New silica hybrids elaborated by sol-gel process from bifunctional thiadiazole and 1,2,4-triazole precursors

GRAPHICAL ABSTRACT

ABSTRACT

New hybrid materials were synthesized from an inorganic precursor, (tetraethoxysilane: TEOS) and bifunctional organic precursors through the sol-gel process. Indeed, monolithic and transparent hybrid gels were obtained by the reaction of tetraethoxysilicate (TEOS) with 1,2,4-thiadiazole-3,5-diamine (1), 5-amino-1,3,4-thiadiazole-2-thiol (2), and 1H-1,2,4-triazole-3-thiol (3) in ethanol as solvent, using chloric acid (HCl 10⁻¹M) as catalyst. It is shown that TEOS has been cross-linked with bi-functional heterocyclic compounds: (1), (2) and (3) leading to the formation of transparent and colorous gels. The characterization was realized by infrared, ²⁹Si and ¹³C CP MAS NMR. The xerogels morphology and texture were studied by scanning electron microscopy (SEM) and Brunauer – Emmet – Teller method (BET). The obtained results show that organic adducts (1), (2) and (3) react with TEOS leading to gels in which Si–N and Si–S bridges were formed. According to N₂-physisorption results, xerogels are mesoporous with specific surface area varied from 105 to 312 m²g⁻¹ and their isotherms are classified as type IV. The optic and magnetic properties of hybrids were studied respectively by UV-Vis spectroscopy and RPE. This study showed that all materials are paramagnetic semiconductors.

KEYWORDS:

• Hybrid material
• Sol-Gel process
• 1,2,4-thiadiazole
• 1,2,4-triazole
• ²⁹Si and ¹³C CP MAS-NMR
• UV-vis and RPE