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

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(CH2)3NHC(¼S)NHPh (SilTu), 1,4- [(EtO)3Si(CH2)3NHC(¼S)NH]2Ph (diSilTu) and (MeO)3Si(CH2)3N[C(S)NH(C6H5)](CH2)2NH[C(S)NH(C6H5)] (SildiTu), were used together with Zn2þ ions to investigate their potential use in the preparation of ZnS–SiO2 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, 13C and 29Si NMR measurements confirmed the formation of stable complexes with Zn2þ ions, especially in the case of SilTu, also under sol–gel conditions. # 2003 Elsevier B.V. All rights reserved