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Licensed Unlicensed Requires Authentication Published by Oldenbourg Wissenschaftsverlag September 25, 2009

Static and time-resolved photocrystallographic studies in supramolecular solids

Philip Coppens, Shao-Liang Zheng and Milan Gembicky

Abstract

The supramolecular solid state is a medium par excellence for photochemical studies of molecules in a well-defined environment. If the photoactive molecule is embedded within a strong photochemically-inert framework, reactions can proceed without breakdown of the crystal lattice. A number of examples of trans-cis and cis-trans reactions are presented. A variable temperature study of Zn-coordinated tiglic acid shows that the reaction is energy-controlled with a small activation energy of approx. 2 kJ/mol, dependent on the size of the cavity in which the molecule is located. Time-resolved studies of the instantaneous dimer-formation of an organic and an inorganic species are presented. The Cu(I)(NH3)2 cation forms a dimeric species with a contracted Cu(I)—Cu(I) distance through promotion of an electron from an antibonding to a weakly bonding orbital, whereas xanthone forms an excimer with decrease interplanar spacing. The concept of the photodifference map is defined and used thoughout the article.

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Received: 2007-September-13
Accepted: 2007-December-03
Published Online: 2009-9-25
Published in Print: 2008-5-1

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