The creation of single-site metal centers (SSMCs) through the formation of metal-organic coordination networks is an area of interest due to the proven ability of SSMCs to improve selectivity for heterogeneous catalysts. In order to better understand the reactivity potential for the SSMCs it is necessary to study the ligand-metal interaction in the metal-organic coordination networks. In the work reported here, we demonstrate the ability to tune the oxidation state of single-atom vanadium active sites from II to IV through the tailoring of redox-active ligand design. Using X-ray photoelectron spectroscopy (XPS) to measure binding energy shifts of metallic vanadium complexed with the N-heterocyclic ligands of bipyrimidine (BP), bispyrimidinyltetrazine (BMTZ), and biimidazole (BIM), we show that the oxidation state of the V metal centers can be tuned to V(II) for BP, V(III) for BMTZ, and V(IV) for BIM. Examination of the resulting surface structure on a Au(111) single-crystal metal surface is performed using scanning tunneling microscopy (STM) showing the formation of 1D chains for BIM and BMTZ, similar to our previously published results for V:DPTZ and V:BMTZ systems on Au(100). Examination of the structure of BP shows no observable structure, likely due to the tilting of the V:BP complex observed via density functional theory (DFT) modelling. These studies of different redox-active ligands demonstrates how subtle changes in ligand design can have a large impact on controlling the oxidation state of the single-site metal center.

Tailoring the redox capabilities of organic ligands for metal-ligand coordination with vanadium single-sites

ACS Spring Meeting 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.