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The Gold Porphyrin First Excited Singlet State ¶
Author(s) -
Andréasson Joakim,
Kodis Gerdenis,
Lin Su,
Moore Ana L.,
Moore Thomas A.,
Gust Devens,
Mårtensson Jerker,
Albinsson Bo
Publication year - 2002
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1562/0031-8655(2002)0760047tgpfes2.0.co2
Subject(s) - porphyrin , excited state , singlet state , photochemistry , state (computer science) , chemistry , physics , atomic physics , computer science , algorithm
Gold porphyrins are often used as electron‐accepting chromophores in artificial photosynthetic constructs. Because of the heavy atom effect, the gold porphyrin first‐excited singlet state undergoes rapid intersystem crossing to form the triplet state. The lowest triplet state can undergo a reduction by electron donation from a nearby porphyrin or another moiety. In addition, it can be involved in triplet–triplet energy transfer interactions with other chromophores. In contrast, little has been known about the short‐lived singlet excited state. In this work, ultrafast time‐resolved absorption spectroscopy has been used to investigate the singlet excited state of Au(III) 5,15‐bis(3,5‐di‐ t ‐butylphenyl)‐2,8,12,18,‐tetraethyl‐3,7,13,17‐tetramethylporphyrin in ethanol solution. The excited singlet state is found to form with the laser pulse and decay with a time constant of 240 fs to give the triplet state. The triplet returns to the ground state with a lifetime of 400 ps. The lifetime of the singlet state is comparable with the time constants for energy and photoinduced electron transfer in some model and natural photosynthetic systems. Thus, it is kinetically competent to take part in such processes in suitably designed supermolecular systems.