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1.
Mar Drugs ; 19(12)2021 Nov 26.
Article in English | MEDLINE | ID: mdl-34940671

ABSTRACT

Agar is a sulfated polysaccharide extracted from certain marine red algae, and its gel properties depend on the seaweed source and extraction conditions. In the present study, the seaweed Gracilaria gracilis (Gracilariales, Rhodophyta) from Dakhla (Moroccan Atlantic Coast) was investigated for its agar content, structure, and gel properties. The agar yields of G. gracilis were 20.5% and 15.6% from alkaline pretreatment and native extraction, respectively. Agar with alkaline pretreatment showed a better gelling property supported by higher gel strength (377 g·cm-2), gelling (35.4 °C), and melting (82.1 °C) temperatures with a notable increase in 3,6-anhydro-galactose (11.85%) and decrease in sulphate (0.32%) contents. The sulfate falling subsequent to alkaline pretreatment was verified through FT-IR spectroscopy. The 13C NMR spectroscopy showed that alkaline-pretreated agar has a typical unsubstituted agar pattern. However, native agar had a partially methylated agarose structure. Overall, this study suggested the possibility of the exploitation of G. gracilis to produce a fine-quality agar. Yet, further investigation may need to determine the seasonal variability of this biopolymer according to the life cycle of G. gracilis.


Subject(s)
Agar/chemistry , Gracilaria , Animals , Aquatic Organisms , Atlantic Ocean , Morocco
2.
Molecules ; 25(18)2020 Sep 22.
Article in English | MEDLINE | ID: mdl-32971782

ABSTRACT

Alginates are widely used as gelling agents in textile print pastes, medical industries, impression material in dentistry, and anticoagulant material in toothpaste. In the present study, the content and spectroscopic characterization (1H NMR and FT-IR) of the sodium alginates were investigated in the eight brown seaweeds Sargassum muticum, Fucus vesiculosus f. volubilis, Carpodesmia tamariscifolia, Bifurcaria bifurcata, Laminaria ochroleuca, Cystoseira humilis, Saccorhiza polyschides, and Fucus guiryi harvested from the NW Atlantic coast of Morocco. The results proved that the most studied algae depicted alginate yields higher than 18% dry weight. The FT-IR analysis showed that the spectra of the extracted alginates exhibited significant similarities to the commercial alginate from Sigma-Aldrich. The 1H NMR spectroscopy indicated that the extracted alginates have a high content of ß-d-mannuronic (M) than α-l-guluronic acid (G) with M/G ratio values ranging from 1.04 to 4.41. The homopolymeric fractions FMM are remarkably high compared to the FGG and heteropolymeric fractions (FGM = FMG) especially for F. guiryi, C humilis, C. tamariscifolia, L. ochroleuca, and S. polyschides. Nevertheless, the heteropolymeric fractions (FGM/FMG) are quite abundant in the alginates of S. muticum, F. vesiculosus f. volubilis, and B. bifurcata accounting for more than 52% of the polymer diads. Based on these results, the investigated algal species (except Fucus guiryi and Bifurcaria bifurcata) could be regarded as potential sources of alginates for industrial uses.


Subject(s)
Alginates/chemistry , Alginates/isolation & purification , Magnetic Resonance Spectroscopy , Seaweed/chemistry , Spectroscopy, Fourier Transform Infrared , Atlantic Ocean , Morocco
3.
Waste Manag Res ; 37(6): 578-589, 2019 Jun.
Article in English | MEDLINE | ID: mdl-30565506

ABSTRACT

Municipal solid waste (MSW) management presents an important challenge for all countries. In order to exploit them as a source of energy, a knowledge of their calorific value is essential. In fact, it can be experimentally measured by an oxygen bomb calorimeter. This process is, however, expensive. In this light, the purpose of this paper was to develop empirical models for the prediction of MSW higher heating value (HHV) from ultimate analysis. Two methods were used: multiple regression analysis and genetic programming formalism. Both techniques gave good results. Genetic programming, however, provides more accuracy compared to published works in terms of a great correlation coefficient (CC) and a low root mean square error (RMSE).


Subject(s)
Refuse Disposal , Waste Management , Heating , Regression Analysis , Solid Waste
4.
Pestic Biochem Physiol ; 143: 26-32, 2017 Nov.
Article in English | MEDLINE | ID: mdl-29183602

ABSTRACT

The metallic complexes µ-chloro-µ-[2,5-bis (2-pyridyl)-1,3,4-thiadiazole] aqua chlorocopper (II) dichlorocopper (II) (abbreviated 2PTH-Cu2-Cl4); aquabis [2,5-bis (2-pyridyl)-1,3,4-thiadiazole-κ2N2,N3] (trifluoromethane-sulfonato-κO) copper(II) trifluoro metrhanesulfonate (2PTH-Cu-tF) and bis[(2,5-bis(pyridine-2-yl)-1,3,4-thiadiazole-di-azido copper(II)] (2PTH-Cu-Az) were compared for their antimicrobial activities in vitro, and their aptitude to control Verticillium wilt and crown gall diseases development of tomato in the greenhouse. Results showed that the complex 2PTH-Cu-Az inhibited drastically the growth of V. dahliae in vitro. 2PTH-Cu2-Cl4 and 2PTH-Cu-tF did not display any noticeable antimicrobial activity in vitro against all of the pathogens tested. However, in planta evaluation revealed that the three complexes protected tomato against crown gall similarly. They also reduced Verticillium wilt disease severity, although the complex 2PTH-Cu-Az was the most efficient. When compared to other complexes, 2PTH-Cu-Az triggered only a weak oxidative burst as revealed by H2O2 measurement and the activity of ascorbate peroxidase and catalase. These results suggest that the superiority of 2PTH-Cu-Az against V. dahliae rely on its direct antifungal activity and its ability to modulate H2O2 accumulation.


Subject(s)
Antifungal Agents/toxicity , Copper/toxicity , Plant Diseases/prevention & control , Pseudomonas syringae/drug effects , Solanum lycopersicum/microbiology , Thiadiazoles/toxicity , Verticillium/drug effects , Agrobacterium tumefaciens/drug effects , Agrobacterium tumefaciens/growth & development , Ascorbate Peroxidases/metabolism , Catalase/metabolism , Erwinia amylovora/drug effects , Erwinia amylovora/growth & development , Hydrogen Peroxide/metabolism , Solanum lycopersicum/metabolism , Pseudomonas syringae/growth & development , Verticillium/growth & development
5.
Article in English | MEDLINE | ID: mdl-38907820

ABSTRACT

The present study focuses on an environmental approach based on the use of an eco-friendly corrosion inhibitor from the Citrullus colocynthis fruit extract for enhancement corrosion resistance of carbon steel (C-S) in acid medium as an alternative to various organic and non-organic chemical inhibitors. The evaluation of the inhibition properties of the fruit methanolic extract of Citrullus colocynthis (CCE) were performed in molar hydrochloric acid (1 M HCl) medium using gravimetric and electrochemical (potentiodynamic polarization and AC impedance) techniques as well as surface analyses. CCE is rich in amino acids, mainly citrulline and ß-(pyrazo-1-yl)-L-analine molecules. Based on the weight loss evaluation, the results demonstrated that this plant extract acts as an effective corrosion inhibitor and a protection level of 93.6% was attained at 500 ppm of CCE after 6 h of metal exposure at 303 K. According to polarization curves, CCE functions as a mixed-type inhibitor. In addition, AC impedance analyses have shown that the incorporation of CCE into the corrosive solution leads to a decrease in load capacity, while improving the charge/discharge function at the interface. This suggests the possibility of the formation of an adsorbed layer on the C-S surface. In addition, scanning electron microscope (SEM) observation, contact angle measurements, and Fourier-transform infrared spectroscopy (FTIR) analyses supported the development of a protective film over CS substrate surface afterwards addition of CCE. Langmuir and/or Temkin isotherms can be used to characterize the adsorption of this organic inhibitor on the C-S surface. X-ray photoelectron spectroscopy (XPS) has revealed that the inhibiting effect of CCE on the corrosion of C-S in 1 M HCl solution is mainly controlled by a chemisorption process and the inhibitive layer is composed of an iron oxide/hydroxide mixture where CCE molecules are incorporated. In order to understand the relationship between the molecular structure and anti-corrosion effectiveness of these inhibitor molecules, quantum chemical studies were carried out using density functional theory (DFT) and molecular dynamics (MD) simulation.

6.
ACS Omega ; 9(12): 13746-13763, 2024 Mar 26.
Article in English | MEDLINE | ID: mdl-38560005

ABSTRACT

The study aims to synthesize two green pyrazole compounds, N-((1H-pyrazol-1-yl)methyl)-4-nitroaniline (L4) and ethyl 5-methyl-1-(((4-nitrophenyl)amino)methyl)-1H-pyrazole-3-carboxylate (L6), and test their action as corrosion inhibitors for carbon steel (CS) in a 1 M HCl solution. Both chemical and electrochemical methods, namely, gravimetric measurements (WL), potentiodynamic polarization (PDP), and electrochemical impedance spectroscopy (EIS), were used to assess the efficiency of the investigated molecules. DFT calculations at B3LYP/6-31++G (d, p) and molecular dynamics simulation were used to carry out quantum chemical calculations in order to link their electronic characteristics with the findings of experiments. The organic products exhibited good anticorrosion ability, with maximum inhibition efficiencies (IE %) of 91.8 and 90.8% for 10-3 M L6 and L4, respectively. In accordance with PDP outcomes, L6 and L4 inhibitors act as mixed-type inhibitors. Assessment of the temperature influence evinces that both L4 and L6 are chemisorbed on CS. The adsorption of L4 and L6 on CS appears to follow the Langmuir isotherm. Scanning electron microscopy and UV-visible disclose the constitution of a barrier layer, limiting the accessibility of corrosive species to the CS surface. Theoretical studies were performed to support the results derived from experimental techniques (WL, PDP, and EIS).

7.
Acta Crystallogr Sect E Struct Rep Online ; 69(Pt 6): m351-2, 2013 Jun 01.
Article in English | MEDLINE | ID: mdl-23795009

ABSTRACT

The self-assembly of an angular 2,5-bis-(pyridin-2-yl)-1,3,4-thia-diazole ligand (L) with silver nitrate (AgNO3) produced a new dinuclear silver(I) coordination complex, [Ag2(C12H8N4S)2(NO3)2]·4H2O, which crystallizes with two Ag atoms bridged by two L ligands. The Ag atom is surrounded by four N atoms of L and by one O from the nitrate anion defining a distorted square pyramid. The atoms comprising the dication are nearly coplanar, with an r.m.s. deviation of 0.1997 Å. Mol-ecules are linked by C-H⋯O and O-H⋯O hydrogen bonds through nitrate anions and water mol-ecules, forming a two-dimensional porous network. The overall structure involves stacking of Ag complex layers along the b axis. The cohesion in the three-dimensional architecture is ensured by O⋯Ag inter-actions.

8.
Acta Crystallogr Sect E Struct Rep Online ; 68(Pt 4): m360-1, 2012 Apr 01.
Article in English | MEDLINE | ID: mdl-22589758

ABSTRACT

2,5-Bis(pyridin-2-yl)-1,3,4-thia-diazole (denoted L) has been found to act as a bidentate ligand in the monomeric title complex, [Cu(CF(3)O(3)S)(C(12)H(8)N(4)S)(2)(H(2)O)](CF(3)O(3)S). The complex shows a distorted octahedrally coordinated copper(II) cation which is linked to two thia-diazole ligands, one water mol-ecule and one trifluoro-methane-sulfonate anion. The second trifluoro-methane-sulfonate anion does not coordinate the copper(II) cation. Each thia-diazole ligand uses one pyridyl and one thia-diazole 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-thia-diazole ring as the S atom. The trifluoro-methane-sulfonate ions are involved in a three-dimensional network of O-H⋯O hydrogen bonds. C-H⋯N inter-actions also occur.

9.
Gels ; 8(11)2022 Nov 04.
Article in English | MEDLINE | ID: mdl-36354622

ABSTRACT

The naturally occurring sodium alginate (SA) biopolymer from the Sargassum muticum (Yendo) Fensholt was employed as a green organocatalyst for the synthesis of 4H-pyran derivatives. The naturally extracted macromolecule was fully characterized using different analyses, including nuclear magnetic resonance (NMR), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and Energy Dispersive X-ray Analysis (EDX). The catalytic activity of SA was investigated in the one-pot reaction between aldehydes, malononitrile, and 1,3-dicarbonyl compounds in water at room temperature, and the corresponding 2-amino-3-cyano-4H-pyran derivatives were obtained with good to excellent yields. This organocatalyst was easily separated from the reaction mixture and reused for at least two consecutive cycles without a significant loss of its catalytic activity or selectivity. From the mechanistic point of view, density functional theory (DFT) and NCI analyses were performed for the first time to explain the regioselectivity outcomes for the synthesis of 2-amino-3-cyano-4H-pyran derivatives using SA as a green organocatalyst.

10.
Acta Crystallogr Sect E Struct Rep Online ; 67(Pt 7): m834-5, 2011 Jul 01.
Article in English | MEDLINE | ID: mdl-21836842

ABSTRACT

The bidentate 1,3,4-thia-diazole ligand substituted by two 2-pyridyl rings (denoted L) has been found to produce the new monomeric title complex, [Co(C(12)H(8)N(4)S)(2)(H(2)O)(2)](BF(4))(2). The thia-diazole 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 Co(2+) cation, located at a crystallographic center of symmetry, is bonded to two ligands and two water mol-ecules in a trans configuration in an octa-hedral environment. The tetra-fluorido--borate 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.

11.
Acta Crystallogr Sect E Struct Rep Online ; 67(Pt 8): m1052-3, 2011 Aug 01.
Article in English | MEDLINE | ID: mdl-22090840

ABSTRACT

The bidentate 1,3,4-thia-diazole ligand, namely, 2,5-bis-(2-pyrid-yl)-1,3,4-thia-diazole (denoted L), untested as a polydentate ligand, has been found to form the monomeric title complex, [Ni(C(12)H(8)N(4)S)(2)(H(2)O)(2)](BF(4))(2). The complex shows an octa-hedral environment of the nickel cation in which the Ni(2+) ion is located on a center of symmetry, linked to two ligands and two water molecules. In this 1:2 complex (one metal for two organic ligands) each thia-diazole ligand uses one pyridyl and one thia-diazole N atom for chelate binding. In the second pyridyl substituent, the N atom is oriented towards the same direction as the S atom of the 1,3,4-thiadiazole ring. The mean plane of the thia-diazole and pyridyl rings linked to the nickel cation forms a dihedral angle with the other pyridine ring of 18.63 (8)°. The tetra-fluorido-borate ions can be regarded as free anions in the crystal lattice. Nevertheless, they are involved in an infinite two-dimensional network parallel to ([Formula: see text]01) through O-H⋯F hydrogen bonds.

12.
Acta Crystallogr E Crystallogr Commun ; 75(Pt 7): 1046-1050, 2019 Jul 01.
Article in English | MEDLINE | ID: mdl-31392022

ABSTRACT

The reaction of 2,5-bis-(pyridin-4-yl)-1,3,4-oxa-diazole (4-pox) and thio-cyanate ions, used as co-ligand with nickel salt NiCl2·6H2O, produced the title complex, [Ni(NCS)2(C12H8N4O)2(H2O)2]. The NiII atom is located on an inversion centre and is octa-hedrally coordinated by four N atoms from two ligands and two pseudohalide ions, forming the equatorial plane. The axial positions are occupied by two O atoms of coordinated water mol-ecules. In the crystal, the mol-ecules are linked into a three-dimensional network through strong O-H⋯N hydrogen bonds. Hirshfeld surface analysis was used to investigate the inter-molecular inter-actions in the crystal packing.

13.
Waste Manag ; 97: 10-18, 2019 Sep.
Article in English | MEDLINE | ID: mdl-31447016

ABSTRACT

Investigation of thermal behaviors of biomass waste, biochar, coal, municipal solid waste (MSW) and their mixtures were aimed in the present study using both thermogravimetric analysis and differential scanning calorimeter techniques. In fact, this paper intends to interpret the influence of mixtures on activation energy. In this purpose, Coats and Redfern were used. Then, the relative error Δmerror was calculated to quantify the synergism degree. Precisely, it was about 5.34% for biomass/coal, 5.52% for biomass/cardboard, 5.67% for biomass/biochar, 5.93% for biomass/synthetic rubber and 6.05% for biomass/plastic mixtures. This phenomenon was justified by the interaction between C-C bond of biochar, coal and MSW radicals with C-H and C-O bonds of biomass.


Subject(s)
Coal , Solid Waste , Biomass , Kinetics , Thermogravimetry
14.
Pest Manag Sci ; 73(1): 188-197, 2017 Jan.
Article in English | MEDLINE | ID: mdl-27040738

ABSTRACT

BACKGROUND: The antifungal properties of the nickel(II) complex bis(azido-κN)bis[2,5-bis(pyridin-2-yl)-1,3,4-thiadiazole-κ2 N2 ,N3 ]nickel(II) [NiL2 (N3 )2 ] and its parental ligand 2,5-bis(pyridin-2-yl)-1,3,4-thiadiazole were examined to evaluate their ability to protect tomato plants against Verticillium dahliae. Our main objectives were to determine their effects on the in vitro growth of the pathogen, and their aptitude for controlling verticillium wilt and activating plant defence responses in the greenhouse. RESULTS: NiL2 (N3 )2 exhibited in vitro an elevated inhibition of radial growth of three strains of the pathogen. According to the strain, the EC50 values ranged from 10 to 29 µg mL-1 for NiL2 (N3 )2 . In the greenhouse, it induced an elevated protection against V. dahliae when it was applied twice as foliar sprays at 50 µg mL-1 . It reduced the leaf alteration index by 85% and vessel browning by 96%. In addition, its protective ability was associated with the accumulation of H2 O2 and the activation of total phenolic content, as well as potentiation of the activity of peroxidase and polyphenol oxidase. CONCLUSION: These results demonstrated that the coordination of the ligand with Ni associated with the azide as a coligand resulted in an improvement in its biological activity by both inhibiting the growth of V. dahliae and activating plant defence responses. © 2016 Society of Chemical Industry.


Subject(s)
Antifungal Agents/pharmacology , Nickel/pharmacology , Plant Diseases/prevention & control , Solanum lycopersicum/microbiology , Thiadiazoles/pharmacology , Verticillium/drug effects , Antifungal Agents/chemistry , Microbial Sensitivity Tests , Plant Diseases/microbiology , Verticillium/growth & development
15.
Waste Manag ; 61: 78-86, 2017 Mar.
Article in English | MEDLINE | ID: mdl-27884618

ABSTRACT

The heating value describes the energy content of any fuel. In this study, this parameter was evaluated for different abundant materials in Morocco (two types of biochar, plastic, synthetic rubber, and cardboard as municipal solid waste (MSW), and various types of biomass). Before the evaluation of their higher heating value (HHV) by a calorimeter device, the thermal behavior of these materials was investigated using thermogravimetric (TGA) and Differential scanning calorimetry (DSC) analyses. The focus of this work is to evaluate the calorific value of each material alone in a first time, then to compare the experimental and theoretical HHV of their mixtures in a second time. The heating value of lignocellulosic materials was between 12.16 and 20.53MJ/kg, 27.39 for biochar 1, 32.60MJ/kg for biochar 2, 37.81 and 38.00MJ/kg for plastic and synthetic rubber respectively and 13.81MJ/kg for cardboard. A significant difference was observed between the measured and estimated HHVs of mixtures. Experimentally, results for a large variety of mixture between biomass/biochar and biomass/MSW have shown that the interaction between biomass and other compounds expressed a synergy of 2.37% for biochar 1 and 6.11% for biochar 2, 1.09% for cardboard, 5.09% for plastic and 5.01% for synthetic rubber.


Subject(s)
Biomass , Charcoal , Solid Waste , Biofuels , Calorimetry, Differential Scanning , Charcoal/chemistry , Lignin , Plastics , Refuse Disposal/methods , Solid Waste/analysis , Thermogravimetry
16.
Acta Crystallogr E Crystallogr Commun ; 72(Pt 8): 1176-8, 2016 Aug 01.
Article in English | MEDLINE | ID: mdl-27536407

ABSTRACT

The mononuclear title complex, [Cu(SCN)2(C12H8N4S)2], was obtained by the reaction of 2,5-bis-(pyridin-2-yl)-1,3,4-thia-diazole and potassium thio-cyanate with copper(II) chloride dihydrate. The copper cation lies on an inversion centre and displays an elongated octa-hedral coordination geometry. The equatorial positions are occupied by the N atoms of two 2,5-bis-(pyridin-2-yl)-1,3,4-thia-diazole ligands, whereas the axial positions are occupied by the S atoms of two thio-cyanate anions. The thia-diazole 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 inter-actions between parallel pyridyl rings of neighbouring mol-ecules [centroid-to-centroid distance = 3.663 (2) Å], leading to a three-dimensional network.

17.
J Agric Food Chem ; 64(13): 2661-7, 2016 Apr 06.
Article in English | MEDLINE | ID: mdl-26991972

ABSTRACT

Verticillium wilt caused by Verticillium dahliae is a major limiting factor for tomato production. The objective of this study was to evaluate the effectiveness of ligand 2,5-bis(pyridin-2-yl)-1,3,4-thiadiazole (L) and its complex bis[µ-2,5-bis(pyridin-2-yl)-1,3,4-thiadiazole-κ(4)N(2),N(3):N(4),N(5)]bis[dihydrato-κO)nickel(II)] as activators of plant defenses in controlling Verticillium wilt. In the greenhouse, they protected tomato plants against V. dahliae when they were applied twice as foliar sprays at 100 µg mL(-1). A synergistic effect was observed between the ligand L and the transition metal Ni, with disease incidence reduced by 38% with L and 57% with Ni2L2. Verticillium wilt foliar symptoms and vascular browning index were reduced by 82% for L and 95% for Ni2L2. This protection ability was associated with the induction of an oxidative burst and the activation of the total phenolic content as well as potentiation of the activity of peroxidase and polyphenol oxidase. These results demonstrated that L and Ni2L2 can be considered as new activators of plant defense responses.


Subject(s)
Nickel/pharmacology , Pyridines/pharmacology , Solanum lycopersicum/metabolism , Thiadiazoles/pharmacology , Verticillium/pathogenicity , Arabidopsis/genetics , Disease Resistance , Gene Expression Regulation, Plant , Hypocreales/metabolism , Ligands , Mitosporic Fungi , Plant Diseases , Plant Proteins/metabolism , Plants, Genetically Modified/metabolism , Pyridines/chemistry , Thiadiazoles/chemistry
18.
Acta Crystallogr E Crystallogr Commun ; 71(Pt 2): m24-5, 2015 Feb 01.
Article in English | MEDLINE | ID: mdl-25878837

ABSTRACT

Reaction of 2,5-bis-(pyridin-2-yl)-1,3,4-thia-diazole and sodium azide with nickel(II) triflate yielded the mononuclear title complex, [Ni(N3)2(C12H8N4S)2]. The Ni(II) ion is located on a centre of symmetry and is octa-hedrally 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 thia-diazole 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 inter-actions between parallel pyridine rings of neighbouring mol-ecules [centroid-to-centroid distance = 3.6413 (14) Å], leading to a layered arrangement of the mol-ecules parallel to (001).

19.
Acta Crystallogr E Crystallogr Commun ; 71(Pt 5): 452-4, 2015 May 01.
Article in English | MEDLINE | ID: mdl-25995853

ABSTRACT

In the mononuclear title complex, [Co(N3)2(C12H8N4S)2], the cobalt(II) atom is located on an inversion centre and displays an axially weakly compressed octa-hedral coordination geometry. The equatorial positions are occupied by the N atoms of two 2,5-bis-(pyridin-2-yl)-1,3,4-thia-diazole ligands, whereas the axial positions are occupied by N atoms of the azide anions. The thia-diazole and pyridine rings linked to the metal are almost coplanar, with a maximum deviation from the mean plane of 0.0273 (16) Å. The cohesion of the crystal is ensured by weak C-H⋯N hydrogen bonds and by π-π inter-actions between pyridine rings [inter-centroid distance = 3.6356 (11) Å], forming a layered arrangement parallel to (001). The structure of the title compound is isotypic with that of the analogous nickel(II) complex [Laachir et al. (2013 ▶). Acta Cryst. E69, m351-m352].

20.
Inorg Chem ; 43(6): 1865-73, 2004 Mar 22.
Article in English | MEDLINE | ID: mdl-15018505

ABSTRACT

Mu-chloro-mu-[2,5-bis(2-pyridyl)-1,3,4-thiadiazole] aqua chlorocopper(II) dichlorocopper(II) is the first characterized dimeric complex of a transition metal and this hetero ligand [C(12)H(10)Cl(4)Cu(2)N(4)OS; triclinic; space group P; a = 9.296(3) A, b = 9.933(3) A, c = 10.412(3) A; alpha = 79.054(5) degrees, beta = 82.478(6) degrees, gamma = 67.099(5) degrees; Z = 2 at room temperature]. The Cu(II) ions are bridged by the N-N thiadiazole bond and a chloride ion [Cu1-Cu2 = 3.7800(8) A]. Thermogravimetric analysis shows this structure to be stable at temperatures up to 348 K. At higher temperatures, the successive loss of a water molecule and one chloride of the dimeric unit is identified. From room temperature to 125 K, half of the Cu(2+) ions are progressively engaged in intermolecular dinuclear antiferromagnetic exchanges, while the other half remain paramagnetic. At lower temperatures, both susceptibility and electron paramagnetic resonance measurements show the paramagnetic-only couplings of this half of the Cu(2+) ions, involving a singlet ground state for interacting Cu(2+). This unusual behavior has been satisfactorily explained on the basis of intermolecular Cu-Cu interactions (J = -180 cm(-1)), involving the magnetic d(z)2 orbital perpendicular to the molecular plane, on which are seen the conjugate effects of the bridging chloride and the planar thiadiazole. It is noteworthy that the behavior of the title compound is original, compared to the systematic in-plane intramolecular antiferromagnetic coupling of other thiadiazole-containing binuclear complexes.

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