In an extension of previous work, this HOT Article, by Kraig Wheeler and co-workers describes their attempts to control the regio- and stereochemical outcomes of [2+2] photochemical dimerization in the solid state.
In their 2011, CrystEngComm article, the team reported on the development of a sulfonamidecinnamic acid framework which could be likened to the shape of a fish-hook. Upon crystallisation, the structures form supramolecular dimers where the neighbouring C=C double bonds are oriented mutally co-planar. It is this feature that allows UV initiated dimerisation into the corresponding cyclobutane product.