Charge Transport of Coordination Polymers Containing Rhodium Paddlewheel Units

To overcome one of the disadvantages of most coordination polymers and metal-organic frameworks (MOFs) being insulators, conjugated coordination polymers are investigated regarding their electrical conductivity. Rhodium paddlewheel units containing coordination polymers are synthesized as bulk. They are deposited on functionalized gold substrates via a layer-by-layer approach using a self-built dipcoater. For the detailed characterization of topography and conductivity, atomic force microscopy (AFM) is used. The exchange of the equatorial coordinated acetates with acetamides leads to a change from insulating to semiconducting behavior. A temperature dependence of the current, more precisely, an increase of current with increasing temperature, is observable. The determined activation energy is between 0.3 and 0.5 eV. Bulk-limitation of charge transport is observed, and related hopping mechanisms are discussed. Conductive AFM allows us to characterize conductive coordination polymers and MOFs for a later potential usage in sensor devices.