|Budget Amount *help
¥2,900,000 (Direct Cost : ¥2,900,000)
Fiscal Year 2000 : ¥700,000 (Direct Cost : ¥700,000)
Fiscal Year 1999 : ¥500,000 (Direct Cost : ¥500,000)
Fiscal Year 1998 : ¥600,000 (Direct Cost : ¥600,000)
Fiscal Year 1997 : ¥1,100,000 (Direct Cost : ¥1,100,000)
In this research, the author first examined an electron donor ability and a nucleophilic ability of trivalent phosphorus compounds individually. Then, the author attempted to elucidate effect of substituents on the phosphorus on discrimination between both abilities.
i) Peak oxidation potentials of various types of trivalent phosphorus compounds Z_3P were measured by cyclic voltarnmetry. These values were compared with each other with taking into consideration conformations of the compounds, showing that an electron donor ability of Z_3P is subjected to stereoelectronic effect from oxygen atoms adjacent to the phosphorus ; thus, the larger the overlap of the p-orbital of the phosphorus atom with lone pair (s) of the oxygen atom (s), the easier the one electron release from Z_3P.
ii) Single electron transfer (SET) processes occurring from Z_3P to an iron (III) complex and rhodamine in the photoexcited state were investigated kinetically. The rate of SET depended on free-energy change, bu
t the dependence was weaker than expected from the Rehm-Weller theory. This fact suggests that the radical cation generated from Z_3P in the SET undergoes a rapid ionic reaction with alcohol or water in the solvent.
iii) Nucleophilic reactions of Z_3P with vic-dibromides were investigated to show that when the bromide possesses phenyl and/or ethoxycarbonyl substituents on the α-position to the bromine, Z_3P attacks preferentially on the bromine atom, resulting in debromination of the vic-dibromide to an olefin. Results from kinetics and stereochemistry were interpreted with considering the results reported previously for the reactions with other types of vtc-dibromides. It was concluded that electronegativity of the α-substituents are important to determine which of carbon, bromine, or hydrogen is preferred in attack from Z_3P.
iv) Upon the reaction with a ruthenium complex in the photoexcited state, Z_3P brought about one-electron reduction of the complex and ligand exchange with a ligand of the complex simultaneously, the former and the latter reactions resulting from single electron transfer (SET) from Z_3P and nucleophilic attack by Z_3P, respectively. Rate constants for both reactions were obtained individually. The SET is controlled by difference in redox potentials between the donor and the acceptor, whereas the ligand exchange is controlled by both electronic and steric effects. Less