Nichtlineare optische Materialien In der Zuschrift auf S. 6598 beschreiben K. Ok, G. Zou et al. die Synthese des Fluoridsulfats CsSbF2SO4 aus KTiOPO4 durch chemische Substitution. CsSbF2SO4 zeichnet sich durch eine ausgeprägte Frequenzverdopplung aus.

Two new antimony sulfate chlorides named (NH4)2SbCl­(SO4)2 and (NH4)­SbCl2(SO4) were successfully synthesized through solvent-free synthesis method. (NH4)2SbCl­(SO4)2 exhibits a three-dimensional framework constructed of [SbCl­(SO4)2]2– chains and NH4 + ions. And the NH4 + cations play the role of charge balance and provide the hydrogen bond constructed with oxygen atoms. (NH4)­SbCl2(SO4) shows a two-dimensional layer structure that is composed of the regularly stacked [SbCl2(SO4)]− chains via hydrogen-bonding interactions. Both of the titled compounds possess the same chemical composition and the similar Sb–Cl–SO4 chains, while hydrogen-bonding interactions and lone-pair cations play the synergistic effect on the framework structures and macroscopic centricities resulting in that the (NH4)2SbCl­(SO4)2 is centrosymmetric and the (NH4)­SbCl2(SO4) is non-centrosymmetric (NCS). Powder second harmonic generation (SHG) measurements indicated that the NCS compound (NH4)­SbCl2(SO4) is type I phase-matchable and exhibits SHG responses of ∼1.7 times that of KH2PO4.

A novel noncentrosymmetric (NCS) polar fluoride sulfate, CsSbF2SO4, was obtained by ionothermal synthesis. A meticulously designed co‐substitution approach was used to successfully replace the [TiO6]8− and [PO4]3− functional groups in KTiOPO4 (KTP) with [SbO4F2]7− and [SO4]2− units, respectively. The structure of CsSbF2SO4 features a pseudo‐3D framework consisting of interconnected 1D [SbF2O2SO4]5− chains of corner‐sharing [SbO4F2]7− octahedra and [SO4]2− tetrahedra. The title compound exhibits a sharply enlarged band gap compared to its parent compound, KTP, benefitting from the introduction of F− ions and the displacement of Sb3+ cations. Second harmonic generation (SHG) measurements manifested that CsSbF2SO4 is phase‐matchable and revealed a strong SHG response of about 3.0 KH2PO4 (KDP), which is the highest value reported for any metal sulfate reported to date. The reported fluoride sulfate is a promising near ultraviolet (UV) nonlinear optical (NLO) material.

Four stoichiometrically equivalent compounds have been successfully synthesized through A+ cations by tuning the framework structures and macroscopic centricities.

Hydroxyapatite (HAP, Ca 10 (PO 4 ) 6 (OH) 2 ) constitutes one of the main components in human bones and teeth. Investigations of the surface structures of HAP could help us to understand the interactions between the implant HAP-based biomaterials and their environment. We, in this work, systematically explored the surface structures of HAP based on two different force fields, Born−Mayer−Huggins (BMH) parameters and interface force fields (IFFs). Their different performances in constructing HAP ordered-to-disordered surface structures were compared and discussed. The annealed HAP ( 001), ( 010), (100), and (110) surface structures were obtained, and their thickness values of the disordered layers have been computed. The thicknesses have the same order of (001) < ( 010) < (100) < (110) even at different annealing temperatures by the two force fields. At the annealing temperature 1800 K, the theoretical prediction for the average disordered layer thickness values is 8.9 Å (BMH) and 10.3 Å (IFF), which are close to the experimental measurement of 10−20 Å. Further studies on the surface models of ( 010) and ( 100) with different ion-rich terminations show that the disordered layer thickness of the P-rich surface are systematically larger than that of the Ca-rich surfaces. In the surface structure analyses, total pair distribution functions, static structure factors, and the coordination numbers for Ca or P were performed. These analyses show that our present HAP surface models have obvious ordered-to-disordered topology. In the present molecular dynamics exploration on the surface structures of HAP, several new surface models with different terminations for HAP-based biomaterials have been suggested, which may be appropriate for further investigation of interactions between biomolecules and HAP material.

A novel synthetic method for flavonol from 2′-hydroxyl acetophenone and benzaldehyde promoted by pyrrolidine under an aerobic condition in water is established. This protocol was supported by efficient synthesis of 44 common examples and three natural products. The α, β-unsaturated iminium ion (enimine ion E) was proved to be the key intermediate in the reaction. H 2 18 O and 18 O 2 isotope tracking experiments demonstrated that both water and the aerobic atmosphere were necessary to ensure the transformation. The selectivity for flavonol or aurone was originated from solvent-triggered intermediates, which were determined by UV−visible spectra from isolated enimine. The phenol-iminium E-A is dominant in water and the ketoenamine intermediate E-B is prevalent in acetonitrile. In the presence of pyrrolidine and oxygen, E-A leads to flavonol through E-I, a zwitterionic-like phenoloxyl-iminium ion, following the key steps of cyclization and a [2 + 2] oxidation; E-B proceeds through path II, a radical process induced by photolysis of E-B with both pyrrolidine and oxygen, to afford aurone. Preliminary mechanistic studies are reported.

No abstract

Antimicrobial peptides (AMPs) are small amphipathic peptides that exhibit bactericidal activity against a wide range of pathogenic microorganisms and are considered to be potential substitutes for antibiotics effective against microbial infection. PSK, an 84-amino-acid AMP recently isolated from Chrysomya megacephala larvae, probably belongs to the mitochondrial ATPase inhibitor family according to its sequence. No member of this family from an insect has been structurally characterized to date. In this study, the crystal structure of full-length PSK determined by molecular replacement using an ab initio modeled ensemble as a search model and a solution structure obtained from small-angle X-ray scattering (SAXS) measurements are reported. The crystal structure reveals a distinct fold compared with those of homologous peptides, in that PSK comprises two antiparallel α-helices rather than a single long helix, which is in good agreement with the SAXS-based ab initio model. However, the peptide exists as a monomer in solution, even though a stable dimer was observed in the crystal structure. This apparent contradiction may reflect different oligomerization states that may be implicated in its bioactivity. The data presented here have established a solid basis for further mechanistic studies of this novel insect AMP.