Recently, molecular electronics, especially that utilizing single molecules, has been attracting much attention. This is mainly because the theoretical limit is approaching in the present silicon-based technology, and the development of an alternative process is strongly desired. Single-molecule electronics is aimed at a breakthrough toward the next generation of computing systems. By designing and synthesizing highly functionalized molecules of nanometer size and incorporating these molecules into electrical circuits, we shall obtain much dense and high-speed processors. The concept of...