Stepwise reactions of two N–CH2CN or two N–CH2C(double bond; length as m-dashNH)OMe groups attached to macrocyclic copper(II) complexes: Preparation of homo- and hetero-di-N-functionalized macrocyclic complexes

The hetero-functionalized macrocyclic complex [CuL2](ClO4)2 bearing one N–CH2C(double bond; length as m-dashNH)OMe and one N–CH2CN groups as well as [CuL3](ClO4)2 bearing two N–CH2C(double bond; length as m-dashNH)OMe groups have been prepared selectively by the reaction of [CuL1](ClO4)2 (L2 = 2,13-bis(cyanomethyl)-5,16-dimethyl-2,6,13,17-tetraazatricyclo[16.4.0.1.1807.12]docosane) with methanol. The N–CH2C(double bond; length as m-dashNH)OCH3 group in [CuL2](ClO4)2 is quite inert against acid hydrolysis. On the other hand, the functional pendant arms in [CuL3](ClO4)2 readily undergo acid hydrolysis. Both [CuL4](ClO4)2 bearing one N–CH2COOCH3 and one N–CH2C(double bond; length as m-dashNH)OCH3 groups and [CuL5](ClO4)2 bearing two N–CH2OOCH3 groups have been prepared by the stepwise hydrolysis of [CuL3](ClO4)2. The reactivity of the functional pendant arms in [CuL1](ClO4)2 or [CuL3](ClO4)2 is quite different from that in [NiL1](ClO4)2 or [NiL3](ClO4)2. The crystal structure of [CuL2](ClO4)2 shows that the complex has a slightly distorted square-pyramidal coordination polyhedron with an apical Cu–N (N–CH2C(double bond; length as m-dashNH)OCH3 group) bond. The N–CH2C(double bond; length as m-dashNH)OCH3 and/or N–CH2COOCH3 groups in [CuL3](ClO4)2, [CuL4](ClO4)2, and [CuL5](ClO4)2 are involved in coordination, and the complexes have distorted trans-octahedral coordination polyhedron. The axial Cu–N (N–CH2C(double bond; length as m-dashNH)OCH3 group) distance (2.396(7) Å) of [CuL4](ClO4)2 is considerably longer than the Cu–N (N–CH2C(double bond; length as m-dashNH)OCH3 group) distance (2.169(3) Å) of [CuL2](ClO4)2.