Syntheses,Crystal Structures,and Properties of the Isotypic Pair [Cr(H2O)6]2[B12H12]3·15H2O and [In(H2O)6]2[B12H12]3·15H2O

Single crystals of [Cr(H₂O)₆]₂[B₁₂H₁₂]₃ · 15H₂O and [In(H₂O)₆]₂[B₁₂H₁₂]₃ · 15H₂O were obtained by reactions of aqueous solutions of the acid (H₃O)₂[B₁₂H₁₂] with chromium(III) hydroxide and indium metal shot, respectively. The title compounds crystallize isotypically in the trigonal system with space group R$\bar{3}$ c (a = 1157.62(3), c = 6730.48(9) pm for the chromium, a = 1171.71(3), c = 6740.04(9) pm for the indium compound, Z = 6). The arrangement of the quasi‐icosahedral [B₁₂H₁₂]^2– dianions can be considered as stacking of two times nine layers with the sequence …ABCCABBCA… and the metal trications arrange in a cubic closest packed …abc… stacking sequence. The metal trications are octahedrally coordinated by six water molecules of hydration, while another fifteen H₂O molecules fill up the structures as zeolitic crystal water or second‐sphere hydrating species. Between these free and the metal‐bonded water molecules, bridging hydrogen bonds are found. Furthermore, there is also evidence of hydrogen bonding between the anionic [B₁₂H₁₂]^2– clusters and the free zeolitic water molecules according to B–H^δ– ··· ^δ+H–O interactions. Vibrational spectroscopy studies prove the presence of these hydrogen bonds and also show slight distortions of the dodecahydro‐closo‐dodecaborate anions from their ideal icosahedral symmetry (I_h). Thermal decomposition studies for the example of [Cr(H₂O)₆]₂[B₁₂H₁₂]₃ · 15H₂O gave no hints for just a simple multi‐stepwise dehydration process.     

反相高效液相色谱法测定陶瓷饰品中六价铬的溶出量

提出了柱前衍生反相高效液相色谱法测定陶瓷饰品中六价铬溶出量的方法。采用人工汗液萃取陶瓷饰品,用1,5-二苯卡巴肼与萃取液中的六价铬在酸性条件下进行衍生反应,衍生物在Waters SunFire ODS C18色谱柱上分离,以pH 2.5的10mmol·L-1磷酸二氢钾缓冲溶液和丙酮为流动相进行梯度洗脱,于波长540nm处进行测定。六价铬的质量浓度在5.0~200.0μg·L-1范围内与峰面积呈线性关系,相关系数为0.999 1,检出限(3S/N)为0.037μg·L-1。空白(实际样品)的加标回收率在97%~101%之间,测定值的相对标准偏差在1.9%~3.2%之间。     

A Rhodamine-based fluorescent sensor for chromium ions and its application in bioimaging

A rhodamine-based sensor (1) has been developed for the detection of chromium ions. Cr³⁺-induced opening of the rhodamine spirocycle in sensor (1) led to the distinct colorimetric and fluorescence responses. Among all the tested ions, only Cr³⁺ generated a significant fluorescence enhancement of up to 13-fold, which indicated the high selectivity of 1. Sensor (1) was successfully applied in the in vivo fluorescence imaging of Cr³⁺ in C. elegans. The results provided solid evidences for the future estimation of Cr³⁺ in environmental applications and tobacco samples.     

Electroanalytical Detection of Cr(VI) and Cr(III) Ions Using a Novel Microbial Sensor

A microbial sensor, namely carbon paste electrode (CPE) modified with Citrobacter freundii (Cf–CPE) has been developed for the detection of hexavalent (Cr(VI)) and trivalent (Cr(III)) chromium present in aqueous samples using voltammetry, an electroanalytical technique. The biosensor developed, demonstrated about a twofold higher performance as compared to the bare CPE for the chosen ions. Using cyclic voltammetry and by employing the fabricated Cf–CPE, the lowest limit of detection (LLOD) of 1x10⁻⁴ M and 5x10⁻⁴ M for Cr(VI) and Cr(III) ions respectively could be achieved. By adopting the Differential Pulse Cathodic Stripping Voltammetric technique, the LLOD could be further improved to 1x10⁻⁹ M and 1x10⁻⁷ M for Cr(VI) and Cr(III) ions respectively using the biomodified electrodes. The reactions occurring at the electrode surface‐chromium solution interface and the mechanisms of biosorption of chromium species onto the biosensor are discussed. The stability and utility of the developed biosensor for the analysis of Cr(VI) and Cr(III) ions in chromite mine water samples has been evaluated.     

Synthesis of enantiopure β-amino alcohols via AKR/ARO of epoxides using recyclable macrocyclic Cr(III) salen complexes

A series of chiral macrocyclic Cr(III) salen complexes 1-8 were synthesized and characterized. These complexes were found to be highly active, regio-, diastereo-, and enantioselective catalysts in aminolytic kinetic resolution (AKR) of racemic trans-epoxides as well as asymmetric ring opening (ARO) of prochiral meso-epoxides with various anilines as nucleophiles at room temperature in 18-24 h. Excellent yields (>99% with respect to the nucleophile) with high enantioselectivity (ee, >99%) of chiral anti-β-amino alcohols was achieved with concomitant recovery of corresponding epoxides in high ee (up to >99%). The complex 1 also catalyzed the ARO of meso-epoxides to provide corresponding syn-β-amino alcohols in high yield (99%) and ee (up to 91%). Due to built-in basic sites in the catalyst, no external base (as an additive) was required to promote AKR and ARO reactions. The catalyst 1 was conveniently recycled several times with retention of its performance. The AKR of trans-stilbene oxide with aniline was successfully demonstrated at relatively higher scale (10 mmol) using the catalyst 1.     

Synthesis and Crystal Structure of [Cr(thd)2(OEt)]2

The mixed‐ligand complex [Cr(thd)₂(OEt)]₂ [(thd)^– = anion of H(thd) = C₁₁H₂₀O₂ = 2,2,6,6‐tetramethylheptane‐3,5‐dione] appears as by‐product when EtOH/H₂O is used as solvent during preparation of Cr(thd)₃. [Cr(thd)₂(OEt)]₂ can be difficult to separate from Cr(thd)₃ by sublimation, but separation is easily accomplished by extracting Cr(thd)₃ with acetone. A detailed account for the sublimation behavior of [Cr(thd)₂(OEt)]₂/Cr(thd)₃ mixtures is advanced. Good yields of [Cr(thd)₂(OEt)]₂ are obtained when CrCl₃, H(thd), and Na(EtO) react in absolute EtOH. [Cr(thd)₂(OEt)]₂ is obtained in the form of green needle‐shaped crystals by recrystallization from toluene. The crystal structure is triclinic [a = 10.2919(15), b = 10.6686(16), c = 14.194(3) Å, α = 106.559(2), β = 107.869(2), and γ = 98.326(2)° at 295 K; space group P . The complex contains two crystallographic equivalent chromium atoms, which are bridged by two cis‐configured ethoxy groups, the four remaining sites in the octahedral coordination around each chromium atom being occupied by oxygen atoms from two thd ligands. The bond lengths and angles concur with the findings for related molecular complexes. The temperature dependence of the magnetic susceptibility of [Cr(thd)₂(OEt)]₂ follows Curie–Weiss law with Weiss constant θ ≈? –65 K and μ_p = 3.87 μ_B.     

The use of 1-phenyl-3-methyl-4-benzoyl-5-pyrazone as chemical modifier for low-temperature electrothermal vaporization for separation and determination of Cr(III) and Cr(VI) by ICP-MS

Based on thermal stability and volatility of 1-phenyl-3-methyl-4-benzoyl-5-pyrazone (PMBP) chelate, a novel method was described for the determination of Cr(III) and Cr(VI) by low-temperature electrothermal vaporization (LETV) combined with inductively coupled plasma mass spectrometry (ICP-MS). It was found that Cr(III) could be rapidly formed in a graphite furnace, and quantitatively vaporized into ICP at a relatively low temperature of 1000 °C with the use of PMBP as a chemical modifier, while Cr(VI) was retained in the graphite tube. Thus, the separation of Cr(III) and Cr(VI) could be realized. The main factors affecting the formation and vaporization of Cr(III)-PMBP chelate were investigated in detail. Under the optimized conditions, the detection limit of Cr(III) for this method was 0.031 ng mL⁻¹ and the relative standard deviation (RSD) for 1.0 ng mL⁻¹ Cr(III) was 5.3% (n = 9, v = 10 μL). The linear range of calibration curve spanned three orders of magnitude. The proposed method was applied to the determination of Cr(III) and Cr(VI) in water samples with satisfactory results.     

Synthesis and Characterization of Two Novel Complexes of Cr(III) with Benzilmonoxime

The reaction of benzilmonoxime (BMOH) with CrCl₃.6H₂O in methanol gives the mono nuclear Cr(III) complex, [Cr(BMO)3₃ ( 1 ). Reaction of complex 1 with a methanolic solution of KOH at room temperature leads to a di‐nuclear Cr(III)‐Cr(III) complex, [Cr(BMO)₂(OH)]₂ ( 2 ). The complexes were characterized on the basis of their elemental analysis, Mass, IR, ¹H and ¹³C‐NMR and electronic spectra. The IR studies were useful in assigning the coordination mode of the benzilmonoxime ligand to the chromium(III) ion. In addition, the presence of a hydroxo bridge in the dimeric complex 2 is inferred from the IR spectral studies. The electronic spectra of the complexes revealed two bands due to d–d transitions, and one band assignable to an oxygen (p_π)→Cr(eg*) LMCT transition observed in both complexes. An additional charge transfer transition, assignable to μ‐OH(p_π)→Cr(eg*), was only observed for the dimeric complex 2 . The splitting energy and Racah parameter were calculated to be 18484 cm^‐1 and 560 cm^‐1 for [Cr(BMO)₃] ( 1 ), 17986 cm^‐1 and 545 cm^‐1 for [Cr(BMO)₂(OH)]₂ ( 2 ) respectively.     

微量元素与脂代谢

铬是人体内必需的微量元素．综述了缺铬对脂代谢的影响、补铬对脂代谢的效应和铬对脂代谢作用的机制．根据动物实验和人群研究调查，阐述了铬与脂代谢有关，且补充铬对胆固醇和某些脂蛋白含量都有良好的作用．指出了铬可能与胰岛素及铬对脂代谢中关键酶的作用密切相关．但是,有关的作用机制仍未充分阐明。有必要进一步研究。