Preparation and properties of new di-N-alkylated 14-membered tetraaza macrocycles and their nickel(II) and copper(II) complexes

New 14-membered tetraaza macrocycles 1,8-diallyl-3,5,7,7,10,12,14,14-octamethyl-1,4,8,11-tetraazacyclotetradecane (L²) and 1,8-bis(n-propyl)-3,5,7,7,10,12,14,14-octamethyl-1,4,8,11-tetraazacyclotetrad ecane (L³) have been prepared by direct reaction of 2,5,5,7,9,12,12,14-octamethyl-1,4,8,11-tetraazacyclotetradecane (L¹) with allyl bromide or n-propyl bromide. The nickel(II) and copper(II) complexes of L² and L³ have been prepared. The macrocycles show high copper(II) selectivity against nickel(II) ion in methanol solutions containing water. The wavelengths (ca. 505 nm) of the d-d bands for the nickel(II) complexes are extraordinarily longer than those for the complexes of L¹ and other related di-N-alkylated 14-membered tetraaza macrocycles. Crystal structure of [NiL²](ClO₄)₂ shows that the average Ni-N bond distance (1.992 Å) of the complex is distinctly longer than those of other related nickel(II) complexes. Effects of the N- and C-substituents on the properties of the macrocyclic compounds are discussed.