E. L. Amma

The adamantane structure in polynuclear Cu4S6 cores: the crystal and molecular structures of Cu4[SC(NH2)2]6(NO3)4·4H2O and Cu4[SC(NH2)2]9(NO3)4·4H2O

The compounds Cu4[SC(NH2)2]6(NO3)4·4H2O and Cu4[SC(NH2)2]9(NO3)4·4H2O have been prepared, their structures determined, and are shown to contain a central Cu4S6 core with four trigonal planar Cu atoms in the former, but only one trigonal planar Cu in the latter.

Circular dichroism as a probe of the allosteric R⇄T transformation in hemoglobins and modified hemoglobins

Abstract The circular dichroism spectra at pH 6.5 of a number of hemoglobins and modified hemoglobins have been recorded in the 280 nm region and interpreted in terms of shifts of the R⇄T allosteric transformation. Inositol hexaphosphate converts aquomet hemoglobin A(S) to the T form but the carbamlyated derivatives are unaffected by inositol hexaphosphate and remain in the R form. Fluorodinitrobenzene and dimethyl adipimidate modified hemoglobins are locked in an intermediate form, and inositol hexaphosphate has little or no effect. The circular dichroism in the 280 nm region is shown to be a useful diagnostic tool for chemical agents that affect the R⇄T allosteric transformation.

The Preparation and Crystal Structure of the Dioxygen Adduct of Bis(diphenylethylphosphine)chlorocarbonyl Iridium(I).

Abstract The synthesis of the titled compound has been accomplished, its infrared vibrational spectra measured and the crystal structure determined. The OO, CO, and IrCl stretching frequencies were found to be 848, 1997 and 293 cm−1, respectively. The OO distance was found from the crystal structure analysis to be 1.469(10) A. These data are in agreement with quadrupole resonance data that indicate this compound and those closely related must be viewed as peroxo-metal species and not molecular oxygen bound to metal. The crystal structure consists of isolated O2IrCOCl[P(C6H5)2C2H5]2 molecules separated by ordinary van der Waals distances. The molecule is most simply described as a trigonal bipyramid with the O2-center, CO and Cl moieties defining the equatorial plane. As expected the O22− is bound to the Ir side on. The metaloxygen(2), metalphosphorous(2), metalchlorine and metalcarbon distances are: 2.033(7), 2.083(7), 2.363(3), 2.363(3), 2.356(3) and 1.900(12) A, respectively. The O distance is 1.469(10) A. Crystallographic Data: Monoclinic P21/a; a = 14.772(2), b = 19.604(4), c = 9.929(1) A and β = 101.02(4)°; Z = 4; Dobs = Dcalc = 1.67 gcm−3; 3306 non-zero hkl reflections were corrected for absorption and decay and used to solve and refine the structure by full matrix least-squares to a final R of 0.0431.

Conformational state andtransformation in Mn(II) and Mn(III) hemoglobins and azide Mn(III) hemoglobin

Summary The circular dichroism of Mn(II) and Mn(III) hemoglobins has been measured in the uv and Soret spectral regions, and the differences are indicative of an R⇄T allosteric transformation, particularly in the 280 nm region. However, Mn(III) hemoglobin in the uv region is distinctly different from aquomet hemoglobin. The addition of inositol hexaphosphate to Mn(III) hemoglobin gives a uv circular dichroic spectrum characteristic of the T form. In contrast to the azide derivative of Fe(III) hemoglobin, the azide derivative of Mn(III) hemoglobin is converted to the T form by the addition of inositol hexaphosphate.

Crystal and molecular structure of dithiobiuret

The crystal and molecular structure of dithiobiuret (S2C2N3H5) has been determined and refined from 1020 intensities measured by counter techniques at room temperature. The full-matrix refinement, including anisotropic temperature factors for the non-hydrogen atoms and isotropic temperature factors for the hydrogen atoms, converged to a finalR of 0·033. The structure consists of almost planar molecules in thetrans configuration with essentially only van der Waals interactions between molecules. The two independent C-S distances are 1·702(3) and 1·673(3) Å. The internal C-N distances are 1·386(4) and 1·367(4) Å, whereas the external C-N distances are 1·331(4) and 1·309(4) Å. The unit cell parameters area = 4·081(1),b = 17·684(5),c = 8·222(3) Å and β = 100·56(2) °;Z = 4,Dm =Dc = 1·54 gcm−3; the space group isP21/c.

Crystal structure and 48113Cd n.m.r. spectrum of di-µ-chloro-dichlorobis-(6-mercaptopurine)diaquodicadmium(II)

The 113Cd n.m.r. spectrum of di-µ-chloro-dichlorobis-(6-mercaptopurine)diaquodicadmium(II) has been observed and the crystal structure determined to consist of dimers with relatively long Cd–S and Cd–N(7) distances.

Molecular packing and intermolecular contacts of sickling deer type III hemoglobin

The X-ray structure of sickling deer type III hemoglobin, solved by the molecular replacement method and refined to an R value of ~25%, has been used to determine the mode of molecular packing and the residues involved in the intermolecular contacts between the hemoglobin tetramers in the crystalline state. The molecules pack in linear arrays (“fibrils”), with adjacent fibrils displaced ~27 A from one another along the long axis of the arrays. A view down this axis shows an hexagonal network of six fibrils surrounding a central solvent cavity (each hexameric unit is termed a fiber) with adjacent fibers sharing a common wall of fibrils. Contacts less than 5 A are observed between the following subunits of different molecules: α1 α′1, α1 α′2, α1 β′1, α1 β′2, α2 β′1, α2 β′2, β2 β′2, in which the primes refer to adjacent molecules.

X-Ray crystal structure and 113Cd n.m.r. spectrum of αβγδ-tetraphenyl-porphinatocadmium(II)-bis(dioxan) solvate

The 113Cd Fourier transform n.m.r. spectrum of the title compound is characterized by a single resonance at ca. 422 p.p.m. deshielded from 0·1 M CdClO4 solution; its crystal structure shows an almost planar CdN4 system with only very weak axial interactions to dioxan molecules.

Crystal and molecular structure of chlorotris(monomethylthiourea)silver(I)

The crystal and molecular structure of chlorotris(monomethylthiourea)silver(I) has been solved and refined by full-matrix least-squares methods to a finalR of 0·039 from 1150 reflections measured by counter techniques at ambient room temperature. The crystals are orthorhombic:Pmcn, a = 14·824(2),b = 8·524(1),c = 12·671(1) Å,Z = 4,Dm = 1·68,Dc = 1·72 gcm−3. The structure consists of independent, distorted tetrahedral Ag(I) moieties with only weak hydrogen bonds and/or van der Waals interactions between molecules. These molecules are packed in such a way that Ag, Cl and one entire monomethylthiourea ligand all lie in a crystallographic mirror plane, and the other two ligands are related by this mirror. This arrangement, plus the alternation of the Ag-Cl bond direction, leads to a non-polar sheet of Ag, Cl and monomethylthiourea groups with other monomethylthiourea groups protruding from either side of the sheet. Only N-H⋯Cl hydrogen bonds and van der Waals interactions exist between sheets. The Ag-S distance is somewhat long at 2·649(3) Å, as is one of the Ag-S distances at 2·665(3) Å. The other two Ag-S distances are 2·520(2) Å. The geometry of the complex makes it clear that the Ag-S bond is formed by donation of an electron pair from a sulfur sp2 orbital.

The crystal and molecular structure of dinitratobis(2- methylmercaptoaniline)Cd(II) monohydrate: A trigonal bipyramidal Cd SN2O2 polyhedron wit

Abstract The single crystal X-ray structure determination of dinitratobis-(2-methylmercaptoaniline) has been carried out. The structure consists of neutral mole