title: Time-resolved electron paramagnetic resonance of the lowest excited triplet state of phenazinium cation.
abstract: Time-resolved and steady-state electron paramagnetic resonance (EPR) spectra have been observed for the lowest excited triplet (T(1)) states of phenazine (Phz) and its singly protonated cation (phenazinium) in sulfuric acid-ethanol mixtures at 77K. The single protonation appears to have little effect on the anisotropic sublevel populating rates of the T(1) state of phenazine. However, the zero-field splitting (ZFS) parameter D decreases on the protonation, reflecting the increase of delocalization of the two unpaired electrons. The sublevel preferentially populated by intersystem crossing (ISC) is T(y) in both phenazine and phenazinium (the y-axis is parallel to the in-plane long axis). From the analysis of the observed anisotropy in the ISC rates and the semi empirical molecular orbital calculations of the ZFS parameters, we concluded that the T(1) state of phenazinium is the (3)A(1)(pipi*) state.
authors.affiliation: Department of Applied Chemistry, Graduate School of Engineering, Yokohama National University, Tokiwadai, Hodogaya-ku, Yokohama 240-8501, Japan.
authors.forename: Makoto
authors.initials: M
authors.lastname: Deguchi
authors.forename: Daisuke
authors.initials: D
authors.lastname: Suzuki
authors.forename: Ryo
authors.initials: R
authors.lastname: Ito
authors.forename: Michiko
authors.initials: M
authors.lastname: Matsumoto
authors.forename: Mikio
authors.initials: M
authors.lastname: Yagi
mesh_terms: D002412:Cations / Q000737:chemistry*; D004578:Electron Spin Resonance Spectroscopy; D000431:Ethanol / Q000737:chemistry; D010619:Phenazines / Q000737:chemistry*; D011522:Protons; D013464:Sulfuric Acids / Q000737:chemistry; D013997:Time Factors
chemical_list: D002412:Cations; D010619:Phenazines; D011522:Protons; D013464:Sulfuric Acids; D000431:Ethanol; C033158:sulfuric acid