Investigation of thiourea-silanes as viable precursors for the sol-gel synthesis of composites containing Zn-S complexes

摘要

Sulphur-functionalised trialkoxysilanes are suitable compounds for the sol-gel synthesis of silica glass embedding metal sulphide nanoclusters. In this study, three different thiourea-functionalised silanes, (EtO)_3Si(CH_2)_3NHC(=S)NHPh (SilTu), 1,4-[(EtO)_3Si(CH_2)_3NHC(=S)NH]_2Ph (diSilTu) and (MeO)_3Si(CH_2)_3N[C(S)NH(C_6H_5)](CH_2)_2NH[C(S)NH(C_6H_5)] (SildiTu), were used together with Zn~(2+) ions to investigate their potential use in the preparation of ZnS-SiO_2 materials. Such precursors provide, in principle, a "molecule-to-nanocomposite" path by a direct anchoring of the metal cations to the forming silica network, via metal-sulphur (M-S) interactions. The sol-gel precursors were characterized by IR and NMR spectroscopies, and by electrospray mass spectrometry (ESI-MS). DiSilTu was also characterized by single crystal X-ray analysis. IR and ~1H, ~(13)C and ~(29)Si NMR measurements confirmed the formation of stable complexes with Zn~(2+) ions, especially in the case of SilTu, also under sol-gel conditions.