Hideo Konami

Inter-ring overlap integrals in dimer complexes of phthalocyanines and porphyrins

Abstract Overlap integrals of phthalocanine (Pc) and porphyrin (Pp) dimers were calculated on changing the distance and rotation angle between two macrocycles. The HOMOs of Pc 2− and Pp 2− are both a 1u and were found to give large overlap integrals. The origin of this strong overlap was clarified by a comparison between the four-orbital model and the perimeter model.

Structures of chlorosomes and aggregated BChlc inChlorobium tepidum from solid state high resolution CP/MAS13C NMR

Cross polarization/magic angle spinning (CP/MAS)13C (solid state high resolution) NMR spectra were observed for chlorosomes and BChlc aggregates. Similarity of both kinds of spectra (except for some signals assignable to proteins and lipids in chlorosomes) indicates that BChlcs in chlorosomes are present just as in synthetic BChlc aggregates. Chemical shifts for C131 carbonyl and C31 hydroxylethyl carbons indicate hydrogen bonding between them. Comparison of solution and solid state13C NMR chemical shifts shows the five coordinated nature of BChlc aggregates. Some chemical shift differences were attributable to ring currents shifts. Their comparisons with calculated ring current shift values predicted structures for the aggregates. Cross polarization dynamics of the CP/MAS13C NMR signals explored dynamic and structural nature of the BChlc aggregates.

Redox potentials of a series of lanthanide-bisphthalocyanine sandwich complexes

Electrochemical measurements on a series of [NBu4][Ln(III)Pc2] ([NBu4]=tetra(n-butyl)ammonium; Ln=Y, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Tm, Er, Yb, and Lu; Pc=phthalocyanine) are reported. The first and second oxidation potentials decrease linearly with a decrease in ionic radii of the center metals, while the reduction potentials showed no observable change. A few complexes of earlier lanthanides showed irreversible redox couples at the second oxidation potentials.

An analysis of paramagnetic shifts in proton NMR spectra of non-radical lanthanide(III)-phthalocyanine sandwich complexes

Abstract Proton NMR spectra of [NBu4] [Ln(III)Pc2] ([NBu4] = tetra (n-butyl)ammonium; Ln = Y, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Tm, Er, Yb and Lu; Pc = phthalocyanine) are reported. Analysis of NMR and UV-visible spectra suggests a highly symmetrical structure for [LnPc2]− in solution. Contact shifts and pseudo-contact shifts were separated from the observed paramagnetic shifts by a statistical analysis and the results compared with data from other LSR complexes.

Third‐order nonlinear optical properties of phthalocyanine and fullerene

We studied the third‐order nonlinear optical properties of phthalocyanine and fullerene in solution and in thin film form through third‐harmonic generation measurement. X‐ray diffraction measurement and scanning electron microscopy observation were also conducted to investigate the relationship between nonlinear optical and structural properties of the thin film. The nonlinearities depend on the π‐conjugated length and the introduction of a central metal atom. We clarify the factors for forming suitable thin films by organic molecular beam deposition. It is shown that both the crystal structure and molecular alignment can be controlled to enhance the nonlinearities of the phthalocyanine thin film, thereby providing the maximum third‐order susceptibility of 3.0×10−10 esu. We show that nonlinearities of the thin films can be estimated experimentally from those of solutions.

THE LOWEST EXCITED TRIPLET STATES OF LANTHANIDE BISPHTHALOCYANINE COMPLEXES STUDIED BY TIME RESOLVED ELECTRON PARAMAGNETIC RESONANCE

Interplanar interactions were analysed for metal bridged phthalocyanine dimers, [NBu4] [M(III)Pc2] (M = Y, Yb and Lu), by using zero field splitting (ZFS) parameters in the T1 states. The observed ZFS D and a triplet lifetime decreased remarkably due to dimerization. From a comparison of D between the monomer and the dimer the interplanar interactions are divided into two types: exciton and charge resonance. It is found that nearly 50% of the charge resonance contribution (b 2) is involved in the T1 state of LuPc- 2. The correlations between b 2, the triplet lifetime and the ionic radius of the central metal are discussed in terms of the charge resonance interaction.

Molecular structures and optical properties of aggregated forms of chlorophylls analyzed by means of magnetic circular dichroism

Abstract Magnetic circular dichroism (MCD) spectra were measured on chlorophylls in different aggregation states formed in organic solvents and in pigment-protein complexes. An index which reflects the magnetic dipole contribution of a specific transition is introduced, that is, a ratio of MCD intensity of Faraday B-term (B) to that of dipole strength (D) (B/D). The absolute value of the index is higher in monomeric chlorophyll a and that in monomeric bacteriochlorophyll a. This index changed depending on the aggregation state of bacteriochlorophyll; in the case of the dimer of bacteriochlorophyll a and bacteriochlorophyll d the value was nearly the half of that of respective monomer, and it decreases further for a higher aggregate of bacteriochlorophyll d. Based on this index, a molecular structure of the primary electron donor in reaction center complexes is discussed.

Electronic spectra of benzo-substituted phthalocyanines

Various types of 2,3- and 1,2-benzo-substituted zinc-phthalocyanines were prepared to investigate the influence of the substitutions on the electronic states of phthalocyanine (Pc) compounds. The experimental data showed that these compounds can be categorized by their spectral patterns. A simple perturbation method based on the group theory (symmetry-adapted perturbation method) is presented to analyse the spectroscopic changes of Pc compounds caused by the substitutions. This method was tested against the experimental data and gave good agreement.

Marked detergents effects on safranine T-mediated photo-induced electron transfer in cytochrome P-450 1A2

Cytochrome P-450 accepts electrons from electron transfer proteins to facilitate monooxidation reactions. It is suggested that basic amino acids such as Lys and Arg on the P-450 molecular surface interact with acidic amino acids such as Glu and Asp of the electron transfer protein. Safranine T is a basic compound which mediates electron transfer with illumination. It was found with flash photolysis that an electron from photo-reduced safranine T quickly reaches the heme iron of cytochrome P-450 1A2 (P-450 1A2). The photo-induced reduction kinetics of P-450 1A2 were analyzed by the Runge-Kutta method on the second order assumption. The electron-transfer rate constant from safranine T to P-450 1A2 was 2.1 x 10(6) M-1s-1. The rate constant was remarkably increased up to 3.1 x 10(8) M-1s-1 by adding cholic acid, while that was drastically reduced down to 3.5 x 10(4) M-1s-1 by adding Emulgen 913. The electron-transfer rate of a His163-Glu mutant, which has a 40 mV lower redox potential than that of the wild type, was the same as that of the wild type in the absence of the detergents, although the reduced fraction of the mutant was 30% lower than that of the wild type. The electron-transfer rate of the mutant also changed significantly by adding the detergents in the same way as the wild type. Based on these results, together with optical absorbance and fluorescence data, we discuss the inter- and intramolecular electron-transfer mechanism of P-450 1A2.

Spectral hole burning on silicon phthalocyanines isolated in an argon matrix

Abstract Irradiation of the monomeric phthalocyanine Hex3SiO(SiPc)OSiHex3 isolated in an Ar matrix at T=13 K with the 632.8 nm line of a He/Ne laser produces a resonant spectral hole in the vibrational sideband located about 700 cm−1 above the origin of the Q band. This hole is accompanied by several sideholes in the origin region. These permit a precise determination of several excited-state vibrational frequencies. For dimeric Hex3SiO(SiPc-O-SiPc)OSiHex3 in the same matrix the changes in the absorption spectra after irradiation into the Q band reveal an out-of-plane polarization of the bands which are not present in the monomer absorption. This points to substantial charge-resonance contributions to the excitonic coupling between the two SiPc units in dimeric Hex3SiO(SiPc-O-SiPc)OSiHex3.