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The Photochemistry of a bis‐Crown Ether Based on Benzobis(thiazole) and Its Alkaline Earth Metal Cation Complexes
Author(s) -
Fedorov Yu.,
Fedorova O.,
Schepel N.,
Alfimov M.,
Turek A. M.,
Saltiel J.
Publication year - 2006
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 - 10.1562/2005-12-11-ra-751
Subject(s) - photoisomerization , chemistry , acetonitrile , crown ether , intramolecular force , cyclobutane , photochemistry , photostationary state , thiazole , medicinal chemistry , ligand (biochemistry) , reactivity (psychology) , metal ions in aqueous solution , ion , stereochemistry , isomerization , organic chemistry , medicine , ring (chemistry) , biochemistry , receptor , alternative medicine , pathology , catalysis
Irradiation of acetonitrile solutions of the bis‐crown ether E,E ‐2,7‐bis[2‐(6,7,9,10,12,13,15,16‐octahydro‐5,8,11,14,17‐pentaoxabenzocyclopentadecen‐2‐yl)vinyl]‐benzo[1,2‐d;3,4‐d′]bisthiazole (hereafter, 1) gives efficient E → Z photoisomerization (initial φ trans°Cis = 0.48), leading to λ exc ‐dependent quasi‐photostationary states composed primarily of E,Z and E,E isomer mixtures. Further irradiation gives [2 + 2]‐cycloadducts of 1. In the presence of Ba 2+ ions, essentially quantitative formation of 2:2 complexes, 1 2 · (Ba 2+ ) 2 controls the photochemical outcome. E → Z photoisomerization of the ligand is entirely suppressed and efficient intramolecular [2 + 2]‐photocycloaddition in the complexes leads to cyclobutane dimers of 1 ( φ CB = 0.26 ). The reactivity of 1 in the presence of Mg 2+ ions for which 1:2 complex formation dominates gives both cis‐trans photoisomerization and enhanced photocycloaddition.