Photochromic molecular recognition of cyclodextrins bearing spiropyran moiety for organic guests

The photochromic behaviors and guest binding properties of spiropyran modified cyclodextrins (1, 2 and 3), have been investigated. Compound 1 and 3 are derivatives of beta-cycIodextrin and 2 is obtained from gamma-cyclodextrin. It is found that those derivatives show a different host-guest binding mechanism and photochromic response. In the system of I,the appended moiety acts as a hydrophobic cap to elevate the binding ability of 1, whereas those appended moieties of 2 and 3 act as a probe to display the binding ability and mechanism together with acting as a hydrophobic cap. In the system of 3, the spiropyran moiety is included into the cyclodextrin cavity whenever a larger or smaller guest is used with a different intensity of the binding ability.