Complexing ability of (−)-cytisine — Synthesis, spectroscopy and crystal structures of the new copper and zinc complexes

Abstract

For the first time the NMR spectra of quinolizidine alkaloid with Cu(II) are studied. Structures of new complexes of (−)-cytisine with Cu+2 and Zn+2 cations are visualized, discussed in detail and characterized by spectroscopic methods: ESI-MS, NMR, UV–vis, EPR and crystallographic methods. In solution metal coordinates through the protonated nitrogen atoms of secondary amino groups (in piperidine ring) of cytisine molecule. While in solid state the most stable structures of the complexes are those in which the coordination of Cu(II) and Zn(II) salts is realized solely through the lactam carbonyl oxygen atom.