Search

A 14-membered macrocyclic Schiff base derived from 3-salicylideneacetylacetone and o-phenylenediamine acts as a tetradentate and strongly conjugated ligand to form a cationic solid complex with CuCl. U.v.-vis. and e.s.r. spectral data reveal a strong ligand to metal π-interaction in the square planar complex. C.v. data reveal that the title ligand is able to stabilize the copper(III) oxidation state more effectively than comparable saturated or partially unsaturated macrocyclic ligands and confers a weaker tendency for reduction of copper(II) to copper(I) and copper(0). While the inclusion of a PPh ligand suppresses the Cu → Cu → Cu oxidation, imidazole and pyridine strongly enhance the Cu → Cu oxidation of the complex. [ABSTRACT FROM AUTHOR]

Halogenation of Ln, Ce and ZrO β-diketone/β-ketoester derivatives and their mixed ligand complexes of the types Ln(AA)(Sal) and Ln(AA)(Sal) by NCS, NBS and PyHBr yield different isomeric products depending on the nature of the solvent medium, the reagent and the reaction time. The halogenation, if carried out in glacial acetic acid, irrespective of the reagent, yields the stable S-hall, product wherein the three chelate rings remain imperturbed in respect of metal coordination. When the reaction is carried out in 5% v/v DMF-CHCl employing N-halosuccinimide and maintaining correct reaction times, it is possible to isolate individually three other isomeric products. The isomers prepared are Ln(OO), Ln(OO)(OX), Ln(OO)(OX) and Ln(OX) where (OO) represents diketone oxygen linkage and (OX) represents diketone oxygen and substituted halogen linkage to the central metal ion. The four linkage isomers have been identified by a comparison of the number of observedH n.m.r. orC n.m.r. signals with those expected for a given isomer on the basis of symmetry considerations in the tris-chelated octahedral structures. [ABSTRACT FROM AUTHOR]