Adsorption of diatomic molecules on iron tape-porphyrin: A comparative study

作者：Nguyen Tien Quang; Escano Mary Clare Sison; Shimoji Nobuaki; Nakanishi Hiroshi; Kasai Hideaki^*

来源：Physical Review B, 2008, 77(19): 195307.

DOI：10.1103/PhysRevB.77.195307

We investigated the adsorption of diatomic molecules, CO, NO, and O(2), denoted by XO on iron tape-porphyrin (FeTP) using first-principles calculations based on density functional theory. In this work, we present the structure and electronic properties of iron tape-porphyrin and its complexes with CO, NO, and O(2). The binding of such diatomic molecules to FeTP gave rise to significant changes on both the geometric structure and electronic properties of FeTR We found that in all FeTP complexes with diatomic molecules, the Fe atom moves out of the porphyrin plane toward the adsorbed molecule. The energy of the iron-diatomic molecule bond increases in the order of Fe-O(2) (0.554 eV) < Fe-CO (1. 225 eV) < Fe-NO (1.719 eV). At its stable position, the Fe-X-O angle increases in the order of Fe-C-O > Fe-N-O > Fe-O-O. The changes in geometric structure are in accordance with other density functional theory calculations and experimental results for porphyrin molecule. As regards the electronic properties, there appears an energy gap between the conduction band and valence band in CO-adsorbed and NO-adsorbed cases with a more pronounced energy gap in the former, while none was observed in the O(2)-adsorbed case. We attribute these changes in electronic properties to the strong interaction involving the d orbitals of the Fe atom and the pi* orbitals of diatomic molecules. Specifically, for the CO and NO adsorbed on FeTP cases, the change in electronic properties is attributed to the strong hybridization of d,, and d(yz) orbitals of the Fe atom and pi* orbitals. For O(2) adsorbed on FeTP, the hybridization of the d,2 orbital of the Fe atom and pi* orbitals plays the key role in O(2)-iron tape-porphyrin interaction.

• 出版日期2008-5