Insertion of methylene groups into functional molecules for high thermal stability and superior functionality of single-molecule transistors: a first-principles study

The π-conjugated rigid molecule Bph is a candidate for use as a channel system of single-molecule transistors. In this first-principles study, the practicality of the chemical modification of the channel molecule Bph for enhancing stability and improving performance is discussed. The insertion of methylene groups into the edges of a channel is suggested to enhance the stability of the cross-linking structures between electrodes because of the relaxation of S bonds. The calculation of electronic states and transmission indicates the sufficient on current of the methylene-inserted Bph derivative (Bph–CH₂) in transistors through resonant tunneling. These results suggest the practicality of inserting methylene groups as a method of modifying channel molecules for achieving high stability and large on currents to realize single-molecule transistors.