Selective molecular recognition by nanoscale environments in a supported iridium cluster catalyst

Area of Science:

• * Inorganic Chemistry
• * Supramolecular Chemistry
• * Surface Science

Background:

• * Enzyme active sites possess nanoscale environments with high molecular specificity.
• * Developing synthetic systems to mimic this selectivity for applications like nanosensing, catalysis, and gas separation is challenging.
• * Controlling reactivity on synthetic surfaces to differentiate between similar molecules is a key hurdle.

Purpose of the Study:

• * To engineer a selective nanoscale environment on a synthetic surface.
• * To control the reactivity of metal sites using tailored ligands.
• * To demonstrate selective binding and catalysis based on site differentiation.

Main Methods:

• * Synthesized a tetrairidium cluster functionalized with three calixarene-phosphine ligands (1.4 nm length).
• * Employed thermal dissociation to remove CO ligands from basal-plane iridium sites.
• * Utilized reactive decarbonylation with trimethylamine-N-oxide to remove CO from apical iridium sites.

Main Results:

• * Calixarene-phosphine ligands created a nanoscale environment that differentiated between basal-plane and apical iridium atoms.
• * Selective CO ligand removal was achieved at basal-plane and apical sites.
• * Apical sites, after reactive decarbonylation, selectively bound ethylene and catalyzed its hydrogenation, unlike basal-plane sites.

Conclusions:

• * Tailored ligands can create synthetic nanoscale environments with enzyme-like selectivity.
• * Controlled manipulation of metal site reactivity is achievable through ligand design.
• * This approach offers potential for developing advanced nanosensing, selective catalysis, and gas separation technologies.