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Various Anions (various + anion)
Selected AbstractsAcute and chronic toxicity of imidazolium-based ionic liquids on Daphnia magnaENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 1 2005Randall J. Bernot Abstract Room-temperature ionic liquids (ILs) are considered to be green chemicals that may replace volatile organic solvents currently used by industry. However, IL effects on aquatic organisms and ecosystems are currently unknown. We studied the acute effects of imidazolium-based ILs on survival of the crustacean Daphnia magna and their chronic effects on number of first-brood neonates, total number of neonates, and average brood size. Lethal concentrations of imidazolium ILs with various anions (X,) ranged from a median lethal concentration (LC50) of 8.03 to 19.91 mg L,1, whereas salts with a sodium cation (Na+ X,) were more than an order of magnitude higher (NaPF6 LC50, 9,344.81 mg L,1; NaBF4 LC50, 4765.75 mg L,1). Thus, toxicity appeared to be related to the imidazolium cation and not to the various anions (e.g., CI,, Br,, PF,6, and BF,4). The toxicity of imidazolium-based ILs is comparable to that of chemicals currently used in manufacturing and disinfection processes (e.g., ammonia and phenol), indicating that these green chemicals may be more harmful to aquatic organisms than current volatile organic solvents. We conducted 21-d chronic bioassays of individual D. magna exposed to nonlethal IL concentrations at constant food-resource levels. Daphnia magna produced significantly fewer total neonates, first-brood neonates, and average neonates when exposed to lower concentrations (0.3 mg L,1) of imidazolium-based ILs than in the presence of Na-based salts at higher concentrations (400 mg L,1). Such reductions in the reproductive output of Daphnia populations could cascade through natural freshwater ecosystems. The present study provides baseline information needed to assess the potential hazard that some ILs may pose should they be released into freshwater ecosystems. [source] Control of Optical Hysteresis in Block Copolymer Photonic Gels: A Step Towards Wet Photonic Memory FilmsADVANCED FUNCTIONAL MATERIALS, Issue 11 2010Eunjoo Kim Abstract Polystyrene- block -poly(2-vinyl pyridine) (PS- b -P2VP) block copolymer photonic gels are fabricated that exhibit controllable optical hysteresis in response to a cyclic pH sweep. The optical hysteresis is tuned by controlling the ion-pairing affinity between various anions and the protonated pyridinium ions on the P2VP block, which is highly dependent on the hydration energy of the ions, the dielectric constant of the solvent, and the ionic strength of the medium. The pH coercivity defining the magnitude of hysteresis of the photonic gels could be varied from 0.26 to 7.4. Photonic gel films with strong optical hysteresis can serve as wet photonic memory films where information can be cyclically recorded and erased at least 15 times and maintained for at least 96,h. The memory colors can be further tuned by selection of the copolymer molecular weight. [source] Flexibility of paramagnetic (d1) organometallic dithiolene complex [Cp2Mo(dmit)]+, studied by Raman spectroscopyJOURNAL OF RAMAN SPECTROSCOPY, Issue 12 2009Roman, wietlik Abstract We report on the experimental and theoretical studies of the flexible organometallic complex Cp2Mo(dmit) which often exhibits a folding in the solid state. Raman spectra of charge-transfer salts formed by Cp2Mo(dmit) with various anions (Br,, BF4,, PF6,, SbF6,, ReO(dmit)2,, TCNQF4,) were measured at room temperature using red (632.8 nm) and near-infrared (780 nm) excitations. The influence of the folding of the MoS2C2 metallacycle in [Cp2Mo(dmit)]+, cation on the Raman spectra was investigated. Due to folding of [Cp2Mo(dmit)]+,, the bands related to the CC and some CS stretching vibrations shift toward lower wavenumbers by about 0.5,0.6 cm,1deg,1. The bond lengths, charge distribution on atoms, highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energies, and dipole moments for neutral and ionized complex with various folding angles were calculated by density functional theory (DFT) methods. Additionally, the normal vibrational modes and theoretical Raman spectra were calculated and compared with experimental data. Our results indicate that vibrational spectroscopy can be applied for investigation of complex deformations in the solid state. Copyright © 2009 John Wiley & Sons, Ltd. [source] Polymer Complexes: supramolecular assemblies and structures of poly[N -(2,-pyridyl)propenamide] complexesAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 5 2004A. T. A. Mubarak Abstract A number of new polymer complexes of palladium(II), platinum(II) and copper(II) containing homopolymer (N -(2,-pyridyl)propenamide; APH) and various anions (Cl,, Br,, I, or NO3,) have been synthesized and characterized by elemental analyses, magnetic susceptibility, electron paramagnetic resonance, IR and reflectance spectral measurements. The homopolymer shows three types of coordination behavior. In the mononuclear polymer complexes 1,6 and 9 it acts as a neutral bidentate ligand chelated through the pyridine-nitrogen and amide-oxygen atoms, whereas in the square-planar [Pd(APH)2X2] (X = Cl, Br) unidentate APH is coordinated through the pyridine-nitrogen atom alone. Under alkaline conditions APH is deprotonated in the presence of palladium(II) to form [Pd(AP)2] (10), AP being an anionic bidentate ligand and chelating through the pyridine-nitrogen and amide-oxygen atoms. The poly-chelates are of 1:1 and 1:3 (metal:homopolymer) stoichiometry and exhibit six-coordination. The polymer complexes of stoichiometric [(APH)2CuX2] contain square planar (APH)2 Cu2+ units and the anions X, are in the axial positions, giving distorted octahedral configurations. From the electron paramagnetic resonance and spectral data, the orbital reduction factors were calculated. Copyright © 2004 John Wiley & Sons, Ltd. [source] Comparison of Physicochemical Properties of New Ionic Liquids Based on Imidazolium, Quaternary Ammonium, and Guanidinium CationsCHEMISTRY - A EUROPEAN JOURNAL, Issue 30 2007Prashant Abstract More than 50 ionic liquids were prepared by using imidazolium, quaternary ammonium, and guanidinium cations and various anions. In these series, different cationic structures such as 1-benzyl-3-methylimidazolium [Bzmim]+, 1,3-dibenzylimidazolium [BzmiBz]+, 1-octyl-3-methylimidazolium [C8mim]+, 1-decyl-3-methylimidazolium [C10mim]+, tricapryl-methylammonium [Aliquat]+, benzyltriethylammonium [BzTEA]+, phenyltrimethylammonium [PhTMA]+, and dimethyldihexylguanidinium [DMG]+ were combined with anions, p -toluenesulfonate [TSA],, dicyanoamide [DCA],, saccharine (2-sulfobenzoic acid imide sodium salt) [SAC],, trifluoroacetate [TFA],, bis(trifluoromethanesulfonyl)imide [Tf2N],, trifluoromethanesulfonate [TfO],, and thiocyanate [SCN],. Important physical data for these ionic liquids are collated, namely solubility in common solvents, viscosity, density, melting point and water content. Apart from the viscosity, the Newtonian and non-Newtonian behavior of these ionic liquids is also disclosed. Stability of these ionic liquids under thermal, basic, acidic, nucleophilic, and oxidative conditions was also studied. The features of the solid,liquid phase transition were analyzed, namely the glass transition temperature and the heat capacity jump associated with the transition from the non-equilibrium glass to the metastable supercooled liquid. A degradation temperature of each ionic liquid was also determined. Comparisons of the properties of various ionic liquids were made. [source] Enantioseparation of extended metal atom chain complexes: Unique compounds of extraordinarily high specific rotationCHIRALITY, Issue 3 2007Molly M. Warnke Abstract Extended metal atom chains (EMACs) contain a linear metal chain wrapped by various ligands. Most complexes are of the form M3(dpa)4X2, where M = metal, dpa = 2,2,-dipyridylamide, and X = various anions. The ligands form helical coils about the metal chain, which results in chiral EMAC complexes. The EMACs containing the metals Co and Cu were partially separated in polar organic mode using a vancomycin-based chiral stationary phase. Under similar conditions, two EMACs with Ni metal and varying anions could be baseline separated. The polar organic mode was used because of the instability of the compounds in aqueous mobile phases. Also, these conditions are more conducive to preparative separations. Polarimetric measurements on the resolved enantiomers of Ni3(dpa)4Cl2 indicate that they have extraordinarily high specific rotations (on the order of 5000 deg cc/g dm). Chirality, 2007. © 2006 Wiley-Liss, Inc. [source] | ||||||||||