Using non-adiabatic excitation transfer for signal transmission between molecular logic gates

Abstract

Molecular logic gates (MLGs) are molecules which perform logic operations. They can potentially be used as building blocks for nano-sized computational devices. However, their physical and functional integration is a difficult task which remains to be solved. The problem lies in the field of signal exchange between the gates within the system. We propose using non-adiabatic excitation transfer between the gates to address this problem while absorption and fluorescence are left to communicate with external devices. Excitation transfer was studied using the modified Bixon–Jortner–Plotnikov theory with the example of the 3H-thioxanthene–TTF–dibenzo-BODIPY covalently linked triad. Several designs of the molecule were studied in a vacuum and cyclohexane. It was found that the molecular logic system has to be planar and rigid to isolate radiative interfaces from other gates. Functioning of these gates is based on dark πσ*-states in contrast to bright ππ*-states of radiative interfaces. There are no fundamental differences between ππ* → πσ* and ππ* → ππ* transitions for cases when an exciton hops from one gate to another. The rates of such transitions depend only on an energy gap between states and the distance between gates. The circuit is highly sensitive to the choice of solvent which could rearrange its state structure thereby altering its behavior. According to the obtained results, non-adiabatic transfer can be considered as one of the possible ways for transmitting a signal between MLGs.