Oxygen donor protection of atomically precise metal nanoclusters

Over the past decades, metal nanoclusters have emerged as a novel class of highly attractive materials, as they can be characterized at atomic precision, achieve complete homogeneity, and exhibit intriguing properties such as luminescence and catalytic activity. Typically, a metal nanocluster comprises a metal core and surface ligands. Despite the crucial role of the metal core, it is increasingly recognized that surface ligands are far more than mere stabilizing agents for metal nanoclusters. Compared to classical organic ligands such as thiolates and phosphines, oxygen (O) donors, including carboxylates, sulfonates, phosphinates, and phosphonates etc., have long been known but underestimated. Firstly, O donors display diverse coordination modes, making them promising candidates for generating novel architectures. Moreover, they are highly effective carriers for introducing chirality, luminescence, and other functionalities into metal nanoclusters. Additionally, most of these donors are inexpensive, readily available, stable under ambient conditions, and easy to handle. In this review, we aim to systematically summarize the development of O donor protection in atomically precise metal nanoclusters, with emphasis on the structures of surface motifs associated with O donors. The properties reported for clusters with O donor protection are also briefly surveyed. We hope this review will attract more attention to O donors as ligands for nanoclusters, which have demonstrated promising potential in generating novel structures and properties of coinage metal nanoclusters.