1. 3. Results and Discussion 2. Computational Methods
NBO ANALYSIS FOR ENCAPSULATION OF H2O2 IN FUNCTIONALIZED β-CYCLODEXTRIN BY
DENSITY FUNCTIONAL THEORY
Elham Barani , Mohammad Izadyar*
Department of Chemistry, Faculty of sciences, Ferdowsi University of Mashhad, Mashhad, Iran
1. Introduction
3. Results and Discussion
Cyclodextrins (CDs) are cyclic oligosaccharides with central hydrophobic cavities and hydrophilic exterior edges. Cyclodextrins are composed of 5–12 α-(1-4)-linked D(+) glucopyranose units linked in macrocyclic ring. The most widely used (CDs) are α-, β- and γ (CDs). The ability of β-CD to form inclusion complexes with different products is well known [1]. Cyclodextrins have been studied extensively as biomimetic catalysts. The popularity of cyclodextrins can be traced to a number of factors:(1) their widespread availability (2) well-established synthetic methods to modify the hydroxyl groups, which allow a variety of substituents to be introduced and (3) the hydrophobic cavity of cyclodextrin, which enables the binding of hydrophobic guests.[2]
In this study we analyzed natural bond orbitals (NBO) for encapsulation of H2O2 in the functionalized β-cyclodextrin when β-cyclodextrin is functionalized by aldehyde group. From NBO analysis, the donor and acceptor interactions between H2O2 and β-CD were analyzed and discussed.
The natural bond analyses (NBO) were applied for investigating the electronic charges and donor–acceptor interactions in the complexes of H2O2-β-cyclodextrin. Table 1 shows some of the significant donor–acceptor interactions and their stabilization energies E(2) .
Lone pair O145 of β-CD interacts with vacant orbital of σ* O144-H146 of H2O2 leading to the formation of H-bond in the complex. As an overall conclusion, we can confirm that Van Der Waals interactions is more important factor in the charge transfer process than the intermolecular hydrogen bond, and is the main driving force of the formation of inclusion complex.
Table1. Donor–acceptor interactions and stabilization energies E(2) (kcal.mol-1).
Donor Acceptor E(2) (kcal.mol-1)
Lp O σ* O144-H
Lp O σ* C132-O
Density functional theory (DFT) have been carried out at the MPW1PW91 level using the Gaussian 09 package [3]. All structures were fully optimized with the G(d,p) basis set, (Figure1). The Donor–acceptor interactions of H2O2 inclusion complex into β-CD cavity were investigated to have an insight into the inclusion mechanism. + 2)
2. Computational Methods
4. Conclusions
NBO analysis reveals that the inclusion of H2O2 with β-CD is stabilized by Van Der Waals interactions. In addition, NBO analysis gives that mutual interactions between donor and acceptor orbital of each H2O2 and β-CD plays an important role to the stabilization of such complex.
5. References
[1] Yap, P.W., Ariff, A.B., Woo, K.K., Hii, S.L., J. Biol. Sci. , 10(2010)676–681.
[2] Louis Marchetti and Mindy Levine, ACS Catalysis, 1(2011)1090–1118.
[3] Gaussian 09 references, Inc., Pittsburgh PA, (2009). TS
Figure 1. Optimized structures for the reactants and product.