Non-contact AFM images showing metal-organic coordination chains of platinum(II)dipyridinyl-tetrazine on the reconstructed Au(100) surface. The model in the lower right panel is based on the molecular resolution image shown in the lower left.
Credits:
Daniel Skomski, Christopher D. Tempas, Kevin A. Smith, and Steven L. Tait*
Department of Chemistry, Indiana University, Bloomington, Indiana 47405, United States
Microscope:
RHK Technology AFM/STM UHV 7500
Control System:
RHK Technology SPM 1000 Control System
Reference:
D. Skomski, C. D. Tempas, K. A. Smith, and S. L. Tait
“Redox-Active On-Surface Assembly of Metal-Organic Chains with Single-Site Pt(II),”
Journal of the American Chemical Society, 136, 9862-9865 (2014).
DOI: 10.1021/ja504850f
Abstract:
The formation and stabilization of well-defined transition-metal single sites at surfaces may open new routes to achieve higher selectivity in heterogeneous catalysts. Organic ligand coordination to produce a well-defined oxidation state in weakly reducing metal sites at surfaces, desirable for selective catalysis, has not been achieved. Here, we address this using metallic platinum interacting with a dipyridyl tetrazine ligand on a single crystal gold surface. X-ray photoelectron spectroscopy measurements demonstrate the metal−ligand redox activity and are paired with molecular-resolution scanning probe microscopy to elucidate the structure of the metal−organic network. Comparison to the redox-inactive diphenyl tetrazine ligand as a control experiment illustrates that the redox activity and molecular-level ordering at the surface rely on two key elements of the metal complexes: (i) bidentate binding sites providing a suitable square-planar coordination geometry when paired around each Pt, and (ii) redox-active functional groups to enable charge transfer to a well-defined Pt(II) oxidation state. Ligand-mediated control over the oxidation state and structure of single-site metal centers that are in contact with a metal surface may enable advances in higher selectivity for next generation heterogeneous catalysts.
