N-methylation of diamino-substituted macrocyclic complexes: intermolecular reactions

Abstract

Two N-based isomeric copper(II) complexes of the macrocycle trans-6,13-dimethyl-6,13-bis(dimethylamino)-1,4,8,11-tetraazacyclotetradecane (L³) have been synthesized and characterised spectroscopically and structurally: α-[CuL³(OH₂)₂]Cl₂, monoclinic, space group C2/m, a= 12.908(4), b= 12.433(2), c= 7.330(2)Å, β= 105.87(2)°, Z= 2; β-[CuL³(OClO₃)₂]·2H₂O, monoclinic, space group P2₁/c, a= 9.708(3), b= 9.686(3), c= 14.202(4)Å, β= 106.17(1)°, Z= 2. The two isomers exhibit very similar co-ordination spheres but significantly different visible electronic maxima. This difference is attributed to an intramolecular N ⋯ H contact between the pendant dimethylamino group and an adjacent secondary amine H atom.