Phillip J. Vergamini

Nitrogen-15 NMR of cis-diamine-platinum(II) complexes in aqueous solution

Samples were prepared and /sup 15/NMR spectra recorded for aqueous solutions of cis-(/sup 15/NH/sub 3/)/sub 2/Pt(H/sub 2/O/sub 2//sup 2 +/(1), /sup 15/N-en Pt(H/sub 2/O)/sub 2//sup 2 +/(3)(N-en = 100% /sup 15/N-labeled-ethylene-diamine), and for derivatives of 1 and 3 in which one or both of the water molecules are replaced by 100% /sup 15/N-labeled-1-methylimidazole (/sup 15/N-Me-Im). Such replacement produces a large change in both the /sup 15/N chemical shift and on the /sup 195/Pt-/sup 15/N coupling constant for the /sup 15/NH/sub 3/ or /sup 15/N-en nitrogens. At the same time, the /sup 15/N resonanes for both /sup 15/N/sub 1/ and /sup 15/N/sub 3/ of the /sup 15/N-MeIm are shifted from their positions in an aqueous solution of /sup 15/N-MeIm, and both resonances display satellites due to /sup 195/Pt-/sup 15/N coupling. These results indicate that /sup 15/N NMR is a sensitive probe for detecting interactions between cis-diamine-Pt(II)/sup 2 +/ species and imidazole-ring nitrogen in biological systems. 1 figure, 1 table.

Time‐of‐flight measurements of pulsed neutrons and 2d detectors for texture analysis of deformed polycrystals

A method is described to measure deformation textures in polycrystals by time‐of‐flight of thermal neutrons with a 2d position sensitive detector. The procedure is illustrated for a standard sample of deformed calcite limestone and results from the Los Alamos Neutron Scattering Center and the Intense Pulsed Neutron Source at Argonne National Laboratory are compared with those from more conventional neutron diffraction experiments.

Electrochemistry of the iron-sulfur cluster compound [(η-C5H5)2Fe2S2(SC2H5)2]. Synthesis and propeties of the oxidation products

Abstract In order to gain some insight into the stability of configuration and the bonding in the novel disulfide-containing complex [(η-C 5 H 5 ) 2 Fe 2 S 2 (SC 2 H 5 ) 2 ], electrochemical properties of this compound and its SCH 3 and SCH 2 C 6 H 5 analogues were studied in various solvents and the magnetic properties of a subsequently isolated paramagnetic monocation were investigated. The cyclic voltammogram of [(η-C 5 H 5 ) 2 Fe 2 S 2 (SC 2 H 5 ) 2 ] shows a reversible one-electron oxidation at E 1 2 = +0.21 V and a quasi-reversible one-electron oxidation at E 1 2 = +0.90 V (vs.saturated calomel electrode). The stable monocation has been electrochemically synthesized and the magnetic suceptibility shows a simple paramagnetic behavior with one unpaired electron per dimeric unit. Frozen solutions of this species at 103K yielded anisotropic ESR spectra with g 1 = 2.135, g 2 = 1.976, and g 3 = 1.934. Labeling the complex with 33 S in the disulfide bridge resulted in no observable hyperfine splitting or line broadening in the ESR. The dicationic species is unstable with respect to loss of the S 2 bridge and formation of a solvent-ligated dication, [(η-C 5 H 5 )Fe(NCCH 3 )(SC 2 H 5 )] 2 2+ , isolated by electrolysis of the monocation at +1.2 V in CH 3 CN.

Texture Analysis by TOF Measurements of Spallation Neutrons with a 2D-Position Sensitive Detector

A new method is introduced to measure preferred crystallographic orientation in deformed polycrystals. A pulsed beam of protons is accelerated in the linear accelerator at Los Alamos. The beam is then compressed in time in a storage ring and directed towards a W spallation target producing bursts of pulsed neutrons of 0.25 μs duration. The neutron beam (107 n cm−2s−1) is scattered by the polycrystal sample and diffractions, including time of flight of neutrons, are recorded on a 2D detector. This offers both simultaneous coverage of a wide d spectrum (many peaks) and a large orientation region (pole figure segment). Results on Al polycrystals obtained with this instrument agree well with pole figures measured by conventional X-ray diffraction.

The structures of trithallium tetraselenophosphate and trithallium tetrathioarsenate at 65 K

[NH4][BeF3] , M r = 84.05; phase I: orthorhombic, Pmnb, a = 5 . 7 4 3 (5), b = 4 . 6 4 3 (5), c = 12.789 (2)A, V=341.O(2)A3, Z = 4 , Dm= 1.63(2), D x = 1 . 6 3 7 ( 3 ) M g m -3, 2 ( M o K c t ) = 0 . 7 1 0 7 / k , g = 0.94 mm -1, F(000) = 168, T = 386 K, final R = 0.057 for 287 observed reflections; phase II: orthorhombic, P212~2 l, a --5.661 (4), b = 4.600 (5), c = 12.990 (3) A, V = 338.3 (4) A 3, Z = 4, O x = 1.650 (3) Mg m -3, ~,(Cu Ka) = 1.5418/k, g = 2.04 mm -1, T = 295 K, final R = 0.051 for 419 observed reflections. Phase II is metastable at room temperature which allowed data collection at room temperature. Both high-temperature phases are closely related to the ferroelastic phase III [Wagkowska (1983). Acta Cryst. C39, 1167-1169]. Rigid BeF 4 groups preserve nearly the same shape through the phase transition. Temperature-induced motion of the rigid molecular units leads to pronounced changes in conformation of the (BeF4) n chains and through a system of hydrogen bonds of N H . . . F type causes reorientation of NH + ions during phase transition. Introduction. NH4BeF 3 belongs to the family of ferroelastic hydrogen-bonded crystals and on heating undergoes phase transitions at T 3 = 252.2, T 2 = 334.3 and T~ = 347.3 K. At room temperature the crystal is ferroelastic (Makita & Suzuki, 1980; Czapla, Czupifiski & Wagkowska, 1982). Thermogravimetri¢ analysis, measurements of specific heat (DSC), X-ray studies of lattice parameters as a function of temperature, and Weissenberg photographs performed in 0108-2701/85/121714-04501.50 temperature regions corresponding to particular phases led to the following phase diagram (Lukaszewicz, Wa~kowska, Tomaszewski & Czapla, 1983):