Redox Isomeric Surface Structures Are Preferred over Odd‐Electron Pt¹⁺

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 . The resultant Pt /Pt 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 . 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 versus Pt surface structures can coexist in this ligand environment.

Structural Transformation of Surface‐Confined Porphyrin Networks by Addition of Co Atoms

“…In light of studying the formation of metal‐ligand interactions in MOCNs on noble metal surfaces, the shift in the binding energies (BE) of a core level spectrum serve as a measure of the chemical environment of a particular atom prior to and after metal coordination. [ 8 , 33 , 37 , 38 , 39 , 40 ] Therefore, in addition to our STM and LEED data, we measured XP spectra for the C 1s, N 1s and Ni 2p 3/2 core levels to check both the chemical composition and possible changes of the electronic structure of Ni‐DPPyP on Au(111) before and after coordination with Co‐atoms. Ni‐DPPyP contains a total of six N‐atoms and forty C‐atoms distributed in two and five chemically different environments, respectively.…”

Alkene Hydrosilylation on Oxide‐Supported Pt‐Ligand Single‐Site Catalysts

“…Table shows that for all six Pt‐ligand SSCs, the binding energy of Pt 4 f 2/7 XPS peak does not deviate significantly from 72.8 eV, suggesting that most Pt are Pt(II) single‐sites. BMTZ has a stronger electron affinity (oxidizing potential) than DPTZ and leads to the formation of +3 metal centers with V in model systems (on single crystal metal supports in UHV), but similar systems with Pt prefer a mixed redox isomer of Pt(II)/Pt(0) over odd‐electron Pt oxidation states . Here, it is interesting that simultaneous impregnation of Pt and BMTZ onto CeO 2 and MgO powders generates mainly Pt(II), similar to DPTZ, due to the difference in support interaction.…”