New families of salts, based on quaternary ammonium, 1-methyl-3-alkylimidazolium or -methyl--alkylpyrrolidinium organic cations together with the dicyanamide (dca, N(CN)) anion are reported. The ...salts are low melting compounds, all those reported are liquid at room temperature, for example 1-methyl-3-ethylimidazolium dicyanamide (mp -21 degreeC) and -methyl--ethylpyrrolidinium dicyanamide (mp -10 degreeC). Some of the salts exhibit multiple crystalline phases below their melting points. Above their melting points they are stable to at least 200 degreeC. Many of the salts were found to be glass forming when cooled rapidly to -100 degreeC. The room-temperature liquids exhibit very low viscosities, for example ethylmethylimidazolium dicyanamide: = 21 cP at ambient temperature (25 degreeC).
A new series of panchromatic ruthenium(II) sensitizers derived from carboxylated terpyridyl complexes of tris-thiocyanato Ru(II) have been developed. Black dye containing different degrees of ...protonation {(C2H5)3NH}Ru(H3tcterpy)(NCS)3 1, {(C4H9)4N}2Ru(H2tcterpy)(NCS)3 2, {(C4H9)4N}3Ru(Htcterpy)(NCS)3 3, and {(C4H9)4N}4Ru(tcterpy)(NCS)3 4 (tcterpy = 4,4‘,4‘ ‘-tricarboxy-2,2‘:6‘,2‘ ‘-terpyridine) have been synthesized and fully characterized by UV−vis, emission, IR, Raman, NMR, cyclic voltammetry, and X-ray diffraction studies. The crystal structure of complex 2 confirms the presence of a RuIIN6 central core derived from the terpyridine ligand and three N-bonded thiocyanates. Intermolecular H-bonding between carboxylates on neighboring terpyridines gives rise to 2-D H-bonded arrays. The absorption and emission maxima of the black dye show a bathochromic shift with decreasing pH and exhibit pH-dependent excited-state lifetimes. The red-shift of the emission maxima is due to better π-acceptor properties of the acid form that lowers the energy of the CT excited state. The low-energy metal-to-ligand charge-transfer absorption band showed marked solvatochromism due to the presence of thiocyanate ligands. The Ru(II)/(III) oxidation potential of the black dye and the ligand-based reduction potential shifted cathodically with decreasing number of protons and showed more reversible character. The adsorption of complex 3 from methoxyacetonitrile solution onto transparent TiO2 films was interpreted by a Langmuir isotherm yielding an adsorption equilibrium constant, K ads, of (1.0 ± 0.3) × 105 Μ-1. The amount of dye adsorbed at monolayer saturation was (n α = 6.9 ± 0.3) × 10-8 mol/mg of TiO2, which is around 30% less than that of the cis-di(thiocyanato)bis(2,2‘-bipyridyl-4,4‘-dicarboxylate)ruthenium(II) complex. The black dye, when anchored to nanocrystalline TiO2 films achieves very efficient sensitization over the whole visible range extending into the near-IR region up to 920 nm, yielding over 80% incident photon-to-current efficiencies (IPCE). Solar cells containing the black dye were subjected to analysis by a photovoltaic calibration laboratory (NREL, U.S.A.) to determine their solar-to-electric conversion efficiency under standard AM 1.5 sunlight. A short circuit photocurrent density obtained was 20.5 mA/cm2, and the open circuit voltage was 0.72 V corresponding to an overall conversion efficiency of 10.4%.
The preparation and characterization of a series of novel salts, based on the -methyl--alkylpyrrolidinium or quaternary ammonium organic cations coupled with sulfonate type anions, namely the ...mesylate (CHSO) and tosylate (CHCHSO) anions are reported. These salts are analogues of the previously described organic cation bis(trifluoromethanesulfonyl)amide (TFSA) salts that form useful ionic liquids of interest in "Green" synthesis. Several of the salts are liquid below 50 degreeC, tributylhexylammonium tosylate and ethylmethylpyrrolidinium mesylate and one is liquid at and below room temperature (tributylhexylammonium mesylate). These new salts have a cost advantage over salts of the TFSA, PF and CFSO anions. Electrochemical and thermal properties have been investigated. The salts are stable to beyond 100 degreeC and exhibit electrochemical potential windows of at least +/-2 V Ag/Ag. Some of the salts exhibit multiple crystalline phases below their melting points, potentially indicative of plastic crystal behaviour, whilst others showed more simple solid-liquid behaviour. Many of the salts were found to be glass forming.
The combination of rare earth metals (REM), such as Ce, La, Pr, or the less-refined mischmetal (consisting of a combination of REM) with dibutyl phosphate or diphenyl phosphate, provides a complex ...that shows excellent corrosion inhibition for AA2024-T3 (UNS A92024) in aqueous chloride environments. In some instances, it is equal to the inhibition provided by the chromate compounds, which are still used by the aircraft industry. The addition of these compounds as an inhibiting pigment in an epoxy coating also shows efficient suppression of filiform corrosion from scribes in the coating, under both alternate immersion and high-humidity conditions. Surface characterization of AA2024-T3 specimens immersed in solutions of these complex salts suggests that a film containing both the organic and rare earth components deposits on the alloy surface. The electrochemical data indicate that this film is acting as a mixed inhibitor, suppressing both the anodic and cathodic processes on the surface.
Corrosion rate measurements based on weight loss (i.e., mild steel immersed for seven days in 0.01 M NaCl) and linear polarization resistance (LPR) techniques have shown that even low concentrations ...(200 ppm) of cerium and lanthanum cinnamates are able to significantly inhibit corrosion. Of all the compounds investigated in this work Ce(4-methoxycinnamate)3DT2 H2O and La(4-methoxycinnamate)3DT2 H2O compounds exhibited the greatest inhibition and, in comparison with the component inhibitors, a synergy was clearly observed. The mechanism of corrosion inhibition was investigated using cyclic potentiodynamic polarization (CPP) measurements. The results suggest that La(4-nitrocinnamate)3DT2 H2O and Ce(4-methoxycinnamate)3DT2 H2O behave as mixed inhibitors and improve the resistance of steel against localized attack.
ABSTRACTThis paper discusses the effectiveness and mechanism of inhibition of a number of novel corrosion inhibitors for mild steel, based on cerium (III) and substituted carboxylates. The organic ...component was chosen to be benign, and known to have some inhibitive action in its own right. The compounds discussed in this work include cerium salicylate (CesalH3·H2O), cerium anthranilate (Ceanth3), and cerium glycolate (Cegly3). Weight-loss measurements of metal coupons conducted over a 7-day time period are presented. Polarization resistance measurements are also reported and usually show identical trends to the weight-loss data. It was seen that the Ce(salH)3·H2O and Ce(anth)3 compounds both showed excellent inhibition for steel; however, there was only a factor of a 2 to 3 decrease in the corrosion rate in the case of Ce(gly)3. Scanning electron microscopy (SEM) combined with energy dispersive x-ray spectroscopy (EDXS) and attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) showed the presence of an adherent film in the case where good corrosion mitigation was observed. These surface films appeared to contain significant amounts of cerium and, in some cases, an organic component. In the case of Ce(salH)3·H2O, a dramatic improvement in corrosion inhibition was observed for very low effective concentrations of Ce(III), consistent with a synergistic phenomenon that leads to a relatively uniform inhibitor compound on the surface of the steel (as indicated by SEM).Several billions of dollars are spent annually on capital replacement and control methods for metal corrosion of infrastructure.1 A significant portion of this cost is associated with corrosion control methods for extensive water recirculating pipe networks and water tanks associated with cooling systems. Without appropriate corrosion mitigation, such systems would have an extremely limited lifetime, thereby making costly maintenance and repairs necessary. As municipal and government regulations for use and disposal of chemicals have become more stringent, recent trends are seeing compounds that are less toxic to the environment, replacing older, more toxic systems.2-3 When applying the ideas of green chemistry to the area of corrosion inhibitors, the major improvement is in the area of eliminating environmentally toxic compounds such as chromates, dichromates, and nitrites and replacing them with more environmentally friendly chemicals. Most attention has been focused on the use of nontoxic oxyanions such as molybdates;4 organic compounds such as thioglycollates5 and phosphonates;6 or mixtures of inorganics such as phosphates, borates, silicates, and surfactants such as phosphonates and sulfonates.7 In a 1984 patent, Goldie and McCarroll first demonstrated the effectiveness of rare-earth metal (REM) salts as inhibitors of corrosion. They found that concentrations of 0.001 M cerium or lan-
The nature of deposits on mild steel surfaces formed by exposure to corrosive and inhibiting solutions has been examined by attenuated total reflectance spectroscopy. For cerium-based inhibitors, ...e.g. CeCl
3 the formation of cerium-containing coatings was detected whilst the cerium carboxylate Ce(sal)
3 (sal=salicylate), which combines the Ce
3+ with the known organic inhibitor sal
−, was shown to involve substantial deposition of both cerium and a salicylate species. These results, combined with corrosion inhibition data for the respective inhibitor compounds clearly indicate a synergistic corrosion mechanism for Ce(sal)
3 which underpins the improved performance of this corrosion inhibitor in comparison to the individual components (i.e. Na(sal) or CeCl
3).
To determine the accuracy of the clinical history performed by epileptologists in the identification of seizures in patients with suspected temporal lobe epilepsy.
The clinical and EEG telemetry ...(EEGT) monitoring data of 88 patients with suspected refractory temporal lobe seizures referred for evaluation of epilepsy surgery were prospectively evaluated. All clinical events obtained by history in these patients were adjudicated as being a seizure or not by two blinded (without access to EEG data) independent epileptologists. Each clinical event was then matched with the corresponding clinical event recorded with EEG telemetry in the epilepsy monitoring unit (gold standard). Sensitivity, specificity, overall accuracy, predictive value, and interrater agreement for the clinical assessment were obtained.
Of 357 clinically different events, 175 (49%) were reproduced in the epilepsy monitoring unit. Only 10 events were misidentified by history as being a seizure or not, resulting in an overall clinical accuracy of 94%. Epileptologists' sensitivity for seizure identification was 96% (95% CI 92, 98%) but specificity was only 50% (95% CI 22, 79%). Accuracy for complex partial seizures and generalized seizures was higher than for simple partial seizures (SPS). Misidentification occurred only with SPS and nonepileptic events. Agreement beyond chance among epileptologists was good.
In this selected group of patients with temporal lobe epilepsy, seizure identification by clinical history is highly accurate. Epileptologists rarely miss seizures (high sensitivity) but more often overcall nonepileptic events as seizures (low specificity).
Another Surprise from Pyrazolate Ligands Cosgriff, Joanna E.; Deacon, Glen B.
Angewandte Chemie (International ed.),
02/1998, Letnik:
37, Številka:
3
Journal Article
Recenzirano
Odprti dostop
The unexpected versatility of pyrazolate ligands R2pz is demonstrated by the synthesis of the homoleptic titanium complexes of the type Ti(η2‐R2pz)4 (1, R = Me, Ph) by Winter et al. Hitherto, ...pyrazolate ions were commonly bridging (µ2) or more rarely unidentate ligands for d‐block transition metals.
Pentafluorophenyl complexes of the heavier alkaline‐earth metals (Ca, Sr, Ba) are stabilized by a novel sterically crowded triazenido ligand. The pendent arene rings of the aryl‐substituted ...triazenide are π bonded to the alkaline‐earth metal atoms, thereby suppressing decomposition pathways or ligand redistribution reactions and allowing the isolation of solvent‐free derivatives (see picture; Ba: green; N: blue; F: light green; C: gray).
