C–H⋯π interactions in the [Co(N-(2-aminomethylpyridyl)ethylenediamine)(2- aminomethylpyridine)Cl]2+ system: syntheses, 2D NMR, X-ray structures and energy minimizations

Ten asymmetric isomers exist for [Co(pema)(ampy)Cl]2+ (pema=N-(2-aminomethylpyridyl)ethylenediamine, ampy=2-aminomethylpyridine) which involve unsymmetrical triamine and diamine ligands. Four of these have been synthesized, two facial (f3, f2′) and two mer (m3 and m4) isomers. Ab initio energy calculations for the [Co(pema)(ampy)Cl]2+ and [Co(pema)(ampy)OH]2+ systems show that the isomers containing a C–H⋯π interaction are the more stable forms. The f3 is the most stable isomer in the chloro system and the m3 form in the hydroxo system. The structures are deduced from the 2D NMR spectra and confirmed by the X-ray crystal structure determinations for the four chloro isomers.