Induced chirality of guest molecules encapsulated into a dendritic box

The internal cavities of a dendritic box, constructed from poly(propylene imine) dendrimers and enantiomerically pure N-tBOC-L-phenylalanine hydroxysuccinimide esters, possess distinct chiral properties as was demonstrated with the observation of induced optical activity of a variety of guests encapsulated in the box. This induced optical activity of guests is measured with CD (circular dichroism) spectroscopy and is remarkable as the optical activity of the amino acid outer shell itself is vanishingly small. Although small, the effects observed are significant in many cases, whilst in other cases the guests encapsulated do not show an induced CD. Indications for an enforced close proximity and some kind of ordering of guests is found by the observation of an exciton-coupled CD spectrum in the case of four Bengal Rose molecules encapsulated in a single dendritic box. It is shown that the effects are dependent on the solvent used and the history of the sample. Therefore, the observation of induced optical activity can be used to study the mode of encapsulation of the guests into the box