trans-Diaqua­bis­[2,5-bis­(pyridin-2-yl)-1,3,4-thia­diazole]cobalt(II) bis­(tetra­fluoridoborate)

The bidentate 1,3,4-thia­diazole ligand substituted by two 2-pyridyl rings (denoted L) has been found to produce the new monomeric title complex, [Co(C12H8N4S)2(H2O)2](BF4)2. The thia­diazole and pyridyl rings surrounding the Co atom are almost coplanar [dihedral angle = 4.35 (7)°]. The mean plane defined by these heterocyclic moieties makes a dihedral angle of 18.72 (6)° with the non-coordinated pyridyl ring. The Co2+ cation, located at a crystallographic center of symmetry, is bonded to two ligands and two water mol­ecules in a trans configuration in an octa­hedral environment. The tetra­fluorido­­borate ions can be regarded as free anions in the crystal lattice. Nevertheless, they are involved in an infinite two-dimensional network along the [010] and [101] directions of O—H⋯F hydrogen bonds

Aqua­bis­[2,5-bis­(pyridin-2-yl)-1,3,4-thia­diazole-κ2 N 2,N 3](trifluoro­methane­sulfonato-κO)copper(II) trifluoro­methane­sulfonate

2,5-Bis(pyridin-2-yl)-1,3,4-thia­diazole (denoted L) has been found to act as a bidentate ligand in the monomeric title complex, [Cu(CF3O3S)(C12H8N4S)2(H2O)](CF3O3S). The complex shows a distorted octahedrally coordinated copper(II) cation which is linked to two thia­diazole ligands, one water mol­ecule and one trifluoro­methane­sulfonate anion. The second trifluoro­methane­sulfonate anion does not coordinate the copper(II) cation. Each thia­diazole ligand uses one pyridyl and one thia­diazole N atom for the coordination of copper. The N atom of the second non-coordinating pyridyl substituent is found on the same side of the 1,3,4-thia­diazole ring as the S atom. The trifluoro­methane­sulfonate ions are involved in a three-dimensional network of O—H⋯O hydrogen bonds. C—H⋯N inter­actions also occur

Hexavalent Chromium Uptake from Aqueous Solutions using Raw Biomass of the Invasive Brown Seaweed Sargassum muticum from the Moroccan Shorelines: Kinetics and Isotherms

Raw biomass of the invasive Japanese brown seaweed Sargassum muticum, recently introduced to the Atlantic coast of Morocco, has been applied for the removal of hexavalent chromium Cr(VI) from aqueous solutions. Various parameters such as biomass dose, initial pH, contact time and initial Cr(VI) concentration were studied to reveal their effects on the biosorption process. At optimum values of the above mentioned parameters, total removal of Cr(VI) can be achieved within 10 min at pH 2, adsorbent dose of 0.5 g/100 mL for initial chromium ions concentration of 50 mg/L. Cr(VI) biosorption follows pseudo second-order kinetics. Adsorption isotherms were determined at room temperature and the experimental data were modelled with the Langmuir, Freundlich and Temkin isotherm equations. The isotherm data were found to be well fitted by linear Langmuir equation. The maximum sorption capacity calculated from Langmuir isotherm was estimated to be about 143 mg per gram of dry biosorbent. Thus, the biomass used in this study can be considered a promising and valuable natural adsorbent for the treatment of aqueous solution containing toxic hexavalent chromium ions

The inhibition of mild steel corrosion in acidic solutions by 2,5-bis(4-pyridyl)-1,3,4-thiadiazole: Structure–activity correlation

International audienceThe effect of 2,5-bis(4-pyridyl)-1,3,4-thiadiazole (4-PTH) on the corrosion of mild steel in acidic media (1 M HCl, 0.5 M H2SO4, 1 M HClO4) has been investigated using weight loss measurements, electrochemical impedance spectroscopy and potentiodynamic polarisation. These studies have shown that 2,5-bis(4-pyridyl)-1,3,4-thiadiazole is good inhibitor for mild steel in 1 M HCl, 0.5 M H2SO4 and 1 M HClO4 solutions, the better performances are seen in the case of 1 M HCl solutions. But in 1 M HClO4, the 4-PTH stimulates corrosion at low concentrations. Polarisation curves indicate that the 4-PTH is a mixed-type inhibitor in all acidic media and E (%) is temperature-dependent. Adsorption on the mild steel surface follows the Langmuir isotherm model in all acidic media. The electronic properties obtained using the Hartree–Fock AB initio 3-21G quantum chemical approach, were correlated with the experimental efficiencies

Experimental and theoretical study for corrosion inhibition of mild steel in normal hydrochloric acid solution by some new macrocyclic polyether compounds

International audienceNew macrocyclic polyether compounds containing a 1,3,4-thiadiazole moiety have been prepared to study the corrosion inhibitive effect of mild steel in normal hydrochloric acid solutions. The salient features obtained from weight loss and electrochemical impedance spectroscopy (EIS) have been discussed. The results of these investigations have shown enhancement in inhibition efficiencies with the extent of the polyethylene glycol unit that forms a cavity. Data obtained from EIS show a frequency distribution and therefore a modelling element with frequency dispersion behaviour, a constant phase element (CPE) has been used

2-Amino-1-(4-aminophenyl)-1H-pyrrolo(2,3-b)quinoxaline-3- carbonitrile as an efficient inhibitor for the corrosion of C38 steel in hydrochloric acid solution

International audienceThe inhibiting properties of 2-Amino-1-(4-aminophenyl)-1H-pyrrolo(2,3-b)quinoxaline-3-carbonitrile (AHPQC) were examined of C38 steel corrosion in molar hydrochloric acid using electrochemical techniques. Impedance data displayed the AHPQC inhibits C38 steel corrosion becoming the adsorbate at metal/electrolyte interfaces. Polarization study indicated that AHPQC is an anodic-cathodic inhibitor. The inhibition efficiencies of AHPQC calculated by both methods reaches 91%. The Langmuir adsorption isotherm was observed for the AHPQC adsorption and its adsorption is realized by physical adsorption; due to the protonated forms of the AHPQC molecule in acid medium. XPS technique was used to discuss the mechanism for the adsorption process of the AHPQC molecule

Study of Temperature Effect on the Corrosion Inhibition of C38 Carbon Steel Using Amino-tris(Methylenephosphonic) Acid in Hydrochloric Acid Solution

Tafel polarization method was used to assess the corrosion inhibitive and adsorption behaviours of amino-tris(methylenephosphonic) acid (ATMP) for C38 carbon steel in 1 M HCl solution in the temperature range from 30 to 60∘C. It was shown that the corrosion inhibition efficiency was found to increase with increase in ATMP concentration but decreased with temperature, which is suggestive of physical adsorption mechanism. The adsorption of the ATMP onto the C38 steel surface was found to follow Langmuir adsorption isotherm model. The corrosion inhibition mechanism was further corroborated by the values of kinetic and thermodynamic parameters obtained from the experimental data

Crystal structure of bis[2,5-bis(pyridin-2-yl)-1,3,4-thiadiazole-κ2N2,N3]bis(thiocyanato-κS)copper(II)

The mononuclear title complex, [Cu(SCN)2(C12H8N4S)2], was obtained by the reaction of 2,5-bis(pyridin-2-yl)-1,3,4-thiadiazole and potassium thiocyanate with copper(II) chloride dihydrate. The copper cation lies on an inversion centre and displays an elongated octahedral coordination geometry. The equatorial positions are occupied by the N atoms of two 2,5-bis(pyridin-2-yl)-1,3,4-thiadiazole ligands, whereas the axial positions are occupied by the S atoms of two thiocyanate anions. The thiadiazole and the pyridyl rings linked to the metal are approximately coplanar, with a maximum deviation from the mean plane of 0.190 (2) Å. The cohesion of the crystal structure is ensured by weak C—H...N hydrogen bonds and π–π interactions between parallel pyridyl rings of neighbouring molecules [centroid-to-centroid distance = 3.663 (2) Å], leading to a three-dimensional network

Crystal structure of bis(azido-κN)bis[2,5-bis(pyridin-2-yl)-1,3,4-thiadiazole-κ2N2,N3]nickel(II)

Reaction of 2,5-bis(pyridin-2-yl)-1,3,4-thiadiazole and sodium azide with nickel(II) triflate yielded the mononuclear title complex, [Ni(N3)2(C12H8N4S)2]. The NiII ion is located on a centre of symmetry and is octahedrally coordinated by four N atoms of the two bidentate heterocyclic ligands in the equatorial plane. The axial positions are occupied by the N atoms of two almost linear azide ions [N—N—N = 178.8 (2)°]. The thiadiazole and pyridine rings of the heterocyclic ligand are almost coplanar, with a maximum deviation from the mean plane of 0.0802 (9) Å. The cohesion of the crystal structure is ensured by π–π interactions between parallel pyridine rings of neighbouring molecules [centroid-to-centroid distance = 3.6413 (14) Å], leading to a layered arrangement of the molecules parallel to (001)