Stereoselective sensing by substrate-controlled synlanti interconversion of a stereodynamic fluorosensor

A stereoselective sensing method that is based on the unique stereodynamic and photochemical properties of 1,8-diquinolylnaphthalenes has been developed. The ability to undergo substrate-induced syn/anti interconversion and the striking difference in the fluorescence intensity of the syn and anti isomers of 1,8-bis(2-isopropyl-4-quinolyl)naphthalene (1) have been utilized for stereoselective sensing of the isomers of 1,2-diaminocyclohexane (5). The conformational stability of 1 at room temperature greatly facilitated spectroscopic and crystallographic studies of this new prototype of stereodynamic fluorosensors. Fluorescence measurements of the anti and syn isomer of 1 revealed a quantum yield of 11.6% and 2%, respectively. NMR spectroscopy experiments confirmed that trans-5 stabilizes the C-2-symmetric anti isomers of 1, whereas cis-5 favors formation of the less fluorescent meso syn-1 isomer, which results in a reduced fluorescence response. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004).