphyrin ((u-O2)Co2(DPB)(DPIm)2)(PF6) and its nonaqueous electrochemistry. The results indicate the development of a new and better total synthesis of the free-base porphyrin H4(DPB). The large scale synthesis of the free-base porphyrin is made possible by the synergism of new reaction sequences, increased reaction scales and better product yields.

A study is made on the synthesis and characterization of novel cobalt aluminum cofacial porphyrins. These heterodinuclear complexes are formed by selective metalation of the cofacial diporhpyrins with cobalt and aluminum and each complex is characterized by mass spectrometry and UV-vis, IR, ESR and 1H NMR spectroscopies. The results reveal the first crystal structure of a heterobimetallic cofacial diporphyrin. An improvement of the synthesis of the (DPA)H4 free-base porphyrin in both scale and yield is also achieved.

A stable, bridged dinitrogen complex ofa biphenylene bridged diporphyrin, diruthenium cofacial diporphyrin, was characterized with respect to its preparation, structure, ligand substitution reactivity, electrochemistry and acid-base properties. It is proposed as a model for a dinitrogen reduction catalyst based on cofacial metallodiporphyrins. Moreover, the chelation of the dinitrogen by the two tethered metal centers is suggested to contribute to the stability of the complex.

The oxidative coupling of two ruthenium (II) ammine ligands to form a bridgeddinitrogen complex of a metallodiporphyrin was examined. The nitrogen hydride intermediates involved were isolated and characterized with respect to electrochemical and acid-base properties of each of the two successive two-electron/two-proton oxidative conversions. In addition, mechanisms of ammonia oxidation are proposed.

New synthetic approaches have been developed for arbor porphyrins, or two potentially useful families of tris(2-aminoethylamine) (TREN)-capped porphyrins with sterically hindered coordination cavities. Nuclear magnetic resonance imaging showed tri- and tetralinked structures. The adduct with tetralinked geometry was afforded by the reaction of 1 equiv of TREN with 1 equiv of meso-(tera-o-chloroacetamidophenyl)porphyrin, while the trilinked derivative corresponding to one of the final compounds was afforded by the use of excess Ag+ to complex with TREN and form a template.

A series of manganese(III) corroles are examined as to their electrochemistry and spectroschemistry in nonaqueous solvents. Complexation with one or two anionic axial ligands has led to an easier oxidation and a harder reduction as compared to the uncomplexed four-coordinate species.

A study was conducted to determine the use of Co(III) corroles as efficient catalysts for the reduction of dioxygen in the presence of perchloric acid in both heterogeneous and homogeneous systems. The results showed that cobalt corroles could be used as effective catalysts in the reduction of [O.sub.2] with HCl[O.sub.4] via the redox couple between Co(III) corroles and Co(III) corrole radical cations.

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.

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.

The catalytic mechanisms of the dehydrogenation vs the oxygenation of 10-methyl-9,10-dihydroacridine (AcrHR) in the two electron and four-electron reduction of O2, catalyzed by monomeric cobalt porphyrins and cofacial dicobalt porphyrins, respectively, are discussed in relation to the C(9)-H or C(9)-C bond cleavage of AcrHR radical cations produced in the electron-transfer oxidation of AcrHR.

Ferrocene derivatives, which are one-electron reductants, are used in the efficient four-electron reduction of dioxygen. Cofacial dicobalt porphyrins, a bimetallic system, essential for the four-electron reduction of oxygen in the case of cobalt porphyrins, are employed as catalysts in the presence of perchloric acid in benzonitrile.

The energy transfer that may occur via short (Dexter) and long distance interactions (Forster) is demonstrated. The energy transfer can occur at long distances for meso-substituted porphyrins because the meso carbons exhibit a large electronic density.

Research has been conducted on alkyl- and aryl-substituted corroles. The authors have investigated the effect of solvents on spectroscopic properties and electrochemistry of these compounds in nonaqueous media.

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.