Chelate ring sequence and enthalpy of formation of copper(II) complexes with tetraaza macrocycles

The heats of formation of the Cu2+ tetraaza macrocycle complexes I, m = n =p = 2, q = 3 (CuL2+); m = n = 2, p = q = 3 [CuL1]2+], and II [69238-28-4] were detd. calorimetrically at 25°. The heat of formation of CuL2+ is intermediate between those for analogous complexes with cyclam and 1,4,7,10-tetraazacyclotridecane. L1(isocyclam) incorporates Cu2+ less exothermically than cyclam due to weaker in-plane Cu-N interactions. II has a much lower heat of complexation.