Effect of Fluorine and Molecular Charge-State on the Aggregation Behavior of (S)-(鈭?-N-Benzylpyrrolidine-2-methanol Confined within the AFI Nanoporous Structure
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- 作者：Luis G贸mez-Hortig眉ela ; Fernando L贸pez-Arbeloa ; Carlos M谩rquez-脕lvarez ; Joaqu铆n P茅rez-Pariente
- 刊名：The Journal of Physical Chemistry C
- 出版年：2013
- 出版时间：May 2, 2013
- 年：2013
- 卷：117
- 期：17
- 页码：8832-8839
- 全文大小：353K
- 年卷期：v.117,no.17(May 2, 2013)
- ISSN：1932-7455
文摘
The effect of the molecular charge-state and of the presence of fluorine atoms on the aggregation behavior of (S)-(鈭?-N-pyrrolidine-2-methanol has been studied by fluorescence and FTIR spectroscopies in aqueous solution and when confined within the nanoporous AFI structure during crystallization or after gas-phase adsorption. Results show that a higher aggregation is achieved via inclusion of the guest molecules in postsynthetic gas-phase adsorption treatments compared to what occurs during crystallization. In the former case, neutral species are incorporated within the aluminophosphate AFI framework, as evidenced by FTIR, which results in a high aggregation because of the lack of electrostatic repulsions. In contrast, a lower aggregation is observed when the organics are occluded during crystallization, which in turn is dependent on the presence of heteroatoms. In the undoped aluminophosphate systems, FTIR results show that the molecules are incorporated mainly as neutral species, which leads to a higher aggregation. On the contrary, on Mg- and Zn-doped systems, FTIR shows that the molecules are protonated; interestingly, this results in a lower aggregation on Mg-doped systems. However, a higher aggregation is observed for Zn-doped systems despite the charged molecular state, suggesting that the chemical nature of the dopant does influence the aggregation behavior. Fluorine in ortho- or meta-positions of the aromatic ring leads to a partial deaggregation of the molecules in solution and within the nanoporous structures, leading to a preferential incorporation of monomers within the AFI framework. This is probably due to an inductive effect caused by fluorine, which withdraws electron density from the aromatic ring, this being the driving-force for this type of aggregation.