The kinetic isotope effects (KIEs), k H /k D , have been determined for reaction of CH 3 I/CD 3 I with several organoplatinum(II) complexes [PtR 2 (NN)], in which the bidentate NN ligand is bpy=2,2 0 -bipyridine, t Bu 2 bpy=4,4 0 -bis(tert-butyl)-2,2 0 -bipyridine, phen=1,10-phenanthroline, or Me 2 phen=2,9-dimethyl-1,10-phenanthroline, at different temperatures and in solvents having different polarities. The values obtained for the secondary R-deuterium KIEs are close to 1 and are dependent on the solvent; values of up to 7-10% larger are obtained for the reactions in the polar solvent acetone as compared to those obtained in the nonpolar solvent benzene. The data also indicate that the steric crowding around the squareplanar coordination sphere of the platinum(II) complexes with the ligand Me 2 phen results in higher KIEs. The reactions involving dimethylplatinum(II) complexes, [PtMe 2 (NN)], were fast, and a 1:1 molar ratio (of complex and reagent) technique was successfully used to measure the rate constants accurately by conventional UV-visible spectroscopy. It is shown that there are significant advantages to measuring the reaction rates under second-order condition, as compared to the usual pseudo-first-order method.

The mechanism of oxidative addition of ethyl iodide to [PtMe 2 (2,2 0 -bipyridine)], 1, has been investigated by product analysis and by study of secondary deuterium kinetic isotope effects (KIEs), using the reagents C 2 H 5 I, C 2 D 5 I, CH 3 CD 2 I, and CD 3 CH 2 I. The reactions in acetone and benzene give [PtIMe 2 Et(bipy)], mostly as the product of trans oxidative addition, but with some of the isomeric product of cis oxidative addition and some [PtIMe 3 (bipy)], resulting from methyl group transfer. The reaction in benzene is light-sensitive, giving additional major products [PtI 2 Me 2 (bipy)] and [PtIMe 2 -(OOEt)(bipy)], as well as several minor products indicative of a photochemically initiated free-radical reaction. No H/D exchange within the ethyl group was observed in any of the products. The dark reactions in acetone and benzene follow second-order kinetics, with large negative values of the entropy of activation, indicating the S N 2 mechanism of oxidative addition of ethyl iodide to 1. However, for reaction with C 2 H 5 I vs C 2 D 5 I, values of the KIE k H /k D range from 1.32 to 1.72 in acetone and from 1.44 to 1.90 in benzene solution, and studies with CH 3 CD 2 I and CD 3 CH 2 I show that Rand β-deuterium KIEs make about equal contributions to the overall KIE. These are the first reports of isotope effects on the rate of oxidative addition reactions of ethyl halides, and the high values of the secondary deuterium KIE were unexpected for the S N 2 mechanism. Possible reasons for these observations are discussed. Scheme 2. a Free-Radical Chain Mechanism of Oxidative Addition with Possible Formation of Alkylperoxo Complexes of Platinum(IV) a R = i-Pr.

Secondary α-deuterium (α-D) kinetic isotope effects (KIEs) have been determined for the reactions of the (diimine)diarylplatinum(II) complexes [Pt(p-MeC6H4)2(NN)] (NN = bipyridine (bpy), 1a; NN = 4,4‘-dimethyl-2,2‘-bipyridine (Me2bpy), 1b; NN = 4,4‘-di-tert-butyl-2,2‘-bipyridine ( t Bu2bpy), 1c) with MeI in acetone solvent at different temperatures. Consistent with an SN2-type mechanism, very small normal secondary deuterium isotope effects (k H/k D) values of 1.00−1.11 are obtained for the reactions studied. The trends in KIEs and activation parameter values are discussed in terms of recent experimental and theoretical investigations. The platinum(IV) products have been fully characterized using 1H and 13C NMR spectroscopy.

A new tetramethylplatinum(IV) complex [PtMe 4 (dppf)] [2; dppf = 1,1Ј-bis(diphenylphosphanyl)ferrocene], as the first platinum(IV) complex to contain a chelating dppf ligand, was prepared by the reaction of the known dimeric tetramethylplatinum(IV) complex cis,cis-[Me 4 Pt(µ-SMe 2 ) 2 PtMe 4 ] (1) with the biphosphane ligand dppf (2 equiv.) at room temperature by replacement of the SMe 2 ligands with the P ligating atoms of dppf. The single-crystal X-ray structure of complex 2 revealed that the dppf chelating ligand is arranged close to the "synperiplanar-eclipsed" conformation, with a Cp(centroid)···Fe···Cp(centroid) twist angle of 17.6°and a dppf bite angle, P1-Pt1-P2, of 95.77(3)°. This is in contrast to the usually preferred "synclinal-staggered" conformation, in which the Cp(centroid)···Fe···Cp(centroid) twist angle is close to 36°as found in Pt II complexes with chelating dppf ligands,

In various pharmaceutical and food industries, sulfite is utilized for the inhibition of nonenzymatic and enzymatic browning. Also, in brewing industries, it acts as an antioxidizing and antibacterial agent. Several toxic and adverse reactions, including vitamin deficiency, hypersensitivity, and allergic diseases, have been attributed to sulfite ingestion that may cause dysbiotic oral and gut microbiota events. Thus, the content of sulfite in foods must be controlled and monitored, and it is essential to find a specific, reproducible, and sensitive method to detect sulfite. Some analytical solutions are being tested to quantify sulfite. However, due to their advantage over traditional techniques, electroanalytical techniques are attracting much attention because they are simple, fast, affordable, and sensitive to implement. In addition, by the electrode modification, the morphology and size can be controlled, resulting in the miniaturization to be used in portable electrochemical devices. Therefore, the present review addressed some articles on the electrooxidation of sulfite from real samples using various electrochemical sensors.

Uremic pruritus is a frequent and prominent symptom in patients with advanced or end-stage renal disease. Lack of an effective treatment for kidney disease-associated pruritus often leads to many problems for these patients and makes it difficult to choose an appropriate treatment. The purpose of this evidence-based hypothesis is to share the scientific reasons and related mechanisms in order to claim that lettuce could be useful in the treatment of uremic pruritus. This hypothesis is based on studies related to lettuce and its anti-inflammatory, antioxidant, antidiabetic, sedative, hypnotic, nephroprotective, potassium balancing, and blood purification properties. As a result, we suggest that lettuce could be a good choice for improving and reducing uremic pruritus due to its certain characteristics. Although proof of this hypothesis requires further clinical trial studies, this hypothesis can nevertheless lead to formulating an appropriate therapy for uremic-induced pruritus. By conducting a molecular docking study, we investigated the interactions between nineteen natural bioactive components of lettuce (Lactuca sativa L.) and human kappa opioid receptors. The in silico docking studies revealed that most of the ligands showed better antipruritic efficacy than gabapentin. Gamma-tocopherol, delta-tocopherol, and campesterol demonstrated the highest binding affinities toward the target protein.

A copper(II) Schiff base complex, [Cu(cd4OMeSalMeen)], methyl-2-{[1-methyl-2-(4methoxy-phenolate)mehylidynenitrilo]ethyl}amino-1-cyclopentene dithiocarboxylate copper(II), was incorporated into triacetylcellulose membrane and applied as ionophore in order to develop an anion-selective optical sensor for the analysis of nitrite by absorption spectrophotometry. At optimum pH 3.0, a linear calibration curve was observed for nitrite in the range of 0.50 to 7.00 mgL -1 with a detection limit of 0.04 mgL -1 . The response time of the optode (t95%) was found to be 8-10 min, depending on the nitrite ion concentration. The proposed sensor was fully recovered in nitric acid solution (0.1 M) and had acceptable reproducibility (RSD=1.9%). The optode exhibited good selectivity toward nitrite ion according to hard-soft acid base (HSAB) principle and the formation constant was calculated. The application of the sensor for determination of nitrite content in meat products was quiet successful.

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