Plasmonic twinned silver nanoparticles with molecular precision.

Determining the structures of nanoparticles at atomic resolution is vital to understand their structure-property correlations. Large metal nanoparticles with core diameter beyond 2 nm have, to date, eluded characterization by single-crystal X-ray analysis. Here we report the chemical syntheses and structures of two giant thiolated Ag nanoparticles containing 136 and 374 Ag atoms (that is, up to 3 nm core diameter). As the largest thiolated metal nanoparticles crystallographically determined so far, these Ag nanoparticles enter the truly metallic regime with the emergence of surface plasmon resonance. As miniatures of fivefold twinned nanostructures, these structures demonstrate a subtle distortion within fivefold twinned nanostructures of face-centred cubic metals. The Ag nanoparticles reported in this work serve as excellent models to understand the detailed structure distortion within twinned metal nanostructures and also how silver nanoparticles can span from the molecular to the metallic regime.

Crystal structure of 3ß-acet-oxy-androsta-5,16-dien-17-yl tri-fluoro-methane-sulfon-ate.

The title compound, C22H29F3O5S [systematic name: (3S,8R,9S,10R,13S,14S)-10,13-dimethyl-17-(tri-fluoro-methylsulfon-yloxy)-2,3,4,7,8,9,10,11,12,13,14,15-dodeca-hydro-1H-cyclo-penta-[a]phenanthren-3-yl acetate], contains a fused four-ring steroidal system. Rings A and C adopt a chair conformation, while rings B and D adopt half-chair and envelope (with the fused CH atom as the flap) conformations, respectively. In the crystal, weak inter-molecular C-H⋯O inter-actions link the mol-ecules into layers parallel to the ab plane.

Crystal structure of (3S)-3-acet-oxy-17-(pyridin-3-yl)androsta-5,16-diene.

In the title compound, C26H33NO2 [systematic name: (3S,8R,9S,10R,13S,14S)-10,13-dimethyl-17-(pyridin-3-yl)-2,3,4,7,8,9,10,11,12,13,14,15-dodeca-hydro-1H-cyclo-penta-[a]phenanthren-3-yl acetate], the steroid A, B, C and D rings adopt chair, half-chair, chair and envelope conformations, respectively. The flap atom of the envelope is the methine C atom fused with the C ring. In the crystal, adjacent mol-ecules, generated by a 21 screw axis, are linked by weak C-H⋯O hydrogen bonds, forming a C(16) helical chain running along the c-axis direction.

All-thiol-stabilized Ag44 and Au12Ag32 nanoparticles with single-crystal structures.

Noble metal nanoparticles stabilized by organic ligands are important for applications in assembly, site-specific bioconjugate labelling and sensing, drug delivery and medical therapy, molecular recognition and molecular electronics, and catalysis. Here we report crystal structures and theoretical analysis of three Ag44(SR)30 and three Au12Ag32(SR)30 intermetallic nanoclusters stabilized with fluorinated arylthiols (SR=SPhF, SPhF2 or SPhCF3). The nanocluster forms a Keplerate solid of concentric icosahedral and dodecahedral atom shells, protected by six Ag2(SR)5 units. Positive counterions in the crystal indicate a high negative charge of 4(-) per nanoparticle, and density functional theory calculations explain the stability as an 18-electron superatom shell closure in the metal core. Highly featured optical absorption spectra in the ultraviolet-visible region are analysed using time-dependent density functional perturbation theory. This work forms a basis for further understanding, engineering and controlling of stability as well as electronic and optical properties of these novel nanomaterials.

Selective hydrogenation of α,ß-unsaturated aldehydes catalyzed by amine-capped platinum-cobalt nanocrystals.

More Greasy, more selective: amine-capped Pt(3)Co nanocatalysts were synthesized and used for the hydrogenation of cinnamaldehyde (CAL). Capping the catalysts with amines that contain long carbon chains results in an ordered surface "array", in which high selectivity towards C=O hydrogenation can be achieved because the C=C bond in CAL does not interact with the surface. The longer the carbon chains in the amine, the higher the selectivity.