Enhancement of desorption resistance of adsorbed monolayers of calix[4]resorcinarenes bearing cinnamoyl residues by photodimerization

The crown conformer of a calix[4]resorcinarene (CRA) possessing eight carbo xymethylated units at the lower rim and four cinnamoyl residues at the uppe r rim was prepared to fabricate photofunctional monomolecular layers. The C RA derivative was adsorbed on a fused silica plate from a THF solution to f orm a monomolecular layer through hydrogen bonds. The monolayer exhibited p hotocycloaddition, together with photoisomerization, upon UV irradiation. W hereas the desorption of the macrocyclic compound from the plate occurred p artially in polar solvents including ethanol, UV irradiation exhibited a su ppressive effect on the desorption, suggesting that the number of hydrogen bonds between the molecules and a silica surface per molecule are much enha nced by intermolecular photodimerization of the cinnamoyl residues leading to an increment of the molecular weight of the adsorbate. The monolayer of the CRA on a silica plate exhibited the ability to transform the alignment of a nematic liquid crystal upon UV irradiation from homeotropic (perpendic ular) to planar (parallel) orientation. The photoalignment of the liquid cr ystal was stabilized toward heat treatment possibly owing to the photodimer ization of cinnamoyl units.