抄録
The adsorption of NO on various metal tape-porphyrins (Mn, Fe, and Co) is studied using first-principles calculations based on density functional theory (DFT). In this work we discuss the geometric structure and electronic properties of metal tape-porphyrins and the effect of the adsorption of NO on their properties. The results show that metal atoms protrude from the porphyrin plane toward the NO molecule. At the stable position, the variation of the metal–N–O angle is in the order: Co–N–O (123°) < Fe–N–O (148°) < Mn–N–O (180°). The N–O bond length in the metal tape-porphyrins is slightly longer than that of the isolated NO molecule. These results are consistent with other DFT calculations and experimental results. We also found that the binding energy of NO with metal porphyrins increases in the order CoTP–NO (1.718 eV) < FeTP–NO (1.719 eV) < MnTP–NO (1.736 eV). As regards the electronic properties, there is a metal–insulator transition in FeTP–NO. For CoTP–NO and MnTP–NO, we found that CoTP shows insulator-like behavior while MnTP is metallic. After interaction with NO, CoTP still shows insulator-like behavior but MnTP has reduced conductance. We attribute the changes in the geometric and electronic structures to the interactions involving the 3d orbitals of the metal atoms and the π* orbital of NO. Specifically, for MnTP, the change in the electronic properties is attributed to the strong hybridization of the dxz and dyz orbitals of the Mn atom with the π* orbital of NO. For CoTP, the hybridization of the dz2 orbital of the Co atom with the π* orbitals of NO plays the key role in the NO–cobalt tape-porphyrin interaction.
