X-ray diffraction and (1)H NMR in solution: structural determination of lanthanide complexes of a Py(2)N(6)Ac(4) ligand

Complexes between the Py(2)N(6)Ac(4) (H(4)L) ligand containing four carboxylate pendant arms and trivalent lanthanide ions have been synthesized, and structural studies have been made both in the solid state and aqueous solution. The crystal structures of the La, Ce, Sm, Tb, Dy, Ho, Er, Tm, and Lu complexes, with chemical formulas [LaH(2)L](NO(3)).3H(2)O (1), [Ce(4)L(2)](NO(3))(4).30H(2)O (2), [SmHL].EtOH.3H(2)O (5), [TbHL].EtOH.3H(2)O (8), [DyHL].2EtOH.2H(2)O (9), [HoHL].3H(2)O (10), [ErHL].EtOH.3H(2)O (11) [TmHL].EtOH.3H(2)O (12), and [LuHL].3H(2)O (14), have been determined by single-crystal X-ray crystallography. In the solid state, the complexes of the lighter lanthanide ions La(3+)-Dy(3+) show a 10-coordinated geometry close to a distorted bicapped antiprism, where the carboxylate pendants are situated alternatively above and below the best plane that contains the nitrogen donor atoms. The complexes of the heavier ions, Ho(3+)-Lu(3+), have a 9-coordinated geometry close to distorted tricapped trigonal prism, with one of the pendant carboxylate groups uncoordinated. The ligand is in a "twist-fold" conformation, where the twisting of the pyridine units is accompanied by an overall folding of the major ring of the macrocycle so that the pyridine nitrogen atoms and the metal are far from linear. The aqueous solution structures of the complexes were thoroughly characterized, the diamagnetic ones (La(3+) and Lu(3+)) by their COSY NMR spectra, and the paramagnetic complexes using a linear least-squares fitting of the (1)H LIS (lanthanide-induced shift) and LIR (lanthanide-induced relaxation) data with rhombic magnetic susceptibility tensors. The solution structures obtained for the La(3+)-Dy(3+) complexes (10-coordinate) and for the Tm(3+)-Lu(3+) complexes (9-coordinate) are in very good agreement with the corresponding crystal structures. However, the 10-coordinate structure is still exclusive in solution for the Ho(3+) complex and predominant for the Er(3+) complex.     

Synthesis and reactivity of a ferrocene-derived PCP-pincer ligand

The 1,3-bis(diphosphinomethyl)ferrocene 3 readily reacts with [(C2H4)2RhCl]2 to form an equilibrating pair of diastereomers 8a and 8b by C-H insertion into the ferrocene.     

First identification of excited states in 59Zn

Excited states in ⁵⁹Zn were observed for the first time following the fusion-evaporation reaction ²⁴Mg + ⁴⁰Ca at a beam energy of 60 MeV. The GASP array in conjunction with the ISIS Silicon ball and the NeutronRing allowed for the detection of γ-rays in coincidence with evaporated light particles. The mirror symmetry of ⁵⁹Zn and ⁵⁹Cu is discussed. Received: 28 May 2002 / Accepted: 10 July 2002 / Published online: 3 December 2002 RID="a" ID="a"Present address: Oliver Lodge Laboratory, University of Liverpool, P.O. Box 147, Liverpool, L69 7ZE, United Kingdom; e-mail: ca@ns.ph.liv.ac.uk. RID="b" ID="b"Present address: Physik-Departament, Technische Universit?t München, D-85748 Garching, Germany. Communicated by W. Henning     

Extreme Estimates for Interpolated Operators by the Real Method

The paper establishes estimates for ideal measures of operatorsinterpolated by the real method in terms of the measures oftheir restrictions to a sequence of spaces modelled on the intersection.It also shows that the estimates are optimal.     

Polarographic study of simple and mixed-ligand complex formation

Theoretical, experimental and statistical aspects of the polarographic method applied to simple and mixed-ligand complex formation have been studied. Some misunderstandings and erroneous interpretations have been clarified according to experimental results obtained with several systems. A criterion for establishing the number of complex species present in a simple system is proposed. For the first time the polarographic method has been applied to a mixed-ligand complex system where fourteen species co-exist.     

Stopped-flow study of the gas-phase reaction of ozone with organic sulfides: Dimethyl sulfide

The autoinhibiting reaction of ozone with dimethyl sulfide (DMS), has been studied at 296°K and 1.1 kPa (8 torr) as a function of the concentrations of both reactants. The major products of the reaction are H₂CO, H₂O, CO, and SO₂. The specific rate of primary attack of O₃ on DMS is immeasurably slow. It is suggested that the rapid overall rate observed for this reaction is due to a chain reaction initiated by the very slow primary reaction. It is concluded that reaction (1) cannot be important under atmospheric conditions and that the major loss process for DMS in the atmosphere is probably reaction with photochemically generated free radicals.     

Observation of the internal luminescence of Cr2+(3d4) in GaAs under hydrostatic pressure

Observation of the internal luminescence of Cr²⁺(3d⁴) in GaAs under hydrostatic pressure is reported. The activation of this luminescence is correlated to the lifting of the degeneracy between the excited level of Cr²⁺ and the conduction band of the host material. The possible mechanisms giving rise to this luminescence are discussed.     

Spectroscopy of 40Ca and negative-parity bands

We have studied the reactions as well as the binary channel , in order to search for deformed states, which form rotational bands in ⁴⁰Ca. We observe positive- and negative-parity bands. The negative-parity band is proposed to be a partner of an inversion doublet with the positive-parity states being based on 4p-4h configurations. The properties of the positive-parity states are discussed on the basis of the shell model and the parity doublet on the basis of a cluster model with intrinsic reflection asymmetric shapes.Received: 2 May 2003, Revised: 23 September 2003, Published online: 20 January 2004PACS: 21.10.-k Properties of nuclei; nuclear energy levels - 21.60.Gx Cluster models     

Ferrocenyl-substituted α,β-unsaturated ketones in synthesis of tetrahydropyrimidinones

Ferrocenyltetrahydropyrimidin-2-ones were prepared by reactions of linear and cyclic ,-unsaturated ketones of the ferrocene series with urea in i-PrOH in the presence of t-BuOK. The structures of the compounds prepared were studied by ¹H and ¹³C NMR and IR spectroscopy, and also by single crystal X-ray diffraction.Translated from Zhurnal Obshchei Khimii, Vol. 74, No. 11, 2004, pp. 1887–1893.Original Russian Text Copyright © 2004 by E. Klimova, Lorez, T. Klimova, Garcia, Hernandez, Ramirez.This revised version was published online in April 2005 with a corrected cover date.     

Mach-Zehnder interferometer employing coupled-resonator optical waveguides

A simple theoretical model of a Mach-Zehnder interferometer (MZI) consisting of two coupled-resonator optical waveguides with different lengths is proposed and experimentally demonstrated at microwave frequencies. Good agreement between theoretical and experimental results is observed. MZIs in planar photonic crystals may become key building blocks in the development of microscale optical integrated devices such as filters, demultiplexers, switches, and modulators.