Alcohols as Latent Hydrophobes: Entropically Driven Uptake of 1,2-Diol Functionalized Ligands by a Porous Capsule in Water

Sourav Chakraborty, Alina Shnaiderman Grego, Somenath Garai, Mark Baranov, Achim Müller, Ira A. Weinstock

Research output: Contribution to journalArticlepeer-review

9 Scopus citations

Abstract

Alcohols, with hydroxyl groups compositionally identical to water itself, are consummate hydrophiles, whose high solubilities preclude spontaneous self-assembly in water. Nevertheless, the solute-solvent interactions associated with their highly favorable solvation enthalpies impose substantial entropic costs, similar in magnitude to those that drive the hydrophobic assembly of alkanes. We now show that under nanoconfined conditions this normally dormant "hydrophobicity" can emerge as the driving force for alcohol encapsulation. Using a porous molecular capsule, the displacement of endohedrally coordinated formate ligands (HCO2-) by 1,2-hydroxyl-functionalized l-glycerate (l-gly, l-HOCH2(HO)CHCO2-) was investigated by van't Hoff analysis of variable-temperature 1H NMR in D2O. At pD 5.8, l-gly uptake is enthalpically inhibited. Upon attenuation of this unfavorable change in enthalpy by cosequestration of protons within the alcoholic environment provided by encapsulated diol-functionalized ligands, -TΔS° dominates over ΔH°, spontaneously filling the capsule to its host capacity of 24 l-gly ligands via an entropically driven hydrophobic response.

Original languageEnglish
Pages (from-to)9170-9174
Number of pages5
JournalJournal of the American Chemical Society
Volume141
Issue number23
DOIs
StatePublished - 12 Jun 2019

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