RESUMEN
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.
RESUMEN
The synthesis of a bowl-shaped trinuclear circular titanium-based helicate is reported. The strategy allowing access to this neutral architecture is based on a multicomponent self-assembly approach in which the ligands involved in the process are a bis-biphenol strand and 2,2'- bipyrimidine. By reacting the bis-biphenol ligand and 2,2'-bipyrimidine with an equimolar amount [Ti(OiPr)4 ], a bowl-shaped architecture is obtained through the formation of 18 new coordination bonds. This aggregate built from three octahedral TiO4 N2 nodes displays an unusually high stability in solution compared to related species. In addition, by modifying the stoichiometry of the initial components, two assemblies incorporating two titanium centers bridged by a 2,2'-bipyrimidine ligand are obtained. The crystal structures of these species are reported.
RESUMEN
A simple strategy to insert functional dendrons at precise positions along a linear polymer backbone is reported. Sequence controlled copolymerization of styrene and polyester dendrons containing a maleimide unit at their focal points was utilized to yield such polymers.