Complexation of phenols by calix[4]arene diethers in a low-permittivity solvent. Self-switched complexation by 25,27-dibenzyloxycalix[4]arene

S. Kunsági-Máté, Kornélia Szabó, Bernard Desbat, Jean Luc Bruneel, I. Bitter, L. Kollár

Research output: Contribution to journalArticle

15 Citations (Scopus)

Abstract

To improve the selectivity of sensing, the thermodynamics of the complex formation of some calix[4]arene hosts with neutral phenol guests was studied in carbon tetrachloride as nonpolar solvent. The molecular shape of calixarenes was varied by the selective functionalization with tBu and O-CH2-Ph (O-benzyl) or OPr groups at the upper and lower rim, respectively. To vary the electron density on the guest's aromatic rings, the parent phenol was functionalized in the para position with electron-withdrawing Cl, as well as H, and electron-releasing CH3 and tBu groups, To study the interaction between calixarene and the guests, PL and quantum-chemical methods were applied. The results revealed an overall 1:1 complex stoichiometry except for the parent dibenzyloxycalix[4]arene, where 1:2 host-guest stoichiometries were observed irrespective of the quality of phenol. In the latter case, the complex formation shows a self-switched character: the first phenol molecule is included in the calixarene cavity, and only afterward, a second guest molecule is bound by the two benzyloxy aromatics. Although the enthalpy change predicts strong interaction between the host and the guest, the Gibbs free energy change of the complex formation is small, resulting in a relatively low complex stability. The solvent-relaxation measurements support that the unexpected entropy change could be the consequence of the reorientation of solvent molecules around the calixarene building block. The reorientation is assisted by dispersive forces between solute and solvent molecules. IR and RAMAN analysis of the complexes exclude a considerable participation of the phenolic OH group in the stabilization of the complex. This result is in agreement with earlier findings where deterministic role of π-π interaction in the complex stability was assumed.

Original languageEnglish
Pages (from-to)7218-7223
Number of pages6
JournalJournal of Physical Chemistry B
Volume111
Issue number25
DOIs
Publication statusPublished - Jun 28 2007

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Calixarenes
Phenols
Phenol
Complexation
phenols
Permittivity
permittivity
Molecules
Stoichiometry
retraining
molecules
stoichiometry
Carbon tetrachloride
Electrons
Carbon Tetrachloride
carbon tetrachloride
releasing
Gibbs free energy
rims
Carrier concentration

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry

Cite this

Complexation of phenols by calix[4]arene diethers in a low-permittivity solvent. Self-switched complexation by 25,27-dibenzyloxycalix[4]arene. / Kunsági-Máté, S.; Szabó, Kornélia; Desbat, Bernard; Bruneel, Jean Luc; Bitter, I.; Kollár, L.

In: Journal of Physical Chemistry B, Vol. 111, No. 25, 28.06.2007, p. 7218-7223.

Research output: Contribution to journalArticle

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abstract = "To improve the selectivity of sensing, the thermodynamics of the complex formation of some calix[4]arene hosts with neutral phenol guests was studied in carbon tetrachloride as nonpolar solvent. The molecular shape of calixarenes was varied by the selective functionalization with tBu and O-CH2-Ph (O-benzyl) or OPr groups at the upper and lower rim, respectively. To vary the electron density on the guest's aromatic rings, the parent phenol was functionalized in the para position with electron-withdrawing Cl, as well as H, and electron-releasing CH3 and tBu groups, To study the interaction between calixarene and the guests, PL and quantum-chemical methods were applied. The results revealed an overall 1:1 complex stoichiometry except for the parent dibenzyloxycalix[4]arene, where 1:2 host-guest stoichiometries were observed irrespective of the quality of phenol. In the latter case, the complex formation shows a self-switched character: the first phenol molecule is included in the calixarene cavity, and only afterward, a second guest molecule is bound by the two benzyloxy aromatics. Although the enthalpy change predicts strong interaction between the host and the guest, the Gibbs free energy change of the complex formation is small, resulting in a relatively low complex stability. The solvent-relaxation measurements support that the unexpected entropy change could be the consequence of the reorientation of solvent molecules around the calixarene building block. The reorientation is assisted by dispersive forces between solute and solvent molecules. IR and RAMAN analysis of the complexes exclude a considerable participation of the phenolic OH group in the stabilization of the complex. This result is in agreement with earlier findings where deterministic role of π-π interaction in the complex stability was assumed.",
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AU - Szabó, Kornélia

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AU - Bruneel, Jean Luc

AU - Bitter, I.

AU - Kollár, L.

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AB - To improve the selectivity of sensing, the thermodynamics of the complex formation of some calix[4]arene hosts with neutral phenol guests was studied in carbon tetrachloride as nonpolar solvent. The molecular shape of calixarenes was varied by the selective functionalization with tBu and O-CH2-Ph (O-benzyl) or OPr groups at the upper and lower rim, respectively. To vary the electron density on the guest's aromatic rings, the parent phenol was functionalized in the para position with electron-withdrawing Cl, as well as H, and electron-releasing CH3 and tBu groups, To study the interaction between calixarene and the guests, PL and quantum-chemical methods were applied. The results revealed an overall 1:1 complex stoichiometry except for the parent dibenzyloxycalix[4]arene, where 1:2 host-guest stoichiometries were observed irrespective of the quality of phenol. In the latter case, the complex formation shows a self-switched character: the first phenol molecule is included in the calixarene cavity, and only afterward, a second guest molecule is bound by the two benzyloxy aromatics. Although the enthalpy change predicts strong interaction between the host and the guest, the Gibbs free energy change of the complex formation is small, resulting in a relatively low complex stability. The solvent-relaxation measurements support that the unexpected entropy change could be the consequence of the reorientation of solvent molecules around the calixarene building block. The reorientation is assisted by dispersive forces between solute and solvent molecules. IR and RAMAN analysis of the complexes exclude a considerable participation of the phenolic OH group in the stabilization of the complex. This result is in agreement with earlier findings where deterministic role of π-π interaction in the complex stability was assumed.

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