SYNTHESIS, CRYSTAL-STRUCTURE AND MAGNETISM OF A MACROCYCLIC BINUCLEAR DICOPPER(II) AMINO ALCOHOL COMPLEX FROM A METAL-DIRECTED REACTION INVOLVING FORMALDEHYDE AND NITROETHANE

Condensation of the bis(l, 5-diaminopentan-3-ol)dicopper(II) ion with formaldehyde and nitroethane in basic methanol yields the macromonocyclic ligand 3, 13-dimethyl-3, 13-dinitro- l, 5, 11, 15-tetraazaeicosane-8, 18-diol as the dicopper(II) complex. The perchlorate salt of the binuclear complex is very strongly antiferromagnetically coupled, with the magnetic properties measured from 10-300 K identifying a singlet-triplet energy gap of -860 cm-1 and a magnetic moment at room temperature of 0·48 BM. The discrete, binuclear nature of the complex was confirmed by a crystal structure analysis of the nitrite salt, which crystallizes in the monoclinic space group C2/c, a 14·789(6), b 14·560(6), c 12·759(9) ì ݼ/i> 99·65(4)°, and consists of the centrosymmetric macrocycle containing two copper ions each coordinated by two secondary nitrogen donors and two (shared) RO- groups, with water and nitrite oxygens occupying axial sites. The macrocycle donors and the copper ions are essentially coplanar. The Cu?Cu distance is 3·031(1) A, with the Cu-O--Cu angle 103·6(2)°. The nitro (and methyl) groups at extremities of the macrocycle are in anti dispositions. © 1990 ASEG.