Functionalised polyhedral oligomeric silsesquioxane with encapsulated fluoride - first observation of fluxional SiF interactions in POSS

The synthesis of a styryl functionalised POSS incorporating an encapsulated fluoride ion within a (SiO_1.5)₈ cage (T₈-F) is reported. It was characterised by single crystal XRD, MALDI-MS, FTIR, solution (²⁹Si, ¹⁹F, ¹³C, ¹H) and solid state (²⁹Si, ¹⁹F) NMR. In the absence of ¹H decoupling, the ²⁹Si solution NMR spectrum exhibited a triplet of doublets. In contrast, ¹H, ¹⁹F and ¹H/¹⁹F double-decoupling resulted in two, three and one signal, respectively, being consistent with a single Si site whose ²⁹Si NMR signal is modulated by both the proximal aromatic-ring protons and fluoride. The associated SiF coupling constant (2.5 Hz) is substantially lower than expected for a covalent Si-F bond and arises from a fluxional SiF covalent effect in which the F^- interacts equivalently with all eight Si atoms. Additional variable temperature NMR studies demonstrated a threshold at -5 °C below which no SiF interactions are observed, and above which an increasing SiF covalent character occurs.

Synthesis, photophysical and electropolymerization properties of thiophene-substituted 2,3-diphenylbuta-1,3-dienes

Electropolymerizable diphenylbuta-1,3-diene derivatives with AIE or AEE properties were synthesized allowing low bandgap polymers to be obtained through electropolymerization processes.

Prospect of Thiazole-based γ-Peptide Foldamers in Enamine Catalysis: Exploration of the Nitro-Michael Addition

As three-dimensional folding is prerequisite to biopolymer activity, complex functions may also be achieved through foldamer science. Because of the diversity of sizes, shapes and folding available with synthetic monomers, foldamer frameworks enable a numerous opportunities for designing new generations of catalysts. We herein demonstrate that heterocyclic γ-peptide scaffolds represent a versatile platform for enamine catalysis. One central feature was to determine how the catalytic activity and the transfer of chiral information might be under the control of the conformational behaviours of the oligomer.

Structure-Driven Selection of Adaptive Transmembrane Na+ Carriers or K+ Channels

Self-assembled alkyl-ureido-benzo-15-crown-5-ethers are selective ionophores for K⁺ cations, which are preferred to Na⁺ cations. The transport mechanism is determined by the optimal coordination rather than classical dimensional compatibility between the crown ether hole and the cation diameter. Herein, we demonstrate that systematic changes of the structure lead to unexpected modifications in the cation-transport activity and suffice to produce adaptive selection. We show that the main contribution to performance arises from optimal constraints on the conformational freedom, which are determined by the binding macrocycles, the nature of the hydrogen-bonding groups, and the hydrophobic tails. Simple changes to the flexible 15-crown-5-ether lead to selective carriers for Na⁺ . Hydrophobic stabilization of the channels through mutual interactions between lipids and variable hydrophobic tails appears to be an important cause of increased activity. Oppositely, restricted translocation is achieved when constrained hydrogen-bonded macrocyclic relays are less dynamic in a pore superstructure.

Drug discovery: phosphinolactone, in vivo bioisostere of the lactol group

In drug discovery, structural modifications over the lead molecule are often crucial for the development of a drug. Herein, we reported the first in vivo bioisosteric effect of phosphinolactone function in relation to the lactol group constituting the bioactive molecule: Hydroxybupropion. The preparation of phosphinolactone analogues and their antidepressant evaluation towards forced swimming test in mice showed that biological activity was regained and even strengthen.