Structural,ion transport parameter and electrochemical properties of plasticized polymer composite electrolyte based on PVA: A novel approach to fabricate high performance EDLC devices

In this study a novel polymer composite electrolytes (PCEs) based on poly (vinyl alcohol) (PVA): Ce(III)-complex:NH₄SCN plasticized with glycerol are prepared by solution cast technique. XRD and FTIR routes are used to study the film structure. The crystalline and amorphous areas are determined through the deconvolution of XRD spectra and their values were used to calculate the degree of crystallinity. The deconvolutions of the FTIR of asymmetric C≡N stretching mode are carried out to establish the bands coupled with free ions, contact ion pairs and ion aggregates. The maximum ambient temperature DC conductivity of 2.07 × 10⁻³ S cm⁻¹ is recorded for the sample with the lowest degree of crystallinity. It was found that the number density (n), mobility (μ) and diffusion coefficient (D) of ions are increased with the glycerol concentration. Field emission scanning electron microscopy (FESEM) is used to examine the effect of plasticizer on film morphology. The DC conductivity trend is interpreted in detail with the help of dielectric properties. It is found that the transference numbers of ions (t_ion) and electrons (t_el) are 0.965 and 0.035, respectively. It is shown by the linear sweep voltammetry (LSV) that the potential window of the PCE is 2.1 V. A shape, which is nearly rectangular at lower scan rates, is identified from cyclic voltammetry (CV). Specific capacitance and energy density are exhibited by EDLC with average of 161.5 F/g and 18.17 Wh/kg, respectively within 400 cycles. The initial power density is shown by EDLC to be 2.825 × 10³ W/kg.     

The synthesis,structure and reactions of the novel cationic bisbut-2-yne complex [W(CO)(NCMe)(S2CNC4H8)(η2-MeC2Me)2][BPh4]

The complex [WI(CO)(S₂CNC₄H₈)(η²-MeC₂Me)₂] reacts with an equimolar amount of Na[BPh₄] in acetonitrile at room temperature to give the cationic bisbut-2-yne complex [W(CO)(NCMe)(S₂CNC₄H₈)(η²-MeC₂Me)₂][BPh₄] (1) by replacement of an iodide ligand by acetonitrile. The crystal structure of 1 has been determined and reveals a pseudo-octahedral geometry with the mid points of the two cis-but-2-yne ligands approximately coplanar with the sulphur atoms of the dithiocarbamate ligand. Carbon monoxide and acetonitrile occupy the axial sites. ¹³C NMR spectroscopy shows the two but-2-yne ligands in 1 donate a total of 6 electrons to the tungsten. Preliminary studies of the chemistry of 1 are also described.     

Metal coordination architectures of triazole-based ligands: Effect of the backbone of bridging ligands on the construction of polymers

In our efforts to investigate the influence of the backbone of different triazole-based bridging ligands on the structure of their metal complexes, four new coordination polymers, {[Cu(L¹)₂(H₂O)₂]Cl₂}_n (1), [Cu(L²)₂Cl₂]_n (2), [Co(L²)₂(SCN)₂]_n (3), and [Cu(L³)₂(NO₃)₂]_n (4), (L¹ = 1,2-bis(triazol-1-ylmethyl)benzene, L² = 1,3-bis(triazol-1-ylmethyl)benzene, L³ = 1,4-bis(triazol-1-ylmethyl)benzene), have been synthesized. All the complexes have been structurally characterized by IR, elemental analysis and single-crystal X-ray diffraction. Structural analyses show that 1 and 4 possess 2D coordination networks with (4,4) topology, and 1 shows a diagonal–diagonal inclined interpenetration. 2 and 3 are isostructural and feature 1D double chain, which further connected by C–H···Cl or π···π weak interactions to form 2D supramolecular frameworks. The results show that the structures of ligands (with different non-coordination backbone spacers) play important roles in the formation of such coordination architectures. Furthermore, EPR (Electron Paramagnetic Resonance) spectra of Cu^II complexes (1, 2, and 4) have been investigated in the solid state at room temperature.     

Fluorinated piperidine iminosugars and their N-alkylated derivatives: Synthesis,conformational analysis,immunosuppressive and glycosidase inhibitory activity studies

The fluorinated piperidine iminosugars 2a-4a and their N-octyl and N-decyl derivatives 2b,c-4b,c were synthesized from d-mannose/d-xylose using nucleophilic fluorination as the key step. The conformation of iminosugars 2/3, either ²C₅ or ⁵C₂, was assigned based on the ¹H NMR studies at different pH. Immunomodulatory activity of 2a,c-4a,c was examined using Mixed Lymphocyte Reaction (MLR) and B-cell assay. The N-alkylated fluorinated d-manno-iminosugars 3b/4b were found to be better immunosuppressive agents (IC₅₀?=?5–6?μM) on T-cells. The fluorinated iminosugar 3a/4a act as potent and selective inhibitors of β-glucosidase (IC₅₀?=?4–8?μM). The N-alkyl-iminosugars 4b-c were found to be moderate inhibitors of α-glucosidase (yeast) and α-galactosidase (coffee beans), respectively.     

Vibrational spectra and structure of methoxysilanes and products of their hydrolysis

Equilibrium geometries and force fields for the series of molecules (MeO)_nSiMe_4−n(I), (OH)_nSiMe_4−n(II), and (MeO)_nSi(OH)_4−n(III) with n = 1–4 are obtained at the DFT/B3LYP level of theory with 6-31G^* and aug-cc-pVDZ basis sets in order to predict the structural parameters and vibrational spectra of these molecules, the larger part of which was not characterized experimentally. The performance of these theoretical methods was assessed on the existing spectral data for series I. The B3LYP/aug-cc-pVDZ method, firstly applied to this class of molecules, demonstrates a fair agreement with experimental vibrational frequencies even without empirical scaling. For molecules of series II and III vibrational spectra are predicted in order to supply spectral data for monitoring the sol–gel processes at the hydrolysis stage. The hyperconjugative strengthening of SiO bonds with the number of oxygen atoms coordinated to silicon leads to the growth of their frequencies, but the larger increase of νSiO (due to kinematic factors) occurs at the SiOMe/SiOH substitution. The predicted distinctive feature of series II and III is the appearance of bands with high IR intensity in the 1000–900 cm⁻¹ spectral region that increase their frequencies with n. In series III it is accompanied with the steady increase of the ν_sSiO₄ frequency in the 700–600 cm⁻¹ range.     

1H and 13C NMR study of cyclopentadienyl metal carbonyls in the solid state

In this paper we deal with some structural and dynamic properties of Cp₂W₂(CO)₆ (I) and Cp₂Ru₂(CO)₄ (II) as shown by solid state ¹³C and ¹H NMR experiments. The IR and ¹³C CPMAS spectra of a polycrystalline sample of I show that this compound possesses the anti rotameric structure found in a previously reported X-ray diffraction study. The analysis of the spinning side-band manifold in the ¹³C CPMAS spectrum of I allows us to assess a different semi-bridging character between two CO-groups not seen from the X-ray results. The spectral features of compound II are fully consistent with the X-ray and solution structures previously reported. In both compounds the cyclopentadienyl ligands are involved in fast reorientation motions which modulate the magnetic interactions responsible for the relaxation of ¹³C resonances. The activation energies (E_a) associated with this reorientation process of the Cp ring along their C₅ coordination axis have been determined to be 15.5 and 10.2 kJ mol⁻¹ for I and II respectively on the basis of ¹H T₁ measurements at different temperatures. Furthermore, we show that an empirical relationship relates E_a values and T_min (the temperature at which proton relaxation is more efficient) in a related series of cyclopentadienyl compounds.     

Mössbauer and NMR studies of intramolecular coordination in thienyltetraorganotin(IV) compounds,and the x-ray crystal structure of {C,N-[3-(2-pyridyl)-2-thienyl]} tri(p-tolyl)tin(IV)

Tetraorganotin(IV) compounds containing the [3-(2-pyridyl)-2-thienyl] group (L), of formula R₃SnL (1: R = p-tolyl; 2: R = Ph; 3: R = p-ClC₆H₄; 4: R = cyclo-C₅H₉; 5; R = cyclo-C₆H₁₁) have been synthesized and their structures examined by ^119mSn Mössbauer and NMR (¹¹⁹Sn and ¹³C modes) spectroscopic techniques, and in the case of compound 1 by X-ray analysis.Compound 1 crystallises in the space group C2/c with a 20.85(1), b 9.521(1), c 26.69(1) Å; β 95.37(3)°; V 5274(3) ų; Z = 8. Its structure was solved by the heavy-atom method from 4251 observed MO-K_α data and refined to R = 0.068. The coordination environment at tin in the compound is best described as a pseudo-trigonal bipyramid, involving a waek intramolecular SnN bond of distance 2.841(7) Å. This view is supported by the observation of partially-resolved Mössbauer spectra for compounds 1–5 (QS 0.57–0.96 mm s⁻¹) which is not evidenced, on the other hand, for (2-thienyl)SnR₃ compounds (7: R = p-tolyl; 8: R = Ph), as well as by similar comparisons of data on ¹¹⁹Sn chemical shifts (−176.3 ppm for 1 relative to −135.5 ppm fr 8) and one-bond coupling constants, ¹J(¹¹⁹Sn-¹³C(1)), where C(1) = ipso-carbon of the aryl group or α-carbon of the cycloalkyl group (647.5 Hz for 1, 726.6 Hz for 2 and 786.2 Hz for 3 relative to 536.9 Hz for 7).     

Purposeful regioselectivity control of the Birch reductive alkylation of biphenyl-4-carbonitrile

Birch's reductive alkylation of biphenyl-4-carbonitrile (1) provides alkylated 1,4-dihydroderivatives of various structural types: 4-alkyl-4-phenylcyclohexa-2,5-dienone, 1,4-dialkyl-4-phenylcyclohexa-2,5-dienecarbonitrile (with the same or different alkyl fragments), and 4-(1-alkylcyclohexa-2,5-dienyl)benzonitrile. Each of these products become dominant depending on the nature of long-living anionic form generated from 1, namely, the stable product of two-electrons reduction – dianion (1^2?); 1-alkyl-4-cyano-1-phenylcyclohexa-2,5-dien-4-yl anion (1-Alk₁^–), originated due to the alkylation of dianion 1^2? at the position 1 of biphenyl moiety; or 1-(4-cyanophenyl)cyclohexa-2,5-dien-1-yl anion (1-H_4’^–), being the product of dianion 1^2? protonation at position 4′ by protonating reagent (MeOH or NH₄Cl). The orientation of alkyl fragment incorporation into biphenyl-4-carbonitrile scaffold is in agreement with calculated electronic structure of the anionic species under investigation. The dominating type of their reactivity towards alkyl halides proved to be nucleophilic (S_N2 mechanism).     

Synthesis and structural characterization of the first trialkylguanidinate and hexahydropyramidopyramidinate complexes of tin

The first guanidinate complexes of tin have been prepared using N,N′,N′′-trialkylguanidinates ([(RN)₂C(NRH)]⁻; R=cyclohexyl; isopropyl) and 1,3,4,6,7,8-hexahydro-2H-pyramido[1,2-a]pyramidinate (hpp⁻) as ligands. The direct reaction between triisopropylguanidine and SnCl₄ provided the complex {[ⁱPrN]₂C[NHⁱPr]}SnCl₃ (1) along with concomitant formation of the guanidinium salt {C[NHⁱPr]₃}⁺[SnCl₅(THF)]⁻ (2). The Sn(II) guanidinate complexes {(C₆H₁₁N)₂C[NH(C₆H₁₁)]}₂Sn (3) and {CN[N(CH₂)₃]₂}₂Sn (4) were prepared through metathesis reactions between 0.5 equiv. SnCl₂ and (C₆H₁₁N)₂C[NH(C₆H₁₁)]Li or hppLi, respectively. Complex 4 is the first reported mononuclear complex of this ligand. In contrast, the reaction of hppLi with 1 equiv. SnCl₂ afforded a bridging dinuclear species, {CN[N(CH₂)₃]₂SnCl}₂ (5). A second mononuclear complex of the hpp⁻ ligand, {CN[N(CH₂)₃]₂}₂SnCl₂ (6), was the product obtained from the reaction of 2 equiv. of hppLi with SnCl₄. The full structural details of compounds 1 and 3–6 are reported. In the case of compounds 1 and 3 these results revealed a distinctly unsymmetrical bonding mode for the bidentate guanidinate ligand and suggest variable degrees of π delocalization with the ligand. The geometries of the Sn centers in 3, 4 are derived from distorted trigonal bipyramidal coordination with a stereochemically active lone pair occupying one coordination site. In contrast, complex 5 displayed a geometry derived from a tetrahedral ligand array with one vertex occupied by a lone pair of electrons. Complex 6 is six coordinate and possesses 2 equiv. chelating bidentate hpp⁻ ligands and two cis-chloro groups.     

Syntheses,crystal structures and magnetic properties of complexes based on [Ni(L-L)3]2+ complex cations with dimethylderivatives of 2,2′-bipyridine and TCNQ

From the aqueous-methanolic systems Ni(NO₃)₂ – LiTCNQ – 5,5′-dmbpy and Ni(NO₃)₂ – LiTCNQ – 4,4′-dmbpy three novel complexes [Ni(5,5′-dmbpy)₃](TCNQ)₂ (1), [Ni(4,4′-dmbpy)₃](TCNQ)₂ (2) and [Ni(4,4′-dmbpy)₃]₂(TCNQ-TCNQ)(TCNQ)₂∙0.60H₂O (3), were isolated in single crystal form. The new compounds were identified using chemical analyses and IR spectroscopy. Single crystal studies of all samples corroborated their compositions and have shown that their ionic structures contain the complex cations [Ni(5,5′-dmbpy)]²⁺ (1) or [Ni(4,4′-dmbpy)]²⁺ (2 and 3). The anionic parts of the respective crystal structures 1–3 are formed by TCNQ^⋅- anion-radicals and in 3 also by a σ-dimerized dianion (TCNQ-TCNQ)^2- with a C-C distance of 1.663(5) Å. The supramolecular structures are governed by weak hydrogen bonding interactions. The variable-temperature (2–300 K) magnetic studies of 1 and 3 confirmed the presence of magnetically active Ni(II) atoms with S = 1 and TCNQ^⋅- anion-radicals with S = 1/2 while the (TCNQ-TCNQ)^2- dianion is magnetically silent. The magnetic behavior was described by a complex magnetic model assuming strong antiferromagnetic interactions between some TCNQ^⋅- anion-radicals.     

Simple aromatic amines from justicia gendarussa. 13C NMR spectra of the bases and their analogues

Four simple 0-disubstituted aromatic amines have been isolated from the leaves of Justicia gendarussa Burm and characterized as 2-amino benzyl alcohol (3), 2-(2′-amino-benzylamino) benzyl alcohol (4) and their respective 0-methyl ethers 1 and 2 from ¹H NMR and mass spectral analyses of the bases and their acetates. Structures 3 and 4 have also been confirmed by synthesis. Intramolecular hydrogen bonding (cf. 9, 13 and 14) has been envisaged to explain the unexpected shielding of -CH₂-OH carbon signals of 34 on acetylation and upfield displacement of -CH₂-N signal of 2a vs 4a in their ¹³C NMR spectra in CDCl₃ solution ₁J_CH values have been found to be useful for the assignment of aromatic methine carbon signals in o-disubstituted compounds. Part 68 of the series Studies on Indian medicinal plants. For Part 67, see P. K. Dutta, D. Bagchi and S.C. Pakrashi, Indian J. Chem. in press.     

Photolysis of Fe(CO)42− in an aqueous NaOH glass at 77 K. formation of solvated electrons

The photolysis of [Fe(CO)₄]²⁻ in 10 M NaOH glass at 77 K leads to the formation of solvated electrons with θ = 0.03 at λ_irr = 254 nm. The solvated electrons, which are stable under these conditions, are identified by their characteristic absorption band at λ_max = 588 nm.     

Three new tellurite halides with unusual Te coordinations and iron honeycomb lattice variants

The crystal structure of three new iron and copper-iron tellurite halides are presented; (I) Cu₃Fe₈Te₁₂O₃₂Cl₁₀ that crystallizes in the orthorhombic space group Pmmn, (II) Fe₈Te₁₂O₃₂Cl₃Br₃ that crystallizes in the monoclinic space group P2₁/c, and (III) Fe₅(TeO₃)₆Cl₂ that crystallizes in the triclinic space group P-1. The crystal structures were solved from single crystal X-ray diffraction data. All three compounds have layered crystal structures where the Fe atoms form variants of the honeycomb lattice. Highly unusual Te⁴⁺ coordination polyhedra are exemplified: [TeO₃₊₁E], [TeO₃XE], [TeO₃₊₁XE], and [TeO₃X₂E] (X=halide ion, E=the lone-pair valence electrons). The crystal structures contain large non-bonding volumes occupied by the stereochemically active lone-pair electrons on Te⁴⁺.     

proton transfers of substituted ammonium salts—XIII : N-inversion of piperidines in aqueous acidic solutions

The kinetics of the nitrogen inversion of 1,2-dimethyl-(2); 1,4-dimethyl-(8); 1-trans(2,6)-trimethyl-(4); 1,4-cis(2,6)-tetramethyl-(7) and 1,2,2,6,6-pentamethyl-(5)piperidines have been investigated in aqueous acidic solution (pH = 6.5–8.5) at 33° by dynamic NMR. In all cases, two isomeric cations AH⁺ and BH⁺ are observed in acidic conditions (pH<6?), and the nitrogen inversion is brought to the NMR time scale as a result of a progressive deprotonation of the cations into their conjugate amines on increasing the pH. Low rate constants K_A are obtained for α-substituted or unsubstituted compounds (k_A ?10³ s^?1), except for piperidine 5 where the rate constant k_A = 4.3 × 10⁵ s^?1 is of the same order of magnitude as the one found for tertiary acyclic amines.     

Syntheses and properties of H-1,2,3-triazoles

About twenty new H-1,2,3-triazoles (T) were readily synthesized by nucleophilic attack of sodium azide on activated acetylenes in dimethylformamide. Typical activating groups were COR, COOR, O₂NC₆H₄ PO(OC₂H₅, COT, and (C₆H₅)₃P⁺. Propynyl 4-triazolyl ketone or phenylethynyl 4-triazolyl ketone may be converted to acylic adducts (triazolylketoenamines), biheteroaromatic systems (isoxazolytriazoles, pyrazolytriazoles), as well as to ditriazolyl ketones. Certain T properties were examined in detail. The apparent pK′s for our group of ca 30 triazoles were in the range 4·95?9·45 in ethanol-water (v/v 1/1) at 25°. The Hammett correlation for five 4-aryl-T was log K_a = 0·89σ^? ?9·21 and for seven 4-aryl-5-carbethoxy-T was log K_a = 1·45σ?6·95. The UV spectra of T are similar to those of other heteroaromatic and phenyl compounds: interesting analogies between triazolyl and phenyl, e.g., ”ortho“ crowding effects, appear to be indicated in the spectra of compounds related to biphenyl, stilhene and benzophenone. With regard to structure assignment on the basis of spectra, characteristic features of UV and IR spectra of the H-1,2,3-triazoles are discussed.     

Temperature effects on positronium formation and inhibition: a contribution to the elucidation of early spur processes. I. Glycerol/water mixtures

In order to elucidate the mechanism of positronium (Ps) formation in liquids, the effect of temperature, T, on the inhibiting properties of various solutes has been investigated in glycerol/water mixtures. Whereas the inhibition constants of Cl^? and I^? are found to increase markedly with T, that of CH₃NO₂ is T insensitive and that of NO₃^? diminishes with T. These findings are consistent with our previous model, according to which Ps would be formed via two pathways, either through the quasi-free entities or by the reaction of localized, not yet fully solvated, electrons and positrons. The increase with T of the Ps yield is found to be due to the fraction arising from the latter reaction. The results confirm Cl^? and I^? react with e_loc⁺, while CH₃NO₂ and NO₃^? scavenge quasi-free electrons. Regarding the behaviour of the inhibition constants of these latter solutes, a provisional explanation is given: CH₃NO₂ would scavenge epithermal electrons while NO₃^? would react with electrons at a lower energy state, in competition with the localization process. Hot Ps atoms are not likely to be involved.     

Synthesis and antimicrobial screening of 1,3,4-oxadiazole and clubbed thiophene derivatives

In the present study, a novel series of 2-{5-[4-(1-aza-2-(2-thienyl)vinyl)phenyl](1,3,4-oxadiazol-2-ylthio)}-N-arylacetamides (IV)_1–12 were synthesized and tested for their antimicrobial activity. Newly synthesized compounds were screened for their antibacterial and antifungal activities on Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, Staphylococcus pyogenes, Candida albicans, Aspergillus niger and Aspergillus clavatus. The chemical structures of newly synthesized compounds were elicited by IR, ¹H NMR, ¹³C NMR and mass spectral data. The synthesized bio-active compounds exhibited excellent to moderate antimicrobial activity. Compounds (IV)₅, (IV)₆ and (IV)₇ possess excellent antibacterial activity whereas compounds (IV)₆, (IV)₉ and (IV)₁₁ possess excellent antifungal activity.     

Stability determining factors in anomeric coumerosides

The thermodynamic equilibrium between the anomeric coumerosides 3 and 4 differs drastically from that which exists between their C(2)-epimers 7 and 8. Stability determining factors which govern the position of these equilibria include in addition to steric interactions the Δ2 effect and the anomeric effect. The latter is discussed in terms of orbital overlap between nonbonding electrons on oxygen and anti-bonding σ orbitals. The α-configuration of the glycoside linkages of coumermycin A₁ was secured by X-ray analysis of compound 12.     

Spectroscopic and structural studies of chromate ions in zinc complexes with 2,2′-bipyridine. Analysis of the lowest triplet states in the CrO42− entity

Two novel complexes of Zn(II) chromate with 2,2′-bipyridine have been synthesised: [Zn(bpy)₃]CrO₄·7.5H₂O (1) and catena-(μ-CrO₄-O,O′)[Zn(bpy)(H₂O)₂]·2H₂O (2). Complex 1 has been characterised by a structural method. The [Zn(bpy)₃]CrO₄·7.5H₂O crystals have a monoclinic symmetry with space group C2/c and eight chemical units. The chromate ion is not coordinated to the zinc(II) ion. The O(3) and O(4) atoms of CrO₄²⁻ and O(8) of the water molecule statistically occupy their position with k=0.5, which means that the chromate ions execute reorientational motion between two equilibrium arrangements with equal probability. 4 K electronic spectra (1) revealed the vibrational fine structure in ν₃(F₂)=820 cm⁻¹ for the spin-forbidden ¹A₁→³T₁ transition. The pure electronic 0–0 transition in ¹A₁→¹T₁ was found at 20 270 cm⁻¹. In complex 2 the broad low intensity band at ca. 16 800 cm⁻¹ has been assigned to a forbidden ZnOCr transition in the bridge.