Photochemistry of nitrogen-bridged cyclophanes: 2,11-Diaza[3 ₂]anthracenoparacyclophane and 2,11-diaza[3₂] paracyclophane systems

This account provides an overview of the photochemical properties of cyclophanes possessing nitrogen atoms in the bridge chains, namely 2,11-diaza[3₂]anthracenoparacyclophane and 2,11-diaza[3 ₂]paracyclophane systems. Although the photoreactions of aromatic molecules that are bound by a linker or fixed in a cyclophane structure have been widely investigated, much less attention has been paid to the photochemistry of aromatic rings incorporated in a nitrogen-bridged cyclophane. During the course of our work on the photoreactions of cyclophanes possessing nitrogen atoms in their bridge chains, the nitrogen-bridged cyclophanes were found to display photoproperties significantly different from those of the nonbridged aromatic chromophores or the corresponding carbonbridged cyclophane analogues. The 2,11-diaza[3₂]anthracenoparacyclophane system displayed an efficient photochemical cycloaddition-adiabatic cycloreversion cycle in the excited singlet state, while in the triplet state, the photoisomer underwent a novel rearrangement and adiabatic cycloreversion. Upon photolysis of the 2,11-diaza[3₂]paracyclophane system, an octahedrane cage was formed. This is the first reported octahedrane formation to occur by the photochemical dimerization of benzene. Thus, the title cyclophane systems display a variety of photoprocesses involving cycloaddition, adiabatic cycloreversion accompanied by photoinduced chemiluminescence, novel rearrangements, and previously unknown benzene dimerization. 1 Introduction 2 Photochemistry of the 2,11-Diaza[3₂]anthracenoparacyclophane System 2.1 General Comments on the Photochemical Cycloaddition and Cycloreversion of Aromatic Molecules in the Singlet State 2.2 Intramolecular Photochemical Cycloaddition and Cycloreversion of the 2,11-Diaza[3₂] anthracenoparacyclophane System 2.3 General Introduction to the Photochemistry of Aromatic Molecules in the Triplet State 2.4 Photoproperties of the 2,11-Diaza[3₂]anthracenoparacyclo-phane System in the Triplet State 3 Photochemistry of the 2,11-Diaza[3₂]paracyclophane System 3.1 General Remarks on the Photoreactions of Cyclophanes Containing Two Benzene Rings 3.2 Construction of the 2,11-Diaza[3₂]paracyclophane Skeleton 3.3 Photoreactions of the 2,11-Diaza[3₂]paracyclophane System 4 Summary.