Photophysical and Electrochemical Studies of Anchored Chromium (III) Complex on Reduced Graphene Oxide via Diazonium Chemistry

Covalently anchored chromium complex on reduced graphene oxide (rGO‐Cr) is successfully synthesised through trimethoxy silyl propanamine (TMSPA) and phenyl azo salicylaldehyde (PAS) coupling. The rGO‐Cr is characterised by Fourier transform infrared spectroscopy (FTIR), X‐ray diffraction (XRD), X‐ray photoelectron spectroscopy (XPS), electron dispersive analysis of X‐rays (EDAX), Raman spectroscopy, scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM). Absorption and emission properties of rGO‐TMSPA‐PAS are studied by excitation dependent photoluminescence emissions at room temperature. Electrochemical sensing activity of rGO‐Cr is monitored for paracetamol using modified glassy carbon electrode. Cyclic voltammetry measurements indicated that rGO‐Cr substantially enhance the eletrochemical response of paracetamol. The experimental factors are investigated and optimized.     

Chromium(III)-Selective Electrodes Based on Titanium Dichalcogenides Intercalated with Chromium

Solid-contact chromium-selective film electrodes were prepared on the basis of titanium diselenide and titanium ditelluride intercalated with chromium. It was found that the titanium diselenide–based electrode with the lowest concentration of the intercalant (Cr_0.1TiSe₂) exhibits the best properties and provides the determination of 5 × 10^–5–1 × 10⁰M chromium(III) in the pH range 2.75–4.7. The slope of the electrode function for all chromium-selective electrodes depends on the pH of the solution and is close to the theoretical slope for the singly charged Cr(OH)⁺ ₂ ion. It was demonstrated that chromium-selective electrodes can be used as indicator electrodes in determining chromium(III) by direct titration with the potentiometric detection of the titration end-point using EDTA and KMnO₄as titrants.     

Chromium Electrodeposition Kinetics in Solutions of Cr(III) Complex Ions

An equation of polarization curve for electroreduction of Cr(II) ions as intermediates in electrolysis of aqueous solutions of Cr(III) complex ions is deduced and analyzed. Kinetic parameters for the discharge of Cr(II) ions are determined. The theoretical results are compared with experimental data obtained from chromium deposition on a rotating disk electrode from Cr(III) solutions containing formate and oxalate.     

Electrolytic Deposition of Cobalt(III) Oxide in the Presence of Nickel(II) and Chromium(III) Ions

Preparation conditions and nature of anodic processes in electrolytic deposition of cobalt(III) oxide in the presence of nickel(II) and chromium(III) ions from mixed aqueous solutions of their sulfates were studied. The deposits obtained are of interest for creating effective cathode materials for lithium batteries.     

Chromium(III) and Chromium(IV) Tetraphenylporphine Complexes

Stable chromium complex (AcO)CrTPP was synthesized through the reaction of meso-tetraphenylporphine with chromium(III) acetate in boiling phenol. Coordination properties of chromium porphyrin in reaction with imidazole and pyridine in o-xylene were studied by electronic absorption spectroscopy and computer modeling. A single-electron oxidation of chromium(III) complex was found to be affected by peroxide compounds. The stability of an extra complex depends on the basic properties of the extra ligand and oxidation number of the central metal atom. The complex stability correlates with the calculated energy of formation of the metal–extra ligand bond. The geometrical structure and energy parameters of hexacoordinated chromium porphyrins were calculated using the quantum-chemical method. The effect of the cis and trans position of ligands in the composition of a macrocyclic compound was established to be significant only in the extra complexes (AcO)CrTPP.     

Electrolytic Synthesis of Binary Oxide Systems Based on Manganese(II) Oxide

Joint anodic deposition of manganese, cobalt, nickel, and chromium oxides, which form binary oxide systems, from two-component sulfate solutions of the constituent metals was studied under different electrolysis conditions.     

A Thermochemical Study on the Formation of Oxalato-Titanium(III) Complex

The thermometric titration of titanium(III) chloride with oxalic acid was carried out at 25°C. The molar ratio of titanium (III): oxalate was found to be 1:2, which indicates the formation of Ti(C₂O₄)₂⁻ ion in acid media. The limiting value of the heat of reaction between Ti(III) ion and oxalic acid in hydrochloric acid solution was found to be −1.5 Kcal mole⁻¹ at 25°C.     

A Spectrophotometric Study on Complex Formation of Chromium (VI) with Glycine Thymol Blue

The composition and stability of the complex formed between chromium (VI) and Glycine Thymol Blue (G. T. B.) has been investigated using a spectrophotometric method. The chelate is reddish brown in colour and has λ_max 570 nm against a reagent blank. The composition has been determined by different methods as 1: 1. The chelate gives maximum absorbance between pH 6.5 and 7.0. The values of log K as determined by two different methods are 5.21±0.1 and 5.24±0.1 and the values of ΔG° are ?7.08±0.1 and ?7.12±0.1 Kcal respectively at pH 6.8 and at 25°C.     

Microcalorimetric Study on Effect of Chromium(III) and Chromium(VI) Species on the Growth of Escherichia coli

The effects of Cr(III) and Cr(VI) species (Cr₂O₇^2?, CrO₄^2? and Cr³⁺) on the growth of Escherichia coli (E. coli) have been investigated in detail by microcalorimetry at 37 °C. Parameters including the growth rate constant (k), inhibitory ratio (I), half‐inhibitory concentration (IC₅₀), total heat output (Q_total), time of the maximum heat production (t_log) in the log phase have been obtained. The results showed that Cr(VI) and Cr(III) had the inhibition effect on the growth of E. coli in aquatic environment; however, the inhibitory ratio of Cr(III) to E. coli was smaller than that of Cr(VI). The k values of E. coli in the presence of Cr(VI) and at high concentrations of Cr(III) were decreased with increasing the concentrations of these chromium species. Among the three chromium species investigated, Cr₂O₇^2? was found to be the most poisonous species against E. coli with an IC₅₀ value of 35.52 µg·mL^?1. CrO₄^2? exhibited moderate toxicity on E. coli with an IC₅₀ of 50.24 µg·mL^?1, and Cr³⁺ had the lowest toxicity with an IC₅₀ of 84.30 µg·mL^?1. Microcalorimetry can provide a convenient, sensitive and reliable method to study the effect of various metal species on the growth of bacteria or other microorganisms.     

Mixed Ligand Complexes of Chromium (III) Ethylenediamine Tartrate: A Polarographic Study

Polarographic techniques have been used to investigate the complexing behaviour of chromium (III)-ethylenediamine-tartrate in aqueous solution. These complexes are reduced irreversibly at the dropping mercury electrode. The stability constants have been calculated by the method of Sundaresan and Sundaram. The values of the kinetic parameters; standard rate constant (K_s), transfer coefficient (α) and activation energy (Q) have also been calculated in each case.     

新型抗糖尿病铬(III)配合物的合成和生物活性及机理探究

为了寻找新型的抗糖尿病分子,以苯乙双胍为前体,制备了苯乙双胍铬（III）配合物.通过元素分析、摩尔电导率、电喷雾质谱、红外光谱、紫外可见光谱和核磁共振波谱对配合物的结构进行了表征,并研究了配合物在不同温度、不同pH值下溶液的稳定性、与H₂O₂的反应性和形貌.同时,构建了糖尿病C57小鼠模型,研究了其生物活性和毒性.结果证明,配合物对其活性指标均有好的抑制作用,保留了苯乙双胍的降糖性质,对机体是无毒的,并且通过MTT（3-（4,5-二甲基噻唑-2）-2,5-二苯基四氮唑溴盐）实验说明配合物的生物相容性较好,实现了金属配合物降糖与控脂的多功能化应用.在此基础上,通过光谱法研究了配合物与胰高血糖素的相互作用,表明配合物对胰高血糖素是静态猝灭以较强的作用力结合,条件结合常数为1.29×10⁵ L·mol^-1,结合位点数约为1,初步提出了配合物的新的降糖机制.     

Chromium(III) Ion Selective Electrode Based on Oxalic Acid Bis(Cyclohexylidene Hydrazide)

A poly(vinyl chloride) membrane sensor based on oxalic acid bis (cyclohexylidene hydrazide) as membrane carrier was prepared and investigated as a Cr(III)‐selective electrode. The electrode reveals a Nernstian behavior (slope 19.8±0.4 mV decade^?1) over a wide Cr(III) ion concentration range 1.0×10^?7–1.0×10^?2 mol dm^?3 with a very low limit of detection (i.e., down to 6.3×10^?8 mol dm^?3). The potentiometric response of the sensor is independent of the pH of the test solution in the pH range 1.7–6.5. The electrode possesses advantage of very fast response, relatively long lifetime and especially good selectivity to wide variety of other cations. The sensor was used as an indicator electrode, in the potentiometric titration of chromium ion and in the determination of Cr(III) in waste water and alloy samples.     

Spectrophotometric Determination of Trace Chromium(VI) in Mass Chromium(III)

There is little conclusive evidence of the toxic effects of Cr(III) so far, but Cr(VI) has carcinogenic activity, so the analysis of the chromine ions is very important in environmental research and the quality control of industry products. Usually Cr(III) and Cr(VI) interfere with each other in the species analysis, the measurement of Cr(VI) of numerous previous papers is related to the Cr(VI) samples, which contain a little Cr(III). When the amount of trivalent chromine exceeds ten …     

Partial Quenching of Parametrical Tetragonality of a Chromium(III) Complex by Pressure Tuning

The ligand-field spectrum of [Cr(NH(3))(4)F(2)]AsF(6) has been pressure-tuned up to 100 kbar. The parametrical analysis shows that the absolute values of the two independent tetragonalities of the chromophoric ion both decrease with increasing isotropic pressure so that the molecular ion becomes more isotropic. Moreover, the Cr-N single bonds appear to be more compressible than the Cr-F bonds, for which it is parametrically clear that they have a partial multiple-bond character. While the spectrochemical parameter for F(-), Delta(F), increases with pressure, its two components Delta(sigma)(F) and Delta(pi)(F) decrease. It is confirmed that nephelauxetism increases with pressure.     

A Thermodynamic Study of Chromotropico-Titanium(III) Complex from Spectrophotometric Measurements

The formation of 1 : 2 titanium(III) complex with chromotropic acid (4, 5-dihydroxy-2, 7-naphthalene-disulfonic acid) was observed by spectrophotometric measurements at various ionic strengths. An expression, [Ti(III)]/D=1/Δ? + α_H²+/KΔ?[H₂R^2?]², was derived for the determination of the formation constant, K=7.2×10² liter² mol^?2 for the Ti(III).(HR)₂ ion in the pH range of 1.3–1.8 at constant ionic strength, I=0.2 M, at 25°C. The thermodynamic data for the reaction, Ti(III)+2H₃R^2?=Ti(III) (HR)₂+2H⁺, were calculated to be ΔG° = ?16 kJ mol^?1 ΔH° = 18 kJ mol^?1, ΔS° = 110 JK^?1 mol^?1, at 25°C.     

Synthesis of Iridium Oxide Nanotubes by Electrodeposition into Polycarbonate Template: Fabrication of Chromium(III) and Arsenic(III) Electrochemical Sensor

For the first time iridium oxide (IrO₂) nanotubes are synthesized by electrodeposition in a polycarbonate (PC) template. Potential cycling (90 cycles) between 0.0 and 0.9 V is used for the preparation of IrO_x nanotubes onto the PC template with a pore diameter of 100 nm. Field‐emission scanning electron microscopy (FESEM) images show, that IrO₂ nanotubes with uniform diameters of 110±10 nm and an estimated length of 1–3 µm are formed. The electrochemical properties and the electrocatalytic activity of a glassy carbon‐IrO_x nanotube modified electrode toward Cr³⁺ and As³⁺ oxidation are investigated. Finally, the modified electrode is used for micromolar detection of the proposed analytes using differential pulse voltammetry.     

Chromium(III) complexes of 2-amino-benzothiazole

The following chromium(III) complexes of 2-amino-benzothiazole (L) were prepared and studied: CrCl₂(OH)L.H₂O, CrCl₃L₃.xS (xS = 2H₂O, MeOH) CrBr₃L₂, Cr₂(SO₄)₃L₃.3H₂O and Cr(NO₃)₃L₃.3H₂O. Infrared spectra show that in these complexes the ligand is coordinated through the aminic nitrogen atom. Electronic spectra indicate a normal six-coordination.     

A Nucleophilic Gold(III) Carbene Complex

The first Au^III carbene complex was prepared by reacting a geminal dianion with a (P,C) cyclometalated Au^III precursor. Its structure and bonding situation have been thoroughly investigated by experimental and computational means. The presence of a high‐energy highest occupied molecular orbital (HOMO) centered at the carbene center suggests nucleophilic character for the Au^III carbene complex. This unprecedented feature was confirmed by reactions with two electrophiles (PhNCS and CS₂), resulting in two types of C=C coupling reactions.