Mechanical switching of transition metal catalysts

We propose to develop mechanoresponsive catalysts ? catalysts which can be switched between dormant and active states by mechanical deformation. For this purpose, we will synthesize derivatives of the well-known Grubbs metathesis catalysts that are inactivated by supramolecular chelating ligands. In solution, these inactive catalysts may be switched on in an allosteric fashion by binding of complementary hydrogen bonding guests. When provided with polymeric arms, and embedded in an elastomeric matrix, these catalysts can be activated by mechanical forces, which result in disruption of the chelate, and allow the dissociation of one of the phosphine ligands. The mechanoresponsive catalysts will be studied (i) as mechanotransductive elements which, upon deformation, catalyze the formation of fluorescent species from nonfluorescent precursors, and (ii) as components in self-healing materials, which respond to stress by catalyzing a (crosslinking) polymerization reaction.