Synthesis and Characterization of a Chromium(V) cis-Dioxo Bis(1,10-phenanthroline) Complex and Crystal and Molecular Structures of Its Chromium(III) Precursor
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- 作者：Colin L. Weeks ; Aviva Levina ; Carolyn T. Dillon ; Peter Turner ; Ronald R. Fenton ; and Peter A. Lay
- 刊名：Inorganic Chemistry
- 出版年：2004
- 出版时间：November 29, 2004
- 年：2004
- 卷：43
- 期：24
- 页码：7844 - 7856
- 全文大小：215K
- 年卷期：v.43,no.24(November 29, 2004)
- ISSN：1520-510X
文摘
The first structurally characterized Cr(V) dioxo complex, cis-[CrV(O)2(phen)2](BF4) (2, phen = 1,10-phenanthroline)has been synthesized by the oxidation of a related Cr(III) complex, cis-[CrIII(phen)2(OH2)2](NO3)3·2.5H2O (1,characterized by X-ray crystallography), with NaOCl in aqueous solutions in the presence of excess NaBF4, andits purity has been confirmed by electrospray mass spectrometry (ESMS), EPR spectroscopy, and analyticaltechniques. Previously reported methods for the generation of Cr(V)-phen complexes, such as the oxidation of 1with PbO2 or PhIO, have been shown by ESMS to lead to mixtures of Cr(III), Cr(V), Cr(VI), and in some casesCr(IV) species, 3. Species 3 was assigned as [CrIV(O)(OH)(phen)2]+, based on ESMS and X-ray absorptionspectroscopy measurements. A distorted octahedral structure for 2 (Cr
tities/tbd1.gif">O, 1.63 Å; Cr-N, 2.04 and 2.16 Å) wasestablished by multiple-scattering (MS) modeling of XAFS spectra (solid, 10 K). The validity of the model wasverified by a good agreement between the results of MS XAFS fitting and X-ray crystallography for 1 (distortedoctahedron; Cr-O, 1.95 Å; Cr-N, 2.06 Å). Unlike for the well-studied Cr(V) 2-hydroxycarboxylato complexes, 2was equally or more stable in aqueous media (hours at pH = 1-13 and 25 tities/deg.gif">C) compared with polar aproticsolvents. A stable Cr(III)-Cr(VI) dimer, [CrIII(CrVIO4)(phen)2]+ (detected by ESMS), is formed during the decompositionof 2 in nonaqueous media. Comparative studies of the oxidation of 1 by NaOCl or PbO2 have shown that [CrV(O)2(phen)2]+ was the active species responsible for the previously reported oxidative DNA damage, bacterialmutagenicity, and increased incidence of micronuclei in mammalian cells, caused by the oxidation products of 1with PbO2. Efficient oxidation of 1 to a genotoxic species, [CrV(O)2(phen)2]+, in neutral aqueous media by a biologicaloxidant, hypochlorite, supports the hypothesis on a significant role of reoxidation of Cr(III) complexes, formedduring the intracellular reduction of Cr(VI), in Cr(VI)-induced carcinogenicity. Similar oxidation reactions may contributeto the reported adverse effects of a popular nutritional supplement, Cr(III) picolinate.
tities/tbd1.gif">O, 1.63 Å; Cr-N, 2.04 and 2.16 Å) wasestablished by multiple-scattering (MS) modeling of XAFS spectra (solid, 10 K). The validity of the model wasverified by a good agreement between the results of MS XAFS fitting and X-ray crystallography for 1 (distortedoctahedron; Cr-O, 1.95 Å; Cr-N, 2.06 Å). Unlike for the well-studied Cr(V) 2-hydroxycarboxylato complexes, 2was equally or more stable in aqueous media (hours at pH = 1-13 and 25 tities/deg.gif">C) compared with polar aproticsolvents. A stable Cr(III)-Cr(VI) dimer, [CrIII(CrVIO4)(phen)2]+ (detected by ESMS), is formed during the decompositionof 2 in nonaqueous media. Comparative studies of the oxidation of 1 by NaOCl or PbO2 have shown that [CrV(O)2(phen)2]+ was the active species responsible for the previously reported oxidative DNA damage, bacterialmutagenicity, and increased incidence of micronuclei in mammalian cells, caused by the oxidation products of 1with PbO2. Efficient oxidation of 1 to a genotoxic species, [CrV(O)2(phen)2]+, in neutral aqueous media by a biologicaloxidant, hypochlorite, supports the hypothesis on a significant role of reoxidation of Cr(III) complexes, formedduring the intracellular reduction of Cr(VI), in Cr(VI)-induced carcinogenicity. Similar oxidation reactions may contributeto the reported adverse effects of a popular nutritional supplement, Cr(III) picolinate.