Synthesis and co-ordination chemistry of the pyridyl pendant-arm azamacrocycles 1-(2-pyridylmethyl)-1,5,9-triazacyclododecane L1 and 1-(2-pyridyl-2′-ethyl)-1,5,9-triazacyclododecane L2, with nickel (II), copper(II) and zinc(II). Crystal structures of [Ni(L1)(O2NO)]NO3 and [ZnL2][Zn(NO3)3.67Cl0.33]

Abstract

The azamacrocyclic ligands 1-(2-pyridylmethyl)-1,5,9-triazacyclododecane L¹ and 1-(2-pyridyl-2′-ethyl)-1,5,9-triazacyclododecane L² have been prepared, and their complexes with hydrated nickel(II), copper(II) and zinc(II) nitrates have been isolated. The nickel(II) complexes are high spin and six-co-ordinate, whilst ¹³C NMR spectroscopy shows that [ZnL¹(OH₂)]²⁺ exists as a symmetric trigonal-bipyramidal isomer in solution, and [ZnL²]²⁺ exists as a 2:1 mixture of tetrahedral and asymmetric trigonal-bipyramidal isomers. X-Ray crystallography has been used to determine the solid-state structures of the octahedral [NiL¹(O₂NO)]⁺, and the tetrahedral isomer of [ZnL²]²⁺.