Jun-ichi Fujisawa

Excited Quartet and Doublet States in the Complex of Tetraphenylporphine Zinc (II) and a Nitroxide Radical in Solution: X- and W-Band Time-Resolved EPR Studies

The photoexcited quartet (Q1) and doublet (D1) states of the complex of tetra-phenyl-porphine zinc (II) and a nitroxide radical have been studied in toluene solution by X-(9.4 GHz) and W-band (94 GHz) time-resolved electron paramagnetic resonance spectroscopy. The spin-polarized signals of the Q1 and D1 states are observed and assigned by analysis of theg-values. Line broadening and spin polarization mechanisms in this system are discussed.

Direct observation of electron spin polarization transfer in triplet–triplet energy transfer between porphyrins and fullerene in fluid solution

Abstract Time-resolved electron paramagnetic resonance (EPR) has been used to investigate electron spin polarization transfer in triplet–triplet (T–T) energy transfer between porphyrins (MOEP and MTPP; M=H 2 , Zn) and fullerene (C 60 ) in toluene solution. EPR spectra of excited triplet (T 1 ) states of both a donor (porphyrins) and an acceptor (C 60 ) were directly observed. The induced spin polarizations of T 1 C 60 were found to be the same as those of T 1 porphyrins. From the analyses of time-profiles of both triplet signals, it was shown that T 1 polarizations of porphyrins are transferred to T 1 fullerene with conservation of spin polarizations via T–T energy transfer.

Pulsed and cw-time-resolved EPR studies of photoinduced electron transfer between zinc(II) porphyrin and fullerene

Abstract Photoinduced electron and energy transfers between ZnTPP- d 20 (TPP; tetraphenylporphyrin) and fullerene (C 60 ) were studied in benzonitrile solution at room temperature by means of pulsed-Fourier transform and cw-time-resolved EPR. Two kinds of EPR signals were observed with absorptive spin polarizations and assigned to those of the ZnTPP- d 20 cation radical (ZnTPP + ) and the lowest excited triplet state of C 60 . Quantitative analysis of the time-evolution of the 3 C 60 and ZnTPP + signals demonstrates that electron transfer occurs from 3 ZnTPP to C 60 and ZnTPP to 3 C 60 and triplet–triplet energy transfer from 3 ZnTPP to C 60 . The induced absorptive polarizations of the 3 C 60 and ZnTPP + signals are explained by electron spin polarization transfer.