TY - JOUR
T1 - Alcohols as Latent Hydrophobes
T2 - Entropically Driven Uptake of 1,2-Diol Functionalized Ligands by a Porous Capsule in Water
AU - Chakraborty, Sourav
AU - Shnaiderman Grego, Alina
AU - Garai, Somenath
AU - Baranov, Mark
AU - Müller, Achim
AU - Weinstock, Ira A.
N1 - Funding Information:
I.A.W. thanks the Israel Science Foundation (170/17), S.C. thanks the Kreitman School of Advanced Graduate Studies of Ben-Gurion University of the Negev for a postdoctoral fellowship, and A.M. the European Union for an Advanced Grant.
Publisher Copyright:
© 2019 American Chemical Society.
PY - 2019/6/12
Y1 - 2019/6/12
N2 - 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.
AB - 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.
UR - http://www.scopus.com/inward/record.url?scp=85067364307&partnerID=8YFLogxK
U2 - 10.1021/jacs.9b03542
DO - 10.1021/jacs.9b03542
M3 - Article
AN - SCOPUS:85067364307
SN - 0002-7863
VL - 141
SP - 9170
EP - 9174
JO - Journal of the American Chemical Society
JF - Journal of the American Chemical Society
IS - 23
ER -