PENTANUCLEAR COPPER(II) COMPLEXES WITH THE NOVEL 6-(PHENYLETHYNYL)-2-PYRIDONATE LIGAND - SYNTHESIS, AND MAGNETIC-PROPERTIES

Three pentanuclear copper(II) complexes, [Cu-5(OMe)(2)(CF3CO2)(pehp)(6 )(Cl)] 1, [Cu-5(OMe)(2)(CF3CO2)(pehp)(6)-(NO3)](2) and [Cu-5(OH)(CF3CO 2)(3)(pehp)(6)] 3, have been prepared via the solid-state reaction of hydrated copper(It) nitrate with the sodium salt of the novel ligand, 6-(phenylethynyl)-2-pyridone (Hpehp) in the presence of sodium trifluo roacetate; Crystal structural analysis at 220 K of 1-3 reveals capped- butterfly arrangements of the five copper atoms with the two shortest Cu ... Cu vectors in 1 and 2 [3.024(6)-3.050(3) Angstrom] occurring be tween the caps and the wingtips while in 3 the wingtip-cap distances a re more asymmetric with one short [3.042(7) Angstrom] and one long [3. 638(7) Angstrom] Cu ... Cu vector. Mass spectroscopic studies of 1-3 s how fragmentation patterns consistent with the observed structures, wh ile magnetic studies of the complexes indicate antiferromagnetic excha nge coupling within the Cu-5 cores and S=1/2 ground states for all com pounds. The trifluoroacetate adduct of Hpehp, Hpehp.0.5CF(3)CO(2)H was synthesised in three steps from 2-bromo-6-benzyloxypyridine via 2-ben zyloxy-6-(phenylethynyl)pyridine and the single crystal X-ray structur e of Hpehp was also determined.