Template Syntheses Involving the Carbon Acid Nitroethane. Synthesis and Characterization of Copper(II) Complexes of a 16-membered Tetraaza Macrocycle

New square-planar Cu(II) complexes of 3,11-dimethyl-3,11-dinitro-1,5,9,13-tetraazacyclohexadecane and 1,11-diamino-6-methyl-6-nitro-4,8-diazaundecane cations have been prepared from the one-pot template condensation of Cu(pn)₂]²⁺ (pn=1,3-diaminopropane) in MeOH with CH₂O and EtNO₂ in the presence of a noncoordinating base. Reduction of the nitro group in the (3,11-dimethyl-3,11-dinitro-1,5,9,13-tetraazacyclohexadecane)copper(II) cation, may be achieved by Zn/acid reduction. The Cu(II) complex of the reduced form of the ligand, namely (3,11-diammonio-3,11-dimethyl-1,5,9,13-tetraazacyclohexadecane)copper(II), has also characterized. With the macrocyclic ligand, rac and meso isomers have been identified, the meso form being the major product. Elemental analyses, i.r. and u.v.–vis. spectroscopy, f.a.b. mass spectra conductometric, magnetic measurements and cyclic voltammetry have been used to characterize the complexes.