Hexanuclear copper(II) complex of a novel poly(pyridine) ligand exhibiting unique long distance ferromagnetic interactions through a nitrato-O,O′ bridge

A novel hexanuclear copper complex [Cu6(NO3)12(opytrizediam)2(H2O)][(CH3)2CO]0.5(CH3CH2CH2OH)0.5 (1) with a NO3 bridge has been synthesized by reaction of Cu(NO3)2 · 3H2O with the new potentially octadentate ligand opytrizediam in n-propanol/acetone solution (opytrizediam=N,N′-{2,4-di[(di-pyridin-2-yl)amine]-1,3,5-triazine} ethylenediamine). A single-crystal X-ray diffraction analysis showed the presence of six structurally different copper centres. The coordination spheres of four copper(II) ions are best described as square-pyramidal CuN2O3 chromophores while the two other copper(II) ions are in a trigonal-bipyramidal CuN4O environment. Variable-temperature studies on 1 revealed a unique ferromagnetic coupling of two copper(II) ions bridged by a didentate nitrate anion and separated by a distance of 6.391(6) Å, with J=8.6(1) cm−1.