Interfacial synthesis of electrofunctional coordination nanowires and nanosheets of bis(terpyridine) complexes

One of the final goals of the research on molecular electronics is to control electron conduction in molecular wires and networks at will by combining appropriate molecular units. In this article we describe interfacial coordination reactions to design and synthesize electro-functional π-conjugated one-dimensional (1D) nanowires and two-dimensional (2D) nanosheets composed of redox-active bis(terpyridine) complexes of iron and cobalt. Stepwise formation of coordination bonds was applied to fabricate linear and branched bis(terpyridine)metal oligomer wires on gold and silicon surfaces. Redox conduction behaviors of the oligomer wires, the electron transfer kinetics at the electrode-molecular wire junction and the dynamics of electron transport between terminal redox units and electrode were quantitatively analyzed to evaluate the contribution of each component to the total performance of the molecular wires. Liquid-liquid interfacial coordination reaction of metal ions and three-way bridging terpyridine ligands was utilized to synthesize a large film of multilayered 2D coordination nanosheets (CONASHs) composed of bis(terpyridine)metal (metal is iron or cobalt) units. The CONASHs thus formed exhibited rapid and durable electrochromism in an electrolyte solution. A solidified device composed of the CONASH, a pair of ITO electrodes, and a polymer electrolyte displayed excellent electrochromic performance. The combination of Fe²⁺ and Co²⁺ CONASHs in one solidified device demonstrated dual-electrochromic behavior.