Effect of confinement on the electronic and optical properties of azobenzene: cucurbituril as a means of confinement

The host-guest complexes of cucurbituril and azobenzene are investigated using dispersion corrected density functional theoretical methods. Different orientations of the guest azobenzene inside cucurbiturils of different sizes are examined. The host-guest interaction and the alteration of the physical properties of constituent units are studied. Among different orientations of azobenzene inside cucurbituril, the horizontally oriented cis complex is found to be the most stable. The maximum absorption wavelength (lambda(max)) of trans isomer undergoes red shift due to the confinement inside the cucurbituril cage whereas that of the cis isomer exhibits a blue shift when aligned horizontally inside the cucurbituril cage. The transfer of electron density and the non-linear optical properties of these complexes are also discussed.