Coordination chemistry of noncyclic and macrocyclic thioether-diazine polydentate ligands

Chen, Liqin (1993) Coordination chemistry of noncyclic and macrocyclic thioether-diazine polydentate ligands. Doctoral (PhD) thesis, Memorial University of Newfoundland.

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Abstract

This thesis describes studies of noncyclic and macrocyclic thioether-diazine polydentate ligands and their coordination chemistry with Cu(II), Cu(I) and Ag(I). In chapter 1, The magnetic interactions in polynuclear copper(II) complexes involving diazine (N-N) bridges are briefly reviewed. The synthesis and properties of a series of polynuclear Cu(II), and Cu(I) complexes of three noncyclic tetradentate (N₄) thioether-diazine ligands are described. The Cu(II) complexes are generally synthesized by the reaction of Cu(II) salts with ligands while some of them are synthesized by oxidation of Cu(I) complexes with air in situ. The X-ray structures of eight complexes were determined. The dinuclear Cu(I) complex is bridged by the diazine group only and dinuclear and tetranuclear Cu(II) complexes are bridged by the diazine and a hydroxide or halogen. Variable-temperature magnetic studies on the Cu(II) complexes indicate moderately strong antiferromagnetic coupling (-2J = 35-537 cm⁻¹). Cyclic voltammetry on the Cu(II) complexes in DMF shows single, essentially nonreversible, redox waves at positive potentials (E¹/² = 0,41-0.48 V vs. SCE) associated with two electron reduction to produce rearranged dinuclear Cu(I) species. In chapter 2, the synthesis, structural, electrochemical, esr and magnetic properties of a series of dinuclear Cu(II) complexes of a potentially octadentate (N⁸) ligand PTAPY (PTAPY=3,6-bis-N,N,N’N’-tetrakis(pyridine-2-ylmethyl)-aminoethanethiolato- pyridazine) are discussed. The X-ray structures of two complexes were determined. In each case the ligand is hexadentate with the pyridazine group remaining uncoordinated and there is no magnetic interaction between the distant copper centres. In chapter 3, five novel thioether-pyridazine macrocycles containing one, two or three pyridazine subunits were synthesized. A series of mononuclear, dinuclear, trinuclear and polymeric polynuclear Cu(II) complexes were isolated. The X-ray structures of six of these complexes were determined. The macrocycles generally act as nitrogen donors with the copper centres in square planar geometries. The esr spectra of these complexes were studied in detail and interpreted according to their structures. The presence of very weak intradimer antiferromagnetic exchange (-2J <18 cm⁻¹), with even weaker interdimer exchange (-zJ’ <0.51 cm⁻¹) was observed. In chapter 4, a series of Cu(I) and Ag(l) complexes with two macrocycles containing one pyridazine or phthalazine subunit and a S₄ linkage were prepared. The X-ray structures of one ligand and four complexes were determined. The complexes have most unusual polynuclear structures including double stranded chains and crosslinked polymers with the ligands acting predominantly as sulfur donors.

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