Search results for "square"
showing 10 items of 1317 documents
Coordinative versatility of the carbonic anhydrase inhibitor benzolamide in zinc and copper model compounds
1999
New benzolamide (H 2 bz, 5-phenylsulfonamide-1,3,4-thiadiazole-2-sulfonamide) zinc(II) and copper(II) complexes with tris(2-benzimidazolyl-methylamine) (L) and ammonia are reported. The crystal structures of the Zn(II) complexes were determined. The [Zn(Hbz)L]ClO 4 · H 2 O compound crystallizes in the triclinic space group with a =11.006(1), b =14.777(2), c =14.918(2) A, α =114.30(1), β =98.90(1), γ =107.36(1)° and Z =2. In this compound the Zn(II) has a distorted trigonal bipyramidal geometry. The {[Zn 2 (bz) 2 (NH 3 ) 4 ] · 2H 2 O} ∞ crystallizes in the monoclinic space group C 2/ c with a =23.530(3), b =10.4124(11), c =15.428(2) A, β =110.591(9)° and Z =4. The metal centre is in a distor…
Countercomplementarity and Strong Ferromagnetic Coupling in a Linear Mixed μ-Acetato, μ-Hydroxo Trinuclear Copper(II) Complex. Synthesis, Structure, …
2001
The structural and magnetic data of the trinuclear compound [Cu3(L)2(CH3COO)2(OH)2(dmf)2] (HL = N-(2-methylpyridyl)toluensulfonylamide) are reported. The compound crystallizes in the monoclinic system, space group P2(1)/n (no. 14), with a = 11.6482(6) A, b = 13.5772(6) A, c = 13.5306(7) A, alpha = 90 degrees, beta = 92.859(5) degrees, gamma = 90 degrees, and Z = 2. The three copper atoms form an exact linear arrangement. Neighboring coppers are connected by a hydroxo bridge and a bidentate syn-syn carboxylato group. The coordination spheres of the terminal copper atoms are square pyramidal with a dmf molecule as the apical ligand. The central copper has a regular square planar geometry. The…
Crystal structures and magnetic properties of the squarate-O1,On-bridged dinuclear copper(II) complexes [Cu2(phen)4(C4O4)](CF3SO3)2 · 3H2O (n=2) and …
1999
Abstract Two dinuclear copper(II) complexes of the formula [Cu2(phen)4(C4O4)](CF3SO3)2 · 3H2O (1) and [Cu2(bipy)4(C4O4)](CF3SO3)2 · 6H2O (2) [phen=1,10-phenanthroline, bipy=2,2′-bipyridine and C4O4 2−=dianion of 3,4-dihydroxy-3-cyclobuten-1,2-dione (squaric acid)] have been synthesized and characterized by single-crystal X-ray diffraction. Their structures consist of [Cu2(phen)4(C4O4)]2+ (1) and [Cu2(bipy)4(C4O4)]2+ (2) dinuclear copper(II) cations, uncoordinated CF3SO3 − anions and crystallization water molecules. The copper is in a distorted square pyramidal environment: one squarate-oxygen atom and three phen- (1) or bipy- (2) nitrogen atoms of two phen (1) or bipy (2) terminal ligands f…
Preparation and structural studies on the tBu2Sn(IV) complexes with aromatic mono- and dicarboxylic acids containing hetero {N} donor atom
2004
Nine complexes of 'Bu2Sn(IV)(2+) were obtained in the solid state with ligands containing -COOH group(s) and aromatic (N) donor atom. The binding sites of the ligands were identified by FT-IR spectroscopic measurements. It was found that in most cases the -COO- groups are co-ordinated in monodentate manner. Nevertheless, in some of our complexes, the -COO- group forms bridges between two central {Sn} atoms resulting in the formation of an oligomeric structure, a motif that is characteristic only to the nicotinate compound. These pieces of information and the rationalisation of the experimental Sn-119 Mossbauer nuclear quadrupole splittings, Delta, - according to the point charge model forma…
Square wave voltammetric determination of the redox state of a reversibly oxidized/reduced depolarizer in solution and in solid state
2012
Abstract Square wave voltammetric measurements allows for determining the composition of system containing a reversibly reducible/oxidable electroactive species in two oxidation states. The method is based on recording the ratio of reverse to forward peak currents. That ratio can be correlated with the molar fraction of the oxidized (or reduced) form of the depolarizer. The method was compared with cyclic voltammetric methods suggested in literature and it was tested using Fe ( CN ) 6 3 - / Fe ( CN ) 6 4 - in solution phase. Application to solid state systems is illustrated by the dehydroindigo/indigo couple in synthetic Maya Blue-type specimens prepared from indigo plus different clays whe…
Comparative study of reflectance cells for PLS-FTIR determination of sugars in soft drinks
1998
A comparative study has been carried out between a horizontal Attenuated Total Reflectance (h-ATR) cell and a Cylindrical Internal Reflection (CIR) cell (CIRCLE cell). Both cells were employed for the determination of glucose, fructose, sucrose and total sugar in soft drinks and fruit juices using absorbance measurements at two resolution values (4 and 8 cm–1). Data were processed by Partial Least Squares regression (PLS). Using a resolution of 4 cm–1, mean relative errors of prediction from 0.6% to 1.3% were obtained using the horizontal-ATR and from 0.6% to 2.8% using the CIRCLE cell resulting in a limit of detection from 0.03% in the case of sucrose to 0.21% for total sugar for the h-ATR…
Analyser of chromium and/or cobalt
2003
Abstract Two stopped-flow manifolds have been proposed for individual or simultaneous determination of chromium and cobalt in water samples. Automated procedures based on multicommutation systems have emphasised the differences of their catalytic effect in luminol–hydrogen peroxide chemiluminescence reaction. A more rapid decay of signal was observed for Co for both configurations (flow injection or continuous injection). The influence of chemical and hydrodynamic variables has been studied in order to establish the robustness of method. The analysis rate was lower 1.5 min per replicate. Chemometric tools have been employed for the resolution of their contributions. Partial least squares (P…
Selection of calibration set samples in determination of olive oil acidity by partial least squares–attenuated total reflectance–Fourier transform in…
2003
Abstract A chemometric method has been applied for the determination of the free fatty acid (FFA) concentration in commercial olive oil samples of different types an origins by using Fourier transform infrared spectroscopy (FTIR) attenuated total reflectance (ATR) measurements. Different methods for selecting the training set, including hierarchical cluster analysis, were applied and compared. The prediction capabilities of partial least squares (PLS) multivariate calibration methods, net analyte signal (NAS) preprocessing followed by PLS or classical least squares (CLS) regression method of ATR–FTIR data were evaluated. Several aspects, like spectral range to be considered, different prepr…
Determination of edible oil parameters by near infrared spectrometry
2006
Abstract A chemometric method has been developed for the determination of acidity and peroxide index in edible oils of different types and origins by using near infrared spectroscopy (NIR) measurements. Different methods for selecting the calibration set, after an hierarchical cluster analysis, were applied. After discrimination of olive oils from maize, seed and sunflower, the prediction capabilities of partial least squares (PLS) multivariate calibration of NIR data were evaluated. Several preprocessing alternatives (first derivative, multiplicative scatter correction, vector normalization, constant offset elimination, mean centering and standard normal variate) were investigated by using…
Ligand effects on the structures and magnetic properties of tricyanomethanide-containing copper(II) complexes.
2007
The preparation, crystal structure and magnetic properties of four heteroleptic copper(II) complexes with the tricyanomethanide (tcm(-)) and the heterocyclic nitrogen donors 3,6-bis(2-pyridyl)pyridazine (dppn), 2,5-bis(2-pyridyl)pyrazine (2,5-dpp), 2,3-bis(2-pyridyl)pyrazine (2,3-dpp) and 2,3-bis(2-pyridyl)quinoxaline (2,3-dpq) are reported, {[Cu(2)(dppn)(OH)(tcm)(2)] x tcm}(n) (1), {[Cu(2,5-dpp)(tcm)] x tcm}(n) (2), {[Cu(2)(2,3-dpp)(2)(tcm)(3)(H(2)O)(0.5)] x tcm x 0.5H(2)O}(n) (3) and [Cu(2,3-dpq)(tcm)(2)](n) (4). 1 has a ladder-like structure with single mu-1,5-tcm ligands forming the sides and a bis-bidentate dppn and a single mu-hydroxo providing the rung. Each copper atom in 1 exhibits…