Tailoring the Structural and Optical Properties of Cerium Oxide Nanoparticles Prepared by an Ecofriendly Green Route Using Plant Extracts.

The present study explores an environmentally friendly green approach to obtain cerium oxide nanoparticles via a biomediated route using Mellisa officinalis and Hypericum perforatum plant extracts as reducing agents. The as-prepared nanoparticles were studied for their structural and morphological characteristics using XRD diffractometry, scanning electron microscopy, Raman, fluorescence and electronic absorption spectra, and X-ray photoelectron spectroscopy (XPS). The XRD pattern has shown the centered fluorite crystal structure of cerium oxide nanoparticles with average crystallite size below 10 nm. These observations were in agreement with the STEM data. The cubic fluorite structure of the cerium oxide nanoparticles was confirmed by the vibrational mode around 462 cm-1 due to the Ce-08 unit. The optical band gap was estimated from UV-Vis reflectance spectra, which was found to decrease from 3.24 eV to 2.98 eV. A higher specific area was determined for the sample using M. officinalis aqueous extract. The EDX data indicated that only cerium and oxygen are present in the green synthesized nanoparticles.

Synthesis and crystal structure of bis-[trans-di-aqua-(1,4,8,11-tetra-aza-cyclo-tetra-decane-κ4 N 1,N 4,N 8,N 11)nickel(II)] trans-(1,4,8,11-tetra-aza-cyclo-tetra-decane-κ4 N 1,N 4,N 8,N 11)bis-[4,4',4''-(1,3,5-tri-methyl-benzene-2,4,6-tri-yl)tris-(hydrogen phenyl-phospho-nato-κO)]nickel(II) deca-hydrate.

The components of the title compound, [Ni(C10H24N4)(H2O)2]2[Ni(C10H24N4)(C27H24O9P3)2]·10H2O are two centrosymmetric [Ni(C10H24N4)(H2O)2]2+ dications, a centrosymmetric [Ni(C10H24N4)(C27H24O9P3)2]4- tetra-anion and five crystallographically unique water mol-ecules of crystallization. All of the nickel ions are coordinated by the four secondary N atoms of the macrocyclic cyclam ligands, which adopt the most energetically stable trans-III conformation, and the mutually trans O atoms of either water mol-ecules in the cations or the phospho-nate groups in the anion in a tetra-gonally distorted NiN4O2 octa-hedral coordination geometry. Strong O-H⋯O hydrogen bonds between the protonated and the non-protonated phospho-nate O atoms of neighboring anions result in the formation of layers oriented parallel to the bc plane, which are linked into a three-dimensional network by virtue of numerous N-H⋯O and O-H⋯O hydrogen bonds arising from the sec-NH groups of the macrocycles, phospho-nate O atoms and coordinated and non-coordinated water mol-ecules.

Probing the supramolecular features via π-π interaction of a di-iminopyrene-di-benzo-18-crown-6-ether compound: experimental and theoretical study.

A novel DPyDB-C[double bond, length as m-dash]N-18C6 compound was synthesised by linking a pyrene moiety to each phenyl group of dibenzo-18-crown-6-ether, the crown ether, through -HC[double bond, length as m-dash]N- bonds and characterized by FTIR, 1H-NMR, 13C-NMR, TGA, and DSC techniques. The quantitative 13C-NMR analysis revealed the presence of two position isomers. The electronic structure of the DPyDB-C[double bond, length as m-dash]N-18C6 molecule was characterized by UV-vis and fluorescence spectroscopies in four solvents with different polarities to observe particular behavior of isomers, as well as to demonstrate a possible non-bonding chemical association (such as ground- and excited-state associations, namely, to probe if there were forming dimers/excimers). The interpretation of the electronic structure was realized through QM calculations. The TD-CAM-B3LYP functional, at the 6-311+G(d,p) basis set, indicated the presence of predominant π → π* and mixed π → π* + n → π* transitions, in line with the UV-vis experimental data. Even though DPyDB-C[double bond, length as m-dash]N-18C6 computational studies revealed a π-extended conjugation effect with predominantly π → π* transitions, thorough fluorescence analysis was observed a weak emission, as an effect of PET and ACQ. In particular, the WAXD analysis of powder and thin films obtained from n-hexane, 1,2-dichloroethane, and ethanol indicated an amorphous organization, whereas from toluene a smectic ordering was obtained. These results were correlated with MD simulation, and it was observed that the molecular geometry of DPyDB-C[double bond, length as m-dash]N-18C6 molecule played a defining role in the pyrene stacking arrangement.

Low toxicity ß-cyclodextrin-caged 4,4'-bipyridinium-bis(siloxane): synthesis and evaluation.

The toxicity of viologens can be significantly reduced by including them in tight [2]rotaxane structures alongside ß-cyclodextrin, thus turning them into candidates of pharmaceutical interest. Here, we report a synthesis pathway for a benign viologen, by capping a small ß-cyclodextrin-caged molecule, the 4,4'-bipyridine, with minimal-length presynthesized axle-stopper segments of the propyl-3-pentamethyldisiloxane type. After 90 min from the oral administration to laboratory mice, the product concentration in the bloodstream reaches a value equivalent to 0.634% of the initial dose of 800 mg·kg(-1). As compared to the nude viologen having the same structure, which proved to be lethal in doses of 40 mg·kg(-1), the product induces reversible morphological changes in the liver, kidney, lung, and cerebellum, up to a dose of 400 mg·kg(-1), with higher dosages giving rise to a chronic slow evolution.

Polysiloxane ionic liquids as good solvents for ß-cyclodextrin-polydimethylsiloxane polyrotaxane structures.

An ionic liquid based on polydimethylsiloxane with imidazolium salt brushes was synthesized as a good solvent for ß-cyclodextrin-polydimethylsiloxane rotaxane. As expected the PDMS-Im/Br ionic liquid had a liquid-like non-Newtonian behavior with rheological parameters dependent on frequency and temperature. The addition of rotaxane to the ionic liquid strengthened the non-Newtonian character of the sample and a type of stable liquid-like network was formed due to the contribution of weak ionic interactions. The structure is stable in the 20 to 80 °C domain as proved by the oscillatory and rotational rheological tests.

Polydiphenylsilanes bearing photosensitive azocrown groups.

This work presents the synthesis and particularities of the reversible trans-cis UV light induced photoisomerization process of a polydiphenylsilane bearing (propyl-oxyphenylazo)dibenzo-18-crown-6 side groups.