title: Novel excited quintet state in porphyrin: bis(quinoline-TEMPO)-yttrium-tetraphenylporphine complex.
abstract: New mono- and bis[4-(3-hydroxy-2-methyl-4-quinolinoyloxy)-2,2,6,6-tetramethylpiperidin-1-oxyl](meso-tetraphenylporphyrinato)yttrium(III) complexes have been synthesized, and the properties of the excited states generated by photoexcitation of porphyrin were studied by time-resolved (TR) and pulsed two-dimensional electron paramagnetic resonance (EPR) spectroscopy. A TR-EPR spectrum was observed in the quartet (S=3/2) or quintet (S=2) states generated from interactions of one or two radicals with the photoexcited triplet state of the porphyrin. The zero-field splitting D values of these states were analyzed in terms of those of the triplet and the radical-triplet pair. The spin states of the excited states were definitely assigned by measuring the mutation frequencies with pulsed EPR.
authors.affiliation: Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Katahira 2-1-1, Aoba-ku, Sendai 980-8577, Japan.
authors.forename: Luca
authors.initials: L
authors.lastname: Maretti
authors.forename: Saiful S M
authors.initials: SS
authors.lastname: Islam
authors.forename: Yasunori
authors.initials: Y
authors.lastname: Ohba
authors.forename: Takashi
authors.initials: T
authors.lastname: Kajiwara
authors.forename: Seigo
authors.initials: S
authors.lastname: Yamauchi