Image of the Month

January 2016

Redox-Active On-Surface Assembly of Metal-Organic Chains with Single-Site Pt(II)


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.

Daniel Skomski, Christopher D. Tempas, Kevin A. Smith, and Steven L. Tait*
Department of Chemistry, Indiana University, Bloomington, Indiana 47405, United States

RHK Technology AFM/STM UHV 7500

Control System:
RHK Technology SPM 1000 Control System

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 Society136, 9862-9865 (2014).
DOI: 10.1021/ja504850f

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.