Synthesis and solid-state NMR structural characterization of polysiloxane-immobilized amine ligands and their metal complexes

Polysiloxane-immobilized amine and diamine ligand systems have been made by hydrolytic condensation of Si(OEt)(4) with (EtO)(3)Si(CH2)(3)NH2 or (MeO)(3)Si(CH2)(3)NH(CH2)(2)NH2. The corresponding triamine ligand was made from the reaction of 3-chloropropylpolysiloxane with diethylenetriamine (H2NCH2CH2NHCH2CH2NH2); solid-state C-13 and N-15 nuclear magnetic resonance (NMR) spectra can identify the structure of the product of this reaction. Si-29, N-15, C-13 and H-1 NMR spectra are in general valuable for characterizing these polysiloxane structures, and provide evidence for the involvement of the amine ligands in hydrogen bonding with surface silanols. Together with results of classical elemental analysis, the NMR data indicate that a portion of the ligand groups are inaccessible to metal ions and remain uncoordinated when these materials are treated with aqueous solutions of divalent metal ions. Si-29 NMR spectra and elemental analysis reveal some details of the leaching of these polysiloxane materials, when they are treated with acids or metal ion solutions. Relaxation times, T-1(H), were measured, based on Si-29 and C-13 detection, on the polysiloxane-immobilized ligand systems. The T-1(H) results suggest that the organofunctionalities in these systems are evenly distributed in the polysiloxane network.