Masatomi Sakamoto

Crystal structures and magnetic properties of bi- and tetra-nuclear copper(II) complexes of 2,6-diformyl-4-methylphenol di(benzoylhydrazone)

The crystal structures of the bi- and the tetra-nuclear copper(II) complexes [Cu2L(OCH3)]·dmf (1) and [{Cu2L(OH)·dmf}2](2) have been determined, where H3L denotes 2,6-diformyl-4-methyl-phenol di(benzoylhydrazone). Complex (1) assumes a binuclear structure, in which two copper(II) ions are bridged by an endogenous phenolic oxygen atom of the dinucleating ligand L and an exogenous methoxide oxygen atom. Two molecules are stacked parallel in the crystal, where the shortest intermolecular Cu ⋯ Cu and Cu ⋯ O distances are 3.572(1) and 3.645(5)A, respectively. Complex (2) assumes a tetranuclear structure composed of two binuclear units related by a centre of symmetry. Two copper(II) ions in the crystallographically unique binuclear unit are bridged by the endogenous phenolic oxygen atom and an exogenous hydroxide oxygen atom. The hydroxide oxygen further co-ordinates to an axial position of a copper(II) ion of an adjacent binuclear unit related by the centre of symmetry with a bond distance of 2.322(5)A. Cryomagnetic data for complexes (1) and (2)(80–300 K) can be reproduced by an equation based on the Heisenberg model (H =–2JS1S2, S1= S2=½) with the parameters of J=–315 cm–1 and g= 2.05 for (1) and J=–190 cm–1 and g= 2.10 for (2) although in the case of (2) the interdimer distances of Cu(2)⋯ Cu(2II)(1 –x, –y, 2 –z) and Cu(1)⋯ Cu(2II) are only 3.186(1) and 3.282(1)A respectively. The magnetism of complex (2) implies that the intradimer antiferromagnetic interaction through the endogenous phenolic oxygen is predominant, and the intra- and inter-dimer magnetic interactions through the exogenous hydroxide oxygen atom contribute little to the magnetic susceptibility, because the hydroxide oxygen atom is bound to four atoms (3Cu and H) and hence has no lone-pair electrons.

Copper(II)-Lanthanoid(III) Hetero-Metal Binuclear Complexes of Compartmental Ligand, N, N'-Bis(3-Carboxy-Salicylidene) Ethylenediamine

Abstract The title complexes have been newly synthesized for the lanthanoid ions except for Ce and Pm. The effect of lanthanoid ions on the ligand field of copper(II) ion are discussed on the basis of electronic spectra.

Synthesis and characterization of lanthanoid(III) complexes with a pentadentate ligand derived from 2,6-diacetylpyridine and benzoylhydrazide

The pentadentate ligand 2,6-diacetylpyridine-bis(benzoylhydrazone) (abbreviated as dapph) was shown to form lanthanoid(III) complexes with the general formula Ln(dapph)(NO3)3(H2O)n(n = 0–2); the La to Eu complexes were obtained as monohydrates, the Tb to Lu complexes as dihydrates, and the Gd complex as an anhydrate. The complexes are classified into two groups based on IR spectral patterns of the nitrate ions: the La to Gd complexes and the Tb to Lu complexes. In the former complexes all three nitrate ions function as bidentate ligands, whereas the latter complexes contain both bidentate and unidentate nitrate ions. Based on 13C NMR spectra, it was suggested that the ligand dapph forms more stable complexes with the heavier metal ions (Tbue5f8Lu) compared to the lighter metal ions (Laue5f8Gd).

Effect of copper(II) and nickel(II) complexes of N,N′-di(salicylidene)-1,3-propanediamine on fluorescence of terbium(III)

Abstract Fluorescence spectra of terbium(III) have been measured in methanolic solutions of copper(II) nitrate hydrate and nickel(II) nitrate hydrate and their complexes of H2saltn, [M(saltn)] (M ue5fc Cu, Ni), where H2saltn denotes N,N′-di(salicylidene)-1,3-propanediamine. It is found that the intensities of the fluorescent bands at 491, 546, 586 and 622 nm are significantly quenched by [M(saltn)], whereas they are little affected by the simple metal salts Cu(NO3)2·3H2O and Ni(NO3)2·6H2O.

IR spectra and thermal decomposition/dehydration of double complex salts of lanthanum(III) sulphate complex anions with several cobalt(III) ammine complex cations

Abstract Double complex salts of lanthanum(III) sulphate complex anions with several cobalt(III) ammine complex cations, [Co(NH3)6][La(SO4)3]·H2O (1), (NH4)3[Co(NH3)5 H2O]-[La(SO4)3]2·2H2O (2), and (NH4)3[Co(NH3)4(H2O)2][La(SO4)3]2·2H2O (3), were prepared by the addition of hexaamminecobalt(III), pentaammineaquacobalt(III), and cis- tetra-amminediaquacobalt(III) complexes to the solution containing lanthanum(III) ion and excess ammonium sulphate. The IR spectra of sulphate groups of these double complex salts were much more complicated than those of the almost free sulphate groups such as (NH4)2SO4 and [Co(NH3)6]2(SO4)3·5H2O. Furthermore, values of activation energy in the dehydration process of 1, 2 and 3 were estimated using modified Doyles and Wiedemanns method. They were 95.6 ± 4.3, 157.1 ± 15.5 and 163.2 ± 20.8 kJ mol−1, respectively. Here, one molecule water is released per molecule of 1, 2 and 3.

Gravimetric determination of the abundance ratio of zirconium and hafnium, based on the in situ thermal decomposition of K4[(Zr,Hf)(C2O4)4]·5H2O

Careful heating of K(4)[(Zr,Hf)(C(2)O(4))(4)].5H(2)O results in a two-step thermal decomposition which can be written as: K(4)[(Zr,Hf(C(2)O(4))(4)].5H(2)O --> K(4)[(Zr,Hf)(C(2)O(4))(4)] --> {2K(2)CO(3)+(Zr,Hf)O(2)}. The weight-ratio of the successive decomposition products depends on the abundance ratio of Zr and Hf, and forms the basis for the present method of gravimetric determination.