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)(3)Si(CH2)(3)NHC(=S)NHPh (SilTu), 1,4-[(EtO)(3)Si(CH2)(3)NHC(=S)NH](2)Ph (diSilTu) and (MeO)(3)Si(CH2)(3)N[C(S)NH(C6H5)](CH2)(2)NH[C(S)NH(C6H5)] (SildiTu), were used together with Zn2+ 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 H-1, C-13 and Si-21 NMR measurements confirmed the formation of stable complexes with Zn2+ ions, especially in the case of SilTu, also under sol-gel conditions. (C) 2003 Elsevier B.V. All rights reserved.