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Thermally Induced trans ‐to‐ cis Isomerization and Its Photoinduced Reversal Monitored using Absorption and Luminescence: Cooperative Effect of Metal Coordination and Steric Substituent
Author(s) -
Zhang JunQuan,
Zhang DeShan,
Chen QiuJie,
Xu HaiBing,
Kurmoo Mohamedally,
Zeng MingHua
Publication year - 2019
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201900204
Subject(s) - isomerization , steric effects , substituent , luminescence , chemistry , ligand (biochemistry) , absorption spectroscopy , cis–trans isomerism , powder diffraction , spectroscopy , irradiation , absorption (acoustics) , crystallography , photochemistry , metal , structural isomer , nuclear magnetic resonance spectroscopy , medicinal chemistry , stereochemistry , materials science , catalysis , organic chemistry , biochemistry , receptor , physics , optoelectronics , quantum mechanics , nuclear physics , composite material
For ethene derivatives with large groups the cis ‐isomer is often quite unstable and unavailable. Herein, we report an exception of two stable coordination complexes, ( cis ‐ L )ZnCl 2 , starting from trans ‐1,2‐bis(1‐R‐benzo[ d ]imidazol‐2‐yl)ethene (R=H, L1 ; R=CH 3 , L2 ) ligands under solvothermal condition ( T ≥140 °C). Using the intensity of the absorption and luminescence spectra as probes we proposed its progressive cis ‐to‐ trans reversal upon irradiation with UV light, which was confirmed by powder X‐ray diffraction (PXRD). Similar results observed in the series of ( cis ‐ L2 )M II Cl 2 [M=Fe ( 4 ), Co ( 5 ), Ni ( 6 )] demonstrate the universal strategy. The results of PXRD, NMR spectroscopy, ESI‐MS and DFT calculations support the above conclusion. NMR spectroscopy indicates that irradiation of 1 converts an optimized 71 % of the cis ‐isomer to trans , whereas the free trans ‐ L1 ligand transforms to only 15 % cis ‐isomer under similar conditions.