Supramolecular adsorption of alkaloids by metallosalphen complexes

Mono and bis-zinc(II)-centered salphen derivatives 1-5 are presented as efficient adsorption materials for pyridine-based alkaloid derivatives. The different alkaloid assemblies were studied by UV-vis and NMR spectroscopy, and high binding constants (Ks approximately 10(5)) were additionally determined for the supramolecular complexes based on nicotine. X-ray analyses furthermore revealed, together with spectroscopic solution data, a preferential positioning of the nicotine guest(s). Upon binding to bis-Zn(II)-bis-salphen complexes, the dinicotine assembly provokes a colorimetric change that may be useful for colorimetric analyses. The adsorption/desorption process of nicotine was studied using a polymeric bis-Zn(salphen) complex (5) and showed a recycling potential of this type of complexes in the binding of alkaloid compounds.