Theoretical investigation on the chemical sensing of metalloporphyrin-based molecular junction

Following the previous study [ N. Wang , J. Phys. Chem. C 113 , 7416 ( 2009 ) ] which focused on specific electron transport pathway in the cyclic molecules, we investigated the chemical sensing of the metalloporphyrin-based molecular junctions. Theoretical calculations have been carried out using density functional theory combined with the nonequilibrium Green's function method. The adsorbed molecules (CO, NO, and O 2 ) show diverse effects which depend on the connecting position between the metalloporphyrin with the electrodes. For iron (II) porphyrin (FeP) and manganese (II) porphyrin (MnP) connected at the 9,11-position (P-connection), the electron only passes through the porphyrin ring and the binding of ligand has no effect on the molecular conductivity. However, for the FeP and MnP connected at the 1,5-position (D-connection), the molecular conductivity decreases dramatically after adsorptions of three diatomic molecules as a result of the electron takes the path through the metallic center. For the potential application of chemical sensing, the selectivities of the FeP and MnP are discussed as well.