Pyrene-appended calix[4]crowned logic gates involving normal and reverse PET: NOR, XNOR and INHIBIT

Abstract

As a novel sensing system, N-(1-pyrenylmethyl) amide-appended calix[4]crown-5 ( 2 ) and crown-6 ( 3 ) have been newly synthesized. Judging from the fluorescence changes upon the addition of cations, 3 having crown-6 ring showed the Pb 2+ ion selectivity over other cations tested regarding fluorescence quenching. Upon the Pb 2+ ion coordination to two amide oxygen atoms with aid of crown ring, a reverse-photo-induced electron transfer (PET) occurs in such a way that electrons transfer from the pyrene groups to the electron deficient amide oxygen atoms to give a quenched fluorescence. By the addition of either HClO 4 or triethylamine in the solution of 3 , the fluorescence intensity decreased because of the reverse-PET from pyrene groups to protonated amide oxygen atoms and because of normal PET from the nitrogen anion formed by triethylamine to pyrene groups, respectively. For 3 , NOR logic gate in which the strong fluorescence signal appears at 395 nm (output: 1) is operated only when neither of triethylamine nor Pb(ClO 4) 2 (inputs A and B) is added (A=B: 0). XNOR gate is also operated only when both of two inputs are added (triethylamine and HClO 4, A=B: 1) or when neither of two inputs is added (A=B: 0). Then, for 3 , new INHIBIT gate system was also designed using such combinational inputs as HClO 4, Pb(ClO 4) 2 and triethylamine.