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In this work, we present a combined experimental and theoretical analysis of two-component ligand shells passivating CdSe quantum dots. Using nuclear magnetic resonance spectroscopy, we first show that exposing oleate capped quantum dots to primary carboxylic acids results in a one-for-one exchange that preserves the overall ligand surface concentration. Exposure to straight-chain acids leads to a binary ligand shell that behaves as an ideal mixture and that has a composition matching the overall acid composition of the dispersion. In the case of branched-chain acids, the exchange is restricted to about 25% of the original ligands. Based on molecular dynamics simulations, we argue that this behavior reflects the more favorable packing of oleates compared to branched carboxylates on the (100) facets of CdSe quantum dots.

We report the synthesis of a family of d- and l-furano-d-apionucleosides, their 3′-deoxy, as well as their 2′,3′-dideoxy analogues with thymine and adenine nucleobases. Single carbon homologation of 1,2-O-isopropylidene-d-glycero-tetrafuranos-3-ulose (15) and optimized glycosylation conditions involving microwave irradiation were key to the successful synthesis of the target compounds. While all target nucleosides failed to show significant antiviral activity, we demonstrated that the triphosphate of 2′,3′-deoxy-d-apio-d-furanoadenosine (1), in contrast to that of its d-apio-l-furanose epimer 2, was readily incorporated into a DNA template by HIV reverse transcriptase to act as a DNA chain terminator. This led us to convert adenine derivative 1 into two phosphoramidate prodrugs. ProTide 9b was found active against HIV-1 and HIV-2 (EC50 = 0.5–1.5 μM), indicating that the lack of activity of the parent nucleoside, and possibly also other members of the d-apio-d-furanose nucleoside family must be sought in the inefficient cellular conversion to the monophosphate.

The cross-linked polystyrene grafted organotin [P-H]((1-t))[P-(CH2)(11)-SnCl3](t), in which [P-H] represents the monomeric unit of the nonfunctionalized polymer and t is the functionalization degree, has been synthesized and characterized by ID and 2D H-1, C-13, and Sn-119 high-resolution magic angle spinning (HRMAS) NMR spectroscopy, elemental analysis, and IR spectrometry. Its catalytic activity was assessed in the transesterification model reaction between ethyl acetate and n-octanol. The catalyst displays an average conversion degree of 76% after 2 h and can be recycled at least nine times. The experimental concentration profiles were fitted to a mechanistic model, from which a turnover frequency in the range of 10(-2) s(-1) was calculated. Residual tin contents on the order of 5 ppm in the reaction products were assessed by inductively coupled plasma/atomic emission spectroscopy (ICP/AES). The combined use of H-1, C-13, and Sn-119 HRMAS NMR and modulated DSC enables one to assess the chemical integrity of the catalyst upon recycling. Detailed analysis of Sn-119 HRMAS NMR spectra under various chemical conditions mimicking the reaction mixtures allows gaining a better insight into the catalysis mechanism.

Branched nanocrystals (NCs) enable high atomic surface exposure within a crystalline network that provides avenues for charge transport. This combination of properties makes branched NCs particularly suitable for a range of applications where both interaction with the media and charge transport are involved. Herein we report on the colloidal synthesis of branched ceria NCs by means of a ligand-mediated overgrowth mechanism. In particular, the differential coverage of oleic acid as an X-type ligand at ceria facets with different atomic density, atomic coordination deficiency, and oxygen vacancy density resulted in a preferential growth in the [111] direction and thus in the formation of ceria octapods. Alcohols, through an esterification alcoholysis reaction, promoted faster growth rates that translated into nanostructures with higher geometrical complexity, increasing the branch aspect ratio and triggering the formation of side branches. On the other hand, the presence of water resulted in a significant reduction of the growth rate, decreasing the reaction yield and eliminating side branching, which we associate to a blocking of the surface reaction sites or a displacement of the alcoholysis reaction. Overall, adjusting the amounts of each chemical, well-defined branched ceria NCs with tuned number, thickness, and length of branches and with overall size ranging from 5 to 45 nm could be produced. We further demonstrate that such branched ceria NCs are able to provide higher surface areas and related oxygen storage capacities (OSC) than quasi-spherical NCs.