Dicopper(II) and dinickel(II) complexes of Schiff-base macrocycles derived from 5,5-dimethyl-1,9-diformyldipyrromethane

The synthesis and characterisation of two dicopper(II) and two dinickel(II) macrocyclic complexes, [CuII2LPr] (10), [CuII2LBu] (11), [NiII2LPr] (12) and [NiII2LBu] (13), are reported. The two new Schiff-base macrocycles (LPr)4− and (LBu)4− are isolated as dimetallic complexes 10–13 by the [2+2] condensation of 5,5-dimethyl-1,9-diformyldipyrromethane (9) and 1,3-diaminopropane or 1,4-diaminobutane, respectively, using Cu2+ or Ni2+ template ions. Single crystal X-ray structure determinations carried out on 10–13 show that each metal atom is in a square planar N4 geometry, being bound to two deprotonated pyrrole nitrogen atoms of one dipyrromethane unit and to the two adjacent imine nitrogen atoms. NMR spectra obtained for the two dinickel(II) complexes 12 and 13 show that in CDCl3 solution they are highly symmetrical and diamagnetic.