Emission properties of cyclodextrin dimers linked with perylene diimide-effect of cyclodextrin tumbling

Perylene diimide (PDI) derivatives with cyclodextrins (PDI-CD(2)s) exhibit specific emission properties, which depend on the type of CDs in an aqueous solution. Herein we successfully create an emission film-kneaded PDI-CD2 derivatives via effective tumbling of the altropyranose unit. PDI-6CD(2)s are crosslinked with PDI between 6-amino-CDs. Although the emission intensities of PDI-6CD(2)s in dimethyl sulfoxide are similar regardless of the type of CD, PDI-6 gamma CD2 has a relatively high emission intensity in aqueous solutions. In contrast, for PDIC7-3CD(2)s, which are linked with N,N'-bis(6-carboxylhexyl)perylene-3,4,9,10-tetracarboxyl diimide (BisC(7)-PDI) between 3-amino-CDs, the emission intensity of PDIC7-3 beta CD2 is stronger than those of PDIC7-3 alpha CD2, PDIC7-3 gamma CD2, and PDI-6CD(2)s in aqueous solutions. The selective emission behavior of PDIC7-3CD(2)s is due to the formation of the pseudo[1]rotaxane dimer through tumbling of the altropyranose unit in an aqueous solution. PDIC7-3 beta CD2 in the solid state does not demonstrate a distinctive emission due to self-quenching, whereas PDIC7-3 beta CD2 kneaded into the polyvinyl alcohol (PVA) film exhibits a bright yellow emission. The order of the emission intensities of PDIC7-3CD(2)s kneaded into PVA films is similar to those in aqueous solutions. Polymer Journal (2012) 44, 278-285; doi:10.1038/pj.2011.128; published online 18 January 2012