DICOPPER CRYPTATES WITH 1,1 AND 1,3 BRIDGING LIGANDS - SPECTROSCOPIC, MAGNETIC AND ELECTROCHEMICAL PROPERTIES

The furan-based hexaiminocryptand L1, N[(CH2)2N=CHRCH=N(CH2)2]3N where R = furan-2,5-diyl, has been found to act as host for dicopper(I) and mu-hydroxo-dicopper(II). The corresponding octa-aminocryptand derivative L2 accommmodated dicopper(II) with hydroxide, imidazolate or azide bridging ligands. A single-crystal X-ray analysis of [Cu2L1[BF4]2 revealed trigonal-pyramidal co-ordination for Cu(I) together with a Cu ... Cu separation of 4.2 angstrom. The mu hydroxo-dicopper(II) cryptate [Cu2L2(OH)] [CF3SO3]2 was found to have trigonal-bipyramidal geometry, with a Cu ... Cu separation of 3.9 angstrom and the Cu-OH-Cu assembly close to linear. Effective magnetic exchange arising from collinear disposition of bridge O 2p(z) and copper(II) magnetic orbitals makes the hydroxo-bridged derivatives effectively diamagnetic.