Effect Of Central Metal Research Articles

Effects of central metal on the photophysical and photochemical properties of non-transition metal sulfophthalocyanine

The photophysical and photochemical properties and quenching (by 1,4-benzoquinone) of metallophthalocyanine sulfonates of aluminium ( AlPcSmix), zinc ( ZnPcSmix), silicon ( SiPcSmix), germanium ( GePcSmix) and tin ( SnPcSmix) are presented. The quantum yield values of fluorescence (ΦF), triplet state (ΦT), singlet oxygen (ΦΔ) and photodegradation (Φd) were determined and the observed trends in their variation among the complexes discussed in terms of aggregation and the heavy atom effect. 1,4-benzoquinone effectively quenched the fluorescence of the complexes. Quenching analyses gave positive deviations from Stern-Volmer behavior, suggesting the existence of static quenching in addition to dynamic quenching. The static and dynamic components of the quenching were separated using a modified Stern-Volmer equation and the “sphere of action quenching model”. The quenching constant was found to be a function of the radius of the central metal ion.

Central metal effect on the organization of porphyrin LB films

Monolayers and Langmuir–Blodgett (LB) films of 5,10,15,20-tetra-4-oxy (2-stearic acid) phenylporphyrin (TSPP) and its complexes TSPPCu(II) and TSPPMn(III)Cl have been studied. π– A isotherms show that the molecular areas of the three molecules are similar to one another, while the polarized UV-vis spectra of the transferred films show different tilt angles of macrocycles with respect to the substrates: TSPP, 31°; TSPPCu(II), 0°; TSPPMn(III)Cl, 52°. The UV-vis spectra show that the π– π interactions between porphyrin macrocycles in monolayers of these three porphyrins are different. The Brewster angle microscopy (BAM) observations suggest that the monolayer behavior is also dependent on the central metal ions. These results indicate that the central metal ions have great influence on the organization of the films.

Remarkable effects of metal ions and axial bases on catalytic and asymmetric oxidation of simple olefins with a “twin-coronet” porphyrin

Effect of central metals and oxidants on the catalytic and asymmetric epoxidation of simple olefins was evaluated with a chiral binaphthalene-linked twin-coronet porphyrin catalyst, whose Mn derivative gave superior ees of resultant epoxide than the corresponding Fe derivative.

Catalytic Epoxidation of Cyclooctene with Oxygen Using Electrochemically Reduced Metalloporphyrins

Abstract Epoxidation of cyclooctene with molecular oxygen was achieved using electrochemically reduced metalloporphyrins in N,N-dimethylformamide (DMF) containing acetic anhydride as an electrophile. Turnover numbers 5–7 based on moles of cyclooctene oxide produced per moles of porphyrin were obtained by the use of [5,10,15,20-tetrakis(pentafluorophenyl)porphinato]iron(III) chloride and [5,10,15,20-tetra(l-naphthyl)porphinato]manganese(III)chloride. The effects of central metals and substituents on phenyl groups of matalloporphyrins were also investigated. Rate constants (k) were estimated by way of digital simulation of cyclic voltammograms based on a simple ECE reaction mechanism. The reaction mechanism in the presence of cobalt(II) complexes seemed to be somewhat different from that in the presence of iron(III) or manganese(III) complexes.

Double Melting Behavior of Disk-like Complexes Substituted by Long Chains, 1: the Substituent Effect

Abstract The bis (β-diketonato) copper (II) complexes, 2c and 2d. exhibit double melting behavior; 2c (m.p. of K1:122.4 - 122.8[ddot]C, m.p. of K2:135.2 - 135.6[ddot]C), 2d (m.p. of K1:168.8 - 169.2[ddot]C. m.p. of K2:208.3 - 208.6[ddot]C). The corresponding β-diketone ligands, 1c and 1d, also exhibit double melting behavior; 1c (m.p. of K1:83.4 - 83.9[ddot]C. m.p. of K1:84.9 - 85.4[ddot]C). 1d (m.p. of K1:103.5 - 103.6[ddot]C, m.p. of K2:108.1 - 108.2[ddot]C). 2c and 2d are the first examples exhibiting double melting behavior in the disk-like transition metal complexes substituted by long chains. Because the previously reported complexes (2a and 2b) exhibit discotic mesomorphism, the double melting behavior of 2c and 2d is thought of as thermal behavior close to mesomorphism. The chief determining factors which lead to either mesomorphism or double melting behavior are the substituent effect and the effect of central metal.