Sung-Nak Choi

Stereoelectronic properties of metalloenzymes—III: A soluble tetrahedral coordination complex of copper(II)—dichloro(sparteine)copper(II)

Abstract Electron spin resonance and optical solution studies of copper(II) complexes of l -sparteine confirm the rare pseudotetrahedral coordination geometry of copper in solution . Crystal field calculations suggest that only the optical transition near 12·0 kK is due to a “ d − d ” transition. Comparisons to the known optical spectra of Type I copper(II) in metalloenzymes suggest the band near 16·0 kK of Type I copper(II) may be due to a forbidden CuS change transfer band.

Relationships among structure and spectroscopic properties in tetrahedrally distorted copper(II) (−)-sparteine dichloride

Abstract The 1:1 mixed crystalline Cu(C15H26N2)Cl2·Zn(C15H26N2)Cl2, 2, and the host lattice material, Zn(C15H26N2)Cl2, 3, were newly prepared and characterized, and the X-ray crystallographic structures of 2 and 3 determined. Further distortion around the Cu(II) center of Cu(C15H26N2)Cl2, 1, was achieved by introducing 1 into the corresponding diamagnetic Zn(II) host lattice. In the 1:1 mixed crystalline, the dihedral angle between the CuN2 and the CuCl2 planes in the Cu(C15H26N2)Cl2 units increased by ∼11° more than that in the neat 1. The ESR and the optical spectral data in solution and solid states were collected for 1 and 2, and the results correlated with the degree of the distortion around the Cu(II) center. The A∥ values of the ESR spectra and the ligand-field transitions are quite sensitive toward the small change in the dihedral angle between the CuCl2 and the CuN2 planes of the Cu(C15H26N2)Cl2 unit.

MOLECULES OF COPPER(II) l-SPARTEINE DINITRATE ARE MIXED FOUR- AND FIVE-COORDINATE IN ONE CRYSTALLINE PHASE AND ONLY FOUR-COORDINATE IN ANOTHER

Abstract A neutral complex of Cu(II) with the chiral bidentate nitrogen-chelating alkaloid (−)-sparteine, with nitrate groups occupying the remaining coordination sites, has been prepared and characterized. Solution conductivity measurements indicate that both nitrate groups are coordinated to copper to give a neutral molecule. Optical and electron-spin-resonance spectra in toluene/CHCl3, did not show a clear picture of the coordination geometry. A frozen-glass ESR spectrum showed the same evidence for mixed species, with the predominant species characterized by a very low A11 value of 118 G. Crystals 1 and 2 of Cu(C15H26N2)(NO3)2 were grown by two methods: 1 at 25°C from saturated acetonitrile, and 2 at 5°C from ethanol/dichloromethane under CCl4 vapor. Their structures were determined by X-ray crystallography. Crystals 1 were monoclinic, space group P21, with a = 7.851(6), b = 14.408(10), c = 16.079(10) A, β = 97.93(6)°, V = 1801(2) A and Z = 4. Crystals 2 were orthorhombic, space group P212121, with a ...

Synthesis, Characterization, and Structure of Metal(II) (-)-Sparteine Complexes Containing Acetate Ligands

The complexes [Co(C15H26N2)(C2H3O2)2] (1), [Ni(C15H26N2)(C2H3O2)2] (2), [Cu(C15H26N2)(C2H3O2)2] (3) and [Zn(C15H26N2)(C2H3O2)2] (4) were prepared from reaction of (−)-sparteine with the corresponding metal(II) acetates in ethanol at stoichiometric ligand to metal ratios. The complexes were characterized by UV-Vis and IR spectroscopies, and magnetic susceptibility measurements. The solid-state structures of 1, 2 and 4 have been determined by X-ray crystallography. The Complexes 1 and 2 display a pseudo-octahedral structure around the metal center, where two acetate ligands coordinate to the metal center in a bidentate fashion, whereas the metal centers in 3 and 4 adopt a pseudo-tetrahedral structure and two acetate ligands in these complexes coordinate to the metal center in a monodentate fashion. The whole set of prepared complexes has been used for comparative structural and spectroscopic studies.

Sparteine copper(II) diacetate

The chiral nitrogen-chelating alkaloid (−)-sparteine acts as a bidentate ligand, reacting with copper(II) acetate in ethanol to form the title complex, [Cu(CH3COO)2(C15H26N2)], with the two acetate groups occupying the remaining coordination sites in a monodentate fashion to produce a distorted four-coordinate tetrahedral structure. The dihedral angle between the N—Cu—N and O—Cu—O planes is 45.8 (3)°.

Sparteine copper(II) dinitrite

The title complex, [Cu(NO2)2(C15H26N2)], has been prepared and its crystal structure determined. The chiral nitrogen-chelating alkaloid (−)-sparteine acts as a bidentate ligand, reacting with one CuII ion in ethanol to form the title complex, with two nitrite groups occupying the remaining coordination sites, to produce a distorted five-coordinate square-pyramidal structure. One nitrite is bound through one O atom and the other nitrite acts as a η2-chelating group.

Bis(azido-κN)[(6R,7S,8S,14S)-(–)-sparteine-κ2N,N′]copper(II)

In the title compound, [Cu(N(3))(2)(C(15)H(26)N(2))], the chiral alkaloid (-)-l-sparteine (Sp) acts as a bidentate ligand, with two azide ligands occupying the remaining coordination sites, forming a distorted CuN(4) tetrahedron. The dihedral angle between the N(Sp)-Cu-N(Sp) and N(azide)-Cu-N(azide) planes is 55.3 (2) degrees. Principal dimensions include Cu-N(Sp) = 2.011 (6) and 2.025 (5) A, and Cu-N(azide) = 1.939 (6) and 1.934 (7) A. The mid-point of the N(Sp)...N(Sp) line does not lie exactly in the N(azide)-Cu-N(azide) plane, but is tilted towards one of the N(Sp) atoms by 0.026 A.

Nicotinium tetra­chloro­cuprate(II)

The structure of the title compound, (C10H16N2)[CuCl4], comprises two crystallographically non-equivalent tetrahedral [CuCl4]2− anions, each of which is linked to two doubly protonated nicotinium cations via hydrogen bonds. There are two different types of hydrogen-bonding interactions present, namely (i) the protonated pyridinium groups exclusively form bifurcated hydrogen bonds to two cis-Cl atoms of both [CuCl4]2− units and (ii) the protonated pyrrolidinium groups exclusively form a two-center hydrogen bond with a chloride of both [CuCl4]2− units.

Ignition delay times of nitromethaneoxygenargon mixtures behind reflected shock

The substituted NO 2 reduced the role of oxygen as the promotor of the detonation and decreased the activation energy, compared with the case of methane. It could be due to one of two factors: the C-N bond energy or the reactivity of the NO 2 radical deriving additional branching chain processes for the detonation reaction

(–)-α-Isosparteine copper(II) diazide

In the title complex, [Cu(N3)2(C15H26N2)], the Cu atom is surrounded by the two N atoms of the chelating (−)-α-isosparteine ligand and another two N atoms from the two azide anions, forming a distorted CuN4 tetrahedron. The two azide anions are terminally bound to the CuII atom, and the dihedral angle between the Nsparteine—Cu—Nsparteine and Nazide—Cu—Nazide planes is 50.0 (2)°.