Molecular Structure of Phosphinidene Phosphates

Abstract

Alkalimetal diphenylphosphinites degrade (Ph-P)₅ and P₄ to give anions containing a chain of 2, 3 or 4 four- and two-coordinated phosphorus atoms. Representatives of the chain with two four-coordinated and one two-coordinated P atoms became first available from the aminolysis of tris (phosphoryl)phosphides¹.     

Ultraviolet-B-induced cyclobutane-pyrimidine dimer formation and repair in Arctic marine macrophytes

The significance of ultraviolet-B radiation (UVBR: 280-315 nm)-induced DNA damage as a stress factor for Arctic marine macrophytes was examined in the Kongsfjord (Spitsbergen, 78 degrees 55.5'N, 11 degrees 56.0'E) in summer. UVBR penetration in the water column was monitored as accumulation of cyclobutane-pyrimidine dimers (CPD) in bare DNA. This showed that UVBR transparency of the fjord was variable, with 1% depths ranging between 4 and 8 m. In addition, induction and repair kinetics of CPD were studied in several subtidal macrophytes obtained from the Kongsfjord (5-15 m). Surface exposure experiments demonstrated CPD accumulation in Palmaria palmata, Devaleraea ramentacea, Phycodrys rubens, Coccotylus truncatus and Odonthalia dentata. In artificial light, field collected material of P. palmata, D. ramentacea, P. rubens and Laminaria saccharina showed efficient CPD repair, with only 10% of the artificially induced CPD remaining after 5 h. No significant differences in repair rate were observed among these species. CPD repair was slower or absent in O. dentata, C. truncatus and Monostroma arcticum, indicating that fast repair mechanisms such as photolyase were not continuously expressed in these species. CPD repair rates were not directly related to the vertical distribution of algae in the water column and to the reported UV sensitivity of the examined species. Dosimeter incubations showed that maximal exposure to DNA damaging wavelengths was low for all examined species. Furthermore, most species collected below the 1% depth for DNA damage displayed efficient CPD repair, suggesting that UVBR-induced CPD currently impose a minor threat for mature stages of these species growing in the Kongsfjord, Spitsbergen.     

Synthesen und Kristallstrukturen neuer heterobimetallischer Tantal‐Münzmetall‐Chalkogenido‐Cluster

Syntheses and Crystal Structures of Novel Heterobimetallic Tantalum Coin Metal Chalcogenido Clusters In the presence of phosphine the thiotantalats (Et₄N)₄[Ta₆S₁₇] · 3MeCN reacts with copper to give a number of new heterobimetallic tantalum copper chalcogenide clusters. These clusters show metal chalcogenide units some of which here already known from the chemistry of vanadium and niobium. New Ta—M‐chalcogenide clusters could also be synthesised by reaction of TaCl₅ and silylated chalcogen reagents with copper or silver salts in presence of phosphine. Such examples are: [Ta₂Cu₂S₄Cl₂(PMe₃)₆] · DMF ( 1 ), (Et₄N)[Ta₃Cu₅S₈Cl₅(PMe₃)₆] · 2MeCN ( 2 ), (Et₄N)[Ta₉Cu₁₀S₂₄Cl₈(PMe₃)₁₄] · 2MeCN ( 3 ), [Ta₄Cu₁₂Cl₈S₁₂(PMe₃)₁₂] ( 4 ), (Et₄N)[Ta₂Cu₆S₆Cl₅(PPh₃)₆] · 5MeCN ( 5 ), (Et₄N)[Ta₂Cu₆S₆Cl₅(PPh₂Me)₆] · 2MeCN ( 6 ), (Et₄N)[Ta₂Cu₆S₆Cl₅(P^tBu₂Cl)₆] · MeCN ( 7 ) [Ta₂Cu₂S₄Br₄(PPh₃)₂(MeCN)₂] · MeCN ( 8 ), [Cu(PMe₃)₄]₂[Ta₂Cu₆S₆(SCN)₆(PMe₃)₆] · 4MeCN ( 9 ), [TaCu₅S₄Cl₂(dppm)₄] · DMF ( 10 ), [Ta₂Cu₂Se₄(SCN)₂(PMe₃)₆] ( 11 ), [Cu(PMe₃)₄]₂[Ta₂Cu₆Se₆(SCN)₆(PMe₃)₆] · 4MeCN ( 12 ), [TaCu₄Se₄(PⁿPr₃)₆][TaCl₆] ( 13 ), [Ta₂Ag₂Se₄Cl₂(PMe₃)₆] · MeCN ( 14 ), _∞[TaAg₃Se₄(PMe₃)₃] ( 15 ). The structures of these compounds were obtained by X‐ray single crystal structure analysis.     

The effect of specific nucleation on molecular and supermolecular orientation in isotactic polypropylene

The molecular and supermolecular orientation, morphology and structural changes observed during cold drawing of injection moulded isotactic polypropylene modified by specific α, and β nucleating agents were studied by polarised photoacoustic FTIR spectroscopy, wide-angle X-ray diffraction and differential scanning calorimetry. Significantly lower molecular orientation was found in the core of the β-nucleated injection moulded specimens as compared to unmodified and α-nucleated materials. This has been ascribed to the fast growth of the β-crystallites which inevitably dislocates the flow-induced orientation within the crystalline regions and in their vicinity. Moreover, it was found that the presence of the developed β-crystallites distinctly diminishes the efficiency of the orientational solid-state drawing assessed on both levels of the hierarchical structure (molecular and crystalline). This structural observation is directly connected with macroscopic softening effect of the β-phase: lowering the yield stress and flattening the neck shoulder. Thus, the interrelation between the microstructural and macroscopic effects of the β-phase could be described as a feedback process.