Synthesis and solid-state NMR structural characterization of polysiloxane-immobilized thiol and thiol-amine ligands

Abstract

Thiol and thiol-amine ligand systems that are immobilized in a polysiloxane matrix have been synthesized via the sol-gel process by hydrolytic condensation of mixtures of Si(OEt) 4 and (MeO) 3Si(CH 2) 3SH, as well as (EtO) 3Si(CH 2) 3NH 2 or (MeO) 3Si(CH 2) 3NH(CH 2) 2NH 2 for thiol-amine systems. In these systems, most of the amine groups can be protonated by aqueous acid solution. Solid-state 29Si nuclear magnetic resonance (NMR) spectra confirm the fact that these materials, in analogy to polysiloxane-immobilized amine systems, undergo leaching of small oligomers containing ligand groups when they are treated with aqueous acid. 15N NMR spectra indicate that the amine groups in these systems may be involved in hydrogen bonding with silanols or with other ligand groups. 13C-detected and 29Si-detected T 1 H values were measured on the polysiloxane-immobilized thiol system, thiol-monoamine system and thiol-diamine system. The T 1 H results suggest that the ligand groups in these systems are evenly distributed in the polysiloxane networks.