Quantum-Chemical Design of Molecular Quantum-Dot Cellular Automata (QCA): A New Approach from Frontier Molecular Orbitals

Abstract

Recently, research and development of next-generation devices have been very active (1). Quantum-dot cellular automata (QCA) (2) which is constructed frommany quantum dot cells (QDC, Fig. 1) is one of such new-generation devices. The QCAdevices such as amajority logic gate and a signal transmissionwire (Fig. 2) are expected to achieve a dramatic saving of energy and an increase in processing speed of computing since these devices are free from a current flow. Successful operations of several QCA devices have been already demonstrated (3; 4). However, for improvement in operation temperature and size of the QCA devices, the idea of molecular quantum-dot cellular automata (molecular QCA) devices (5), in which a QDC constructed from small metallic dots is replaced by a single molecule, was proposed. Toward the experimental operation of molecular QCA devices, syntheses of tetranuclear complexes (6–10) and simplified dinuclear complexes (11; 12), and single-molecule observation of the dinuclear complexes (13–16) have been paid attention. However, the capacity of molecular QCA devices for molecular computing is still not clear.