- Chromium(III) Compounds with Some Organic Ligands
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Abstract: The equilibrium acquisition times in chromium(III)?organic ligand systems were determined under various conditions. Chromium(III) compounds with picolinic acid Cr(C6H4NO2)3 ? H2O, nicotinic acid CrOH(C6H4NO2)2 ? 2H2O, and citric acid CrC6H5O7 ? 3H2O were isolated; their gravimetric and thermogravimetric analyses carried out; and IR spectra measured. The major chromium(III) complex species with the above-listed acid anions in solutions were found to have a (1 : 1) stoichiometry using isomolar series; their stability constants were determined by potentiometric measurements. The electronic absorption spectra of the systems were analyzed. The photometric determination of chromium picolinate in solutions was developed, the solubility constant KS was determined (log KS = –21.52 ± 0.29), quantum-chemical calculations carried out for a gaseous molecule, and energy and geometric parameters calculated.
- Alimova, R. R.,Skorik, N. A.
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- Synthesis, structure, chemical and bioactivity behavior of eight chromium(III) picolinate derivatives Cr(R-pic)3
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The worldwide use of chromium(III) picolinate Cr(pic)3 as nutrition additives has aroused more and more controversies. To reevaluate the?safety and validity of Cr(pic)3, seven new derivatives Cr(R-pic)3 (pic?=?picolinic acid, R?=?H (1), 5-Br (2), 5-CF3 (3), 4-Cl (4), 5-COOH (5), 3-CH3 (6), 5-OH (7), 3-OH (8)) were synthesized and characterized by X-ray crystal diffraction, ESI-MS, IR and elemental analysis. It was found that different substituent group affected physicochemical activities of the complex such as the Fenton-like reaction and oxidation reaction. Especially, –OH group derivatives lose their hydroxyl radical-generation and Cr(VI)-generation abilities comparing with halogen group in tube experiment. Even so, these differences in chemistry properties may be ignored in live cells and animal tests: no obvious cellular?damage (MTT assay) and tissue injury (acute toxicity study) were observed for both Cr(pic)3 and its derivatives. In addition, hypoglycemic activity study indicated that these Cr(III) complexes have no significant influence than CrCl3 salt on the blood glucose, serum insulin, total cholesterol, triglyceride, high density lipoprotein and low density lipoprotein of diabetic mice through two months’ study. Therefore, these substituent group is unable to improve the biological activities of Cr(pic)3 obviously and the validity of Cr(pic)3 used as a nutrition additives is doubted.
- Chai, Jie,Liu, Yanfei,Dong, Jinglong,Liu, Bin,Yang, Binsheng
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supporting information
p. 151 - 159
(2017/06/13)
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- Estimation of the pKa for various Br?nsted acids in polar aprotic media using electrochemical measurements of chromium (III) with picolinic acid
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The electrochemical reduction of Crpic and the effect of various proton-donors in DMF were investigated in this work. Measurements showed important electrochemical changes in the presence of proton-donors such as ascorbic acid, benzoic acid and acetic acid. Dissociation constants and acid strength are estimated using the Nernstian behavior of the chromium (III) complex and the proportional relation between ΔEp vs pKa are assistance to estimate the dissociation constants and the acid strength.
- Rodríguez Cordero, Mildred I.,Piscitelli, Vincent,Borras, Carlos,Martínez, José Daniel,Araujo, Mary Lorena,Silva, Pedro,Lubes, Vito
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p. 401 - 405
(2015/08/06)
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- Mononuclear and binuclear chromium(III) picolinate complexes
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The chromium(III) picolinate complexes [Cr(pic)3] (1) and [Cr(pic)2OH]2 (2) (where pic = 2-carboxypyridine) have been isolated from the reaction of chromium(III) chloride and picolinic acid in aqueous solution. The monomeric complex 1·H2O (CrC18H14N3O7) crystallizes in the monoclinic space group C2/c with a = 30.219 (3) A?, b = 8.529 (1) A?, c = 13.942 (2) A?, β = 95.141 (1)°, V = 3579 (2) A?3, Z = 4, R = 0.032, and Rw = 0.043 for 1815 reflections (I > 3σ(I)). The binuclear complex 2·5H2O (Cr2C24H28N4O15) crystallizes in the monoclinic space group P21/n with a = 12.569 (2) A?, b = 18.839 (3) A?, c = 13.000 (4) A?, β = 105.823 (3)°, V = 2962 (2) A?3, Z = 8, R = 0.046, Rw = 0.067 for 3250 reflections (I > 3σ(I)). The mononuclear complex 1 is the meridional isomer, not the facial isomer as previously assumed. For 2 the bridging geometry is as follows: Cr-Cr = 2.999 (1) A?; Cr-O(bridge) range = 1.934 (3)-1.980 (3) A?; Cr-O-Cr = 99.0 (1), 101.6(1)°; O-Cr-O = 79.4 (1), 79.9 (1)°. Magnetic susceptibility data for 2 were measured from 280 to 6 K and can be fit using an isotropic spin-exchange Hamiltonian, H = -2JS?1·S?2 with a weak antiferromagnetic interaction (J=-8.02(4)cm-1), g = 1.844, and a 2.23 (4) mol% paramagnetic impurity. The extent of magnetic coupling in 2 is compared to predictions made by the Glerup-Hodgson-Pedersen (GHP) equation. Compounds 1 and 2 are discussed in the general context of biologically active chromium.
- Stearns, Diane M.,Armstrong, William H.
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p. 5178 - 5184
(2008/10/08)
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- Kinetics of Substitution of Aquo Ligands from Hexaaquochromium(III) Ion by Picolinic Acid in Water-Ethanol Medium
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The kinetics of substitution of aquo ligands from hexaaquochromium(III) ion by picolinic acid in water-ethanol medium (30percent, v/v) has been studied spectrophotometrically.The following rate law has been established in the pH range 3.72 to 4.98, where KE is the ion pair equilibrium constant and k, the rate constant for conversion of outer sphere complex to inner sphere complex.The reaction rate is found to be pH dependent in the pH range 3.72 to 4.98.Activation parameters have been calculated and compared with water exchange reaction and other substitution reactions of hexaaquochromium(III) ion.A mechanism involving outer sphere association between the two reactant species, followed by transformation of this outer sphere complex into the product by an associative path has been suggested.
- Bhattacharya, Malika,De, G. S.
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p. 780 - 783
(2007/10/02)
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