An ionically driven molecular IMPLICATION gate operating in fluorescence mode

Abstract

An asymmetrically core-extended boron-dipyrromethene (BDP) dye was equipped with two electrondonating macrocyclic binding units with different metal ion preferences to operate as an ionically driven molecular IMPLICATION gate. A Na+-responsive tetraoxa-aza crown ether (R2) was integrated into the extended K system of the BDP chromophore to trigger strong intramolecular charge transfer (ICT2) fluorescence and guarantee cation-induced spectral shifts in absorption. A dithia-oxa-aza crown (R 1) that responds to Ag+ was attached to the meso position of BDP in an electronically decoupled fashion to independently control a second ICT1 process of a quenching nature. The bifunctional molecule is designed in such a way that in the absence of both inputs, ICT1 does not compete with ICT2 and a high fluorescence output is obtained (InA = InB = 0→Out = l). Accordingly, binding of only Ag+ at R1 (InA = l, InB = 0) as well as complexation of both receptors (InA = InB = l) also yields Out = 1. Only for the case in which Na+ is bound at R2 and R1 is in its free state does quenching occur, which is the distinguishing characteristic for the InA = 0 and In B = l →Out = 0 state that is required for a logic IMPLICATION gate and Boolean operations such as IF-THEN or NOT. © 2007 Wiley-VCH Verlag GmbH & Co. KGaA,.