Bonding trends of thiosemicarbazones in mononuclear and dinuclear copper(I) complexes: syntheses, structures, and theoretical aspects

Reactions of copper(I) halides with a series of thiosemicarbazone ligands (Htsc) in the presence of triphenylphosphine (Ph(3)P) in acetonitrile have yielded three types of complexes: (i) monomers, [CuX(eta1-S-Htsc)(Ph3P)2] [X, Htsc = I (1), Br (2), benzaldehyde thiosemicarbazone (Hbtsc); I (5), Br (6), Cl (7), pyridine-2-carbaldehyde thiosemicarbazone (Hpytsc)], (ii) halogen-bridged dimers, [Cu2(mu2-X)2(eta1-S-Htsc)2(Ph3P)2] [X, Htsc = Br (3), Hbtsc; I (8), furan-2-carbaldehyde thiosemicarbazone (Hftsc); I (11), thiophene-2-carbaldehyde thiosemicarbazone (Httsc)], and (iii) sulfur-bridged dimers, [Cu2X2(mu2-S-Htsc)2(Ph3P)2] [X, Htsc = Cl (4), Hbtsc; Br (9), Cl (10), pyrrole-2-carbaldehyde thiosemicarbazone (Hptsc); Br (12), Httsc]. All of these complexes have been characterized with the help of elemental analysis, IR, 1H, 13C, or 31P NMR spectroscopy, and X-ray crystallography (1-12). In all of the complexes, thiosemicarbazones are acting as neutral S-donor ligands in eta()S or mu2-S bonding modes. The Cu...Cu separations in the Cu(mu2-X)2Cu and Cu(mu2-S)2Cu cores lie in the ranges 2.981(1)-3.2247(6) and 2.813(1)-3.2329(8) Angstroms, respectively. The geometry around each Cu center in monomers and dimers may be treated as distorted tetrahedral. Ab initio density functional theory calculations on model monomeric and dimeric complexes of the simplest thiosemicarbazone [H2C=N-NH-C(S)-NH2, Htsc] have revealed that monomers and halogen-bridged dimers have similar stability and that sulfur-bridged dimers are stable only when halogen atoms are engaged in hydrogen bonding with the solvent of crystallization or H2O molecules.     

New reagents for the facile and sensitive spectrophotometric determination of carbofuran in its formulations and environmental samples

Facile and sensitive spectrophotometric methods were developed for the determination of carbofuran in its formulations and environmental samples by using new reagents. The methods were based on the coupling reaction of hydrolysed product of cabofuran with diazotized reagents, namely, 2,6-dibromo-4-methylaniline, 2,6-dibromo-4-nitroaniline, and 2,4,6-tribromoaniline in basic medium to give color derivatives having the absorption maximum at 468, 474, and 410 nm, respectively. The color derivatives were correspondingly stable for 40, 30, and 16 h. Beer’s law was obeyed in the carbofuran concentration range 0.2–10.0 μg/mL. The proposed methods have been found to be applicable to the determination of carbofuran in its formulations, tap and distilled water, grains, polluted water, plant material (cabbage), and soil samples. The text was submitted by the authors in English.     

Metal–thiosemicarbazone interactions. Synthesis of an iodo-bridged dinuclear [diiodobis(pyrrole-2-carbaldehydethiosemicarbazone)dicopper(I)] complex

Reaction of copper(I) iodide with pyrrole-2-carbaldehydethiosemicarbazone (Hptsc) in a 1:1 mole ratio in MeCN, followed by addition of one mole of Ph₃P, yielded a complex of empirical formula, CuI(Hptsc)(Ph₃P), whose X-ray structure determination has shown that it exists as an iodo-bridged dinuclear copper(I) complex, [Cu₂(-I)₂( ¹-S-Hptsc)₂(PPh₃)₂](1). The central kernel, Cu(-I)₂Cu forms a parallelogram with unequal Cu—I distances {Cu—I, 2.644(2), 2.707(2)Å} and bond angles {Cu—I—Cu, 70.72(7), I—Cu—I, 109.28(7)°}. Each Cu atom is further bonded to one S atom of Hptsc and one P atom of Ph₃P, thus completing tetracoordination. The Cu...Cu separation of 3.097(4)Å is close to the sum of the van der Waals radius of the Cu atom, 2.80 Å. Compound (1) involves relatively strong inter-dimer hydrogen bonding via hydrazinic and pyrrole ring hydrogens with sulfur and iodine atoms respectively of the adjacent dimer {N(1)H...S^#2, 2.50 Å; N(4)H...I^#3, 2.91 Å}. The complex represents the first report of a copper(I) dimer with a thiosemicarbazone.     

Structure and dynamics of poly(oxyethylene) cholesteryl ether wormlike micelles: rheometry, SAXS, and cryo-TEM studies

In this article, we provide direct evidence for 1-D micellar growth and the formation of a network structure in an aqueous system of poly(oxyethylene) cholesteryl ether (ChEO(20)) and lauryl diethanolamide (L-02) by rheometry, small-angle X-ray scattering (SAXS), and cryo-transmission electron microscopy (cryo-TEM). The ChEO(20) self-assembles into spheroid micelles above the critical micelle concentration and undergoes a 1-D microstructural transition upon the incorporation of L-02, which because of its lipophilic nature tends to be solubilized into the micellar palisade layer and reduces the micellar curvature. The elongated micelles entangle with each other, forming network structures of wormlike micelles, and the system shows viscoelastic properties, which could be described by the Maxwell model. A peak observed in the zero-shear viscosity (η(0)) versus L-02 concentration curve shifted toward higher L-02 concentrations and the value of maximum viscosity (η(0?max)) increased with the increasing ChEO(20) mixing fraction with water. We observed that η(0?max) increased by 2 to 4 orders of magnitude as a function of the ChEO(20) concentration. The Maxwell relaxation time (τ(R)) shows a maximum value at a concentration corresponding to η(0?max) (i.e., τ(R) increases with L-02 concentration and then decreases after attaining a maximum value, whereas the plateau modulus (G(0)) shows monotonous growth). These observations demonstrate microstructural transitions in two different modes: L-02 first induces 1-D micellar growth and as a result the viscosity increases, and finally after the system attains its maximum viscosity, L-02 causes branching in the network structures. The microstructure transitions are confirmed by SAXS and cryo-TEM techniques.     

Persistence of trifloxystrobin and tebuconazole in banana tissues and soil under the semi-arid climatic conditions of Karnataka,India

Trifloxystrobin and tebuconazole are used for control of Sigatoka leaf spot disease of banana. This study was conducted to evaluate residue persistence of the fungicides in/on banana fruit, other edible parts and soil after spray application of the combination formulation, Nativo 75 WG, at the standard dose, 87.5 + 175 and double dose, 175 + 350 g a.i. ha^?1. The fungicides were extracted from banana and soil with acetone, partitioned into dichloromethane and cleaned-up using activated charcoal for trifloxystrobin and primary/secondary amine (PSA) for tebuconazole samples. The limit of quantification of the method was 0.05 mg kg^?1 for both fungicides. Initial residues of trifloxystrobin were 0.444 and 0.552 mg kg^?1 in/on banana with peel (whole fruit), which reached <0.05 and 0.065 mg kg^?1 after 30 days from treatment at the standard and double doses, respectively. Tebuconazole residues were 0.636 and 960 mg kg^?1 initially and reduced to 0.066 and 0.101 mg kg^?1 after 30 days. Trifloxystrobin and tebuconazole degraded with the half-life of about 11 days. Trifloxystrobin or its metabolite was not detected in the fruit pulp. Tebuconazole being systemic in nature moved to the fruit pulp which was highest on the 3rd day (0.103 and 0.147 mg kg^?1) and remained for 15 days. Matured banana fruit, flower, pseudostem and field soil were free from fungicide residues. For consumption of raw banana 43 days pre-harvest interval (PHI) is required after treatment of the combination formulation. Therefore application of the fungicides towards maturity stage of the fruits may be avoided.     

Formulation and modification of physicochemical parameters of p-Coumaric acid by cyclodextrin nanosponges

Journal of Inclusion Phenomena and Macrocyclic Chemistry - Reactive oxygen species triggered oxidative stress contributes to the pathogenesis of numerous ailments such as myocardial infraction,...     

RETRACTED: Preconcentration and solid-phase extraction of beryllium, lead, nickel, and bismuth from various water samples using 2-propylpiperidine-1-carbodithioate with flame atomic absorption spectrometry (FAAS)

This article has been retracted at the request of the Editors-in-Chief. Please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy). REASON: Considerable concern was raised about the research purportedly conducted at Sri Venkateswara University, India with the alleged involvement of Professor P. Chiranjeevi. Questions were raised as to the volume of publications, the actual capacity (equipment, orientation and chemicals) of the laboratory in which Professor Chiranjeevi worked, the validity of certain of the research data identified in the articles, the fact that a number of papers appear to have been plagiarized from other previously published papers, and some aspects of authorship. Professor Chiranjeevi was given the opportunity to respond to these allegations. Thereafter, a committee was constituted by the University to look into these allegations. Based on the enquiry committee report, we have been informed by the head of the Department of Chemistry at Sri Venkateswara University that the university authorities have taken disciplinary action against Professor Chiranjeevi, as the university considers that there are grounds for such action. Therefore, based on the results of this investigation, the Editors-in-Chief are retracting this article.     

Graphical designs and gale duality

Mathematical Programming - A graphical design is a subset of graph vertices such that the weighted averages of certain graph eigenvectors over the design agree with their global averages. We use...