Issue 24, 2000

Kinetic study of the radiationless deactivation of singlet oxygen (1Δg) in liquid solution under high pressure

Abstract

The mechanism of the radiationless deactivation of singlet oxygen, 1O2(1Δg), in several solvents at pressures up to 400 MPa was investigated. The lifetime decreased significantly with increasing pressure and the activation volume, ΔVD, for the bimolecular quenching constant, kD, was determined to be in the range from − 12.0 to − 7.0 cm3 mol−1. It was found for a series of n-alkanes (C5–C8 and C12) that kD increases linearly with increasing number of methylene groups at pressures up to 400 MPa (additivity relationships). The activation volume separated by the additivity relationships was determined to be from − 14.4 to − 12.5 cm3 mol−1 for CH3 and from − 9.2 to − 7.3 cm3 mol−1 for CH2, depending on the solvents examined. The lifetime of 1O2 was also measured in methylcyclohexane at temperatures from − 37 to 84°C and 0.1 MPa, and the activation energy for kD was found to be positive (1.6 kJ mol−1). These results are interpreted successfully by assuming a kinetic model in which encounter and collision complexes formed between 1O2 and solvent are involved. It was also shown that the kinetic model can be applied to systems with charge transfer interactions between 1O2 and solvent.

Article information

Article type
Paper
Submitted
13 Jun 2000
Accepted
24 Oct 2000
First published
23 Nov 2000

Phys. Chem. Chem. Phys., 2000,2, 5571-5577

Kinetic study of the radiationless deactivation of singlet oxygen (1Δg) in liquid solution under high pressure

M. Okamoto and F. Tanaka, Phys. Chem. Chem. Phys., 2000, 2, 5571 DOI: 10.1039/B004702N

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