Highly Active Catalysis of Cobalt Tetrakis(pentafluorophenyl)porphyrin Promoted by Chitosan for Cyclohexane Oxidation in Response-Surface-Methodology-Optimized Reaction Conditions.

We aimed at elevating catalytic performances of cobalt tetrakis(pentafluorophenyl)porphyrin (Co TPFPP) through axial coordination, nanocavities, and covalently grafting action. The Co TPFPP was immobilized onto nanoporous and nonporous chitosan, forming Co TPFPP/np- and nonp-CTS catalysts, respectively. The catalysts were characterized by various spectroscopic techniques. The catalytic performances of these catalysts for cyclohexane oxidation under response-surface-methodology-optimized oxidation reaction conditions were estimated and compared. Co TPFPP/np-CTS was an excellent catalyst at aspect of catalytic activity, exhibiting the considerable potential reusability, 24.2 mol % yields (KA oil : cyclohexanone and cyclohexanol) in average, and total turnover frequencies (TOFs) of 3.25×106 h-1. This is attributed to the structural characteristics of the Co TPFPP/np-CTS catalyst: the cobalt porphyrin molecules could be highly scattered on CTS, forming the independent active sites, and were not leached. The axial coordination exerted the most important effect on the catalytic activity, and the covalent grafting action had a decisive effect on the increase of the total TOFs and on the reusability of the catalyst.

Population Genetic Structure and Phylogeography of Camellia flavida (Theaceae) Based on Chloroplast and Nuclear DNA Sequences.

Camellia flavida is an endangered species of yellow camellia growing in limestone mountains in southwest China. The current classification of C. flavida into two varieties, var. flavida and var. patens, is controversial. We conducted a genetic analysis of C. flavida to determine its taxonomic structure. A total of 188 individual plants from 20 populations across the entire distribution range in southwest China were analyzed using two DNA fragments: a chloroplast DNA fragment from the small single copy region and a single-copy nuclear gene called phenylalanine ammonia-lyase (PAL). Sequences from both chloroplast and nuclear DNA were highly diverse; with high levels of genetic differentiation and restricted gene flow. This result can be attributed to the high habitat heterogeneity in limestone karst, which isolates C. flavida populations from each other. Our nuclear DNA results demonstrate that there are three differentiated groups within C. flavida: var. flavida 1, var. flavida 2, and var. patens. These genetic groupings are consistent with the morphological characteristics of the plants. We suggest that the samples included in this study constitute three taxa and the var. flavida 2 group is the genuine C. flavida. The three groups should be recognized as three management units for conservation concerns.

Porous chitosan-supported metal tetra(4-carboxyphenyl)porphyrin as a practical model for the hydrophobic pocket/cavity of cytochrome P-450 enzyme.

The objective of this study was to investigate porous chitosan-supported metal tetra(4-carboxyphenyl)porphyrin [Me TCPP/p-CTS] as a practical model for the structure and function of the hydrophobic pocket cavity in cytochrome P-450 enzyme. Porous and non-porous chitosan-supported Me TCPPs [Me TCPP/p- and nonp-CTS] were prepared by a similar procedure, characterized using various techniques, and then used as catalysts for the aerobic oxidation of cyclohexane. The Me TCPP/p-CTS, which contained many cavities, showed higher catalytic activity than the Me TCPP/nonp-CTS. The catalytic activities of Mn TCPP/p-CTS and Fe TCPP/p-CTS were 12.4% and 24.4% greater than those of Mn TCPP/nonp-CTS and Fe TCPP/nonp-CTS, respectively. These differences in catalytic activity were mainly influenced by the characteristics and numbers of cavities (or pores) contained in the supported catalysts.