Two new bis(pyridine)-bis(amide)-based copper(II) coordination compounds for the electrochemical detection of trace Cr(VI) and efficient electrocatalytic oxygen evolution

Two new metal-organic compounds (MOCs) [Cu(L)0.5(3-nba)2] (1) and [Cu(L)(2,5-tdc)] (2) have been hydrothermally synthesized by employing the ligand N,N′-di(3-pyridyl)adipoamide (L) and two carboxylic acids (3-Hnba = 3-nitrobenzoic acid, 2,5-H2tdc = 2,5-thiophenedicarboxylic acid) as ligands. Compound 1 displays a metal-organic chain-like structure formed by the {Cu2(3-nba)4} double-paddle wheel units and the µ 2-bridging L ligands. The adjacent polymeric chains form a supramolecular layered structure through hydrogen bonding. Compound 2 shows a 3D metal-organic polymeric framework derived from Cu-L layers and µ 2-bridging 2,5-tdc ligands, which presents a 3,5-connected {4.62}{4.66.83} topology. The electrochemical and electrocatalytic behavior of the two compounds has been studied in detail. Carbon paste working electrodes modified with compounds 1 and 2 can be used as highly selective sensors for detecting traces Cr(VI). Both electrodes show also electrocatalytic performance in oxygen evolution reactions (OERs).

Nanocomposites of PCL and SBA-15 Particles Prepared by Extrusion: Structural Characteristics, Confinement of PCL Chains within SBA-15 Nanometric Channels and Mechanical Behavior

A study of different nanocomposites based on poly(ε-caprolactone) (PCL) and mesoporous SBA-15 silica that were prepared by melt extrusion was carried out by analyzing the possible effect of this filler on the crystalline details of PCL, on its mechanical behavior, and on the eventual observation of the confinement of the polymeric chains within the hollow nanometric silica channels. Thus, simultaneous Small-Angle and Wide-Angle X-ray Scattering (SAXS/WAXS) synchrotron experiments at variable temperature were performed on these PCL nanocomposites with different mesoporous silica contents. The importance of the morphological and structural features was assessed by the changes that were observed during the mechanical response of the final materials, which determined that the presence of mesoporous particles leads to a noticeable reinforcing effect.

Investigation of frictional impact on polyester yarn during knitting

The usage of polyester (PET) in fabrication is increasing day by day due to its properties, ease of physical and chemical modification. The aim of this work is to understand the effect of temperature on Polyester (PET) during knitting. For checking the rise of temperature Infrared (IR) camera is used. Microscopic images are used for studying the effect of temperature on fibre/yarn structure. Morphological analysis is also done by X-ray diffraction (XRD) which shows disturbance of polymeric chains, causing change in crystal size due to elevated temperature. The beads formation and filament breakage are clearly seen in images. Due to this knitting fault, shade variation after dyeing occurred. It is concluded that structural morphology of polyester yarn changes due to friction of yarn with knitting machine parts. Fabric appearance and fabric quality also disturbed which leads to rejections and high losses.

Thermal Conductivity of Polybutadiene Rubber from Molecular Dynamics Simulations and Measurements by the Heat Flow Meter Method

Thermal conductivities of polybutadiene rubbers crosslinked by 2.4 and 2.8 phr of sulfur have been found to be functions of temperature via molecular dynamics (MD) simulations using the Green–Kubo method. From an analysis of the heat flux autocorrelation functions, it has been revealed that the dominant means of heat transport in rubbers is governed by deformations of polymeric chains. Thermal conductivities of rubber samples vulcanized by 2.4 and 2.8 phr of sulfur have been measured by the heat flow meter method between 0 ∘C and 60 ∘C at atmospheric pressure. The temperature dependencies of the thermal conductivities of rubbers and their glass transition temperatures derived from MD simulations are in good agreement with the literature and experimental data. Details are discussed in the paper.

Structural and Electrochemical Studies of Cobalt(II) and Nickel(II) Coordination Polymers with 6-Oxonicotinate and 4,4′-Bipyridine

The 6-oxonicotinate (6-Onic) salts of a one-dimensional cationic cobalt(II) or nickel(II) coordination polymers with 4,4′-bipyridine (4,4′-bpy), namely {[Co(4,4′-bpy)(H2O)4](6-Onic)2·2H2O}n (1) and {[Ni(4,4′-bpy)(H2O)4](6-Onic)2·2H2O}n (2), were prepared hydrothermally by reactions of cobalt(II) nitrate hexahydrate or nickel(II) nitrate hexahydrate, respectively, 6-hydroxynicotinic acid and 4,4′-bipyridine in a mixture of ethanol and water. In the hydrogen-bonded frameworks of 1 and 2, the one-dimensional polymeric chains of {[M(4,4′-bpy)(H2O)4]2+}n (M = Co, Ni), the 6-oxonicotinate anions and the lattice water molecules were assembled via strong intermolecular O–H···O and N–H···O hydrogen bonds and π–π interactions, leading to the formation of the representative hydrogen-bond ring motifs: trimeric R23(10) motif, the centrosymmetric tetrameric R24(8) and R24(12) motifs and the pentameric R45(12) motif. The isostructural coordination polymers 1 and 2 exhibited a different electrochemical behavior, as observed by cyclic voltammetry, which can be attributed to the nature of the metal ions (cobalt(II) vs. nickel(II)).

The first coordination complex of (5R,6R,7S)-5-(furan-2-yl)-7-phenyl-4,5,6,7-tetrahydro-[1,2,4]triazolo[1,5-a]pyrimidin-6-amine with zinc(II) acetate-chloride

The title complex, systematic name catena-poly[[[acetatochloridozinc(II)]-μ-(5R,6R,7S)-5-(furan-2-yl)-7-phenyl-4,5,6,7-tetrahydro[1,2,4]triazolo[1,5-a]pyrimidin-6-amine] monohydrate], {[Zn(C2H3O2)Cl(C15H15N5O)]·H2O} n , is the first coordination complex in which the neutral tetrahydrotriazolopyrimidine derivative acts as bridging ligand between two zinc molecules. As a result, polymeric chains of the coordination complex are found. The coordination of the zinc metal atom occurs with the lone pairs of the triazolo nitrogen atom and amino group. The positive charge of the zinc atom is compensated by the chlorine anion and deprotonated acetic acid. The coordination complex exists as a monohydrate in the crystalline phase. The water molecules bind neighbouring polymeric chains by the formation of O—H...O, O—H...Cl and N—H...O hydrogen bonds.

Kinetic and Thermodynamic Control in Rare Earth Cyamelurates Synthesis

If various compounds exist in the metal cation – C6N7O33– – H2O system, the synthesis temperature can affect the isolation of a particular product. Low temperatures favor the release of metastable kinetic products, and high temperatures, on the contrary, of thermodynamic ones. It is found that several structural types exist in the row of rare-earth cyamelurates. Room temperature synthesis leads to the formation of [Ln(H2O)7C6N7O3] (Ln=Y, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er), an increase in temperature yields thermodynamically more stable [Ln(H2O)4C6N7O3]n·nH2O (Ln=Y, Ho, Er, Tm, Yb, Lu) and [Ln(H2O)5C6N7O3]n (Ln = Pr, Nd). The change in the synthesis temperature did not affect the structures of Sm, Eu, Gd, Tb, Dy cyamelurates, as well as the structure of lanthanum cyamelurate [La(H2O)6C6N7O3]·H2O.In synthesized at increased temperature [Ln(H2O)4C6N7O3]n·nH2O and [Ln(H2O)5C6N7O3]n cyamelurates polymeric chains exist due to the fact that the cyamelurate anion acts as a bridging ligand. Kinetically trapped Y, Pr, Nd, Ho, Er cyamelurates, in contrast, consist of individual complex molecules [Ln(H2O)7C6N7O3]. Probably, steric difficulties caused a decrease in the coordination number of Y, Ho, Er from 9 to 8 in the thermodynamic product. The coordination number of Pr and Nd remains equal to 9 in both types of compounds.

Obtaining and characterization films of a bioplastic obtained from passion fruit waste (Passiflora edulis)

Objective: Obtaining films from a vegetable biopolymer from the peel (a by-product) of passion fruit (Passiflora edulis) (BPM) and contribute to reduce the environmental pollution generated by the consumption of petroleum-derived plastics.Design / methodology / approach: By acid hydrolysis at four concentrations of citric acid (0, 1, 2, and 3 %), pectin was extracted of passion fruit peels, making a paste mixture with glycerol. The obtained biofilms with an approximate 1 mm thickness wereNcharacterized by transformed Fourier infrared spectroscopy (FTIR), X-ray diffraction (XRD) and scanning electron microscopy (SEM) with coupled elemental analyzer (EDS).Results: XRD diffractograms revealed that passion fruit bioplastic had a semi-crystalline structure and a calculated crystallinity index of 74.6 %. Its value reduced by the half as the citric acid increased concentration, the samples with lower concentration with greater flexibility (1 %). FTIR analysis suggested alterations in the BMP structures and adecrease of methoxyl groups in the polymeric chains with the increasing in citric acid content. Limitations/implications: SEM micrographs showed homogeneity in the films, although with some granular irregularities and folding.Findings/conclusions: The increase in citric acid concentration decreased the degree of gelation in the writing of the obtained biofilms, suggested by EDS and FTIR results, with a consequent reduced flexibility of the GMP films.

Tin Complexes of 4-(Benzylideneamino)benzenesulfonamide: Synthesis, Structure Elucidation and Their Efficiency as PVC Photostabilizers

Poly(vinyl chloride) (PVC) suffers from photo-xidation and photodegradation when exposed to harsh conditions. Application of PVC thus relies on the development of ever more efficient photostabilizers. The current research reports the synthesis of new complexes of tin and their assessment as poly(vinyl chloride) photostabilizers. The three new complexes were obtained in high yields from reaction of 4-(benzylideneamino)benzenesulfonamide and tin chlorides. Their structures were elucidated using different tools. The complexes were mixed with poly(vinyl chloride) at a very low concentration and thin films were made from the blends. The effectiveness of the tin complexes as photostabilizers has been established using a variety of methods. The new tin complexes led to a decrease in weight loss, formation of small residues, molecular weight depression, and surface alteration of poly(vinyl chloride) after irradiation. The additives act by absorption of ultraviolet light, removal the active chlorine produced through a dehydrochlorination process, decomposition of peroxides, and coordination with the polymeric chains. The triphenyltin complex showed the greatest stabilizing effect against PVC photodegradation as a result of its high aromaticity.

Stereochemical Geometries and Photoluminescence in Pseudo-Halido-Zinc(II) Complexes. Structural Comparison between the Corresponding Cadmium(II) Analogs

Six pseudohalide zinc(II) containing a variety of N-donor auxiliary amines were structurally characterized. These include two mononuclear trigonal bipyramidal [Zn(NTB)(N3)]ClO4·½H2O (3) and [Zn(TPA)(NCS)]ClO4 (4), two distorted octahedral [Zn(1,8-damnph)2(dca)2] (5) and [Zn(8-amq)2(dca)2] (6a) as well as two 1D polymeric chains catena-[Zn(isq)2(μ1,5-dca)2] (7) and catena-[Zn(N,N-Me2en)2(μ1,5-dca)]dca (8), where NTB = tris(2-benzimidazolylmethyl)amine, TPA = tris(2-pyridylmethyl)amine, 1,8-damnph = 1,8-diaminonaphthalene, 8-amq = 8-amino-quinoline, isq = isoquinoline (isq) and N,N-Me2en = N,N-dimethylethylenediamine. In general, with the exception of 6 and 8, the complexes exhibited luminescence emission in MeOH associated with red shift of the emission maxima, and the strongest visible fluorescence peak was detected at 421 nm (λex = 330 nm) in the case of Complex 5.