Do Cyclodextrins Encapsulate Volatiles in Deep Eutectic Systems?

Abstract

Efficient renewable and non-toxic absorbents can now be designed to eliminate air pollutants such as volatile organic compounds (VOCs) from confined atmospheres. New hybrid materials result from the combination of Deep Eutectic Systems (DES) with well-known VOCs capture agents like β-cyclodextrin (βCD). Yet, a question arises: does βCD retain its encapsulation ability in DES? Multiple NMR techniques are used here to demonstrate the formation of inclusion complexes of βCD with two VOCs, aniline and toluene, in the pure DES reline and in reline/water mixtures. Complexation-induced chemical shift changes and intermolecular hostguest NOEs in the rotating frame give evidence of a genuine encapsulation in the βCD cavity, and complementary information on the dynamics of the VOC is gathered via relaxation and diffusion experiments. This work shows how different NMR techniques can contribute to the design of task-specific sustainable materials for absorption/extraction processes.

Determination of Binding Strengths of Host‐Guest Complexes in Deep Eutectic Solvents Using Spin Probe Methodology

“…With large cavity of γ‐CD, in DES, desolvation effects on both rate constants account for a K eq very similar to that measured in water when using BTBN as spin probe. With small cavity of β‐CD, complexation of BTBN in DES is significantly depressed although still maintained, as previously observed with VOC [8–10] …”

“…Probing the binding properties of macrocycles in DES is not as straightforward as in aqueous environments or traditional organic solvents. The combination of high ionic strength and viscosity of the solvent does not allow an easy use of traditional 1 H NMR and isothermal titration calorimetry (ITC) for quantitative measure of binding and very few data on complexation in DES are available in literature [8–10] . In particular, affinity constants for the complexation of methyl orange or volatile organic compounds (VOC) by different CDs were measured by UV‐Vis, [8] static headspace gas chromatography (SH‐GC) [8] and DOSY NMR experiments [9–10] .…”

Inclusion complexes of tricyclic drugs and β-cyclodextrin: Inherent chirality and dynamic behaviour

“…More in detail, AMT and CBZ tend to have similar mobilities and diffusivities close to βCD, as also observed for other tricyclic antidepressants (De Sousa et al, 2008). Following a commonly used methodology (see Theoretical toolbox in the SI for more details) (Brand et al, 2005;Cohen et al, 2005;Di Pietro et al, 2019;Lis-Cieplak et al, 2014;Uccello-Barretta et al, 2005), DOSY measurements can be exploited to determine the mole fraction of the bound guest . Basically, when the host and guest are tightly bound in a complex, they diffuse as a single entity and display the same diffusion coefficient.…”

Band-Gap Energies of Choline Chloride and Triphenylmethylphosphoniumbromide-Based Systems

“…These organic mixtures are named deep eutectic systems or, sometimes, deep eutectic solvents (DESs) and are exploitable in several fields. To cite only some applications of DESs, they have been proposed as new solvents [1][2][3][4], catalysts [5], electrodeposition agents [6,7], and stabilizing agents for antibiotics [8].…”