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Nanosecond time‐resolved resonance Raman and absorption studies of the photochemistry of chlorpromazine and related phenothiazine derivatives
Author(s) -
Sarata Gaku,
Sakai Makoto,
Takahashi Hiroaki
Publication year - 2000
Publication title -
journal of raman spectroscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.748
H-Index - 110
eISSN - 1097-4555
pISSN - 0377-0486
DOI - 10.1002/1097-4555(200008/09)31:8/9<785::aid-jrs611>3.0.co;2-6
Subject(s) - phenothiazine , promazine , phototoxicity , chemistry , photochemistry , chlorpromazine , raman spectroscopy , porphyrin , resonance (particle physics) , nanosecond , absorption (acoustics) , absorption spectroscopy , materials science , laser , optics , medicine , biochemistry , physics , particle physics , composite material , in vitro , pharmacology , endocrinology
Abstract Nanosecond time‐resolved resonance Raman and absorption spectra of chlorpromazine and related phenothiazine derivatives were measured with the purpose of obtaining information on the photo‐produced chemical species responsible for phototoxicity and photoallergy of chlorpromazine, a major tranquilizing drug. It was observed that the photoreaction of chlorpromazine in the nanosecond time domain involved four transients: T 1 (absorption peak at 480 nm), cation radical CR (at 525 nm), and two unknown transients X (at 560 nm) and Y (at 380 nm). T 1 was characterized as an n–π * state on the basis of resonance Raman results. The production of CR was a biphotonic process via S 1 with 308 nm excitation. X was generated from CR and was converted into Y. Neither process was affected by oxygen. A species corresponding to X was also observed for 2‐chlorophenothiazine but not for phenothiazine and promazine which have no C—Cl bond, suggesting that the generation of X may be related to a photoinduced cleavage of the C—Cl bond. It was not clarified, however, whether X is a direct product of the photo‐induced dechlorination or a compound derived from it. Since the generation of Y from X was not affected by the presence of oxygen, Y is not a complex compound with O 2 . Chlorpromazine is known to be an order of magnitude more phototoxic and photoallergic than promazine and it therefore seems probable that either X or Y or both play important roles in the adverse side effects of the drug. Copyright © 2000 John Wiley & Sons, Ltd.