Über Quecksilberemulsionen,die mit Hilfe von Ultraschallwellen hergestellt wurden

Ohne Zusammenfassung Fellow of the National Research Council of the U. S. A. Es ist uns eine angenehme Pflicht, auch an dieser Stelle Herrn Prof. Dr. H. Freundlich für seine Anteilnahme und dauernde Hilfe bei dieser Arbeit unseren verbindlichsten Dank auszusprechen.     

Zur quantitativen Bestimmung des Harnstoffs und indirekt des Allantoins

Ohne Zusammenfassung     

Die Bestimmung von Sulfid- und Sulfatschwefel im Kautschuk und die Wirkung von L?sungsmitteln auf vulkanisierten Kautschuk

Ohne Zusammenfassung     

Divergent Stabilities of Tetravalent Cerium,Uranium, and Neptunium Imidophosphorane Complexes**

The study of the redox chemistry of mid-actinides (U−Pu) has historically relied on cerium as a model, due to the accessibility of trivalent and tetravalent oxidation states for these ions. Recently, dramatic shifts of lanthanide 4+/3+ non-aqueous redox couples have been established within a homoleptic imidophosphorane ligand framework. Herein we extend the chemistry of the imidophosphorane ligand (NPC=[N=P^tBu(pyrr)₂]⁻; pyrr=pyrrolidinyl) to tetrahomoleptic NPC complexes of neptunium and cerium ( 1-M , 2-M , M=Np, Ce) and present comparative structural, electrochemical, and theoretical studies of these complexes. Large cathodic shifts in the M^4+/3+ (M=Ce, U, Np) couples underpin the stabilization of higher metal oxidation states owing to the strongly donating nature of the NPC ligands, providing access to the U^5+/4+, U^6+/5+, and to an unprecedented, well-behaved Np^5+/4+ redox couple. The differences in the chemical redox properties of the U vs. Ce and Np complexes are rationalized based on their redox potentials, degree of structural rearrangement upon reduction/oxidation, relative molecular orbital energies, and orbital composition analyses employing density functional theory.     

From Gas‐Phase to Liquid‐Water Chemical Reactions: The Fluorine Atom Plus Water Trimer System

The potential energy profile for the F+(H₂O)₃→HF+(H₂O)₂OH reaction has been investigated using the “gold standard” CCSD(T) method with correlation‐consistent basis sets up to cc‐pVQZ. Four different reaction pathways have been found and these are related, both geometrically and energetically. The entrance complexes F???(H₂O)₃ for all four reaction pathways are found lying ca. 7 kcal mol^?1 below the separated reactants F+(H₂O)₃. The four reaction barriers on their respective reaction coordinates lie ca. 4 kcal mol^?1 below the reactants. There are also corresponding exit complexes HF???(H₂O)₂OH, lying about 13 kcal mol^?1 below the separated products HF+(H₂O)₂OH. Compared with analogous F+(H₂O)₂ and F+H₂O reactions, the F+(H₂O)₃ reaction is somewhat similar to the former but qualitatively different from the latter. It may be reasonable to predict that the reactions between atomic fluorine and water tetramer (or even larger water clusters) may be similar to the F+(H₂O)₃ reaction.     

Ground and excited state properties of photoactive platinum(IV) diazido complexes: theoretical considerations

Recently synthesized by the group of Sadler, the platinum(IV) diazido complexes [Pt(N(3))(2)(OH)(2)(L')(L')] (L' and L' are N-donor ligands) have potential to be used as photoactivatable metallodrugs in cancer chemotherapy. In the present study optimized structures and UV-Vis electronic spectra of trans,trans,trans- and cis,trans,cis-[Pt(N(3))(2)(OH)(2)(NH(3))(2)] (1t and 1c, respectively) as well as cis,trans,cis-[Pt(N(3))(2)(OH)(2)(L)(2)] (L = NH(3), NH(2)CH(3), NF(3), PH(3), PF(3), H(2)O, CO, OH(-), CN(-), py, imid; 2c-11c) and cis,trans-[Pt(N(3))(2)(OH)(2)(bpy)] (12c) complexes were predicted using density functional theory (DFT). The ground state electronic structures of all complexes were analyzed with the help of the natural bond orbital analysis (NBO). The electronic spectra of 1c and 1t were computed using time-dependent density functional theory (TDDFT) with five different density functionals and the ab initio CASSCF/CASPT2 method (for the five lowest energy transitions). The best agreement with available experiments was found in the case of the long-range corrected ωB97X functional. The electronic transitions were characterized by the analysis of the natural transition orbitals (NTO). The low-lying excited singlet states of 1t and 1c have significant azide-to-platinum(IV) charge-transfer character (LMCT). Geometry optimization of the three lowest singlet excited states performed using TDDFT results in the simultaneous dissociation of two azide ligands with the formation of the azidyl radicals N(3)˙ and photoreduction of Pt(IV) to Pt(II). Variation of the ligand L does not strongly affect the nature and the relative energies of the low-lying states. It is shown that the replacement of the OH(-) groups in 1c by OPh(-) ligands results in the red shift of the intense N(3)(-)→Pt LMCT band and the appearance of transitions with significant intensity in the visible region of the spectrum. The dissociative nature of the low-lying unoccupied orbitals remains unaffected. These theoretical results may suggest new experimental routes for the improvement of the photochemical activity of Pt(IV) diazido complexes.