Surface Engineering of Atomically Precise M(I) Nanoclusters: From Structural Control to Room Temperature Photoluminescence Enhancement

Conspectus Understandingthe structural architecture of nanoparticles is essentialfor investigating their fundamental properties because these materialshave become more desirable in modern nanoscience research. Designinga proper synthetic strategy to control their growth with atomic precisionis crucial. The polydispersed nature of the nanoparticles makes determiningtheir precise structural information challenging. Metal nanoclusters(NCs) have emerged as a promising solution to this problem as theybridge the gap between metal nanoparticles and discrete molecularcomplexes. Well-ordered molecular structures provide opportunitiesto look at structure-property correlations and find quantumconfinement effects at the atomic level that reveal their similarityto molecular-like properties. While most M-(0)/(I)-basedNCs exhibit exceptional photoluminescence (PL) emission at room temperature,M(I)-based NCs are less likely to exhibit PL emissions due to theirelectronic environment. Developments in the field of metal nanoparticleshave made it intriguing to achieve room-temperature PL emission inM(I) NCs. Efforts have focused on developing efficient methods forpreparing luminescent M(I) NCs to better comprehend fundamental aspectsof their PL emission properties. We provide an overview of varioussynthetic strategies for preparing NCs and their selective functionalizationfor generating room-temperature PL emissions. Our focus has been creatingan Ag(I) NC with a core-shell architecture, as this uniquestructural design complements the charge transition phenomenon. Themolecular structure obtained from single-crystal X-ray diffraction(SCXRD) and associated theoretical calculation revealed that our effortresults in a unique hexagonal closed pack core and Keplerate shellcontaining [S@Ag50S12((SBu)-Bu- t )(20)](4+) NC where the charge transitionbetween the core and the metal-ligand shell facilitates emissionproperties. We also explored the approach of host-guest supramolecularadduct formations to engineer the surface of ligands that reduce nonradiativerelaxation rates by restricting surface molecular vibrations and controllingthe generation of PL emission. To do this, we capped precisely structured[Cl@Ag16S(S-Adm)(8)(CF3COO)(5)(DMF)(3)(H2O)(2)]& BULL;DMF with & beta;-cyclodextrinvia adamantane moieties. We also describe the effects of bimetalliccluster formation on increasing surface rigidity and modulating thefrontier molecular orbital arrangement, which helps to attain synergyto generate room-temperature PL emission. We focused on the structuralintegrity of Ag(I) NCs, allowing us to incorporate heterometal atomsat peripheral positions that lead to the formation of [CO2@Ag20Cu2S2((SBu)-Bu- t )(10)(CF3COO)(8)(DMA)(4)]& BULL;(DMA). We also explored the impact of introducing extra ligandsinto the Ag(I) cluster node on the generation of PL emission at room-temperature.These strategies are not limited to Ag NCs. We discussed the possibilityof combining core-shell architecture and surface modificationsto enhance PL emission in [Cu18H3(S-Adm)(12)(PPh3)(4)Cl-2] NC at room temperature. SCXRD studies revealed its distinct core-shell architecturethat ensures electronic transitions and that transition is controlledby the imposed surface rigidity that yields a higher PL emission.We believe that this innovative structural engineering holds potentialfor the advancement of NC research, and this Account will inspirethe scientific community to synthesize functional M(I) NCs.