Photochemical properties of macrobicyclic complexes

For realization of photochemical processes (Fig. 58) and their practical application, there is a need to use molecules that, when photoexcited, are able to luminesce (luminophores) and/or to transfer the energy of electrons (photosensitizers) without undergoing photodecomposition. 

The main requirements needed for luminophores and photosensitizers were formulated in Ref 373  

From a spectral and photophysical point of view, clathrochelate complexes would be quite suitable to play these roles [340, 373-380]. 

Most of the investigations in this field have focused on the use of cobalt sepulchrate and sarcophaginates as electron-transfer sensitizers in photocatalytic cyclic solar energy conversion processes [340, 375-378]. This is mainly due to their specific redox behaviour stipulated by peculiarities of the cobalt ion electronic structure and screening of this ion by an encapsulating ligand. 

Since both E1/2 values and electron-transfer rates are responsible for the photochemical and photocatalytical behaviour of cobalt clathrochelates, their variation by the introduction of substituents makes these compounds especially promising as photosensitizers. 

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