RESUMO
A bis-bisurea receptor (L) based on the R,R-cyclohexane-1,2-diamino scaffold forms an uncommon 2 : 2 complex (1) with the monohydrogen phosphate ion (HPO(4)(2-)) and a 1 : 1 complex (2) with the sulfate ion (SO(4)(2-)). Solution binding properties of the two anions were studied by (1)H NMR, UV-vis, and circular dichroism (CD) methods.
Assuntos
Cicloexanos/química , Fosfatos/química , Sulfatos/química , Ureia/análogos & derivados , Ânions/química , Dicroísmo Circular , Cristalografia por Raios X , Espectroscopia de Ressonância Magnética , Modelos MolecularesRESUMO
A bis-trisurea ligand assembles with the tetraalkylammonium halides to form the flat 'stave' structures or 'barrels' that encapsulate multiple R(4)N(+) guests, depending on the size of the halide anion (Cl(-) or Br(-)) and the R(4)N(+) cation.
Assuntos
Biureias/química , Compostos de Amônio Quaternário/química , Cátions/química , Estrutura Molecular , UreiaRESUMO
The surface morphology of hollow silica microspheres has influence on their applications. After a thorough investigation of the deposition of silica nanoparticles on polystyrene (PS) beads and the surface morphology and texture of the resultant hollow silica shells with scanning electron microscopy, transmission electron microscopy, and N2-sorption measurements, the influence of surfactant [cetyltrimethylammonium bromide (CTAB)] concentration on the surface morphology of hollow silica microspheres templated by PS beads is explained. Previously, CTAB was believed to turn the surface charge of PS beads from negative into positive so that negatively charged silica could be deposited on the PS template. Here, we show CTA+ cations preferentially assemble with silica species to form silica-CTA+ composite nanoparticles. Since the zeta potential of silica-CTA+ composite nanoparticles is smaller than that of pure silica nanoparticles, these composite nanoparticles encounter less repulsion when they are deposited on the surface of PS beads and close to each other. As more CTAB is added, the silica-CTA+ nanoparticles are less negatively charged, and more compact and smooth hollow silica microspheres are obtained.
