Synthesis and characterization of nickel(II) complexes of di-N-alkylated 14-membered tetraaza macrocycles containing cyclohexane rings via regioselective alkylation reaction

Square-planar nickel(II) complexes of new di-hr-alkylated 14-membered tetraaza macrocycles 6,17-dimethyl (L-5), 6,17-diethyl (L-6), and 6,17-bis(n-propyl) (L-7) derivatives of 3,14-dimethyl-2,6,13,17-tetraazatricyclo-[16.4.0.(1,18)0.(7.12)]docosane (L-1) have been prepared by onestep, regioselective reaction of [NiL1](2+) with R-I (R = Me, Et, or n-Pr) in basic Me2SO solutions. The nickel(II) complexes were characterized by H-1 and C-13 NMR spectroscopy and/or by single crystal X-ray crystallography. Crystal structures of [NiL1] (ClO4)(2) and the di-N-propyl derivative [NiL7] (ClO4)(2) show that the two complexes have normal square-planar coordination geometries with the nickel atoms lying on the N-4 planes; however, the Ni-N bond distances of the latter are about 0.03 Angstrom longer than those of the former. The electronic spectra, redox potentials and/or structures of the nickel(II) complexes are strongly affected by the presence of N- and C-substituents, but little affected by the nature of the N-alkyl groups. (C) 1998 Elsevier Science S.A. All rights reserved.