Multistable Self-Assembling System with Three Distinct Luminescence Outputs: Prototype of a Bidirectional Half Subtractor and Reversible Logic Device

We have designed and investigated a self-assembling system composed of a crown ether containing π-electron donating naphthalene units (1) and a 2,7-diazapyrenium π-electron acceptor (2²⁺). In organic solution, these components associate with a large equilibrium constant to yield a pseudorotaxane-type complex. Interestingly, this pseudorotaxane can be disassembled either by adding an acid or a base as chemical inputs. In the first case, the protonated host and the uncomplexed guest are formed, whereas in the second case the free host and an adduct between the guest and the amine added as a base are obtained. The three states of this systemassembled, disassembled(acid), and disassembled(base)are characterized by distinct and specific absorption and luminescence spectra. Reset to the starting (assembled) state can be obtained on addition of base to the disassembled(acid) state, or on addition of acid to the disassembled(base) state. By monitoring the luminescence output signals at selected wavelengths upon fixing appropriate threshold values, one XOR and two complementary INH functions are obtained, thus enabling Boolean subtraction of two one-bit digits, x and y, in either order (x − y and y − x). As the ions generated by input annihilation affect the stability of the pseudorotaxane, the starting state (no input applied) can be experimentally distinguished from the reset state (both inputs applied). This behavior leads to an interesting and unprecedented observation, that is, chemical irreversibility translates into logic reversibility of the device.