Search results for "Ionic"

Cobalt bis(dicarbollides)(1-) covalently attached to the calyx[4]arene platform: the first combination of organic bowl-shaped matrices and inorganic …

2005

Various calix[4]arene and resorc[4]arene ionic compounds substituted by cobalt bis(dicarbollide) anions (1) have been prepared for the first time. From tBu-calix[4]arene (A) the complete series of mono-, di-, tri- and tetrasubstituted derivatives bearing one to four cluster anions on the lower rim (3-6) have been obtained in the form of their alkali-metal salts by O-alkylation with the 1-dioxane derivative [8-O(CH2CH2)2O(+)-1,2-C2B9H10)-(1',2'-C2B9H11)-3,3'-Co] (2), all of which are syn or cone isomers. In contrast, disubstitution of the dipropyl ether of tBu-calix[4]arene (B) led to a mixture of the cone and 1,3-alternate conformers 7a and 7b, respectively. Starting from tetrapropoxy-calix…

Anionic halide···alcohol clusters in the solid state.

2014

The cationic (1,3,5-triazapentadiene)Pt(II) complexes [1](Cl)2, [2](Cl)2, [3](Br)2, and [4](Cl)2, were crystallized from ROH-containing systems (R = Me, Et) providing alcohol solvates studied by X-ray diffraction. In the crystal structures of [1-4][(Hal)2(ROH)2] (R = Me, Et), the Hal(-) ion interacts with two or three cations [1-4](2+) by means of two or three or four contacts thus uniting stacked arrays of complexes into the layers. The solvated MeOH or EtOH molecules occupy vacant space, giving contacts with [1-4](2+), and connects to the Hal(-) ion through a hydrogen bridge via the H(1O)O(1S) H atom forming, by means of the Hal(-)···HOR (Hal = Cl, Br) contact, the halide-alcohol cluster.…

Ionic transport and heat capacity of glass-forming metalnitrate mixtures

1997

Abstract Ionic transport of the glass-forming metalnitrate mixtures [Ca(NO 3 ) 2 ] 0.44 [KNO 3 ] 0.56 (MKN), and [Mg(NO 3 ) 2 ] 0.44 [NaNO 3 ] 0.56 (MNN) was investigated near the glass transition using broadband spectroscopy of the complex conductivity to 300 MHz. The real part of the conductivity exhibits a transition from frequency independent to power law behavior as found in most ionic conductors. At high frequencies the frequency exponent approaches unity and becomes larger at low temperatures. In the real part of the dielectric constant, a relaxation step could be observed in CRN. A detailed evaluation of the results within the modulus formalism is presented. The imaginary part of t…

General occurrence of polar twisted minima in the ionic singlet excited surfaces of polyenes

1982

Except for a few cases, the lowest closed shell SCF solutions for the twisted geometries of polyenes involves delocalized nonpolarized MO’s, and represents a meaningless mixture of radicalar gound state and ionic excited states. Higher (quasi) solutions allow a realistic approach of the polarized ionic states. Orthogonality to the radicalar ground state may be imposed without important loss of energy. Further extensive CI does not modify significantly the situation. These statements are illustrated through ab initio calculations of butadiene and hexatriene. This approach allows us to show that slight distortions stablize polar minima even in ’’homosymmetric’’ molecules such as all‐trans hex…

Calculations of F centers in KNbO 3 ferroelectric crystals

1997

Semi-empirical method of the intermediate neglect of the differential overlap (INDO) combined with the supercell model is applied to the calculations of the F center optical properties in ferroelectric KNbO 3 perovskite crystals. It is shown that two electrons of the defect are weakly localized inside the O vacancy, unlike similar defects in ionic alkali halides, but are considerably spread over two nearest Nb atoms. For the orthorhombic phase stable at room temperatures three absorption bands are predicted to be at 2.72 eV, 3.04 eV and 3.11 eV, respectively. The first energy is close to the band at 2.7 eV observed in electron- irradiated crystals. In the high temperature, cubic phase only …

Solvent induced single-crystal to single-crystal structural transformation and concomitant transmetalation in a 3D cationic Zn(II)-framework.

2015

A 3D cationic Zn(II) framework, based on Zn2(CO2)4 paddle-wheel secondary building units (SBUs) and Zn16(CO2)32 polyhedral supramolecular building blocks (SBBs), has been synthesized. At room temperature, the framework undergoes guest solvent triggered reversible structural transformation and concomitant Zn(II) to Cu(II) transmetalation in a single-crystal to single-crystal fashion.

Cationic mono- and bi-nuclear iron complexes as Lewis acid catalysts in Mukaiyama reactions

1992

Organometallic Lewis acids derived from photolysis of mono- and bi-nuclear cationic iron carbonyl complexes function as excellent catalysts for the Mukaiyama aldol reaction.

CONVERSIONE CHEMO-ENZIMATICA DI GLUCOSIO IN 5-HMF IN MISCELE IL/H2O, PROMOSSA DA ESTRATTO CELLULARE BATTERICO E ULTRASUONI

Inhibitory effects of N-acetylcysteine on the functional responses of human eosinophils in vitro

2007

Background Oxidative stress appears to be relevant in the pathogenesis of inflammation in allergic diseases like bronchial asthma. Eosinophils are oxidant-sensitive cells considered as key effectors in allergic inflammation. Objective The aim of this work was to study the effects of the clinically used antioxidant N-acetyl-L-cysteine (NAC) on the functional responses of human-isolated eosinophils. Methods Human eosinophils were purified from the blood of healthy donors by a magnetic bead separation system. The effects of NAC were investigated on the generation of reactive oxygen species (chemiluminescence and flow cytometry), Ca2+ signal (fluorimetry), intracellular glutathione (GSH; flow c…

Influence of Feeding and Oviposition by Phytophagous Pentatomids on Photosynthesis of Herbaceous Plants

2010

Abstract Feeding by herbivorous insects may change photosynthetic activity of host plants. We studied how feeding and oviposition by herbivorous stink bugs, Murgantia histrionica and Nezara viridula (Heteroptera: Pentatomidae), affect photosynthetic parameters of Brassica oleracea (savoy cabbage) and Phaseolus vulgaris (French bean). First, we measured photosynthetic gas exchange, chlorophyll fluorescence imaging, and emission of induced volatile organic compounds (VOC) immediately after feeding and during a post-feeding period. Photosynthesis decreased rapidly and substantially in B. oleracea and P. vulgaris infested by feeding bugs. Stomatal conductance did not decrease proportionally wit…