Chiral Recognition with Room-Temperature Phosphorescence in Guest-Host Energy-Transfer Systems

Chiral recognition with molecular luminescence is a beneficial but challenging method due to an often lack of dramatic difference in intermolecular interactions between the chiral analyte/substrate pair versus their enantiomeric counterpart. Here we show that the difference in room-temperature phosphorescence (RTP) can be substantially augmented by employing guest-host energy-transfer systems. By covalent attachment of chiral amino compounds to a phthalimide host and a naphthalimide guest, respectively, RTP intensity difference of two orders of magnitude with a detection limit of >98% enantiomeric excess (ee) could be achieved. For example, S-enantiomeric guests in S-enantiomeric hosts produce strong red RTP afterglow while no appreciable RTP could be observed in an S/R guest-host combination. The huge spectroscopic difference in RTP results in conspicuous steady-state and delayed-emission variations, which could easily be discriminated by the naked eye. A generalized concept in solid-state RTP chiral recognition is proposed to expand the application scope of the reported method.