Photodimerization in the solid state

Abstract

Following a brief historical review of solid-state photochemistry current research is discussed under four parallel headings: first, analysis of the topochemical postulate according to which the course of the solid-state reaction and the stereochemistry of the photodimer (if any) can be predicted from the configuration and nearest-neighbour geometry of closest monomer molecules in the crystal lattice; secondly, the study of the locus of the reaction, that is the dependence of the course of the reaction or (dimerization, cis → trans isomerization) on crystal texture (dislocation, grain and phase boundaries); thirdly, a better understanding of the packing principles of organic molecules in their crystal structure to enable us to construct photoreactive (or lightstable) crystal structures of any given monomer as well as mixed crystals of potentially codimerizable monomers for synthetic purposes or energy-transfer studies. Several approaches to this problem of ‘crystal engineering’ based on generalizations of packing modes of primary amides and of dichlorophenyl derivatives are outlined, and their application to a systematic photochemistry of the solid state discussed. © 1971, Walter de Gruyter. All rights reserved.