How Do Secondary Phosphine Oxides Interact with Silver Nanoclusters? Insights from Computation

Air-stable nanoparticles stabilized with secondary phosphine oxides (SPOs) can have a remarkable role as catalysts. Since size and activity depend both on the clusterligand interaction and the nature of the employed ligand, the present work provides a fresh perspective on the prospects of bonding analysis, rationalizing for the first time the physical nature of interactions between silver nanoclusters (SNCs) and tp secondary phosphine oxides (SPOs) in the light of energy decomposition (EDA-NOCV) and noncovalent interaction hi (NCI) analyses, using the silver core of the X-ray structure for a highly symmetric, ligand-decorated Ag-44 cluster available in the literature. Our findings reveal that phosphines containing aliphatic substituents are more stabilized when interacting with Ag cluster, in contrast to aromatic groups, and that SPOs containing aromatic moieties become aligned to the silver surface upon adsorption. This alignment of aromatic substituents substantially contribute to dispersion interactions, which is observed by both EDA-NOCV and NCI analyses, showing ligand to metal donations and fragment polarizations, as well as metal to ligand backdonations in some cases. Adsorption conformations bearing hydrogen bonds to the surface were found to be the most favorable ones, and models for SPO-cluster hydrogen transfer are in line with previous experimental findings on gold nanoparticles. The present contribution will help pave the way for the rational development of new SPO-protected nanoparticles and nanoclusters, which may become cheaper and more efficient catalysts in the future.