Cationic rare-earth metal SALEN complexes

Complexes (Salpren(tBu,tBu))Y[N(SiHMe2)2](thf) and (SALEN(tBu,tBu))La[N(SiHMe2)2](thf) (SALEN(tBu,tBu) = Salcyc(tBu,tBu) and Salpren(tBu,tBu)) were prepared from Ln[N(SiHMe2)2]3(thf)2 and H2SALEN(tBu,tBu). The yttrium complex was characterized by X-ray crystallography revealing intrinsic solid-state structural features: the metal centre is displaced by 1.05 angstroms from the [N2O2] least squares plane of a highly bent Salpren(tBu,tBu) ligand (angle(Ph,Ph) dihedral angle of 80.4(1) degrees ) and is coordinated asymmetrically by the silylamide ligand exhibiting one significant Y---(HSi) beta-agostic interaction (Y-N1-Si1, 106.90(9) degrees; Y---Si1, 3.2317(6) angstroms). Complexes (SALEN(tBu,tBu))Ln[N(SiHMe2)2](thf)n (n = 1, Sc; n = 2, Y, La) react with ammonium tetraphenylborate to form the ion pairs [(SALEN(tBu,tBu))Ln(thf)n][BPh4]. The cationisation was proven by X-ray crystal structure analyses of [(Salpren(tBu,tBu))Sc(thf)2][B(C6H5)4].2(thf) and [(Salpren(tBu,tBu))Ln(thf)3][B(C6H5)4].4(thf) (Ln = Y, La), showing an octahedral and pentagonal-bipyramidal coordination geometry, respectively.     

Hydrogen peroxide decomposition by a non-heme iron(III) catalase mimic: a DFT study

Non-heme iron(III) complexes of 14-membered tetraaza macrocycles have previously been found to catalytically decompose hydrogen peroxide to water and molecular oxygen, like the native enzyme catalase. Here the mechanism of this reaction is theoretically investigated by DFT calculations at the (U)B3LYP/6-31G* level, with focus on the reactivity of the possible spin states of the FeIII complexes. The computations suggest that H2O2 decomposition follows a homolytic route with intermediate formation of an iron(IV) oxo radical cation species (L.+FeIV==O) that resembles Compound I of natural iron porphyrin systems. Along the whole catalytic cycle, no significant energetic differences were found for the reaction proceeding on the doublet (S=1/2) or on the quartet (S=3/2) hypersurface, with the single exception of the rate-determining O--O bond cleavage of the first associated hydrogen peroxide molecule, for which reaction via the doublet state is preferred. The sextet (S=5/2) state of the FeIII complexes appears to be unreactive in catalase-like reactions.     

Isolation and Characterization of Wax Esters in Fennel and Caraway Seed Oils by SPE-GC

A rapid method for the isolation and quantitative determination of wax esters in vegetable oils was developed. For the first time wax esters in oils were separated from the triglyceride matrix by means of solid-phase extraction, which allows rapid sample preparation in parallel and therefore a high sample throughput. The thus obtained wax ester fractions of fennel and caraway seed oils were analyzed by high temperature gas chromatography. GC-MS analyses were carried out using electron impact ionization in order to characterize the wax ester fraction. With respect to the results of the GC-MS analyses different isomers of saturated wax esters with the same carbon number were observed. Additional monounsaturated wax esters with an unsaturated fatty acid moiety were identified.     

Zur Frage der Isolierung und Bestimmung des Serumglobulins mittels Elektrodialyse

Zusammenfassung Die Ausscheidung des Globulins w?hrend der Elektrodialyse h?ngt in einer zun?chst noch unübersichtlichen Weise von den Beziehungen zwischen Schutzstoff und Globulin und von der Beeinflussung dieser durch Aenderung der H⁺Konzentration und Entsalzungsgeschwindigkeit ab. Es ist auffallend, da? unter den untersuchten, gegen Ausflockung schützenden Stoffen solche am wirksamsten sind, die-auch die Gerinnung hemmen. Unter diesen kommt m?glicherweise unter physiologischen Verh?ltnissen das Heparin in Betracht. Die Wirkung dieser Stoffe besteht in der Verschiebung des isoelektrischen Punktes nach der sauren Seite, was eine st?rkere Aufladung bei neutraler Reaktion nach sich zieht. Im Gegensatze zu den Behauptungen von Ettisch und Ewig wird festgestellt, da? die von Reiner benützten, mit Eiwei? beladenen Kolloidmembranen bei der Elektrodialyse sehr gute Dienste leisten. Es wird die Entstehung einer elektrischen Polarisation in Kolloidmembranen beschrieben, die bei der Elektrodialyse zu beobachten war.