When nanoparticles
(NPs) are assembled from solution, a common
assembly method of choice is either solution destabilization or solvent
evaporation technique. The destabilization of the NP solution by non-solvents
results in the formation of faceted supercrystals (SCs) while periodic
film-like assemblies are typically formed by solvent evaporation.
Here, we reveal the effect of non-solvents in washing, dispersing,
and crystallizing NPs. Small angle neutron scattering (SANS) is employed
for monitoring the ligand shell of NPs in solutions upon introduction
of various non-solvents. The SC crystallization process is traced
in situ with small-angle X-ray scattering (SAXS), and the structures
of the resulting single-crystalline SCs are examined in detail by
mapping the reciprocal space using SAXS and wide-angle X-ray scattering.
Our study suggests that the relative miscibility of the non-solvent
with solvents and ligands determines the solvation and thickness of
the ligand shell and thereby the resulting structure of SCs. In the
early stage of crystallization, truncated octahedral PbS NPs form
SCs with face-centered cubic (fcc) symmetry. In the later stage, the
fcc symmetry is preserved in the SC formed by larger (5.60 nm) NPs,
but the SC assembled from smaller (4.14 nm) NPs undergoes a phase
transition into body-centered cubic (bcc) lattice via Bain transformation,
becoming a polycrystalline SC containing three structurally correlated
bcc domains and one untransformed fcc domain. Our study provides the
detailed understanding of the non-solvent effect that impacts beyond
the formation of SCs, enabling the judicious selection of solvent/non-solvent
mixtures for NP purification.
C-H/C-N activation: The first palladium/copper-catalyzed aerobic oxidative C-H alkenylation/N-dealkylative carbonylation of tertiary anilines has been developed. Various functional groups were tolerated and acrylic ester could also be suitable substrates. This transformation provided efficient and straightforward synthesis of biologically active 3-methyleneindolin-2-one derivatives from cheap and simple substrates.
A novel Pd/Cu-catalyzed chemoselective aerobic oxidative N-dealkylation/carbonylation reaction has been developed. Tertiary amines are utilized as a "reservoir" of "active" secondary amines in this transformation, which inhibits the formation of undesired by-products and the deactivation of the catalysts. This protocol allows for an efficient and straightforward construction of synthetically useful and bioactive (E)-α,β-unsaturated amide derivatives from easily available tertiary amines, olefins and CO.
C‐H/C‐N‐Aktivierung: Die erste Palladium/Kupfer‐katalysierte aerobe oxidative C‐H‐Alkenylierung/N‐desalkylierende Carbonylierung von tertiären Anilinen wurde entwickelt. Die Reaktion ist mit vielen funktionellen Gruppen kompatibel, kann auch Acrylester umsetzen und ermöglichte die effiziente Synthese von biologisch aktiven 3‐Methylenindolin‐2‐onen aus preiswerten und einfachen Substraten.
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