Synthesis and properties of a mono- N-hydroxyethylated tetraaza macrocycle and its nickel(II) and copper(II) complexes

Abstract

A new 14-membered tetraaza macrocycle 2-(2-hydroxyethyl)-5,16-dimethyl-2,6,13,17-tetraazatricyclo[16.4.0.0 7.12]docosane (L 3), in which only one 2-hydroxyethyl pendant arm is appended, has been prepared by direct reaction of 3,4-dimethyl-2,6,13,17-tetraazatricyclo[16.4.0.0 7.12]docosane (L 1) with 2-bromoethanol. Two nickel(II) complexes [NiL 3](ClO 4) 2 and [Ni(L 3–H)(H 2O)]ClO 4 (L 3–H=a deprotonated form of L 3) can be prepared under acidic and basic conditions, respectively. On the other hand, only one form of copper(II) complex [CuL 3](ClO 4) 2 was isolated as a solid under acidic and basic conditions. In the complex [CuL 3](ClO 4) 2, the hydroxyl group is involved in coordination. However, the hydroxyl group of [NiL 3] 2+ is not involved in coordination in the solid state and in nitromethane. The nickel(II) complex is deprotonated to form the octahedral complex [Ni(L 3–H)(H 2O)] +, in which the hydroxoalkyl group and the water molecule are coordinated to the metal ion, in basic aqueous solutions. In water and acetonitrile, the nickel(II) complex exists as a mixture of the square-planar [NiL 3] 2+ and octahedral [NiL 3(S)] 2+ or [NiL 3(S) 2] 2+ (S=solvent molecule) species. Synthesis and properties of the mono- N-functionalized macrocycle L 3 and its nickel(II) and copper(II) complexes are reported.