High-spin nickel(II) complexes of pentaaza macrocycles: characterization, electronic spectra, and thermodynamic properties

High-spin complexes [NiL][ClO4]2 were prepd., where L = 1,4,7,10,13-pentaazacyclopentadecane (L1), 1,4,7,10,13-pentaazacyclohexadiene (L2), and 1,4,7,11,14-pentaazacycloheptadecane (L3). Their electronic spectra, magnetic moments, and heats of formation were detd. The complexes form distorted octahedrons in soln., with the macrocycles folded. In the complexes of L2 and L3 one 6-membered ring lies in the equatorial plane of the mol. The heats of formation of the complexes lie in the order of L: L1 < L3 < L2. These complexes do not show a pos. macrocyclic enthalpy effect