Photochemical Reactions and Physical Property Control

2) and fulgides (Table 2.2) in polymers. The reaction occurs at several mobile sites even at temperatures below Tr since the critical free volume (sweep volume) required for the reaction to occur is very small in this case. Azobenzene is known to photoisomerize up to 15% even at liquid helium temperature (4 K) in polycarbonate film, suggesting an inversion mechanism with the change of sp2— sp— sp2 in hybrid orbital of the N atom. 

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Shape selectivity and orbital confinement effects are direct results of the physical dimensions of the available space in microscopic vessels and are independent of the chemical composition of nano-vessels. However, the chemical composition in many cases cannot be ignored because in contrast to traditional solution chemistry where reactions occur primarily in a dynamic solvent cage, the majority of reactions in nano-vessels occur in close proximity to a rigid surface of the container (vessel) and can be influenced by the chemical and physical properties of the vessel walls. Consequently, we begin this review with a brief examination of both the shape (structure) and chemical compositions of a unique set of nano-vessels, the zeolites, and then we will move on to examine how the outcome of photochemical reactions can be influenced and controlled in these nanospace environments. 

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