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Please use this identifier to cite or link to this item: http://dspace.library.iitb.ac.in/jspui/handle/10054/3745

Title: Characterization of covalent linkages in organically functionalized MCM-41 mesoporous materials by solid-state NMR and theoretical calculations
Authors: WIENCH, JW
AVADHUT, YS
MAITY, N
BHADURI, S
LAHIRI, GK
PRUSKI, M
GANAPATHY, S
Keywords: silica nanosphere
molecular-sieves
chemical-shifts
parameters
catalysts
si-29
condensation
recognition
adsorption
morphology
Issue Date: 2007
Publisher: AMER CHEMICAL SOC
Citation: JOURNAL OF PHYSICAL CHEMISTRY B, 111(15), 3877-3885
Abstract: The covalent linkages formed during functionalization of MCM-41 mesoporous molecular sieves with five chloroalkylsilanes ((EtO)(3)Si(CH2Cl), (MeO)(3)Si(CH2CH2CH2Cl), Cl3Si(CH2CH2CH3), Cl2Si(CH3)(CH2Cl) and Cl2Si(CH3)(2)) have been investigated using high-resolution solid-state NMR spectroscopy and DFT calculations. Structural information was obtained from H-1-C-13 and H-1-Si-29 heteronuclear (HETCOR) NMR spectra, in which high resolution in the H-1 dimension was obtained by using fast MAS. The H-1-C-13 HETCOR results provided the assignments of H-1 and C-13 resonances associated with the surface functional groups. Sensitivity-enhanced H-1-Si-29 HETCOR spectra, acquired using Carr-Purcell-Meiboom-Gill refocusing during data acquisition, revealed the identity of Si-29 sites (Q(n), T-n, and D-n) and the location of functional groups relative to these sites. Optimal geometries of local environments representing the Q(n), T-n and D-n resonances were calculated using molecular mechanics and ab initio methods. Subsequently, DFT calculations of Si-29, C-13, and H-1 chemical shifts were performed using Gaussian 03 at the B3LYP/6-311++G(2d,2p) level. The theoretical calculations are in excellent accord with the experimental chemical shifts. This work illustrates that state-of-the-art spectroscopic and theoretical tools can be used jointly to refine the complex structures of inorganic-organic hybrid materials.
URI: http://dx.doi.org/10.1021/jp067417x
http://dspace.library.iitb.ac.in/xmlui/handle/10054/3745
http://hdl.handle.net/10054/3745
ISSN: 1520-6106
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