Journal of Porphyrins and Phthalocyanines

Bis(phthalocyaninato(2-)iridium(II)) reacts in methanol with excess tetra(n-butyl)ammonium hydroxide to yield tetra(n-butyl)ammonium hydroxomethoxophthalocyaninato(2-)iridate(III). The complex salt crystallizes as a methanol solvate in the monoclinic space group P2₁/n(No. 14) with cell parameters a = 12.510(1) Å, b = 19.561(3) Å, c = 18.489(2) Å, = 90.42(1) °, Z = 4. The Ir atom is hexacoordinated with four isoindole N atoms (N_iso) of the severely saddled pc ligand and two O atoms of the hydroxide (O1) and methoxide (O2) ligand respectively in a mutual trans arrangement. The average Ir-N_iso distance is 1.981(5) Å, the Ir-O1 distance 2.038(7) Å and the Ir-O2 distance 2.061(6) Å. The O atom of the solvate (O3) is bound to O2 by a strong hydrogen bond with an O2-O3 distance of 2.60(1) Å.

Liquid secondary ion mass spectrometry (LSIMS) and collision-induced dissociation (CID) were used for the characterization of sulfonamide derivatives of meso-tetraphenylporphyrin (TPP). The spectra obtained using LSIMS show abundant molecular ions and fragment ions from losses of the sulfonamide moieties. The main fragmentation observed in the LSI mass spectra and in the CID spectra of the protonated or cationized molecules involves the loss of one sulfonamide group. In addition, in the CID spectra of these compounds the fragment ions formed by the elimination of two, three and/or four sulfonamide groups are also observed. The CID spectra of the protonated or cationized molecules of these derivatives do not display the ions formed by the cleavage of the S-N bond which have been reported for other sulfonamide compounds. The LSI mass spectra and CID spectra of sulfonamide derivatives of meso-tetraphenylporphyrin provide an easy and reliable means of identification of the number and nature of sulfonamide groups in the porphyrinic ring.

Mn(III) complexes of meso-tetra(o,o′-dichlorophenyl)porphyrin, tetra-tert-butyl-tetraazaporphine and 3,5-octanitrophthalocyanine are efficient catalysts of naphthalene oxidation by peracetic acid in acetonitrile solution. The pathways of the reaction and the nature of intermediates and final products depend on the catalyst structure. For meso-tetra(o,o′-dichlorophenyl)porphyrin MnCl and tetra-tert-butyl-tetraazaporphine MnCl the single primary oxidation product is 1-naphthol. For 3,5-octanitrophthalocyanine MnCl, two pathways of naphthalene oxidation yielding 1-naphthol (as the primary product) and 1,4-naphthoquinone are proposed. The pathway of 1,4-naphthoquinone formation in the 3,5-octanitrophthalocyanine MnCl-catalysed reaction seems to involve two intermediates, 1,4-endo-peroxy-1,4-dihydro- and 2,3-epoxy-1,4-endo-peroxy-1,2,3,4-tetrahydronaphthalene.

Electronic absorption spectroscopy was used to measure the molecular association of copper phthalocyanine tetrasulfonate in micellar solutions, a microemulsion made with cationic surfactant, and homogeneous solvents. Analysis of absorbance versus concentration data using a multiple-aggregation model and non-linear regression analysis gave values of association constants, molar absorptivities and estimates of average aggregation number. Microemulsions and aqueous micellar solutions made with alkylammonium surfactants inhibited aggregation, probably because of interactions between the phthalocyanine sulfonate groups and the cationic surfactant head groups at interfacial surfaces. Similar aggregation behavior was observed previously in multiple-bilayer films of cationic surfactants. Water and aqueous solutions containing tetraethylammonium bromide or anionic SDS micelles provide environments facilitating extensive aggregation of Cu^IIPcTS⁴⁻. The major species are dimers in water and acetonitrile/water, but the formation of higher aggregates is promoted by addition of SDS or TEAB. Aprotic organic solvents provide environments intermediate between these two extremes, giving relatively large aggregation numbers (i.e. five to seven) but smaller association constants than aqueous media not containing cationic surfactants.

Interactions between planar Cu phthalocyanine molecules, CuPc, arranged in vertical stacking sequence are studied by first-principles density functional (DF) and semiempirical molecular dynamics (MD) methods. Dependence of electronic structure upon interplanar spacing and staggering angle is analyzed in order to interpret observed electrical conductivity and magnetic coupling behavior of partially oxidized Cu(pc)I. MD predictions of equilibrium structure of dimers and tetramers are in excellent agreement with experiment on the linear chain species. DF predictions of interaction energy of dimers are compared with MD and experiment.

Catalytic systems consisting of cobalt phthalocyanine grafted to maleic anhydride-styrene copolymer chemically linked with γ-aminopropylated silochrome have been prepared. In the process of sulfide oxidation with air oxygen the specific catalytic activity of these systems depends strongly on the phthalocyanine concentration in the catalyst. At low phthalocyanine concentrations (below 0.4 × 10⁻⁶ mol g⁻¹) the catalytic activity is more than an order of magnitude larger than that of homogeneous catalysts and cobalt phthalocyanine adsorbed on a silochrome surface. The different ways of preparing the catalysts are reflected in the kinetic characteristics of the oxidation process.

The crystal structure of the triflate salt of the title compound, [Me₃TPP][CF₃SO₃], was investigated to obtain structural information on the conformation of N-trimethylated 5,10,15,20-tetraarylporphyrins. The molecular stereochemistry of the cation is characterized by an up/down/up arrangement for the three N-methyl groups with significant pyramidalization at the nitrogen atoms. The macrocycle is severely distorted with an average deviation from planarity of 0.438 Å. The distortion mode is an asymmetric saddle with deviations from the 4N plane of the C_b atoms at N-methylated pyrrole rings exceeding 1.1 Å. The out-of-plane displacements of pyrrole ring IV are significantly smaller than those of the methylated pyrrole rings.

Tetrakis(trimethysilyl)phthalocyaninatoruthenium(II) (5) has been synthesized via the biaxially coordinated ((CH₃)₃Si)₄PcRu(3-Clpy)₂ (2) complex by thermal decomposition of the axial ligands of 2. ((CH₃)₃Si)₄PcRu (5) was characterized by NMR, IR and UV-vis spectroscopy and elemental analysis. The trisubstituted ((CH₃)₃Si)₃PcRu(3-Clpy)₂ (3) and disubstituted ((CH₃)₃Si)₂PcRu(3-Clpy)₂ (4) complexes, formed as side products during the thermolysis of 2, could be isolated and characterized.

Several zinc(II) and aluminum(III) phthalocyanines substituted by carboxylic acid and sulfonic acid groups were anchored to nanocrystalline TiO₂ films. By irradiation with visible light the photovoltaic behavior of the electrodes containing LiI/LiI₃/propylene carbonate electrolyte was measured. Most efficient results were found using zinc(II) 2,9,16,23-tetracarboxyphthalocyanine, with a current conversion efficiency at 700 nm approaching 45%. It is shown that electron injection into TiO₂ occurs from the excited singlet state of the phthalocyanine derivatives. High stability of the cell performance under continuous irradiation was found.

Potential step chronoamperospectrometry (PSCAS) measurement was carried out to investigate the one-electron transfer in the reduction of tetraphenylporphyrin cobalt(III) ([Co^IIITPP(−2)]⁺) incorporated into a Nafion or poly(4-vinylpyridine-co-styrene) (P(VP-St)) film coated on an ITO electrode. The electron transfer of the redox centers in the two systems occurred by a physical diffusion mechanism. The fraction of the electroactive complex (R_ct) was independent of the CoTPP concentration in P(VP-St) but decreased with increasing CoTPP concentration in Nafion, especially at high concentrations. In both systems the apparent diffusion coefficient D_app decreased with increasing CoTPP concentration. The D_app value in Nafion (1.6 × 10⁻⁸cm²s⁻¹ at 0.02 M) was much higher than that in P(VP-St) (1.1 × 10⁻¹⁰cm²s⁻¹ at 0.02 M). The difference in the electron transfer process in the two systems was ascribed to the interaction of the redox center with the polymer framework, the morphology of the polymer matrix, the localization of the redox species in the hydrophilic/hydrophobic region, and the counterion migration under the potential step.