Nm For Cl Research Articles

How Chemical Bonding Impacts Halide Perovskite Nanocrystals Growth to Bulk Films: Implication of Pb-X Bond on Growth Kinetics.

Lead halide perovskites nanocrystals have emerged as a leading candidate in perovskite solar cells and light-emitting diodes. Given their favorable, tunable optoelectronic properties through modifying the size of nanocrystals, it is imperative to understand and control the growth of lead halide perovskite nanocrystals. However, during the nanocrystal growth into bulk films, the effect of halide bonding on growth kinetics remains elusive. To understand how a chemical bonding of Pb-X (covalency and ionicity) impact on growth of nanocrystals, we have examined two different halide perovskite nanocrystals of CsPbCl3 (more ionic) and CsPbI3 (more covalent) derived from the same parent CsPbBr3 nanocrystals. Tracking the growth of nanocrystals by monitoring the spectral features of bulk peaks (at 445 nm for Cl and at 650 nm for I) enables us to determine the growth activation energy to be 92 kJ/mol (for CsPbCl3 ) versus 71 kJ/mol (for CsPbI3 ). The electronegativity of halides in Pb-X bonds governs the bond strength (150-240 kJ/mol), characteristics of bonding (ionic versus covalent), and growth kinetics and resulting activation energies. A fundamental understanding of Pb-X bonding provides a significant insight into controlling the size of the perovskite nanocrystals with more desired optoelectronic properties.

To Love and to Kill: Accurate and Selective Colorimetry for Both Chloride and Mercury Ions Regulated by Electro-Synthesized Oxidase-like SnTe Nanobelts

Herein, SnTe nanobelts (NBs) with efficient oxidase-mimetic activity were synthesized by the simple electrochemical exfoliation method. A specific inhibition effect of Cl- on the enzymatic behavior of the pure SnTe NBs was discovered, which was accordingly used for establishing a highly feasible, sensitive, selective, and stable Cl- colorimetric assay. The detection concentration range was 50 nM to 1 mM, and the lowest detection limit was 20 nM for Cl-. In addition, a signal on-off-on route based on the SnTe NB nanozyme was designed to realize the reliable and specific detection of Hg2+. Therein, the SnTe NBs were grafted with gold nanoparticles to form a hybrid of SnTe/Au, resulting in the depression of the oxidase-like activity, which can then be recovered in the presence of the Hg2+ due to the formation of a gold amalgam. Especially, it was found that the high concentration of Cl- over 3 mM could again exert suppression influence toward the enzymatic activity of the SnTe/Au-Hg system. Based on the to-love-and-to-kill interaction between Cl- and Hg2+, the detection range for Cl- can be extended to 40 to 250 mM. In return, the assays of Cl- could avoid in advance its interference toward the accurate Hg2+ assays. We systematically clarified the oxidase-like catalytic mechanism of the SnTe-derived nanozyme systems. The as-proposed colorimetry can be successfully applied in practical samples including the sweat, human serum, or seawater/tap water, relating to cystic fibrosis, hyper-/hypochloremia, or environmental control, respectively.

A Pore-Forming Tripeptide as an Extraordinarily Active Anion Channel.

Compared to the most active anion-transporting channel that requires a channel:lipid molar ratio of 1:330 (0.3 mol % relative to lipid) to achieve 50% activity, a structurally simple pore-forming tripeptide 6L310 was found to exhibit an extraordinarily strong ability to self-assemble into stable possibly barrel-shaped exceptionally active channels, with record-low EC50 values of 4.0, 3.0, 1.6, 2.6, and 2.6 nM (e.g., 0.005-0.013 mol % relative to lipid) for Cl-, Br-, I-, NO3-, and ClO4-, respectively.

Demonstration of a Light-Driven SO42- Transporter and Its Spectroscopic Characteristics.

In organisms, ion transporters play essential roles in the generation and dissipation of ion gradients across cell membranes. Microbial rhodopsins selectively transport cognate ions using solar energy, in which the substrate ions identified to date have been confined to monovalent ions such as H+, Na+, and Cl-. Here we report a novel rhodopsin from the cyanobacterium Synechocystis sp. PCC 7509, which inwardly transports a polyatomic divalent sulfate ion, SO42-, with changes of its spectroscopic properties in both unphotolyzed and photolyzed states. Upon illumination, cells expressing the novel rhodopsin, named Synechocystis halorhodopsin (SyHR), showed alkalization of the medium only in the presence of Cl- or SO42-. That alkalization signal was enhanced by addition of a protonophore, indicating an inward transport of Cl- and SO42- with a subsequent secondary inward H+ movement across the membrane. The anion binding to SyHR was suggested by absorption spectral shifts from 542 to 536 nm for Cl- and from 542 to 556 nm for SO42-, and the affinities of Cl- and SO42- were estimated as 0.112 and 5.81 mM, respectively. We then performed time-resolved spectroscopic measurements ranging from femtosecond to millisecond time domains to elucidate the structure and structural changes of SyHR during the photoreaction. Based on the results, we propose a photocycle model for SyHR in the absence or presence of substrate ions with the timing of their uptake and release. Thus, we demonstrate SyHR as the first light-driven polyatomic divalent anion (SO42-) transporter and report its spectroscopic characteristics.

Eu(2+)-Activated Alkaline-Earth Halophosphates, M5(PO4)3X:Eu(2+) (M = Ca, Sr, Ba; X = F, Cl, Br) for NUV-LEDs: Site-Selective Crystal Field Effect.

Eu(2+)-activated M5(PO4)3X (M = Ca, Sr, Ba; X = F, Cl, Br) compounds providing different alkaline-earth metal and halide ions were successfully synthesized and characterized. The emission peak maxima of the M5(PO4)3Cl:Eu(2+) (M = Ca, Sr, Ba) compounds were blue-shifted from Ca to Ba (454 nm for Ca, 444 nm for Sr, and 434 nm for Ba), and those of the Sr5(PO4)3X:Eu(2+) (X = F, Cl, Br) compounds were red-shifted along the series of halides, F → Cl → Br (437 nm for F, 444 nm for Cl, and 448 nm for Br). The site selectivity and occupancy of the activator ions (Eu(2+)) in the M5(PO4)3X:Eu(2+) (M = Ca, Sr, Ba; X = F, Cl, Br) crystal lattices were estimated based on theoretical calculation of the 5d → 4f transition energies of Eu(2+) using LCAO. In combination with the photoluminescence measurements and theoretical calculation, it was elucidated that the Eu(2+) ions preferably enter the fully oxygen-coordinated sites in the M5(PO4)3X:Eu(2+) (M = Ca, Sr, Ba; X = F, Cl, Br) compounds. This trend can be well explained by "Pauling's rules". These compounds may provide a platform for modeling a new phosphor and application in the solid-state lighting field.

Experimental study of a glow discharge of CH2-C12

Low-pressure DC plasma discharges sustained in a glow discharge of CH2-Cl2 are studied. This plasma was generated at a pressure of 1.0 Torr, power of 20 W and a flow of 12 l/min. The diagnostic has been made by optical emission spectroscopy (OES) using a spectrometer. The principal species observed were: were at 339.61, 358.60 and 377.96 nm for C2(c'1Πg-b1Πu); at 392.50 nm for C3('Πu-'Σ+g); at 431.42 nm for CH(A2Δ-X2Π); at 778.28 nm for Cl; at 657.80 nm for C+; at 471.90 and 487.30 nm for H2; at 380.61 nm for CH+A'Π-X'Σ) and at 317.73 nm for HCL+(A2ΣI-X2Π). In the study, special attention was given to the behavior of material deposition in the electrodes. The time dependence of material deposition in the electrodes was also investigated. When the discharge time of CH2CL2 plasma was increased, the mass deposition was increased. It can observe that the mass deposition display an increased behavior until 30 min, and then shows an saturation behavior. Fourier Transform Infrared (FTIR) spectroscopy was applied for the surface analysis. The variations of the size of the thin film may change the subsequent chemical reactions in the gas phase significantly. As the reaction time was increased signal from structural fragment containing chlorine atom were loosed, which can explain the behavior observed in the chlorine signal using emission spectroscopy measurements.

CH2Cl2 thin film formation on low-pressure DC plasma discharge

Low-pressure DC plasma discharges sustained in a glow discharge of CH2Cl2 are studied. The plasma conditions were: 1.0 Torr, 20 W and 12 l/min. The electron temperature and ion density were estimated to be 5.47±0.27 eV and (1.57±0.06)×1016 m−3, using a double Langmuir probe. The diagnostic of the species was made by optical emission spectroscopy using a spectrometer. The main species identified were at 339.61, 358.60 and 377.96 nm for C2(c’1Πg–b1Πu); at 392.50 nm for C3(‘Πu–‘); at 431.42 nm for CH(A2Δ–X2Π); at 778.28 nm for Cl; at 657.80 nm for C+; at 471.90 and 487.30 nm for H2; at 380.61 nm for CH+(A’Π–X’Σ) and at 317.73 nm for HCl+(A2Σ–X2Π). Special attention was given to the behavior of material deposited on the electrode and the time discharge dependence was also investigated. The material deposited was analyzed with the aid of a scanning electron microscope (SEM) and Fourier transform infrared spectroscopy. The SEM observation shows an increment in the particle size which is in agreement with the observation of less bands in the infrared spectra.

Utility of some .PI.-Acceptors for Spectrophotometric Determination of Gatifloxacin in Pure Form and in Pharmaceutical Preparations

Four simple, quick and sensitive methods are described for the spectrophotometric determination of gatifloxacin. The methods are based on the reaction of gatifloxacin as n-electron donor with 7,7,8,8-tetracyanoquinodimethane (TCNQ); 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ); chloranilic acid (CLA) and p-chloranil (CL) as pi-acceptors to give highly colored complex species. The colored products are quantitated spectrophotometrically at 460, 841, 530 and 545 nm for DDQ, TCNQ, CLA and CL, respectively. Optimization of the different experimental conditions is described. Beer's law is obeyed in the concentration ranges 5-60, 1.5-18, 30-360 and 20-240 microg ml(-1) of gatifloxacin, but for more accurate analysis, Ringbom optimum concentration range was found to be 7.5-55, 3-16, 35-350 and 25-230 microg ml(-1) of gatifloxacin for DDQ, TCNQ, CLA and CL, respectively. The limits of detection and quantification were calculated and the relative standard deviations for different concentrations of gatifloxacin using various acceptors were <1.28%. The association constants of 1 : 1 complexes and standard free energy changes using Benesi-Hildebrand plots were studied. The proposed methods were successfully applied to the determination of gatifloxacin in pharmaceutical dosage forms without interference from common additives encountered.

Chitosan adsorption to salivary pellicles

The salivary pellicle is a negatively charged protein film, to which oral bacteria readily adhere. Chitosans are cationic biomolecules with known antimicrobial properties that can be modified in different ways to enhance its antimicrobial activity. Here, we determined the changes in surface chemical composition using X-ray photoelectron spectroscopy (XPS), in hydrophobicity by analyzing water contact angles, in charge through measuring streaming potentials, and evaluated morphology using atomic force microscopy (AFM), of salivary pellicles upon adsorption of different chitosans. The adsorption of chitosans to pellicles was chemically evident from altered carbon functionalities and the presence of an N(1s) peak at 401.1 eV as a result of protonated amines in XPS. Chitosan adsorption made the pellicle (zeta potential of untreated pellicles 29 mV) positively charged and more hydrophobic. A chemically modified chitosan (CL) and an unmodified chitosan (UC) caused aggregation of adsorbed salivary proteins, and AFM revealed clumps of protein after treatment with these chitosans, yielding an increase in pellicle surface roughness from 5.1 nm to between 16.3 and 35.6 nm for CL and UC, respectively. In summary, chitosans have a clear tendency to adsorb to salivary pellicles with a profound effect on the surface properties of the pellicle. Therefore, chitosans may provide anchoring molecules to affix antimicrobials to pellicle surfaces.

Maximal β3-Adrenergic Regulation of Lipolysis Involves Src and Epidermal Growth Factor Receptor-dependent ERK1/2 Activation

Catecholamine-stimulated lipolysis is primarily a beta-adrenergic and cAMP-dependent event. In previous studies we established that the beta(3)-adrenergic receptor (beta(3)AR) in adipocytes utilizes a unique mechanism to stimulate extracellular signal-regulated kinases 1 and 2 (ERK) by direct recruitment and activation of Src kinase. Therefore, we investigated the role of the ERK pathway in adipocyte metabolism and found that the beta(3)AR agonist CL316,243 regulates lipolysis through both cAMP-dependent protein kinase (PKA) and ERK. Inhibition of PKA activity completely eliminated lipolysis at low (subnanomolar) CL316,243 concentrations and by 75-80% at higher nanomolar concentrations. The remaining 20-25% of PKA-independent lipolysis, as well as ERK activation, was abolished by inhibiting the activity of either Src (PP2 or small interfering RNA), epidermal growth factor receptor (EGFR with AG1478 or small interfering RNA), or mitogen-activated protein kinase kinase 1 or 2 (MKK1/2 with PD098059). PD098059 inhibited lipolysis by 53% in mice as well. Finally, the effect of estradiol, a reported acute activator of ERK and lipolysis, was also totally prevented by PP2, AG1478, and PD098059. These results suggest that ERK activation by beta(3)AR depends upon Src and epidermal growth factor receptor kinase activities and is responsible for the PKA-independent portion of the lipolytic response. Together these results illustrate the distinct and complementary roles for PKA and ERK in catecholamine-stimulated lipolysis.

A photodissociation study of CH2BrCl in the A-band using the time-sliced ion velocity imaging method

Employing a high-resolution (velocity resolution deltanu/nu<1.5%) time-sliced ion velocity imaging apparatus, we have examined the photodissociation of CH2BrCl in the photon energy range of 448.6-618.5 kJ/mol (193.3-266.6 nm). Precise translational and angular distributions for the dominant Br(2P32) and Br(2P12) channels have been determined from the ion images observed for Br(2P32) and Br(2P12). In confirmation with the previous studies, the kinetic-energy distributions for the Br(2P12) channel are found to fit well with one Gaussian function, whereas the kinetic- energy distributions for the Br(2P32) channel exhibit bimodal structures and can be decomposed into a slow and a fast Gaussian component. The observed kinetic-energy distributions are consistent with the conclusion that the formation of the Br(2P32) and Br(2P12) channels takes place on a repulsive potential-energy surface, resulting in a significant fraction (0.40-0.47) of available energy to appear as translational energy for the photo fragments. On the basis of the detailed kinetic-energy distributions and anisotropy parameters obtained in the present study, together with the specific features and relative absorption cross sections of the excited 2A', 1A", 3A', 4A', and 2A" states estimated in previous studies, we have rationalized the dissociation pathways of CH2BrCl in the A-band, leading to the formation of the Br(2P32) and Br(2P12) channels. The analysis of the ion images observed at 235 nm for Cl(2P(32,12)) provides strong evidence that the formation of Cl mainly arises from the secondary photodissociation process CH2Cl + hnu --> CH2 + Cl.

Controlled inert gas environment for enhanced chlorine and fluorine detection in the visible and near-infrared by laser-induced breakdown spectroscopy

Efficient quantitative detection for halogens is necessary in a wide range of applications, ranging from pharmaceutical products to air polluting hazardous gases or organic compounds used as chemical weapons. Detection of the non-metallic elements such as fluorine (F) and chlorine (Cl) presents particular difficulty, because strong emission lines originating from their resonance states lie in the VUV spectral range (110–190 nm). In the present work we detect F and Cl in the upper visible and in the near IR (650–850 nm) under controlled inert gas ambient atmosphere. Investigation of the controlled atmosphere effects suggests that there exists an optimum pressure range that optimizes signal strength and quality. Ablation and ionization were achieved with a UV laser at 355 nm, and a gated GaAs photocathode-based detector was used for detection with quantum efficiency in the range of 20% in the wavelengths of interest. Our results indicate that our approach provides quantitative detection with linearity over at least two orders of magnitude that is achieved without the need for Internal Standardization Method, and improved limits of detection. In particular, fluorine has been detected for concentration values down to 0.03 wt.% Definite spectral assignment revealing all major emission lines centered around 837 nm for F and 687 nm for Cl has been obtained for the first time in Laser-induced breakdown spectroscopy application.

UTILITY OF SOME π-ACCEPTORS FOR THE SPECTROPHOTOMETRIC DETERMINATION OF TRIMETAZIDINE HYDROCHLORIDE

ABSTRACT Three simple, quick and sensitive spectrophotometric methods are described for the determination of trimetazidine hydrochloride. The methods are based on the reaction of this drug as an n-donor with 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ), 7,7,8,8-tetracyano-quinodimethane (TCNQ) and p-chloranil (CL) as π-acceptors to give highly coloured complex species. The colored products are quantitated photometrically at 458, 842 and 545 nm for DDQ, TCNQ and CL, respectively. Optimization of the different experimental conditions is described. Beer's law is obeyed in the concentration ranges 5–50, 1–15 and 10–150 µg ml−1of trimetazidine hydrochloride, but the concentration ranges for best accuracy are: 6.3–50, 2.5–14.4 and 21.4–150 µg ml−1 of drug for the DDQ, TCNQ and CL, respectively. The relative standard deviations are less than 1%. The proposed methods are successfully applied to the determination of trimetazidine in Vastarel tablets. The association constants of the 1 : 1 complexes were: 1540, 400 and 2550 l mol−1 for DDQ, TCNQ and CL, respectively.

A laser flash photolysis study of the decay of SO 4− and Cl 2− radical anions in the presence of Cl − in aqueous solutions

The rate constant for the reaction of sulphate radical (SO 4 −) with Cl − has been determined using laser photolysis, at 248 nm, of peroxodisulphate anions to produce the radicals and time resolved optical absorption of the transient species (at 450 or 480 nm for SO 4 − and 350 nm for Cl 2 −) for the kinetic determinations. The experiments were performed, in the absence of added sulphate, as a function of temperature and ionic strength and yielded (at an ionic strength of 0.0157 M): k IV=(9.90±0.16)×10 9exp((−7.12±2.0) kJ mol −1/ RT) M −1 s −1, where the errors reflect the 2 σ statistical error. This reaction produces Cl 2 −, the formation and decay of which were also monitored allowing a determination of the rate constant of its second-order self-recombination reaction which gave k=(6.50±1.40)×10 8 M −1 s −1 at 293 K and zero ionic strength.

Spectrophotometric determination of ciprofloxacin in pure form and in tablets through charge-transfer complexation reactions

Three simple, quick and sensitive spectrophotometric methods are described for the determination of ciprofloxacin. The methods are based on the reaction of this drug as ann-electron donor with 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ), 7,7,8,8,-tetracyanoquinodimethane (TCNQ) andp-chloranil (CL) as π-acceptors to give highly coloured complex species. The coloured products are quantitated spectrophotometrically at 460, 843 and 550 nm for DDQ, TCNQ and CL, respectively. Optimization of the different experimental conditions is described. Beer's law is obeyed in the concentration ranges 5–50, 1.5–15 and 20–200 μg ml−1 ciprofloxacin, but the concentration ranges for best accuracy are 10–48, 2.5–15 and 35– 195 μg ml−1 of drug for DDQ, TCNQ and CL, respectively. The relative standard deviations are less than 1.5%. Applications of the suggested methods to ciprofloxacin tablets are presented and compared with the USP method. The stability constants of the 1∶1 DDQ and CL complexes were 1.086 × 104 and 2.581 × 104 lmol−1, respectively, whereas for the 1∶2 TCNQ complex it was 3.62 × 1081. mol−1.

Utility of certain π-acceptors for the spectrophotometric determination of norfloxacin

Simple, rapid, accurate and sensitive spectrophotometric methods are described for the determination of norfloxacin. The methods are based on the reaction of this drug as a π-electron donor with 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ), 7,7,8,8-tetracyanoquinodimethane (TCNQ), p-chloranil (CL) or chloranilic acid (CLA) as π-acceptors to give highly coloured complex species. The coloured products are measured spectrophotometrically at 460, 843, 550 and 531 nm for DDQ, TCNQ, CL and CLA, respectively. Optimization of the different experimental conditions is described. Beer's law is obeyed in the range 10–400 µg ml–1 and colours were produced in non-aqueous media and were stable for at least 3 h. Applications of the suggested methods to representative pharmaceutical dosage forms are presented and compared with the official method. Interferences from additives and common degradation products were investigated.

CL 284,846, a novel sedative‐hypnotic: Evaluation of its metabolites for pharmacological activity in vitro and in vivo

AbstractCL 284,846, N‐[3‐3‐cyanopyrazolo[1,5‐a]pyrimidin‐7‐yl(phenyl)]‐N‐ethylacetamide, is a novel non‐benzodiazepine sedative‐hypnotic with benzodiazepine‐like sedative effects, but with less apparent liability for accompanying undesired side effects. Three metabolites of the parent sedative‐hypnotic have been isolated and identified, a desethyl metabolite, CL 284,859, a desethyl‐5‐keto metabolite, CL 345,644, and a 5‐keto metabolite, CL 345,905. In experiments to determine the ability of these compounds to displace [3H]‐flunitrazepam from rat cortical benzodiazepine receptors, the IC50 values were 205 nM for CL 284,846 compared to 4.5 nM for diazepam as a positive control, and 11 μM for CL 284,859. The other two metabolite, CL 345,644 and CL 345,905, failed to displace [3H]‐flunitrazepam. In a second experiment designed to evaluate in vivo receptor‐mediated activity, CL 284,846 (3.0 mg/kg; 9.836 μmol/kg) was established as a discriminative stimulus (DS) in rats. While CL 284,846 (0.03ndash;3.0 mg/kg; 0.098–9.836 μmol/kg) showed a doserelated increase in drug‐appropriate responding and one dose of triazolam (0.3 mg/kg; 0.875 μmol/kg) substituted as a positive control, all three metabolites (3.0–100.0 mg/kg; 10.3–341.3 μmol/kg for CL 284,859; 6.0–201.2 μmol/kg for CL 345,644; 9.3–311.5 μmol/kg for CL 345,905) failed to substitute for the DS effects of CL 284,846. These results suggest that CL 284,859, CL 345,644, and CL 345,905, the metabolites of the sedative‐hypnotic CL 284,846, have no significant neuropharmacological effects at central benzodiazepine receptors and, thus, do not contribute to the activity of the parent compound. © 1994 Wiley‐Liss, Inc.

Cl (2Pj)_ fine structure quantum yields from UV dissociation of PCl3, CCl4, CHCl3 and Cl2 in a supersonic jet

Jet-cooled phosphorus trichloride, carbon tetrachloride, chloroform and molecular chlorine are photodissociated in the UV wavelength range 235–238 nm. Chlorine atom photofragments Cl ( 2 P 3 2 ) and Cl* ( 2 P 1 2 ) are detected via resonance-enhanced (2+1) ionization throughout the 232–238 nm wavelength region. The relative Cl* yields, φ*=[Cl*]/([Cl]+[Cl*]), are measured for both 35 Cl and 37 Cl isotopes using the two-photon atomic transitions at 235.3 nm for Cl and 237.8 nm for Cl*. Preliminary results indicate that the Cl* yields are different for the two isotopes for some of the precursors. In addition, we obtained the two-photon oscillator strength of the Cl transition at 237.7 nm relative to the Cl* transition at 237.8 nm. The advantage of using the two-photon Cl transition at 237.7 nm for quantum yield measurements is discussed.

Quenching rate constants of excited halogen atoms in quartet states

Excited halogen atoms in quartet spin states F*(2p43s, 4P5/2), Cl*(3p44s, 4P5/2), and Br*(4p45s, 4P5/2) were produced from helium sensitized radiation chemical decomposition of SF6, CF3Cl, CF3Br, and CF2Br2. Quenching rate constants of these excited halogen atoms by simple gas molecules such as O2, N2, H2, CO, CO2, NO, NO2, N2O, CH4, C2H6, and Xe including parent molecules were determined from absorption decay curves at 685.8 nm for F*, 837.5 nm for Cl*, and 827.4 nm for Br*. The optical densities were assumed to be proportional to (number of excited atoms per one cubic centimeter)0.9. The quenching rate constants obtained here were compared to those reported of metastable rare-gas atoms and an excited oxygen atom O*(2p33s, 5S2), and further discussed in terms of several theoretical kinetic models.

Synthesis and characterization of the complexes [Cu(II)(Et 4todit)X 2] n· nTHF (Et 4todit=4,5,6,7-tetrathiocino[1,2- b:3,4-b′]-diimidazolyl-1,3,8,10-tetraethyl-2,9-dithione; XCl, Br). Crystal and molecular structure of [Cu(II)(Et 4todit)Cl 2] n· nTHF

By reacting CuX 2 (XCl or Br) with Et 4todit (Et 4todit=the title ligand) in THF, the new ligand- bridged polynuclear complexes [Cu(II)(Et 4todit)X 2] n · nTHF have been obtained. The X-ray crystallographic studies on the Cl derivative show that the compound crystallizes in the orthorhombic space group Fdd2, with a=32.674(6), b=34.547(6), c=10.162(3) Å, Z=16. The coordination around the metal involves two Cl − ions and two S-thioamide atoms of two ligand molecules related by a screw axis, and is nearer to a square planar than to a tetrahedral arrangement. The bridging ligands form helical chains running parallel to c. The copper-copper distances in and between the chains are 7.601(4) and 9.185(5) Å, respectively. ESR measurements on this polymer give g values in accordance with a strongly distorted rhombic structure. The magnetic susceptibility data within the temperature range 5–150 K exhibit a Curie behaviour for both complexes (μ= 1.82 and 1.72 BM for Cl and Br complexes, respectively). Electronic spectroscopic results show that: (i) the environment around the copper(II) is the same in the solid state and in THF solution; (ii) reagents and products exist in THF at supersaturation conditions; (iii) S-(thioamide)copper(II) LMCT bands are observed at 555 and 620 nm for Cl and Br complexes, respectively. IR spectra agree with the X-ray structural results.