1.Toward Controlled Syntheses of Diphosphine-Protected Homochiral Gold Nanoclusters through Precursor Engineering
ACS Nano. 2021 Oct 26;15(10):16019-16029. doi: 10.1021/acsnano.1c04421.
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.
2.Bicarbonate insertion triggered self-assembly of chiral octa-gold nanoclusters into helical superstructures in the crystalline state
Chem Sci. 2022 Aug 15;13(35):10523-10531. doi: 10.1039/d2sc03463h.
Constructing atomically precise helical superstructures of high order is an extensively pursued subject for unique aesthetic features and underlying applications. However, the construction of cluster-based helixes of well-defined architectures comes with a huge challenge owing to their intrinsic complexity in geometric structures and synthetic processes. Herein, we report a pair of unique
P-
and
M-
single stranded helical superstructures spontaneously assembled from
R
- and
S
-Au8c individual nanoclusters, respectively, upon selecting chiral BINAP (2,2'-bis(diphenylphosphino)-1,1'-binaphthalene) and hydrophilic
o
-H
2
MBA (
o
-mercaptobenzoic acid) as protective ligands to induce chirality and facilitate the formation of helixes. Structural analysis reveals that the chirality of the Au8c individual nanoclusters is derived from the homochiral ligands and the inherently chiral Au
8
metallic kernel, which was further corroborated by experimental and computational investigations. More importantly, driven by the O-H⋯O interactions between (HCO
3
-
)
2
dimers and achiral
o
-HMBA
-
ligands,
R
/
S
-Au8c individual nanoclusters can assemble into helical superstructures in a highly ordered crystal packing. Electrospray ionization (ESI) and collision-induced dissociation (CID) mass spectrometry of Au8c confirm the hydrogen-bonded dimer of Au8c individual nanoclusters in solution, illustrating that the insertion of (HCO
3
-
)
2
dimers plays a crucial role in the assembly of helical superstructures in the crystalline state. This work not only demonstrates an effective strategy to construct cluster-based helical superstructures at the atomic level, but also provides visual and reliable experimental evidence for understanding the formation mechanism of helical superstructures.
