First row divalent transition metal complexes of aryl-appended tris((pyridyl)methyl)amine ligands: syntheses, structures, electrochemistry, and hydroxamate binding properties

Divalent manganese, cobalt, nickel, and zinc complexes of 6-Ph(2)TPA (N,N-bis((6-phenyl-2-pyridyl)methyl)-N-((2-pyridyl)methyl)amine; [(6-Ph(2)TPA)Mn(CH(3)OH)(3)](ClO(4))(2) (1), [(6-Ph(2)TPA)Co(CH(3)CN)](ClO(4))(2) (2), [(6-Ph(2)TPA)Ni(CH(3)CN)(CH(3)OH)](ClO(4))(2) (3), [(6-Ph(2)TPA)Zn(CH(3)CN)](ClO(4))(2) (4)) and 6-(Me(2)Ph)(2)TPA (N,N-bis((6-(3,5-dimethyl)phenyl-2-pyridyl)methyl)-N-((2-pyridyl)methyl)amine; [(6-(Me(2)Ph)(2)TPA)Ni(CH(3)CN)(2)](ClO(4))(2) (5) and [(6-(Me(2)Ph)(2)TPA)Zn(CH(3)CN)](ClO(4))(2) (6)) have been prepared and characterized. X-ray crystallographic characterization of 1A.CH(3)()OH and 1B.2CH(3)()OH (differing solvates of 1), 2.2CH(3)()CN, 3.CH(3)()OH, 4.2CH(3)()CN, and 6.2.5CH(3)()CN revealed mononuclear cations with one to three coordinated solvent molecules. In 1A.CH(3)()OH and 1B.2CH(3)()OH, one phenyl-substituted pyridyl arm is not coordinated and forms a secondary hydrogen-bonding interaction with a manganese bound methanol molecule. In 2.2CH(3)()CN, 3.CH(3)()OH, 4.2CH(3)()CN, and 6.2.5CH(3)()CN, all pyridyl donors of the 6-Ph(2)TPA and 6-(Me(2)Ph)(2)TPA ligands are coordinated to the divalent metal center. In the cobalt, nickel, and zinc derivatives, CH/pi interactions are found between a bound acetonitrile molecule and the aryl appendages of the 6-Ph(2)TPA and 6-(Me(2)Ph)(2)TPA ligands. (1)H NMR spectra of 4 and 6 in CD(3)NO(2) solution indicate the presence of CH/pi interactions, as an upfield-shifted methyl resonance for a bound acetonitrile molecule is present. Examination of the cyclic voltammetry of 1-3 and 5 revealed no oxidative (M(II)/M(III)) couples. Admixture of equimolar amounts of 6-Ph(2)TPA, M(ClO(4))(2).6H(2)O, and Me(4)NOH.5H(2)O, followed by the addition of an equimolar amount of acetohydroxamic acid, yielded the acetohydroxamate complexes [((6-Ph(2)TPA)Mn)(2)(micro-ONHC(O)CH(3))(2)](ClO(4))(2) (8), [(6-Ph(2)TPA)Co(ONHC(O)CH(3))](ClO(4))(2) (9), [(6-Ph(2)TPA)Ni(ONHC(O)CH(3))](ClO(4))(2) (10), and [(6-Ph(2)TPA)Zn(ONHC(O)CH(3))](ClO(4))(2) (11), all of which were characterized by X-ray crystallography. The Mn(II) complex 8.0.75CH(3)()CN.0.75Et(2)()O exhibits a dinuclear structure with bridging hydroxamate ligands, whereas the Co(II), Ni(II), and Zn(II) derivatives all exhibit mononuclear six-coordinate structures with a chelating hydroxamate ligand.     

A novel general route for the preparation of enantiopure imidazolines

A novel procedure for the preparation of enantiopure 1,4-disubstituted 2-imidazolines is reported. Enantiopure beta-amino alcohols are converted into N-hydroxyethylamides, which are reacted with excess thionyl chloride, or with thionyl chloride followed by phosphorus pentachloride to yield N-chloroethylimidoyl chlorides. These intermediates are treated with amines and anilines to produce N-chloroethylamidines, which are converted into imidazolines upon workup with aqueous hydroxide. The method is simple and efficient and has been used to prepare a wide variety of enantiopure imidazolines, in a modular fashion, from readily available amino alcohols.     

Epoxy‐functionalized,low‐glass‐transition‐temperature latex. II. Interdiffusion versus crosslinking in the presence of a diamine

This article describes the results of experiments examining the competition between the polymer diffusion rate and the crosslinking rate in low‐glass‐transition‐temperature, epoxy‐containing latex films in the presence of a diamine. We examined films formed from donor‐ and acceptor‐labeled poly(butyl acrylate‐co‐methyl methacrylate‐co‐glycidyl methacrylate) copolymer latex and studied the influence of several parameters on the growth rate of gel content and the rate of polymer diffusion. These factors include the molecular weight of the latex polymer, the presence or absence of a diamine crosslinking agent, and the cure protocol. The results were compared to the predictions of a recent theory of the competition between crosslinking and polymer diffusion across interfaces. In the initially formed films, polymer diffusion occurs more rapidly than the chemical reaction rate. Therefore, these films fall into the fast‐diffusion category of this model. In our system (unlike in the model), the latex polymer has a broad distribution of molecular weights and a distribution of diffusivities. The shortest chains contribute to the early time diffusion that we measure. At later stages of our experiment, slower diffusing species contribute to the signal that we measure. The diffusion time decreases substantially, and we observe a crossover to a regime in which the chemical reaction dominates. The increases in chain branching and gel formation bring polymer diffusion to a halt. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4098–4116, 2002     

The thermal decomposition of manganese(II) sulphite trihydrate

Thermal studies have shown that manganese(II) oxide and trimanganese tetroxide are the final decomposition products when manganese(II) sulphite trihydrate is heated in nitrogen and oxygen respectively. However, in each atmosphere, there are several decomposition routes involving the intermediate formation of manganese(II) sulphate and manganese(II) sulphide. The reactions can be summarized as follows:

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Zusammenfassung Thermische Untersuchungen haben gezeigt, da\ Mangan(II)oxid und Trimangan-Tetroxid die Endprodukte der Zersetzung sind, wenn Mangan(II)sulfit Trihydrat in Stickstoff bzw. Sauerstoff erhitzt wird. In jeder der AtmosphÄren gibt es jedoch erschiedene Zersetzungswege, wobei vorübergehend Mangan(II)sulfat und Mangan(II)sulfid gebildet werden. Die Reaktionen können, wie folgt, zusammengefa\t werden:

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Résumé Les études thermiques montrent que l'oxyde de manganèse(II) et le tétroxyde de trimanganèse constituent les produits finaux de la décomposition du sulfite de manganèse(II) chauffé respectivement dans l'azote et dans l'oxygène. Cependant dans chacune de ces atmosphères, plusieurs chemins de décomposition peuvent Être suivis. Ils font intervenir la formation intermédiaire de sulfate de manganèse(II) et de sulfure de manganèse(II). Les réactions peuvent Être résumées comme suit:

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, , , , MnO Mn₃O₄. , , - (II). :

     

Comparison of Methionine α,γ‐Lyase and Homocysteine α,γ‐Lyase for Electrochemical Determination of Homocysteine

Recently, a novel enzymatic method was developed for determination of homocysteine. This method utilizes the electrochemical hydrogen sulfide sensor along with methionine α,γ‐lyase to accomplish the fast, accurate, sensitive and selective measurements. As a continuation of this work, another enzyme, homocysteine α,γ‐lyase, was used and the parallel experiments of using both enzymes were carried out against the effect of pH, sensitivity, linearity, and interferences, in an intended comparison between these two enzymes. The excellent linearity of amperometric currents against homocysteine concentrations, high sensitivities and low detection limits for both enzymes reconfirmed that the electrochemical method is superior over other analytical means. The high enzymatic activity of methionine α,γ‐lyase surpassing homocysteine α,γ‐lyase endowed the former higher sensitivity, lower detection limit and faster response than the latter, suggesting methionine α,γ‐lyase a better candidate for homocysteine measurement by electrochemical method. The differences between these two enzymes on the trends of response time and sensitivity at different pH environments, reactivity toward several forms of homocysteine as well as on the interference from several agents were also addressed and discussed.     

THE Py SCALE OF SOLVENT POLARITIES. SOLVENT EFFECTS ON THE VIBRONIC FINE STRUCTURE OF PYRENE FLUORESCENCE and EMPIRICAL CORRELATIONS WITH ET and Y VALUES

Abstract— Pyrene fluorescence spectra have been run in 62 solvents of widely differing solvent polarity. As has been noted previously, the intensity ratio of the first (the 0–0 band) and third bands in vibronic fine structure of these spectra are very sensitive to solvent polarity. These I ₁/ I ₃ values, however, are not sensitive to hydrogen bonding aspects of solvent-solute interactions. Correlations are reported with Winstein's Y values and with Dimrotb's E _T values. On this basis the I ₁/ I ₃ values for pyrene fluorescence are suggested as the basis for a new empirical scale of solvent polarity, called the Py scale, which offers certain conveniences over other scales of solvent polarity.