Metal Dependence of Signal Transmission through Molecular Quantum-Dot Cellular Automata (QCA): A Theoretical Study on Fe, Ru, and Os Mixed-Valence Complexes

Dynamic behavior of signal transmission through metal complexes [L [Formula: see text] M-BL-ML [Formula: see text]] [Formula: see text] (M=Fe, Ru, Os, BL=pyrazine (py), 4,4’-bipyridine (bpy), L=NH [Formula: see text]), which are simplified models of the molecular quantum-dot cellular automata (molecular QCA), is discussed from the viewpoint of one-electron theory, density functional theory. It is found that for py complexes, the signal transmission time ([Formula: see text]) is Fe(0.6 fs) < Os(0.7 fs) < Ru(1.1 fs) and the signal amplitude (A) is Fe(0.05 e) < Os(0.06 e) < Ru(0.10 e). For bpy complexes, [Formula: see text] and A are Fe(1.4 fs) < Os(1.7 fs) < Ru(2.5 fs) and Os(0.11 e) < Ru(0.12 e) < Fe(0.13 e), respectively. Bpy complexes generally have stronger signal amplitude, but waste longer time for signal transmission than py complexes. Among all complexes, Fe complex with bpy BL shows the best result. These results are discussed from overlap integral and energy gap of molecular orbitals.