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Supramolecular Solids as a Medium for Single‐Crystal‐to‐Single‐Crystal E / Z Photoisomerization: Kinetic Study of the Photoreactions of Two Zn‐Coordinated Tiglic Acid Molecules
Author(s) -
Zheng ShaoLiang,
Vande Velde Christophe M. L.,
Messerschmidt Marc,
Volkov Anatoliy,
Gembicky Milan,
Coppens Philip
Publication year - 2008
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.200701037
Subject(s) - photoisomerization , isomerization , chemistry , molecule , supramolecular chemistry , crystallography , photostationary state , reaction rate constant , ligand (biochemistry) , photochemistry , crystal structure , kinetics , catalysis , organic chemistry , biochemistry , physics , receptor , quantum mechanics
Abstract [Zn(TA) 2 (H 2 O) 2 ] (H‐TA=tiglic acid) has been embedded in a framework composed of CECR (CECR= C ‐ethylcalix[4]resorcinarene) molecules to examine its E → Z photoisomerization in a periodic framework. The photoisomerization of tiglic acid in CECR‐[Zn(TA) 2 (H 2 O) 2 ] ⋅ 4 H 2 O proceeds without the [2+2]‐dimerization reaction that often occurs in crystals of uncomplexed analogues, and without breakdown of the crystal lattice that frequently occurs in neat crystals. The two Zn‐coordinated TA molecules are located in different size cavities. The rate constants of the isomerization reaction are strongly affected by the size of the reaction cavity. Analysis of the temperature dependence of the reaction rates and the occupancies in the final photostationary state shows that the activation energies and the standard enthalpies of activation are dependent on the difference between the reaction cavities. This is the first quantitative diffraction study of solid‐state E / Z isomerization of a metal‐coordinated ligand in a periodic host environment.