R3Mn1.5CuV0.5O9 (R = Y, Ho, Er, Tm, Yb and Lu) and Lu3Mn3-3xCu2xVxO9: New noncentro symmetric oxides related to YMnO3

We report formation of new noncentrosymmetric oxides of the formula, R3Mn1.5CuV0.5O9 for R = Y, Ho, Er, Tm, Yb and Lu, possessing the hexagonal RMnO3 (space group P6(3)cm) structure. These oxides could be regarded as the x = 0.5 members of a general series R3Mn3-3xCu2xVxO9. Investigation of the Lu-Mn-Cu-V-O system reveals the existence of isostructural solid solution series, Lu3Mn3-3xCu2xVxO9 for 0 < x <= 0.75. Magnetic and dielectric properties of the oxides are consistent with a random distribution of Mn3+, Cu2+ and V5+ atoms that preserve the noncentrosymmetric RMnO3 structure. (c) 2006 Elsevier Ltd. All rights reserved.

Simplified theory of optical nonlinearities in spin-polarized bulk GaAs

Apart from their intrinsic physical interest, spin-polarized many-body effects are expected to be important to the working of spintronic devices. A vast literature exists on the effects of a spin-unpolarized electron-hole plasma on the optical properties of a semiconductor. Here, we include the spin degree of freedom to model optical absorption of circularly polarized light by spin-polarized bulk GaAs. Our model is easy to implement and does not require elaborate numerics, since it is based on the closed-form analytical pair-equation formula that is valid in 3d. The efficacy of our approach is demonstrated by a comparison with recent experimental data.

Structural and spectral investigations on some new Ni(II) complexes of di-2-pyridyl ketone N(4)-phenylthiosemicarbazone

Ni(II)complexes(1-5)ofdi2pyridylketoneN(4)-phenylthiosemicarbazone (HL) have been synthesized and spectrochemically characterized. Elemental analyses revealed a NiL2 center dot 2H(2)O stoichiometry for compound 1. However, the single crystals isolated revealed a composition NiL, - 0.5(H,0)0.5(DMF). The compound crystallizes into a monoclinic lattice with the space group P-21/n. Complexes 2. 3 and 4 are observed to show a 1:1:1 ratio of metal: thioseicarbazone:gegenion, with the general formula NiLX center dot yH(2)O [X = NCS. Y = 2 for 2; X = Cl, Y = 3 for 3 and X = N-3, y = 4.5 for 4]. Compound 5 is a dimer with a metal:thiosemicarbazone:gegenion ratio of 2:2: 1. with the formula [Ni,L,(SO4)1 - 4H(2)O (c) 2007 Elsevier Ltd. All rights reserved.

Structural and spectral investigations on some new Ni(II) complexes of di-2-pyridyl ketone N(4)-phenylthiosemicarbazone

Ni(II) complexes (1-5) of di-2-pyridyl ketone N(4)-phenylthiosemicarbazone (HL) have been synthesized and spectrochemically characterized. Elemental analyses revealed a NiL2 center dot 2H(2)O stoichiometry for compound 1. However, the single crystals isolated revealed a composition NiL, - 0.5(H,0)0.5(DMF). The compound crystallizes into a monoclinic lattice with the space group P-21/n. Complexes 2. 3 and 4 are observed to show a 1:1:1 ratio of metal: thioseicarbazone:gegenion, with the general formula NiLX center dot yH(2)O [X = NCS. Y = 2 for 2; X = Cl, Y = 3 for 3 and X = N-3, y = 4.5 for 4]. Compound 5 is a dimer with a metal:thiosemicarbazone:gegenion ratio of 2:2: 1. with the formula [Ni,L,(SO4)1 - 4H(2)O (c) 2007 Elsevier Ltd. All rights reserved.

Simultaneous observation of positive and negative nuclear Overhauser effects in oligopeptides due to segmental motio

Nuclear Overhauser effect (NOE) studies of the symmetrical cystine peptides (Formula: see text) (n = 1-3) in dimethylsulfoxide, have resulted in the simultaneous observation of both positive and negative NOEs. Positive NOEs are observed on the Trp C2H and C4H protons of the indole ring upon irradiation of Trp C alpha H and C beta H2 resonances in the peptides where n = 1 and 2. Negative NOEs are observed between backbone NH and C alpha H protons. The magnitudes of the observed NOEs are sensitive to changes in molecular size and solvent viscosity. The results demonstrate that NOEs may be a useful probe of sidechain segmental motion in oligopeptides.

Cystine peptides Antiparallel β-sheet conformation of the cyclic biscystine peptide [Boc-Cys-Ala-Cys-NHCH3]2

The crystal structure analysis of the cyclic biscystine peptide [Boc-Cys1-Ala2-Cys3-NHCH3]2 with two disulfide bridges confirms the antiparallel ?-sheet conformation for the molecule as proposed for the conformation in solution. The molecule has exact twofold rotation symmetry. The 22-membered ring contains two transannular NH ? OC hydrogen bonds and two additional NH ? OC bonds are formed at both ends of the molecule between the terminal (CH3)3COCO and NHCH3 groups. The antiparallel peptide strands are distorted from a regularly pleated sheet, caused mainly by the L-Ala residue in which ?=� 155° and ?= 162°. In the disulfide bridge C? (1)-C? (1)-S(1)-(3')-C?(3')-C?(3'), S�S = 2.030 Å, angles C? SS = 107° and 105°, and the torsional angles are �49, �104, +99, �81, �61°, respectively. The biscystine peptide crystallizes in space group C2 with a = 14.555(2) Ã…, b = 10.854(2) Ã…, c = 16.512(2)Ã…, and ?= 101.34(1) with one-half formula unit of C30H52N8O10S4· 2(CH3)2SO per asymmetric unit. Least-squares refinement of 1375 reflections observed with |F| > 3?(F) yielded an R factor of 7.2%.

Simplified theory of optical nonlinearities in spin-polarized bulk GaAs

Apart from their intrinsic physical interest, spin-polarized many-body effects are expected to be important to the working of spintronic devices. A vast literature exists on the effects of a spin-unpolarized electron-hole plasma on the optical properties of a semiconductor. Here, we include the spin degree of freedom to model optical absorption of circularly polarized light by spin-polarized bulk GaAs. Our model is easy to implement and does not require elaborate numerics, since it is based on the closed-form analytical pair-equation formula that is valid in 3d. The efficacy of our approach is demonstrated by a comparison with recent experimental data.

Structure of Ferroverdin

FERROVERDIN, a green iron-containing pigment, was isolated in 1955 by Chain, Tonolo and Carilli1 from an unidentified species of Streptomyces. It was at first assigned the formula C30H24O8N2Fe and the iron was shown by measurements of magnetic susceptibility to be in the ferrous state2. Later the ligand present was proved to be the p-vinyl phenyl ester of 3-nitroso-4-hydroxy-benzoic acid3,4. X-ray crystallographic measurements were undertaken to find the atomic arrangement in this unusual complex; they show, in two different crystal structures, that each iron atom is attached to three nitrosophenyl ligands and that the charge is balanced by sodium ions.

Family of Mixed-Valence Oxovanadium(IV/V) Dinuclear Entities Incorporating N4O3-Coordinating Heptadentate Ligands: Synthesis, Structure, and EPR Spectra

Dinuclear ((VVV)-V-IV) oxophenoxovanadates of general formula [V2O3L] have been synthesized in excellent yields by reacting bis(acetylacetonato)oxovanadium(IV) with H3L in a 2:1 ratio in acetone under an N-2 atmosphere. Here L3- is the deprotonated form of 2,6-bis[{{(2-hydroxybenzyl)(N',N'-(dimethylamino)ethyl)}amino}methyl]-4-methylphenol (H3L1), 2,6-bis[{{(5-methyl-2-hydroxybenzyl)(N',N'-(dimethylamino)ethyl)}amino}methyl]-4-methylphenol (H3L2) 2,6-bis[ {{(5-tert-butyl-2-hydroxybenzyl)(N',N'-(dimethylamino)ethyl)}amino}methyl]-4-methylphenoI (H3L3), 2,6-bis[{{(5-chloro-2-hydroxybenzyl)(N',N'-(dimethylamino)ethyl)}amino}methyl]-4-methylphenol (H3L4) , 2,6-bis[{{(5-bromo-2-hydroxybenzyl)(N',N'-(dimethylamino)ethyl)}amino}methyl]-4-methylphenol (H3L5), or 2,6-bis[{{(5-methoxy-2-hydroxybenzyl)(N',N'-(dimethylamino)ethyl)}amino}methyl]-4-methylphenol (H3L6). In [V2O3L1], both the metal atoms have distorted octahedral geometry. The relative disposition of two terminal V=O groups in the complex is essentially cis. The O=V...V=O torsion angle is 24.6(2)degrees. The V-O-oxo-V and V-O-phenoxo-V angles are 117.5(4) and 93.4(3)degrees, respectively. The V...V bond distance is 3.173(5) Angstrom. X-ray crystallography, IR, UV-vis, and H-1 and V-51 NMR measurements show that the mixed-valence complexes contain two indistinguishable vanadium atoms (type 111). The thermal ellipsoids of O2, O4, C10, C14, and C15 also suggests a type III complex in the solid state. EPR spectra of solid complexes at 77 K display a single line indicating the localization of the odd electron (3d(xy)(1)). Valence localization at 77 K is also consistent with the V-51 hyperfine structure of the axial EPR spectra (3d(xy)(1) ground state) of the complexes in frozen (77 K) dichloromethane solution: S = 1/2, g(parallel to) similar to 1.94, g(perpendicular to) similar to 1.98, A(parallel to) similar to 166 x 10(-4) cm(-1), and A(perpendicular to) similar to 68 x 10(-4) cm(-1). In contrast isotropic room-temperature solution spectra of the family have 15 hyperfine lines (g(iso) similar to 1.974 and A(iso) similar to 50 x 10(-4) cm(-1)) revealing that the unpaired electron is delocalized between the metal centers. Crystal data for the [V2O3L1].CH2Cl2 complex are as follows: chemical formula, C32H43O6N4C12V2; crystal system, monoclinic; space group, C2/c; a = 18.461(4), b = 17.230(3), c = 13.700(3) Angstrom; beta = 117.88(3)degrees; Z = 8.

Diphenyl sulphoxide complexes of some divalent metal ions*1

Diphenyl sulphoxide (DPSO) complexes of some divalent metal perchlorates and chlorides are prepared The perchlorates of Mn, Co, Ni, Zn and Cd have the general formula [M(DPSO)6](CIO4)2. The Cu(II) complex is found to have the composition [Cu(DPSO)4] (CIO42. The chloro complex having the formula ZnCl2. 2DPSO, CdCl2.DPSO, HgCl2. DPSO and PdCl2. 2 DPSO have also been obtained. Infrared spectra indicate that the DPSO complexes of Mn, Co, Ni, Cu and Zn are oxygen-bonded while those of Cd, Hg and Pd are sulphur-bonded. The magnetic susceptibility and the optical spectral data reveal octahedral coordination for Mn, Co and Ni complexes. From the electronic spectra of Co and NI complexes, the ligand field parameters, Dq and β, are calculated.

Fine Structure of the Rayleigh Line in Amorphous Substances

As is well known, when monochromatic light scattered by a liquid is examined under high resolution it exhibits a fine structure: an undisplaced central line and two lines on either side with wavelengths slightly different from that of the incident light. The appearance of the displaced components was first predicted by Brillouin1. On the basis of his theory, the observed displacements of frequency are regarded as a Doppler effect arising from the reflexion of the light wave by the progressive sound waves of thermal origin in the scattering medium. The frequency shift of the so-called Brillouin components is given by the formula where nu and c are the velocities of sound and light in the medium and theta is the angle of scattering. That the effect contemplated by Brillouin does arise in liquids and crystals is now a well-established experimental fact.

Rare-earth trichloroacetates

The rare-earth trichloroacetates having the formula Ln(Cl3CCOO)3. 3H2O, where Ln = La, Pr, Nd, Sm, Gd or Y, were investigated by conductimetric, cryoscopic and infrared methods. The results suggest a structure in which the acetate anion coordinates to the metal through both the oxygen and the water molecules remain outside the coordination sphere.

Dimethyl sulphoxide complexes of lanthanide and yttrium nitrates

Dimethyl sulphoxide complexes of lanthanide and yttrium nitrates of the general formula M(DMSO)n(NO3)3 where M = La, Ce, Pr, Nd, Sm or Gd; n = 4 and M = Y, Ho or Yb; n = 3 have been isolated and characterized. The i.r. data besides excluding the presence of D3h nitrate, reveal co-ordination through the oxygen atom of the dimethyl sulphoxide. The complexes are monomeric in acetonitrile. Molecular conductance data in acetone, acetonitrile, dimethyl formamide and dimethyl sulphoxide suggest a co-ordination number of eight for the lighter lanthanides and seven for yttrium and the heavier lanthanides.

Antipyrine complexes of rare earth perchlorates

Rare earth perchlorate-antipyrine (ap) complexes of the formula Ln (ClO4)3.6 ap have been prepared and characterised. Infrared and electronic spectra showed the co-ordination through carbonyl oxygen. Conductivity and molecular weight data indicated a co-ordination number of six for these complexes.

Dimethyl sulphoxide complexes of rare-earth perchlorates

Dimethylsulphoxide (DMSO) complexes of rare-earth perchlorates of the formula M(ClO4)3·n DMSO (M = La, Ce, Pr and Nd, n = 8; M = Sm, Gd and Y, n = 7) have been prepared. I.r. studies indicate co-ordination through oxygen. Cryoscopic and conductivity data show co-ordination number of 7 and 8.