title: Protonation behaviour of chiral tetradentate polypyridines derived from alpha-pinene.
abstract: Detailed protonation experiments of the [5,6]-pinenebipyridine molecule and the unsubstituted [4,5]- and [5,6]-CHIRAGEN[0] ligands in various solvents indicate a variety of structures of the protonated species. UV-visible and NMR measurements (including (15)N chemical shifts) show the transition from trans to cis conformation of [5,6]-pinenebipyridine upon protonation. The [4,5]-CHIRAGEN[0] ligand, in which the protonation sites of the nitrogen atom donors are at opposite sides of the molecule, behave essentially like two independent bipyridine moieties; this behaviour was monitored by UV-visible, CD and NMR spectroscopy (including (15)N data). In the case of the [5,6]-CHIRAGEN[0], a pocket of donor atoms provides a chiral environment for two protons per ligand.
authors.affiliation: Department of Chemistry, University of Fribourg, Pérolles, 1700 Fribourg, Switzerland.
authors.forename: Mathias
authors.initials: M
authors.lastname: Düggeli
authors.forename: Tobias
authors.initials: T
authors.lastname: Christen
authors.forename: Alexander
authors.initials: A
authors.lastname: von Zelewsky