Influence of the halogen ligand on the near-UV-visible spectrum of [Ru(X)(Me)(CO)2(alpha-diimine)] (X = Cl, I; alpha-diimine = Me-DAB, iPr-DAB; DAB = 1,4-diaza-1,3-butadiene): an ab initio and TD-DFT analysis

The near-UV-vis electronic spectroscopy of [Ru(X)(Me)(CO)(2)(iPr-DAB)] (X = Cl or I; iPr-DAB = N,N'-di-isopropyl-1,4-diaza-1,3-butadiene) is investigated through CASSCF/CASPT2 and TD-DFT calculations on the model complexes [Ru(X)(Me)(CO)(2)(Me-DAB)] (X = Cl or I). Convergence of the calculated transition energies for the low-lying metal-to-ligand charge-transfer (MLCT), X-to-ligand charge-transfer (XLCT, X halide ligand), or sigma-bond-to-ligand charge-transfer (SBLCT) to experimental values is analyzed for both methods. On the basis of these accurate calculations, it is shown that whereas the lowest singlet state can be assigned to a nearly pure XLCT state in [Ru(I)(Me)(CO)(2)(Me-DAB)], its character is mainly MLCT in [Ru(Cl)(Me)(CO)(2)(Me-DAB)]. These results are in agreement with time-resolved emission/IR and resonance Raman experimental data. The experimental UV-vis bands are well reproduced by the CASSCF/CASPT2 calculations. The TD-DFT transition energies to the long-range charge transfer states are dramatically affected by the nature of the functional, with lowering leading to meaningless values in the case of nonhybrid functionals. Both methods reproduce well the red shift of the absorption bands on going from the chloride to the iodide complex as well as the shift of the strongly absorbing higher MLCT transition from the visible to the UV domain of energy.     

Synthetic Strategies To Obtain V-P-O Open Frameworks Containing Organic Species as Structural Directing Agents. Crystal Structure of the V(IV)-Fe(III) Bimetallic Phosphate [H(3)N(CH(2))(2)NH(3)](2)[H(3)N(CH(2))(2)NH(2)][Fe(III)(H(2)O)(2)(V(IV)O)(8)(OH)(4)(HPO(4))(4)(PO(4))(4)].4H(2)O

A general synthetic approach to rationalize the solution preparative chemistry of oxovanadium phosphates containing organic species as structural directing agents is presented. Careful attention is payed to the hydrolysis and condensation processes involving the ionic species in solution, and a simple restatement of the partial charge model (PCM) has been used in order to organize the experimental results. The structure of a new V(IV)-Fe(III) bimetallic oxovanadium phosphate, [H(3)N(CH(2))(2)NH(3)](2)[H(3)N(CH(2))(2)NH(2)] [Fe(III)(H(2)O)(2)(V(IV)O)(8)(OH)(4)(HPO(4))(4)(PO(4))(4)].4H(2)O, has been determined by X-ray single crystal diffraction methods. This compound crystallizes in the monoclinic system, space group P2(1)/n and the cell dimensions are as follows: a = 14.383(3) ?, b = 10.150(2) ?, c = 18.355(4) ?, and beta = 90.39(3) degrees (Z = 2). The existence of a complex intercrossing channel system, including a very large channel of 18.4 ? of diameter (in which both water molecules and ethylenediamine species are located), is the more interesting feature of this structure. Thermal decomposition, including the dehydration/rehydration process, has been studied by thermal analysis and variable temperature X-ray powder diffraction techniques. A complementary SEM study of the different intermediate decomposition products is presented.     

Double Orthogonal Click Reactions for the Development of Antimicrobial Peptide Nanotubes

A new class of amphipathic cyclic peptides, which assemble in bacteria membranes to form polymeric supramolecular nanotubes giving them antimicrobial properties, is described. The method is based on the use of two orthogonal clickable transformations to incorporate different hydrophobic or hydrophilic moieties in a simple, regioselective, and divergent manner. The resulting cationic amphipathic cyclic peptides described in this article exhibit strong antimicrobial properties with a broad therapeutic window. Our studies suggest that the active form is the nanotube resulted from the parallel stacking of the cyclic peptide precursors. Several techniques, CD, FTIR, fluorescence, and STEM, among others, confirm the nanotube formation.     

New ion exchange membrane derived from sulfochlorated polyether sulfone for electrodialysis desalination of brackish water

The purpose of this work is to study the desalination of brackish water using a new ion exchange membrane, made from sulfochlorated polyethersulfone (Cl‐PES), and crosslinked using aminated polyethersulfone (NH2‐PES) as a crosslinking reagent. This membrane, named ClNH2 membrane, has been obtained by reaction between Cl‐PES with 1.3 SO₂Cl groups per monomer unit and 0.2 equivalent amount of NH2‐PES. ClNH2 membrane has been characterized in terms of contact angle, transport number, intrinsic conductivity, and water uptake (as a function of temperature). Electrodialysis performances of the newly synthetized membranes have been measured using an electrodialysis cell at a laboratory scale and compared to commercial membranes. All the experiments have been performed using synthetic brackish water solutions prepared from sodium chloride salts with different concentrations (varying from 0.5 to 5.0 g/L). The concentration of different water samples obtained has been found to be below the amount recommended by the World Health Organization (WHO) for drinking water.     

Theoretical Study of a Hybrid Organic–Inorganic Heteropolyoxometalate Compound

Crystallography Reports - Large study of theoretical calculations for the hybrid organic-inorganic heteropolyoxometalate (C6H8N)5[HAs2Mo6O26(H2O)]⋅3H2O (1) is reported. The results of...     

Crystal structure,thermal behavior and IR investigation of 1,6‐diammonium hexan dihydrogenodiphosphate dihydrate

Physicochemical properties of (C₆H₁₈N₂)H₂P₂O₇·2H₂O denoted DHDP are discussed on the basis of X‐ray crystal structure investigation. The compound crystallises in the triclinic system with P space group. Its unit cell dimensions are a = 13.719(1) Å, b = 14.188(3) Å, c = 9.177(1) Å, α = 108.50(1)°, β = 91.11(1)°, γ = 115.47(1)°, V = 1503.8(4) ų and Z = 4. The structure has been solved using direct methods and refined to a reliability R factor 0.0401 for 4778 reflections. The main feature of the atomic arrangement of DHDP is the existence of infinite rows, parallel to the c direction of the unit cell, composed of H₂P₂O₇ groups. These phosphoric rows are organised to create, with the help of the organic cation, large rectangular channels in which the unstable water molecule are located since they have high thermal parameters. Phosphoric anions and organic cations have no internal symmetry. DSC and TG‐DTA show that dehydration occurs in one step. Such dehydration process may be related to the similar environments on the water molecules residing in the channel. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Synthesis, structure of [H3dien]·(MF6)·H2O (M=Cr, Fe) and Fe Mössbauer study of [H3dien]·(FeF6)·H2O

Single crystals of [H₃dien]·(FeF₆)·H₂O (I) and [H₃dien]·(CrF₆)·H₂O (II) are obtained by solvothermal synthesis under microwave heating. I is orthorhombic (Pna2₁) with a=11.530(2) Å, b=6.6446(8) Å, c=13.787(3) Å, V=1056.3(2) Å³ and Z=4. II is monoclinic (P2₁/c) with a=13.706(1) Å, b=6.7606(6) Å, c=11.3181(9) Å, β=99.38(1)°, V=1034.7(1) Å³ and Z=4. The structure determinations, performed from single crystal X-ray diffraction data, lead to the R₁/wR₂ reliability factors 0.028/0.066 for I and 0.035/0.102 for II. The structures of I and II are built up from isolated FeF₆ or CrF₆ octahedra, water molecules and triprotonated amines. In both structures, each octahedron is connected by hydrogen bonds to six organic cations and two water molecules. The iron-based compound is also characterized by ⁵⁷Fe Mössbauer spectrometry: the hyperfine structure confirms the presence of Fe³⁺ in octahedral coordination and reveals the existence of paramagnetic spin fluctuations.     

A Nitrite Electrochemical Sensor Based on Boron‐Doped Diamond Planar Electrochemical Microcells Modified with a Monolacunary Silicotungstate Polyoxoanion

A new boron doped diamond microcells (BDD) was modified, for rapid, selective and highly sensitive determination of nitrite, using a coating film of polyoxometalates (POMs), formed by cyclic voltammetry on the molecular p‐phenylenediamine (PPD) functionalized BDD. The scanning electron microscopy (SEM) technique was used to examine the morphology of (PPD/SiW₁₁) modified (BDD) electrode. It was found that (SiW₁₁) layer was uniformly formed on the electrode surface. It was observed that (BDD/PPD/SiW₁₁) showed excellent electrocatalytic activities towards nitrite ion. Under the selected conditions, the anodic peak maximum at ?0.6 V was linear versus nitrite concentration in the 40 µM–4 mM range, and the detection limit obtained was 20 µM. The newly developed electrode has been successfully applied to the determination of nitrite content in real river water samples.     

Spectral study of Eriochrome Blue Black R in different cationic surfactant solutions

Interactions of anionic dye Eriochrome Blue Black R (EBBR) with various cationic micelles of surfactants n-alkyltrimethylammonium CnTAB (n=12; 14; 16 and 18) have been investigated spectrophotometrically at 25°C in premicellar and postmicellar region. The results have shown that with increasing the alkyl chain length of surfactants, the maximum absorbance of EBBR shifted to a higher wavelength and the binding constants of EBBR to cationic micelles (Kb) increases. This confirms that the surfactant micelle, which has a longer alkyl hydrocarbon chain, enables greater solubilization of dye. Thus, the hydrophobic interaction of the dye with micelles increases in the order: C12TAB相似文献