Redox Isomeric Surface Structures Are Preferred over Odd‐Electron Pt1+. Issue 59 (20th September 2018)

• Record Type: Journal Article
• Authors: Tempas, Christopher D.; Skomski, Daniel; Cook, Brian J.; Le, Duy; Smith, Kevin A.; Rahman, Talat S.; Caulton, Kenneth G.; Tait, Steven L.
• Is Part Of: Chemistry. Volume 24:Issue 59(2018)
• Page Start: 15852
• Page End: 15858
• Publication Date: 2018-09-20
• Subjects: charge transfer -- density functional calculations -- reduction-oxidation isomers -- self-assembly -- valency; Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.201802943
• Languages: English
• ISSNs: 0947-6539

Abstract

Abstract: The formation of metal–ligand coordination networks on surfaces that contain redox isomers is a topic of considerable interest and is important for bifunctional metallochemistry, including heterogeneous catalysis. Towards this end, a tetrazine with two electron withdrawing pyrimidinyl substituents was co‐deposited with platinum metal on the Au(100) surface. In a 2:1 metal:ligand ratio, only half of the platinum is oxidized to the +2 oxidation state, with the remainder coordinating to the ligand without charge transfer, as Pt 0 . The resultant Pt 0 /Pt II mixed valence structure is thought to form due to the aversion of the ligand towards a four‐electron reduction and the strong preference of Pt towards 0 and +2 oxidation states. These results were confirmed through a series of experiments varying the on‐surface metal:ligand stoichiometry in the redox assembly formed: added oxidant does not oxidize the already complexed Pt 0 . Scanning tunneling microscopy reveals irregular chain structures that are attributed to the mixture of Pt valence states, each with distinct local coordination geometries. Density functional theory calculations give further detail about these local geometries. These results demonstrate the formation of a mixture of valence states in on‐surface redox assembly of metal‐organic networks that extends the library of single‐site metal structures for surface chemistry and catalysis. Redox‐isomeric Pt 0 versus Pt 2+ surface structures can coexist in this ligand environment. Abstract : Irregular redox isomer chains form by self‐assembly of metallic Pt and bis‐pyrimidinyltetrazine on gold surfaces. The chains contain a mixture of Pt 0 and Pt 2+ coordination centers that lead to irregular structures.