Wetting transitions and depinning of the triple line

Physical mechanisms of Cassie-Wenzel wetting transitions are discussed. The origin of the potential barrier separating the Cassie and Wenzel wetting states is clarified. It may contain contributions originating from the filling of hydrophobic pores and displacement of the triple line along the smooth portions of the relief. One- and two-dimensional scenarios of wetting transitions are considered. We demonstrate that the contribution to the potential barrier because of the displacement of the triple line is not negligible in both cases.     

Orientations of polyoxometalate anions on gold nanoparticles

Cryogenic transmission electron microscopy of polyoxometalate-protected gold nanoparticles reveals that the Preyssler ion, [NaP(5)W(30)O(110)](14-), lies "face down" with its C(5) axis perpendicular to the gold surface, while the Finke-Droege ion, [P(4)W(30)Zn(4)(H(2)O)(2)O(112)](16-), is "tilted", with its long axis close to 60° from the normal to the surface.     

β-Diketiminate complexes of Group 4: active complexes for the isomerization of α-olefins and the polymerization of propylene towards elastomeric polypropylene

The β-diketiminate lithium ligand [{N(SiMe₃)C(Ph)}₂CH][Li] reacted with Group 4 metal salts (Ti and Zr) to yield the complexes [{N(SiMe₃)C(Ph)}₂CH]₂TiCl₂ (5) and [{N(SiMe₃)C(Ph)}₂CH][N(SiMe₃)C(Ph)NC(Ph)CH(SiMe₃)]ZrCl₂ (6). The crystal structure of 6 shows that one of the two ketamidinate ligands undergoes an isomerization to the corresponding substituted benzamidinate. A mechanism for the catalyzed isomerization of the β-diketiminate ligand is presented. Complex 5 was found to be active in the polymerization of propylene, producing remarkably high-molecular weight (>100,000 g mol⁻¹) elastomeric polymer, whereas the zirconium complex was found inactive. Complex 5, and surprisingly complex 6, were found to be active catalysts, in the presence of MAO (methylalumoxane), for the isomerization of aliphatic olefins (1-octene, allylbenzene). Each complex catalyzed the olefins by different mechanisms. Kinetic studies for the isomerization of allylbenzene by complex 5 show that the reaction rate follows a first order in both catalyst and olefin concentrations with ΔH^‡=14.7(4) kcal mol⁻¹ and ΔS^‡=−33(1) e.u. These findings support the epimerization mechanism of the last inserted monomer that is proposed for as the primary cause for the elastomeric properties of polypropylene produced by this complex. In addition, we show how complementary isomerization studies of α-olefins shed light on the polymerization mechanism.     

A simple route to tetrahydro-1,4-benzodiazepin-3-ones bearing diverse N1, N4, and C10 functionalization

We describe an efficient synthesis of enantiopure tetrahydro-1,4-benzodiazepine-3-ones derived from l-alanine. Diverse substitution at N1, N4, and C10 can be achieved by coupling various N-alkyl derivatives of l-alanine and N-allyl-(2-fluoro-5-nitro)benzylamine. Cyclization of this intermediate proceeds in high yield and without racemization, providing diversity at N1. The NO₂ group was easily transformed into other functional groups or removed, providing diversity at C10. Finally, oxidative deallylation allows diverse substitution to be installed at N4.     

Single-site catalysis by bimetallic zinc calixarene inclusion complexes

[reaction: see text] Bimetallic alkylzinc calixarene inclusion complexes were prepared and used in the ring-opening polymerization of L-lactide. Polymers with high molecular weight and a low degree of polydispersity were obtained. 1H NMR and diffusion NMR experiments suggest that a single-site mechanism is operative.     

A Novel and Effective Strategy for the Construction of "Tube-Like" Double Resorcin[4]arenes

The synthesis of rigid tube-shape structures from resorcin[4]arene unitscombined in the ``head-to-tail'' manner is described.Tetrabromomethylenecalix-[4]resorcinarene with all OH-groups connected viamethylene bridges was used as a starting material. Reaction withp-hydroxybenzaldehyde led to the tetraaldehyde derivative and the following condensation with resorcinol resulted in formation of a third aromatic rim. An electrochemical study comparing properties of both resorcin[4]arene and itstube-shaped analogs was performed.