Reactions of N-cyanomethyl groups attached to a tetraaza macrocyclic copper(II) complex leading to the formation of various hetero-functionalized macrocyclic complexes

New hetero-functionalized macrocyclic complexes [CuL2](ClO4)2 (I) and [CuL3](ClO4)2 (II) bearing one N-CH2CONH2 or one N-CH2C(NH)NH(CH2)2CH3 pendant arm as well as one N-CH2CN group have been prepared by the selective reaction of water or n-propylamine with one of the two N-CH2CN groups in [CuL1](ClO4)2 (L1 = 2,13-bis(cyanomethyl)-5,16-dimethyl-2,6,13,17-tetraazatricyclo[16.4.0.1.1807.12]docosane). The complex [CuL4](ClO4)2 (III) bearing both N-CH2CONH2 and N-CH2C(NH)NH(CH2)2CH3 pendant arms can be prepared by either the reaction of I with n-propylamine or the hydrolysis of II. The N-CH2CONH2 and/or N-CH2C(NH)NH(CH2)2CH3 groups of I, II, and III are coordinated to the metal ion. The crystal structure of II shows that the complex has distorted square-pyramidal coordination polyhedron with a considerably strong apical Cu–N (N-CH2C(NH)NH(CH2)2CH3) bond (2.101(6) Å). The addition of HClO4 (⩾0.01 M) to an acetonitrile (or DMSO) solution of II or III produces [Cu(HL3)](ClO4)3 (IIa) or [Cu(HL4)](ClO4)3 (IIIa), showing that the N-CH2C(NH)NH(CH2)2CH3 pendant arm of each complex is readily protonated in the non-aqueous solvent; the resulting N-CH2C(NH2+)NH(CH2)2CH3 group of IIa or IIIa is not involved in coordination. However, the N-CH2C(NH)NH(CH2)2CH3 group of II is not protonated even in ⩾1.0 M HClO4 aqueous solution. In the case of III, most of the complex exists as the protonated form [Cu(HL4)]3+ in ⩾0.1 M HClO4 aqueous solutions.

Various hetero-functionalized macrocyclic complexes can be prepared selectively by stepwise reactions of two N-CH2CN groups attached to a macrocyclic copper(II) complex.Figure optionsDownload as PowerPoint slide