Copper Complexes of Dicarboxy‐Functionalized Tetramethylcyclam. Crystal Structures of Complexes with the Axial Ligands Perchlorate,Chloride, and Iodide

6,13‐Dicarboxy‐1,4,8,11‐tetramethyl‐1,4,8,11‐tetraazacyclotetradecane‐copper(II) perchlorate ( 2 a ) was synthesized via one‐step cyclocondensation from bis(N,N′‐dimethyl‐ ethylenediamine‐copper(II) perchlorate, formaldehyde and malonic acid. Anion exchange yielded the analogous copper(II) chloride ( 2 b ) and iodide ( 2 c ) complexes. Crystal structures of 2 a – 2 c show a square‐planar N₄‐co‐ordination of the copper(II) ion with RRSS configuration of the nitrogens and perchlorate, chloride or iodide ions weakly co‐ordinated axially. Relating to the macroring, the carboxy groups are in trans‐position. In 2 a , the packing is typical of parallel strands of complex subunits effected by dimerization of the carboxy groups, while in 2 b and 2 c formation of the supramolecular strands involve hydrogen bond interactions between carboxy groups and halide anions.