Synthesis of Trimetallic (HPd@M2Au8)3+ Superatoms (M = Ag, Cu) via Hydride-Mediated Regioselective Doping to (Pd@Au8)2.

Haru Hirai,Shinjiro Takano,Tatsuya Tsukuda

doi:10.1021/acsomega.9b00575

Abstract

We have recently reported that hydride (H–) doped superatom (HPd@Au8)+ protected by eight PPh3 ligands selectively grew into (HPd@Au10)3+ by the nucleophilic addition of two Au(I)Cl units. In the present study, (HPd@Au8)+ was successfully converted to unprecedented trimetallic (HPd@M2Au8)3+ superatoms (M = Ag, Cu) by controlled doping of two Ag(I)Cl or Cu(I)Cl units, respectively. Single-crystal X-ray diffraction analysis demonstrated that two Ag(I) or Cu(I) ions were regioselectively incorporated. Theoretical calculations suggested that hydrogens in (HPd@M2Au8)3+ (M = Au, Ag, Cu) occupy the same bridging site between the central Pd atom and the surface Au atom. (HPd@Ag2Au8)3+ exhibited photoluminescence at 775 nm, with the enhanced quantum yield of 0.09%, although it is structurally and electronically equivalent with (HPd@Au10)3+. This study demonstrates that hydride-mediated growth process is a promising atomically-precise bottom-up synthetic method of new multimetallic superatoms.

Highlights

Gold clusters protected by ligands have gained much interest as promising building units of functional nanoscale materials because of their size-specific properties.[1−6] Recent progress in atomically precise synthesis has revealed that their physicochemical properties can be tuned dramatically by the number of constituent atoms of the core and by doping foreign atoms.[7−20] For instance, optical properties[15,19] and catalytic activities[7] of thiolate (RS) protected Au25(SR)[18] cluster are modulated significantly by doping heterometal atoms
Is initiated by the activation of [Au9(PPh3)8]3+ and [PdAu8(PPh3)8]2+ through doping of an H− anion to form [HAu9(PPh3)8]2+ and [HPdAu8(PPh3)8]+, respectively. This step is followed by sequential nucleophilic attack of the hydride-doped clusters to AuCl(PPh3) complex
Electrospray ionization (ESI) mass spectra of the reaction mixtures indicated that the main products were

Summary

Introduction

Gold clusters protected by ligands have gained much interest as promising building units of functional nanoscale materials because of their size-specific properties.[1−6] Recent progress in atomically precise synthesis has revealed that their physicochemical properties can be tuned dramatically by the number of constituent atoms of the core and by doping foreign atoms.[7−20] For instance, optical properties[15,19] and catalytic activities[7] of thiolate (RS) protected Au25(SR)[18] cluster are modulated significantly by doping heterometal atoms. To establish the correlation between structure and functionalities of protected gold clusters, it is required to control precisely the chemical compositions and the location of dopant atoms. Co-reduction of gold and dopant metal precursor ions has been used frequently as a straightforward method to synthesize doped gold clusters. It is still a challenge to obtain the doped clusters with the desired composition in high yield due to the difference in the relative reduction rates of the precursor metal ions. Is initiated by the activation of [Au9(PPh3)8]3+ and [PdAu8(PPh3)8]2+ through doping of an H− anion to form [HAu9(PPh3)8]2+ and [HPdAu8(PPh3)8]+, respectively. This step is followed by sequential nucleophilic attack of the hydride-doped clusters to AuCl(PPh3) complex. Hydride is released in the form of proton during the formation of [Au11(PPh3)8Cl2]+, whereas the H atom remained in 1 due to the high affinity of hydrogen to palladium.[32,33]

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Results

Conclusion