PHOTOIONIC DEVICES WITH RECEPTOR-FUNCTIONALIZED FLUOROPHORES

Fluorophores can be connected to ion receptors so as to permit extensi ve overlap, be geometrically orthogonal or be separated by a spacer. E ach of these three formats 1-3 has led to applications as ion sensors or switches. We focus on 'fluorophore-spacer-receptor' systems whose m odular structure allows semiquantitative design according to the princ iple of photoinduced electron transfer (PET). The fluorescence of thes e systems can be switched 'on' or 'off' when confronted with ions. Sev eral new examples 15-17 responding to Na+, H3N+CH2CH2CH2CO2 and H+ are described. 17 and 18 are cases where kinetic factors become important in addition to the usual thermodynamic design criteria. Expansion of the basic three-module system by the addition of a separate receptor w ith a different ion binding profile as in 19 gives rise to molecular A ND logic gates. On the other hand, OR logic gates such as 20 can be ob tained from the basic system provided that the receptor is deliberatel y chosen to be nonselective under the conditions of use.