Copper(II) ion hydrolysis in aqueous solution

A copper(II) ion-selective-electrode potentiometric method was used to determine the first and second hydrolysis constants of Cu²⁺. Special techniques prevented copper(II) hydroxide precipitation, and copper(II) carbonate and cipper(II) organic complexation during the titration of the experimental solution over the pH range 6.8–8.4. The large change in the total copper concentration during the titration due to adsorption of copper onto the vessel walls was accounted for by measuring the total copper concentration at each pH by atomic absorption spectrophotometry. The two hydrolysis constants were determined at 25°C in 0.7 and 0.05m NaClO₄ media. The measured stability constants are independent of the copper concentration and yield similar zero ionic strength values. Also, the stepwise equilibrium constants decrease as the ligand number increases.     

Matrix elements of the Coulomb Green function between Slater orbitals

Analytic expressions are given for integrals of the Coulomb Green function with Slater type atomic orbitals. The results involve hypergeometric functions.Supported by the National Institutes of Health, Grant No. GM23223.     

The structure of N,N′-bis(2-hydroxyphenyl)butanediamide

The structure of N,N-bis(2-hydroxyphenyl)butanediamide has been determined. The molecule consists of two 2-hydroxyphenyl moieties which are attached (at the 2 position) to the two nitrogens of the butanediamide. The compound C₁₆H₁₆N₂O₄ crystallizes in the monoclinic space group P2₁/c witha=5.576(1),b=4.8853(6),c=25.397(6) Å and =90.58(1)°.     

Synthetic studies towards lagunamide C: Polyketide assembly investigations

Lagunamide C is a depsipeptide natural product with low nM cytotoxicity towards numerous cancer cell lines. Synthetically, it is disconnected to a pentapeptide backbone and polyketide unit that possesses four stereogenic centers, of which two of centers are in question (C38 & 40). Our model system highlights a high-selective aldol addition via a Crimmin’s auxiliary setting the C40 ester linkage, and a non-facially selective cyclopropanation with subsequent ring opening for the installation of the C38 methyl center.     

Reduced Gorenstein codimension three subschemes of projective space

It is known, from work of Diesel, which graded Betti numbers are possible for Artinian Gorenstein height three ideals. In this paper we show that any such set of graded Betti numbers in fact occurs for a reduced set of points in , a stick figure in , or more generally, a good linear configuration in . Consequently, any Gorenstein codimension three scheme specializes to such a ``nice' configuration, preserving the graded Betti numbers in the process. This is the codimension three Gorenstein analog of a classical result of arithmetically Cohen-Macaulay codimension two schemes.

     

Criteria for -continuity

Bernoullicity is the strongest mixing property that a measure-theoretic dynamical system can have. This is known to be intimately connected to the so-called metric on processes, introduced by Ornstein. In this paper, we consider families of measures arising in a number of contexts and give conditions under which the measures depend -continuously on the parameters. At points where there is -continuity, it is often straightforward to establish that the measures have the Bernoulli property.

     

A new monoclinic crystal phase of [Bu4N][Ni(dmit)2]

The crystal structure of the title compound, tetrabutylammonium bis(2-thioxo-1,3-dithiole-4,5-dithiolato)nickelate(III), [N(C₄H₉)₄][Ni(C₃S₅)₂], is the fourth known phase of this polymorphous compound. It is monoclinic space group P2₁/c, with a = 20.040(2) Å, b = 13.1151(17) Å, c = 12.1093(15) Å, = 105.456(15)°, and V = 3067.5(6) ų with Z = 4, for D _calc = 1.503 g cm^–3. The [Ni(dmit)₂] anion packing arrangement consists of arrays of side-on touching anions and these arrays are connected via head-to-tail close S S contacts.     

Synthesis, spectroscopy, magnetism, and X-ray structures of hexakis(1-(2-chloroethyl)-tetrazole-N4)copper(II) salts

The compounds hexakis(1-(2-chloroethyl)-tetrazole-N4)copper(II) tetrafluoroborate mono(1-(2-chloroethyl)-tetrazole) (1) and hexakis(1-(2-chloroethyl)-tetrazole-N4) copper(II) perchlorate mono(1-(2-chloroethyl)-tetrazole) (2) were obtained from the crystallization of 1-(2-chloroethyl)-tetrazole (teec) with the respective copper salt. The X-ray structures are reported. Both compounds crystallize in the monoclinic space group C2/c for 1: a = 25.754(3) Å, b = 18.162(3) Å, c = 10.298(2) Å = 104.294(7)° and Z = 4 and for 2: a = 25.745(3) Å, b = 18.197(3) Å, c = 10.29355(3) Å = 104.512(10)° and Z = 4. The Cu^II ions are octahedrally surrounded by six teec ligands. One free teec ligand is present in the structures. The Cu–N distances in the centrosymmetrical units are 2.01, 2.04, and 2.39 Å in both compounds, consistent with a Jahn–Teller elongated octahedron. The ligand field spectra of both compounds show a signal in the visible range at about 15.200 cm^–1 and by an EPR spectrum the following values are found: g _| = 2.29 and g = 2.03. The compounds are both paramagnetic and the T value of 0.37 cm^–1 K mol^–1, which is associated with S = 1/2, is what would be expected for a mononuclear Cu^II complex.     

Crystal structure and spectroscopy of the low-spin iron(II) compound: tris(bipyrimidine)iron(II) bis(triflate), [Fe(bipym)33](CF3SO3)2

The compound [Fe(bipym)₃3](CF₃SO₃)₂ (in which bipym = 2,2-bipyrimidine) crystallizes in the space group P2₁/c, with a = 13.7641(11), b = 18.7557(19), c = 12.3627(11) Å, = 103.085(8)° and Z = 4. The low-spin Fe(II) atom is octahedrally surrounded by six nitrogen atoms of three bipyrimidine groups with Fe—N distances that vary from 1.968(4) to 1.975(4) å. In the far-infrared region the Fe—N vibrations are observed at 359 and 372 cm^-1.