PHOTO-CLEAVABLE CRYPTANDS - SYNTHESIS AND STRUCTURE

The four photo-cleavable ligands 1-4 of the macrobicyclic-cryptand type have been synthesized by introducing a photo-sensitive 2-nitrobenzyl- or 4,5-dimethoxy-2-nitrobenzyl-ether bond into one of the bridges. These compounds are expected to retain the selective binding features of the parent cryptands and to allow the photolytically induced release of alkali ions in aqueous solution. The crystal structures of the ligand 5-(2-nitrophenyl)-4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.?? 8.8]hexacosane (3) and of its KSCN complex 13 have been determined. They are analogous to those of the corresponding parent species, confirming the macrobicyclic geometry and the cryptate nature of the complex. Spectroscopic properties are reported.