Nahid Amstutz

Ground-State Electronic Structure of Vanadium(III) Trisoxalate in Hydrated Compounds

The ground-state electronic structures of K3V(ox)3.3H2O, Na3V(ox)3.5H2O, and NaMgAl1-xVx(ox)3.9H2O (0 < x <or= 1, ox = C2O42-) have been studied by Fourier-transform electronic absorption and inelastic neutron scattering spectroscopies. High-resolution absorption spectra of the 3Gamma(t2g2) --> 1Gamma(t2g2) spin-forbidden electronic origins and inelastic neutron scattering measurements of the pseudo-octahedral [V(ox)3]3- complex anion below 30 K exhibit both axial and rhombic components to the zero-field-splittings (ZFSs). Analysis of the ground-state ZFS using the conventional S = 1 spin Hamiltonian reveals that the axial ZFS component changes sign from positive values for K3V(ox)3.3H2O (D approximately +5.3 cm-1) and Na3V(ox)3.5H2O (D approximately +7.2 cm-1) to negative values for NaMgAl1-xVx(ox)3.9H2O (D approximately -9.8 cm-1 for x = 0.013, and D approximately -12.7 cm-1 for x = 1) with an additional rhombic component, |E|, that varies between approximately 0.8 and approximately 2 cm-1. On the basis of existing crystallographic data, this phenomenon can be identified as due to variations in the axial and rhombic ligand fields resulting from outer-sphere H-bonding between crystalline water molecules and the oxalate ligands. Spectroscopic evidence of a crystallographic phase change is also observed for K3V(ox)3.3Y2O (Y = H or D) with three distinct lattice sites below 30 K, each with a unique ground-state electronic structure.

Crystal structure and 63Cu NQR of bis[1-aza-2-(1-pyrrolidinyl)]copper(I) chloride and bromide

Abstract The crystal structures and 63Cu NQR spectra of two complexes of Cu(I), bis[1-aza-2-(1-pyrrolidinyl)]copper(I) chloride and bromide. 1 and 2, are reported. Like the corresponding iodide, both are planar two-coordinated cations with a linear NCuN fragment. Neither the crystal structure nor the 63Cu NQR spectra show any evidence of coordination between the halide anion and the Cu+ centre. 1: [Cu(C6H12N2)2]+Cl−, monoclinic, C2/c, a = 15.528(1), b = 6.9027(2), c = 15.112(2) A , β = 116.892(2)°, Z = 4 ; 2: [Cu(C6H12N2)2]+Br−, monoclinic, C2/c, a = 15.269(1), b = 7.0807(2), c = 15.302(2) A , β = 115.726(2)°, Z = 4 .

Optical properties of thin films of [Ru(bpy)3][NaCr(ox)3] polymeric networks

The optical properties of a thin film of the [Ru(bpy)3][NaCr(ox)3] network structure obtained by pulsed laser deposition are described. The luminescence shows the characteristic doublet of R lines at 14400cm−1 of the spin-forbidden ligand field transition E2(t2g3)→A24(t2g3) of the [Cr(ox)3]3− chromophore. The resonant energy migration within the R1 line shows that the three-dimensional crystallographic structure is preserved during the coating process. The observation of the R lines of [Cr(bpy)3]3+ at 13710cm−1 indicates that a small fraction of Cr3+ ions migrate from the oxalate network to the tris-bipyridine cation site in the cavities of the network.

Copper-63,65 nuclear quadrupole resonance of complexes of copper(I) halides with phosphorus-containing ligands

The 63Cu NQR spectra have been recorded for ten complexes of Cu1 with phosphine and halide ligands that, either on the basis of their previously determined crystal structures or of their analogy to complexes of known structure, were believed to contain three-co-ordinated copper atoms. The NQR resonance frequencies support these attributions and the structure determination of two of the complexes, [{CuX(L)}2][X = Cl or Br, L = P(C6H4Me-o)3], confirms the co-ordination number of three. The NQR results indicated that the previously reported structure for [Cu4Br4(Ph2PCH2PPh2)2] was incorrect and a redetermination of the structure confirmed this conclusion.

63Cu NQR and Structural Studies of Complexes Formed Between Cu(I) Halides and tris(o-methoxyphenyl)- or tris(p-tolyl)phosphine Ligands

Abstract The crystal structure of [tri(o-methoxyphenvl)phosphine]2 Cu2Br2 shows it to be a halogen-bridged dimer with three-coordinated Cu (I) sites. The 63Cu NQR frequency of the corresponding chloride indicates that it has a similar structure. The 63Cu NQR frequencies of the complexes of tri(p-tolyl)phosphine, L3Cu2X2 , with cuprous chloride and bromide are consistent with their having halogen-bridged structures with both three- and four-coordinated Cu(I) sites analogous to those formed by triphenyl-phosphine and tri(m-tolyl)phosphine. Cu(I) sites. [CuBr(P(C7H7O)3]2 ; Triclinic, P l̄, Z=2, a = 8.969(1), b= 10.510(2), c=l 1.428(2) Å, α=99.46(l), β=91.95(\), γ= 104.17(1)°, R=3.5%, Rω=2.2% .

63,65Cu and 79,81Br NQR studies of halogenocuprate complexes of triphenylphosphine

Abstract 63,65Cu and 79,81Br spectra of halogenocuprate (I) complexes containing [CuPPh3 X2]- (X = Cl, Br, I) anions with different cations were recorded in the range 77 K -300 K. The results confirm the previous trend that, for a given ligand, 63Cu NQR frequencies are in the order Cl> Br > I. 63Cu NQR frequencies in [CuPPh3 X2]- are compared with those in neutral Cu(Ph3)2 X(X = Cl, Br) complexes and with the [CuX2]- (X = Cl, Br) anions, other three-coordinate Cu(I) complexes.