Olefins 2 + 2 intermolecular photodimerization

The examples of ex situ steady-state X-ray photodiffraction utihzed to follow the photodimerizations of olefin bonds in a single-crystal-to-single-crystal (or nearly so) manner are ubiquitous in the chemical literature. The interest of sohd-state chemists in this reaction dates back to the work of Cohen and Schmidt [30, 31], and it has become much of a guinea pig in organic solid-state photochemistry. In 1993, Enkelmann and collaborators published two seminal papers in the Journal of the American Chemical Society [32] and in Angewandte Chemie [33], where they presented a series of structures of a-tra s-cinnamic acid crystals reacted to various extents. These reports laid the way for a plethora of later studies on the olefin photodimerization reaction. The convenience of the high conversion and the simple mechanism, combined with the relatively small structural perturbation that it requires, has turned this reaction into a very useful tool to probe intermolecular... 

The intermolecular reactive bonds, separated by 4.023(9) A for C(7) C(I4) and by 4.097( 10) A for C(8)"-C(13), are nonparallel, while these distances are within those of normal reactive bonds. The topochemical [2+2] photodimerization of the double bonds oriented nonparallel has been reported for several olefinic crystals in recent papers (11,13b,21a-d). 

Coordination assemblies also show unique properties and functions through their architectures. Coordination cage 5 shows the stereo- and regiocontrol of intermolecular [2- -2] photodimerizations of olefins as well as the acceleration of the reactions (Figure 18a and This result means... 

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