Toward Controlled Syntheses of Diphosphine-Protected Homochiral Gold Nanoclusters through Precursor Engineering

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Controllable syntheses of Au nanoclusters (NCs) with different nuclearities are of great significance due to the kernel-dependent physicochemical properties. Herein, two pairs of enantiomeric Au NCs [Au 19 ( R / S -BINAP) 4 (PhC≡C)Cl 4 ] ( SD/Au19 ) and [Au 11 ( R / S -BINAP) 4 (PhC≡C) 2 ]·Cl ( SD/Au11 ), both with atropos (rigid axial chirality) diphosphine BINAP (2,2′-bis(diphenylphosphino)-1,1′-binaphthalene) as the predominant organic ligands, were controllably synthesized through precursor engineering. The former was obtained by direct reduction of HAuCl 4 ·4H 2 O, while the latter was obtained by reduction of [Au(SMe 2 )Cl] instead. Intriguingly, the kernel of SD/Au19 contains an Au 7 pentagonal bipyramid capped by two boat-like Au 6 rings, which represents another type of Au 19 kernel, making SD/Au19 a good candidate for comparative study with other Au 19 NCs to get more insight into the distinct structural evolution of phosphine-protected Au NCs. Despite the previous chiroptical studies on some other chiral undecagold NCs, the successful attainment of the X-ray crystal structures for SD/Au11 not only provides a step forward toward better correlating the chiroptical activities with their structural details but also reveals that even the auxiliary protecting ligands also play a nontrivial role in tuning the geometrical structures of the metal NCs. The chiroptical activities of both SD/Au19 and SD/Au11 were found to originate from the chiral ligands and core distortions; the extended π-electron systems in the BINAP ligands have proved to positively contribute to the electronic absorptions and thus disturb the corresponding circular dichroism (CD) responses.