Design And Research Of Polynuclear Etalcomplexes Containing N,O Ligands

Polynuclear metal complexes have attracted increasing interest because of their novel topology, special physical or chemical properties and a wide range of potential use. In this thesis, ten complexes have been synthesized by the reactions of polydentate Schiff-base ligands with transition metal ions or lanthanides ions. The ligands are DFMP-based Schiff-Base ligands parepared by in situ condensations of 2,6-diformyl-4-methylphenol with a range of methylamines. The compounds were characterized by single crystal X-ray analysis, elemental analysis. IR analysis, and magnetic properties. This thesis could be divided into two aspects as following:1. Schiff-Base ligands of H3L1, H3L2, H3L3, HL4 and HL5 reacted with a series of transition metal salts, respectively, and we obtained four nickel complexes (1-4) and one manganese complexe (5), one dinuclear cobalt complex CO2 (6), and one decanuclear iron complex (7). Then we studied in detail each molecular structure and magnetic properties of complexes (1-3). Complexes (1-5) were centrosymmetric tetranuclear units in the form of a face-shared dicubane-like core with two missing vertices; For 6, each cobalt ion was six-coordinated octahedral configuration; 7 had a "ladder" core, four adjacent Fe(III) ions and bridging oxygens form defective double-cubane structure. We studied magnetic properties of (1-3), and fitting results of their magnetic susceptibility confirmed that these complexes were ferromagnetically coupled with positive J values. For 6, three theoretical models were used to fit susceptibility, and all results indicated a weak intramolecular antiferromagnetic interaction between the cobalt(II) ions.2. One-dimensional chain complexes (8) and triple-stranded homometallic helicates complexes (9) and (10) were synthesized by in-situ reactions of Schiff-Base Ligand H3L6 and HL'with responding lanthanide salts. Complex (8) consisted of alternating eight- and nine-coordinate Sm(III) ions bridged by benzoate ligands in different coordination modes. A treatment of the variable-temperature magnetic susceptibility using an expression deduced from free-ion approximation and molecular field theory suggests the existence of a weak antiferromagnetic coupling between the samarium ions. For complex (9-10), the crystal structures demonstrated that right-handed and left-handed helixes were contained within unit cell, leading to a'meso'-relation between the two complex units. Alternating current (ac) susceptibility measurements of complex (9) revealed a frequency-dependent out-of-phase signal, indicative of slow relaxation of magnetization.