1997 Fiscal Year Final Research Report Summary
A Novel Magnetic Field Effect observed in the Photochemical Reactions of Phosphorous Compounds
| Project/Area Number |
08640662
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Physical chemistry
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| Research Institution | The Institute of Physical and Chemical Research (RIKEN) |
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Principal Investigator |
SAKAGUCHI Yoshio RIKEN,Molecular Photochemistry Laboratory, Senior Scientist, 分子光化学研究室, 副主任研究員 (30167423)
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| Project Period (FY) |
1996 – 1997
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| Keywords | triarylphosphine / magnetic field effects / heavy atom effects / viscosity dependence / triplet mechanism / molecular triplet mechanism |
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| Research Abstract |
The photochemical reactions of triarylphosphines in the non-viscous homogeneous solutions were investigated by the nanosecond laser photolysis. Triarylphosphines were found to decompose into diaryphosphinyl and aryl radicals from their triplet excited states. The yields of diarylphosphinyl radicals reduced in the presence of the external magnetic fields. The magnetic field less than 0.1T has little effect. Most of the reduction of the yiled appeared from 0.1 to 5T.Above it, little effect was observed. The observed magnetic field dependence could not be interpreted by the conventional mechanisms such as, hyperfine coupling, DELTAg, and relaxation mechanisms which describe the magnetic field effects of radical pairs. The Steiner's triplet mechanism proposed for radical pair complexes partially interprets the observation, the magnetic field dependence and the heavy atom effects. The expected solvent viscosity dependence among n-alkane solvents is larger than the observation and the results in 2-propanol and cyclohexane solutions did not obey the viscosity relationship.
We found that the discrepancy of the viscosity dependence can be avoided by regarding the triplet excited molecule to be a key intermediate instead of the radical pair complex. Other inconsistencies are also removed by this assumption. Consequently, the magnetic field effects of triarylphosphines are interpreted by a novel mechanism which is originated not from the radical pairs but from the magnetic field dependent deactivation of triplet excited state of the phosphine molecules.
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