Carrier Concentration Dependent Conduction in Insulator-Doped Donor/Acceptor Chain Compounds

On the basis of the concept that the design of a mixed valence system is a key route to create electronic conducting frameworks, we propose a unique idea to rationally produce mixed valency in an ionic donor/acceptor chain (i.e., D⁺A^– chain). The doping of a redox-inert (insulator) dopant (P) into a D⁺A^– chain in place of neutral D enables the creation of mixed valency A⁰/A^– domains between P units: P–(D⁺A^–)_nA⁰–P, where n is directly dependent on the dopant ratio, and charge transfer through the P units leads to electron transport along the framework. This hypothesis was experimentally demonstrated in an ionic DA chain synthesized from a redox-active paddlewheel [Ru₂^II,II] complex and TCNQ derivative by doping with a redox-inert [Rh₂^II,II] complex.