Development of new precursors for immobilizing dyes onto silica surfaces

• Silatranes as precursors for immobilization of useful functionalities on to silica surface.
• Linkage of different azo dyes with immobilizable precursor.
• 3-Aminopropylsilatrane is used as immobilizable precursor due to silatranyl ring.
• Synthesis of D-SNP using Stöber's method.
• D-SNP are capable of capturing copper ions.

A series of new precursors for immobilization of dyes onto silica surface have been synthesized and characterized. Diazobenzene-derived dyes were synthesized by coupling salicylaldehyde and a diazotized aniline derivative. Condensation of the resultant carbaldehyde functionalized dyes with 3-aminopropylsilatrane afforded diazo-azomethine functionalized compounds containing silatranyl moiety, which were characterized using spectroscopic techniques, elemental analysis and single-crystal X-ray diffraction. Substituent dependent variation in electronic properties of silatranyl dyes was studied and the capability of immobilization of silatranyl substituted dyes was tested by synthesizing silica nanoparticles coated with immobilized dye. The derivatization of silica was confirmed by spectrophotometric, thermogravimetric and microscopic studies. The functionalized silica exhibit uniformly dispersed spherical particles of 170 nm diameter with an estimated approximate 8 nm coating of dye. As the silatranyl substituted dyes can be isolated in crystalline forms, they proved to be better precursors for immobilization in terms of purity and uniform distribution onto silica surfaces. The modified silica surfaces possess binding sites for capturing copper ions.

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