PhD: Characterization and properties of chemisorbed ferrocene derivatives on different solid surfaces for their application in heterogeneous catalysis, by means of vibrational spectroscopic methods and techniques

Miha Bukleski
Institute of Chemistry, Faculty of Natural Sciences and Mathematics, Ss. Cyril and Methodius University, Skopje, Macedonia
February, 2015
 

Abstract

3-aminopropylsilyl (APS) modified silica gel plays an important role as a precursor for further modifications, where APS acts as a spacer or bridging molecule. A monolayer of APS which is most suitable for this purpose was obtained in anhydrous conditions.
In this doctoral thesis, the results concerning the quantification of maximal chemisorbed APS groups on silica gel activated at 600 ºC are presented. The conditions under which the maximal chemisorption occurs are also determined starting from the optimal activation temperature of the silica gel until the conditions under which the IR recordings were performed.
The quantification using IR spectroscopic methods was done using two approaches: with indirect and direct method. The suggested indirect method is based on the analysis of toluene solution on the quantity of the non-reacted APTMS after the saturation of the silica gel surface with APS. The process of chemisorption was monitored via the increasing band intensity of ν(О–CH3), ν(Si–O) and ω(NH2) + τ(NH2) modes of the adsorbent using the transmission IR spectroscopy. The proposed direct method of analysis is by using the Diffuse Reflectance Infrared Fourier Transform (DRIFT) spectroscopy. In this case, the process of chemisorption was monitored via the increasing band intensity of ν(CH2), ν(NH2) and δ(NH2) vibrational modes of the adsorbent and decreasing ν(OH) band intensity characteristic for the free isolated OH groups of silica gel using DRIFT spectroscopy. The obtained results on maximum adsorption from both indirect and direct methods are in line with the previously obtained, using carbon elemental analysis. The conclusion was that the proposed methodology can be used for the quantification of APS groups chemisorbed on silica gel when the grafting chemical reaction was mainly irreversible.
Also, an additional modification of the amino-functionalized silica gel with acetyl ferrocene was performed. An IR characterization by the means of DRIFT spectroscopy technique of the obtained product was done. According to the bands in the DRIFT spectrum, it was found that Schiff base is being formed and bands from the ν(C=N) mode appear.