An Ionically Driven Molecular IMPLICATION Gate Operating in Fluorescence Mode

An asymmetrically core‐extended boron–dipyrromethene (BDP) dye was equipped with two electron‐donating macrocyclic binding units with different metal ion preferences to operate as an ionically driven molecular IMPLICATION gate. A Na + ‐responsive tetraoxa‐aza crown ether (R 2 ) was integrated into the extended π system of the BDP chromophore to trigger strong intramolecular charge transfer (ICT 2 ) 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 ICT 1 process of a quenching nature. The bifunctional molecule is designed in such a way that in the absence of both inputs, ICT 1 does not compete with ICT 2 and a high fluorescence output is obtained (In A =In B =0→Out=1). Accordingly, binding of only Ag + at R 1 (In A =1, In B =0) as well as complexation of both receptors (In A =In B =1) also yields Out=1. Only for the case in which Na + is bound at R 2 and R 1 is in its free state does quenching occur, which is the distinguishing characteristic for the In A =0 and In B =1→Out=0 state that is required for a logic IMPLICATION gate and Boolean operations such as IF‐THEN or NOT.