Synthesis, characterisation, and fluorescence spectroscopic mobility studies of fluorene labeled inorganic-organic hybrid polymers

In the attempt to find catalyst supports with improved accessibilities for tethered transition metal complexes, a series of inorganic-organic hybrid p olymers was synthesised by sol-gel processing of three different silyl-func tionalised alkyl derivatives. The resulting materials were characterised by solid-state NMR spectroscopy, BET measurements and elemental analysis. Mol ecular mobilities in the solvent-swollen polymers were determined by fluore scence spectroscopy. As fluorescent probe, fluorene was covalently attached to the polymer matrix by a T-silyl-functionalised alkyl spacer. The rotati onal mobilities of the probe were determined by steady-state and time-resol ved fluorescence depolarisation experiments. Translational mobilities of mo lecular species dissolved in the liquid phase were investigated by the kine tics of luminescence quenching after pulsed laser excitation. Both rotation al and translational mobilities in hybrid materials are significantly highe r than in conventional Q-type polysiloxanes. However, the mobilities are st ill about one to two orders of magnitude lower than in homogeneous solution s, and thus contribute to the reduced accessibilities of matrix bound trans ition metal catalysts. The highest mobilities were observed in dichlorometh ane and organic ethers, which have the strongest swelling capabilities for the hybrid polymers. Compared to D-silyl polymers, mobilities in T-silyl ba sed materials are significantly higher.