B. Jeżowska-Trzebiatowska

Optical properties of Cr3+ in MgAl2O4 spinel

Abstract Absorption and luminescence spectra of Cr 3+ in the disordered synthetic MgAl 2 O 4 spinel are reported. The splitting of the 4 T 2g absorption band and the excitation wavelength dependence of luminescence indicate the presence of two different Cr 3+ sites in this crystal. An excitation of Cr 3+ in site A leads to broad band fluorescence whereas an excitation of the B site leads to the narrow band luminescence similar to that of the natural spinel. The nature of luminescence is discussed.

Nature of the hydrogen bridge in transition metal complexes: II. Molecular orbital calculations of binuclear carbonyls of Mn, Re, Cr, Mo and W with double hydrogen bridges

Abstract Determination of the electronic structure was performed by the parameter-free Fenske-Hall method for the complexes [(CO) 5 MHM(CO) 5 ] − with D 4 h , C 2 v and C 2 symmetries (wehre M = Cr, Mo) as well as for the complex [(CO) 3 NiHNi(CO) 3 ] − with C 2 v and D 3 h symmetries and for the complex [(CO) 4 FeHFe(CO) 4 ] + with a D 3 h symmetry. The character and stability of the metalhydrogenmetal bridge bond in each of these complexes was compared. The effect of lowering the symmetry on the electronic structure of these complexes is also discussed. The influence of the bridging hydrogen atom on terminal ligands, i.e. its cis effect, was characterized.

The nature of Cr(III) luminescence in MgAl2O4 spinel

Abstract The broad-band emission of Cr(III) in the MgAl2O4 synthetic spinel was observed. Following the absorption measurements and excitation wavelength dependence of luminescence spectra the nature of luminescence is combined with two different Cr(III) sites in this crystal. The temperature dependence of luminescence and the time resolved spectra indicate that the broad-band luminescence may be attributed to the 4T2 → 4A2 fluorescence.

Vibrational properties of the YBa2Cu3O7−x superconductor: Part I. infrared and raman scattering spectra: librational mechanism of superconductivity

Abstract Infrared absorption and reflectance spectra as well as Raman scattering spectra of YBa 2 Cu 3 O 7− x have been measured at temperatures above and below the critical point. The results are compared to those obtained for pure substrates. The vibrational properties of the polymeric copper-oxygen system are discussed in terms of factor group analysis for the tetragonal and orthorhombic structure of the unit cell. The role of librational-rotational modes in the superconduction transition is discussed. The mechanism of superconductivity on YBa 2 Cu 3 O 7− x is proposed based on the electron-libron coupling.

Magnetic and ESR studies of copper(II) complexes with N-(aminoalkyl)salicylaldimines

Abstract The magnetic susceptibility and electron spin resonance (ESR) spectra have been studied for copper(II) complexes with N-(aminoalkyl)salicylaldimines, tridentate Schiff bases containing O(phenol), N(imine) and N(amine) donor atoms. It has been stated that the compounds are anti-ferromagnetically coupled dimers. The ESR spectra show the depolimerization of the dimers by the polar solvents and formation of two types of adducts. On the basis of the ESR hyperfine structural parameters the structure of the adducts has been proposed.

Studies on the cobalt(II)-dipeptide-imidazole system; a new dioxygen carrier

Abstract A series of new mixed cobalt(II) complexes with dipeptide and imidazole, which are dioxygen carriers, was synthesized. The oxygen-free, high-spin octah

Spectroscopic properties of lanthanide perchlorates in nonaqueous solutions

Abstract Absorption and emission spectra of lanthanide perchlorates were measured in alcohol and amide solutions. In particular an attention is directed into the intensities of hypersensitive band. It was observed that these bands are not relative to polarizability change in these two series of solvents. An applicability of the ligand polarizability mechanism is chalenged and the possible reasons of its discrepancy are discussed.

Crystal structure of ((C4H9)4N)3(Pr(NCS)6)

Abstract The crystal structure of tris(tetra-n-butylammonium)hexaisothiocyanatopraseodymate coordination compound ((C4H9)4N)3(Pr(NCS)6) has been determined from four-circle single-crystal X-ray diffractometer data obtained at room temperature. The crystals are triclinic, space group P 1 , with two formula units in the unit cell. The dimensions of the unit cell are as follows: a = 12.4186(50) A , b = 12.9268(31) A , c = 22.8477(60) A , α = 90.936(22)°, β = 92.423(35)° and γ = 96.752(38)°. A least-squares refinement based on F values gave a final R value of 0.077. The structure consists of praseodymium atoms coordinated to six nitrogens from thiocyanate groups. The coordination polyhedron approaches an ideal octahedron with only minor distortions. The thiocyanate groups are nearly linear. The coordination of n-butyl groups to the nitrogen is tetrahedral and the butyl groups were found to be partly disordered.

Spectroscopic behaviour of Cr(CN)3−6 ion isolated in KCl host

Abstract Vibrational, electron spin resonance (ESR), absorption and luminescence spectra of the Cr(CN) 3− 6 ion in a KCl matrix are reported. The results indicate the complex ion is trapped in three non-equivalent symmetries. However, the metal ion in the CrC 6 polyhedron possesses practically undistorted octahedral symmetry. Following the vibrational analysis the vibronic assignment of the phosphorescence spectrum is proposed.

Laser excited fluorescence of neodymium compounds in non-aqueous solutions

Abstract The luminescence spectra of neodymium compounds excited by a strong argon laser were recorded at room and liquid nitrogen temperatures. It was found that the spectra were dependent on excitation wavelength. This peculiar behaviour is discussed in terms of the two-photon absorption.