Titanium(iv)-based helicates incorporating the ortho-phenylenediamine ligand: a structural and a computational
Nathalie Baradel1, Pierre Mobian, Georges Khalil
1Laboratoire de Chimie Moléculaire de l'Etat solide, UMR 7140, University of Strasbourg, Strasbourg, France. mobian@unistra.fr.
Abstract:
The multicomponent coordination chemistry involving Ti(OPri)4, the ortho-phenylenediamine ligand (opda) and 2,2'-biphenol-based proligands (L2H4 and L3H6) is described. The proligands L2H4 and L3H6 incorporate two and three 2,2'-biphenol units linked with p-phenylene bridges (p-PLB) respectively. We demonstrate that this selected set of components allows the spontaneous formation of neutral double-stranded helicates. In particular, we report the X-ray crystal structure of a multicomponent helicate formed with L2, named Ti2(L2)2(opda)2. The molecular structure of the helicate shows two inequivalent L2 ligands. 1H NMR analysis at variable temperature highlights an intramolecular fluxional phenomenon for this species. An insight into this dynamic behaviour is obtained via the energy profiles of Ti2(L2)2(opda)2 resulting from the full rotation of the p-PLB rings. Additionally, the thermodynamic parameters associated with the formation of the Ti2(L2)2(opda)2 complex are modelled and discussed related to the ones linked to the formation of a related monomeric complex.
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