Am unexpected entry into the silver(I) chemistry of diphosphazane ligands: Crystal and molecular structures of [Ag{Ph2PN(Pr-i)PPh2}(CF3SO3)](2), [Ag{Ph2PN(Pr-i)PPh(OC6H3Me2-2,6)}(2)]PF6, and [Ag-3(mu-Cl)(2){Ph2PN(R)PPh2}(3)]PF6 (R = H, Pr-i)

Mononuclear, binuclear and trinuclear silver(l) complexes were obtained unexpectedly while probing the reactivity of diphosphazane ligands of the type X2PN(Pr-i)PXY towards the ruthenium-based precursor Ru(bipy)(2)Cl-2 center dot 2H(2)O, in the presence of a silver salt as a chloride scavenger. Subsequently, the reactions of AgX [X = Cl, NO3 or CF3SO3] with Ph2PN(R)PPh(Y) [R = H, Y = Ph; R = Pr-i, Y = Ph or OC6H3Me2-2,6] in a 1: 1 or 1:2 molar ratio have been investigated. Mononuclear or binuclear Ag(I) complexes containing either chelating or bridging diphosphazane ligands are obtained. Trinuclear silver(l) complexes are accessible by the treatment of diphosphazane ligands, Ph2PN(R)PPh2 [R = H, Pr-i] with AgCl using piperidine as the solvent. In the presence of a suitable chloride donor species, the mononuclear and binuclear complexes of Ph2PN(Pr-i)PPh2 are transformed slowly to the trinuclear complex [Ag-3(mu-Cl)(2){Ph2PN(Pr-i)PPh2}(3)]X, over a period 20 h. The structures of representative complexes have been confirmed by X-ray crystallography and the salient structural features are discussed

Temperature- and pressure-dependent study of Cl-35 NQR frequency and spin lattice relaxation time in 2,3-dichloroanisole

The temperature and pressure dependence of Cl-35 NQR frequency and spin lattice relaxation time (T-1) were investigated in 2,3-dichloroanisole. Two NQR signals were observed throughout the temperature and pressure range studied. T-1 were measured in the temperature range from 77 to 300 K and from atmospheric pressure to 5 kbar. Relaxation was found to be due to the torsional motion of the molecule and also reorientation f motion of the CH3 group. T-1 versus temperature data were analyzed on the basis of Woessner and Gutowsky model, and the activation energy for the reorientation of the CH3 group was estimated. The temperature dependence of the average torsional lifetimes of the molecules and the transition probabilities were also obtained. NQR frequency shows a nonlinear behavior with pressure, indicating both dynamic and static effects of pressure. The pressure coefficients were observed to be positive for both the lines. A thermodynamic analysis of the data was carried out to determine the constant volume temperature coefficients of the NQR frequency. The variation of spin lattice time with pressure was very small, showing that the relaxation is mainly due to the torsional motions of the molecules. Copyright (C) 2010 John Wiley & Sons, Ltd.

Transport and magnetic properties of conducting polyaniline doped with BX3 (X=F, Cl, and Br)

We report transport and magnetic properties of a different class of highly conducting polyaniline, doped with boron trihalides BX3 (X=F, Cl, and Br). In order to understand the transport mechanism we analyze the temperature dependence of resistivity of a large number of samples, made by pelletizing doped polyaniline powder and by doping films of polyaniline. We find that the charge transport in this class of conducting polyaniline is driven by the charging-energy limited transport of charge carriers, in contrast to the quasi-one-dimensional variable range hopping conduction prevalent in conventional proton-doped polyaniline samples. Magnetic susceptibility provides further insight into the unusually high intrinsic conductivity behavior.

Analysis of Cl center dot center dot center dot Cl and C-H center dot center dot center dot Cl intermolecular interactions involving chlorine in substituted 2-chloroquinoline derivatives

Six crystal structures of substituted 2-chloroquinoline derivatives have been analysed to evaluate the role of Cl atom as a self recognizing unit resulting in the formation of Cl center dot center dot center dot Cl and C-H center dot center dot center dot Cl interactions to generate supramolecular assembly in the solid state. The features of Type I and Type II geometries associated with Cl center dot center dot center dot Cl interactions have been analysed to show directional preferences leading to differences in the packing motifs in these crystal structures. C-H center dot center dot center dot Cl interactions are generated exclusively in structures depicting Type II Cl center dot center dot center dot Cl interaction have been observed in these structures.

Nucleophilic attacks of 1,2-diaminoethane on MeCN ligands: synthesis, x-ray structure, and spectral and electrochemical properties of [Ru(.mu.-O)(.mu.-O2CAr)2[NH2CH2CH2NHC(Me)NH]2(PPh3)2](ClO4)2(Ar = C6H4-p-X; X = H, Me, OMe, Cl)

The diruthenium(III) complex [Ru2O(O2CAr)2(MeCN)4(PPh3)2](ClO4)2 (1), on reaction with 1,2-diaminoethane (en) in MeOH at 25-degrees-C, undergoes nucleophilic attacks at the carbon of two facial MeCN ligands to form [(Ru2O)-O-III(O2CAr)2-{NH2CH2CH2NHC(Me)NH}2(PPh3)2](ClO4)2 (2) (Ar = C6H4-p-X, X = H, Me, OMe, Cl) containing two seven-membered amino-amidine chelating ligands. The molecular structure of 2 with Ar = C6H4-p-OMe was determined by X-ray crystallography. Crystal data are as follows: triclinic, P1BAR, a = 13.942 (5) angstrom, b = 14.528 (2) angstrom, c = 21.758 (6) angstrom, alpha = 109.50 (2)-degrees, beta = 92.52 (3)-degrees, gamma = 112.61 (2)-degrees, V = 3759 (2) angstrom 3, and Z = 2. The complex has an {Ru2(mu-O)(mu-O2CAr2)2(2+)} core. The Ru-Ru and average Ru-O(oxo) distances and the Ru-O-Ru angle are 3.280 (2) angstrom, 1.887 [8] angstrom, and 120.7 (4)-degrees, respectively. The amino group of the chelating ligand is trans to the mu-oxo ligand. The nucleophilic attacks take place on the MeCN ligands cis to the mu-oxo ligand. The visible spectra of 2 in CHCl3 display an absorption band at 565 nm. The H-1 NMR spectra of 2 in CDCl3 are indicative of the formation of an amino-amidine ligand. Complex 2 exhibits metal-centered quasireversible one-electron oxidation and reduction processes in the potential ranges +0.9 to +1.0 V and -0.3 to -0.5 V (vs SCE), respectively, involving the Ru(III)2/Ru(III)Ru(IV) and Ru(III)2/Ru(II)Ru(III) redox couples in CH2Cl2 containing 0.1 M TBAP. The mechanistic aspects of the nucleophilic reaction are discussed.

Functional expression and subcellular localization of the Cl- cotransporters KCC2 and NKCC1 in rodent hippocampal and neocortical neurons

The work presented here has focused on the role of cation-chloride cotransporters (CCCs) in (1) the regulation of intracellular chloride concentration within postsynaptic neurons and (2) on the consequent effects on the actions of the neurotransmitter gamma-aminobutyric acid (GABA) mediated by GABAA receptors (GABAARs) during development and in pathophysiological conditions such as epilepsy. In addition, (3) we found that a member of the CCC family, the K-Cl cotransporter isoform 2 (KCC2), has a structural role in the development of dendritic spines during the differentiation of pyramidal neurons. Despite the large number of publications dedicated to regulation of intracellular Cl-, our understanding of the underlying mechanisms is not complete. Experiments on GABA actions under resting steady-state have shown that the effect of GABA shifts from depolarizing to hyperpolarizing during maturation of cortical neurons. However, it remains unclear, whether conclusions from these steady-state measurements can be extrapolated to the highly dynamic situation within an intact and active neuronal network. Indeed, GABAergic signaling in active neuronal networks results in a continuous Cl- load, which must be constantly removed by efficient Cl- extrusion mechanisms. Therefore, it seems plausible to suggest that key parameters are the efficacy and subcellular distribution of Cl- transporters rather than the polarity of steady-state GABA actions. A further related question is: what are the mechanisms of Cl- regulation and homeostasis during pathophysiological conditions such as epilepsy in adults and neonates? Here I present results that were obtained by means of a newly developed method of measurements of the efficacy of a K-Cl cotransport. In Study I, the developmental profile of KCC2 functionality during development was analyzed both in dissociated neuronal cultures and in acute hippocampal slices. A novel method of photolysis of caged GABA in combination with Cl- loading to the somata was used in this study to assess the extrusion efficacy of KCC2. We demonstrated that these two preparations exhibit a different temporal profile of functional KCC2 upregulation. In Study II, we reported an observation of highly distorted dendritic spines in neurons cultured from KCC2-/- embryos. During their development in the culture dish, KCC2-lacking neurons failed to develop mature, mushroom-shaped dendritic spines but instead maintained an immature phenotype of long, branching and extremely motile protrusions. It was shown that the role of KCC2 in spine maturation is not based on its transport activity, but is mediated by interactions with cytoskeletal proteins. Another important player in Cl- regulation, NKCC1 and its role in the induction and maintenance of native Cl- gradients between the axon initial segment (AIS) and soma was the subject of Study III. There we demonstrated that this transporter mediates accumulation of Cl- in the axon initial segment of neocortical and hippocampal principal neurons. The results suggest that the reversal potential of the GABAA response triggered by distinct populations of interneurons show large subcellular variations. Finally, a novel mechanism of fast post-translational upregulation of the membrane-inserted, functionally active KCC2 pool during in-vivo neonatal seizures and epileptiform-like activity in vitro was identified and characterized in Study IV. The seizure-induced KCC2 upregulation may act as an intrinsic antiepileptogenic mechanism.

Reactivity Of Pph3 Toward Ruiiruiiicl(O2car)4 - Syntheses, Molecular-Structures, And Spectroscopic And Electrochemical Properties Of Ruiiruiii(Oh2)Cl(Mecn)(O2car)4(Pph3)2 And Ruii2(Oh2)(Mecn)2(O2car)4(Pph3)2

By the reaction of Ru2Cl(O2CAr)4 (1) and PPh3 in MeCN-H2O the diruthenium(II,III) and diruthenium(II) compounds of the type Ru2(OH2)Cl(MeCN)(O2CAr)4(PPh3)2 (2) and Ru2(OH2)(MeCN)2(O2CAr)4(PPh3)2 (3) were prepared and characterized by analytical, spectral, and electrochemical data (Ar is an aryl group, C6H4-p-X; X = H, OMe, Me, Cl, NO2). The molecular structure of Ru2(OH2)Cl(MeCN)(O2CC6H4-p-OMe)4(PPh3)2 was determined by X-ray crystallography. Crystal data are as follows: triclinic, P1BAR, a = 13.538 (5) angstrom, b = 15.650 (4) angstrom, c = 18.287 (7) angstrom, alpha = 101.39 (3)-degrees, beta = 105.99 (4)-degrees, gamma = 97.94 (3)-degrees, V = 3574 angstrom 3, Z = 2. The molecule is asymmetric, and the two ruthenium centers are clearly distinguishable. The Ru(III)-Ru(II), Ru(III)-(mu-OH2), and Ru(II)-(mu-OH2) distances and the Ru-(mu-OH2)-Ru angle in [{Ru(III)Cl(eta-1-O2CC6H4-p-OMe)(PPh3)}(mu-OH2)(mu-O2CC6H4-p-OMe)2{Ru(II)(MeCN)(eta-1-O2CC6H4-p-OMe)(PPh3)}] are 3.604 (1), 2.127 (8), and 2.141 (10) angstrom and 115.2 (5)-degrees, respectively. The compounds are paramagnetic and exhibit axial EPR spectra in the polycrystalline form. An intervalence transfer (IT) transition is observed in the range 900-960 nm in chloroform in these class II type trapped mixed-valence species 2. Compound 2 displays metal-centered one-electron reduction and oxidation processes near -0.4 and +0.6 V (vs SCE), respectively in CH2Cl2-TBAP. Compound 2 is unstable in solution phase and disproportionates to (mu-aquo)diruthenium(II) and (mu-oxo)diruthenium(III) complexes. The mechanistic aspects of the core conversion are discussed. The molecular structure of a diruthenium(II) compound, Ru2(OH2)(MeCN)2(O2CC6H4-p-NO2)4(PPh3)2.1.5CH2Cl2, was obtained by X-ray crystallography. The compound crystallizes in the space group P2(1)/c with a = 23.472 (6) angstrom, b = 14.303 (3) angstrom, c = 23.256 (7) angstrom, beta = 101.69 (2)-degrees, V = 7645 angstrom 3, and Z = 4. The Ru(II)-Ru(II) and two Ru(II)-(mu-OH2) distances and the Ru(II)-(mu-OH2)-Ru(II) angle in [{(PPh3)-(MeCN)(eta-1-O2CC6H4-p-NO2)Ru}2(mu-OH2)(mu-O2CC6H4-p-NO2)2] are 3.712 (1), 2.173 (9), and 2.162 (9) angstrom and 117.8 (4)-degrees, respectively. In both diruthenium(II,III) and diruthenium(II) compounds, each metal center has three facial ligands of varying pi-acidity and the aquo bridges are strongly hydrogen bonded with the eta-1-carboxylato facial ligands. The diruthenium(II) compounds are diamagnetic and exhibit characteristic H-1 NMR spectra in CDCl3. These compounds display two metal-centered one-electron oxidations near +0.3 and +1.0 V (vs SCE) in CH2Cl2-TBAP. The overall reaction between 1 and PPh3 in MeCN-H2O through the intermediacy of 2 is of the disproportionation type. The significant role of facial as well as bridging ligands in stabilizing the core structures is observed from electrochemical studies.

Structure of a monochloro bridged polymeric copper(II)-di-2-pyridylamine complex: [Cu(dipyam)Cl(NO3)].0.5H2O

Di-2-pyridylaminechloronitratocopper(II) hemihydrate, [CuCl(NO3)(C10H9N3)].0.5H2O, M(r) = 341.21, monoclinic, P2(1)/a, a = 7.382 (1), b = 21.494 (4), c = 8.032 (1) angstrom, beta = 94.26 (1)-degrees, V = 1270.9 angstrom 3, Z = 4, D(m) = 1.78, D(x) = 1.782 g cm-3, lambda(Mo K-alpha) = 0.7107 angstrom, mu(Mo K-alpha) = 19.47 cm-1, F(000) = 688. The structure was solved by the heavy-atom method and refined to a final R value of 0.034 for 2736 reflections collected at 294 K. The structure consists of polymeric [Cu(dipyam)Cl(NO3)] units bridged by a chloride ion.

Synthesis, Characterization and Structure of (N2H5)3MnX5 (X = Cl and Br)

Two new hydrazinium complexes of manganese, (N2H5)3MnX5 (X = Cl and Br), have been prepared and characterized by analysis, infrared and visible spectra. The single crystal X-ray structure of the chloride complex has been determined. Only one of the three N2H+5 cations is coordinated to the metal. In the anion, [Mn(N2H5)Cl5]2-, the coordination polyhedron around the manganese atom is a slightly distorted octahedron.

Nature of Cl center dot center dot center dot Cl Intermolecular Interactions via Experimental and Theoretical Charge Density Analysis:Correlation of Polar Flattening Effects with Geometry

The experimental charge density distribution in three compounds, 2-chloro-3-quinolinyl methanol, 2-chloro-3-hydroxypyridine, and 2-chloro-3-chloromethyl-8-methylquinoline, has been obtained using high-resolution X-ray diffraction data collected at 100 K based on the aspherical multipole modeling of electron density. These compounds represent type I (cis), type I (trans), and type II geometries, respectively, as defined for short Cl center dot center dot center dot Cl interactions. The experimental results are compared with the theoretical charge densities using theoretical structure factors obtained from a periodic quantum calculation at the B3LYP/6-31G** level. The topological features derived from the Bader's theory of atoms in molecules (AIM) approach unequivocally suggest that both cis and trans type I geometries show decreased repulsion, whereas type II geometry is attractive based on the nature of polar flattening of the electron density around the Cl atom.

Pulsed NMR study of molecular motions and phase transitions in [N(CH3)4]PbX3 (X=Cl, Br, I)

Proton spin—lattice relaxation time (T1) is measured in [N(CH3)4]PbX3 (X=Cl, Br, I) from 300-77 K at 9.75 MHz. All the compounds show discontinuous changes in T1 values (at 256, 270 and 277 K, respectively), indicating phase transitions. Single T1 minimum is observed in all the cases and the T1 variation is explained in terms of [N(CH3)4] and CH3 group dynamics. The activation energy Eα decreases from chloride to iodide (from 4 to 2 kcal/mol). In bromide and iodide, T1 is found to decrease with increase in temperature at higher temperatures, indicating the presence of spin—rotation interaction.

Charge Density Analysis of Heterohalogen (Cl center dot center dot center dot F) and Homohalogen (F center dot center dot center dot F) Intermolecular Interactions

Experimental charge density distribution in 2-chloro-4-fluorobenzoic acid and 4-fluorobenzamide has been carried out using high resolution X-ray diffraction data collected at 100 K using Hansen-Coppens multipolar formalism of electron density. These compounds display short Cl center dot center dot center dot F and F center dot center dot center dot F interactions, respectively. The experimental results are compared with the theoretical charge densities using theoretical structure factors obtained from periodic quantum calculation at the B3LYP/6-31G** level. The topological features were derived from Bader's ``atoms in molecules'' (AIM) approach. Intermolecular Cl center dot center dot center dot F interaction in 2-chloro-4-fluorobenzoic acid is attractive in nature (type II interaction) while the nature of F center dot center dot center dot F interactions in 4-fluorobenzamide shows indication of a minor decrease in repulsion (type I interaction), though the extent of polarization on the fluorine atom is arguably small.

Role of Hetero-Halogen (F center dot center dot center dot X, X = Cl, Br, and I) or Homo-Halogen (X center dot center dot center dot X, X = F, Cl, Br, and I) Interactions in Substituted Benzanilides

A series of halogen-substituted benzanilides have been synthesized and characterized, and crystallization studies directed toward generation of polymorphs have been performed to delineate the importance of interactions involving halogens. The effect of halogen substitution on the molecular conformation and supramolecular packing has been investigated. The N-H center dot center dot center dot O H-bond is a key structure-directing element acting in conjunction with C-H center dot center dot center dot O and C-H center dot center dot center dot pi interactions. In addition, it is of importance to note that organic fluorine prefers Type I F center dot center dot center dot F contacts, whereas Cl, Br, and I prefer Type II contacts. Hetero-halogen center dot center dot center dot halogen interactions on the other hand are predominately of Type II geometry, and this is due to the greater polarizability of the electron density associated with the heavier halogens. It is of importance to evaluate the contributing role of these interactions in crystal structure packing and the co-operativity associated with such interactions in the solid state.