The chemistry of coordinate polymerization of dienes

Conclusions This review has brought together the diverse ionic initiators for dienes into a consistent series of four polymerization mechanisms. The ionic freedom characteristic of the electrophilic and free anionic initiators catalyze the rapid formation of 1–4 trans structures. Coordinate initiation produces 1–4 cis structures via a cyclic transition state while anionic initiation produces 1–2 (3–4) structures.The catalytic activity in the coordinate and anionic catalysts depends largely on complex formation. The equilibrium characteristics of complex formation produces the different rate, structure and molecular weight effects observed in coordinate initiation studies.I wish to thank Drs. P. H.Moyer and M. R.Frederick for many helpful discussions of the mechanisms of coordinate polymerizations.     

Untersuchungen über Phenthiazinderivate, 19. Mitt. Neue piperazinsubstituierte Phenthiazine

Zusammenfassung Es wird über die Einführung weiterer Substituenten, z. B. Cyanäthyl und Aminopropyl, in Piperazinylalkylphenthiazine und -Piperazinyl-4,10-trimethylenphenthiazin berichtet.18. Mitt. dieser Reihe:O. Hromatka, M. Knollmüller undF. Sauter, Mh. Chem.93, 723 (1962).     

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Isomer Information from Ion Mobility Separation of High-Mannose Glycan Fragments

Extracted arrival time distributions of negative ion CID-derived fragments produced prior to traveling-wave ion mobility separation were evaluated for their ability to provide structural information on N-linked glycans. Fragmentation of high-mannose glycans released from several glycoproteins, including those from viral sources, provided over 50 fragments, many of which gave unique collisional cross-sections and provided additional information used to assign structural isomers. For example, cross-ring fragments arising from cleavage of the reducing terminal GlcNAc residue on Man₈GlcNAc₂ isomers have unique collision cross-sections enabling isomers to be differentiated in mixtures. Specific fragment collision cross-sections enabled identification of glycans, the antennae of which terminated in the antigenic α-galactose residue, and ions defining the composition of the 6-antenna of several of the glycans were also found to have different cross-sections from isomeric ions produced in the same spectra. Potential mechanisms for the formation of the various ions are discussed and the estimated collisional cross-sections are tabulated.

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Ultraparamagnetic Cells Formed through Intracellular Oxidation and Chelation of Paramagnetic Iron

Making cells magnetic is a long‐standing goal of chemical biology, aiming to enable the separation of cells from complex biological samples and their visualization in vivo using magnetic resonance imaging (MRI). Previous efforts towards this goal, focused on engineering cells to biomineralize superparamagnetic or ferromagnetic iron oxides, have been largely unsuccessful due to the stringent required chemical conditions. Here, we introduce an alternative approach to making cells magnetic, focused on biochemically maximizing cellular paramagnetism. We show that a novel genetic construct combining the functions of ferroxidation and iron chelation enables engineered bacterial cells to accumulate iron in “ultraparamagnetic” macromolecular complexes, allowing these cells to be trapped with magnetic fields and imaged with MRI in vitro and in vivo. We characterize the properties of these cells and complexes using magnetometry, nuclear magnetic resonance, biochemical assays, and computational modeling to elucidate the unique mechanisms and capabilities of this paramagnetic concept.     

Mimicking Class I b Mn2‐Ribonucleotide Reductase: A MnII2 Complex and Its Reaction with Superoxide

A fascinating discovery in the chemistry of ribonucleotide reductases (RNRs) has been the identification of a dimanganese (Mn₂) active site in class I b RNRs that requires superoxide anion (O₂^.?), rather than dioxygen (O₂), to access a high‐valent Mn₂ oxidant. Complex 1 ([Mn₂(O₂CCH₃)(N‐Et‐HPTB)](ClO₄)₂, N‐Et‐HPTB=N,N,N′,N′‐tetrakis(2‐(1‐ethylbenzimidazolyl))‐2‐hydroxy‐1,3‐diaminopropane) was synthesised in high yield (90 %). 1 was reacted with O₂^.? at ?40 °C resulting in the formation of a metastable species ( 2 ). 2 displayed electronic absorption features (λ_max=460, 610 nm) typical of a Mn‐peroxide species and a 29‐line EPR signal typical of a Mn^IIMn^III entity. Mn K‐edge X‐ray absorption near‐edge spectroscopy (XANES) suggested a formal oxidation state change of Mn^II₂ in 1 to Mn^IIMn^III for 2 . Electrospray ionisation mass spectrometry (ESI‐MS) suggested 2 to be a Mn^IIMn^III‐peroxide complex. 2 was capable of oxidizing ferrocene and weak O?H bonds upon activation with proton donors. Our findings provide support for the postulated mechanism of O₂^.? activation at class I b Mn₂ RNRs.     

Extraktiv-photometrische Bestimmung von Rhodium unter Verwendung von Diphenylselenoxid

Zusammenfassung Innerhalb der substituierten Selenoxide eignet sich Diphenylselenoxid, das in salzsaurer Lösung die Verbindung RhCl₃·OSe(C₆H₅) bildet, zur extraktiv-photometrischen Bestimmung des Rhodiums besonders neben Co²⁺, Ni²⁺ und Fe³⁺.

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Summary Among the substituted selenium oxides, diphenylselenium oxide, that in hydrochloric acid solution yields the compound RhCl₃·OSe(C₆H₅)₂, is especially suitable for the extractive-photometric determination of rhodium, particularly in the presence of Co²⁺, Ni²⁺ and Fe³⁺.

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Résumé Dans le cadre des oxydes de sélénium substitués, le diphényloxyde de sélénium qui forme le composé RhCl₃·OSe(C₆H₅) en solution chlorhydrique se prête au dosage photométrique par extraction du rhodium, en particulier en présence de Co²⁺, Ni²⁺ et Fe³⁺.

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Der Deutschen Forschungsgemeinsehaft und dem Fonds der chemischen Industrie danken wir für die Förderung unserer Arbeit durch Sachbeihilfen.     

Introduction á l'étude des sels basiques insolubles: Généralités sur la définition et l'étude des sels basiques. Détermination de l'indice de basicité d'un sel basique insoluble

In the course of this study, it has been attempted to give a precise definition of basic salts. These salts must be difterentiated from the adsorption compounds and even from the neutral salts correspondmg to an acid of which all the acidic functions have not been demonstrated.After havmg reviewed the principal techniques used up to now a potentiometric method is proposed, permitting the rapid determination of the basicity index of an insoluble basic salt. It consists, in principle, in precipitating the salt with an alkali hydroxide and deteminining the pH in the course of precipitation,Two measurements suffice theoretically to obtain the constitution of the salt studied.     

Metal ion-dependent molecular inclusion chemistry: inclusion of aromatic anions by coordinated 1,4,7,10-tetrakis((S)-2-hydroxy-3-phenoxypropyl)-1,4,7,10-tetraazacyclododecane

The ability of the pendant donor macrocyclic ligand 1,4,7,10-tetrakis((S)-2-hydroxy-3-phenoxypropyl)-1,4,7,10-tetraaza- cyclododecane((S)-thphpc12) (or [Cd((S)-thphpc12)](2+)) to act as a metal ion-dependent receptor for aromatic anions has been investigated in solution and in the solid state. [Cd((S)-thphpc12)](2+) adopts a stable conical conformation with a large hydrophobic cavity, which has been shown to contain, via complementary multiple hydrogen bonding, p-nitrophenolate, aromatic carboxylates, p-toluenesulfonate, certain aromatic amino acid anions, phenoxyacetate, and acetate. In the case of p-nitrophenolate only, one or two anions can be contained within the receptor cavity. The crystal structure of [Cd((S)-thphpc12)(p-nitrophenolate)(2)] shows a coplanar arrangement of the p-nitrophenolates, where each is retained in the cavity by a pair of hydrogen bonds to cis hydroxyl groups. The crystal structure of the p-aminobenzoate inclusion complex indicates retention of the guest via a pair of hydrogen bonds to each oxygen atom of the carboxylate moiety. The crystal structure of the (L)-phenylalaninate inclusion complex indicates that the amino acid is retained by five hydrogen bonds, two involving the nitrogen atom and three to the oxygen atoms of the carboxylate moiety. Binding constants (10(3)-10(5) M(-1)) for the inclusion of some of the aforementioned anions in [Cd((S)-thphpc12)](2+) and related receptors were measured by (1)H NMR titration in DMSO-d(6) at 298 K.