Kinetic Stabilities and Exchange Dynamics of Water-Soluble Bis-Formamide Caviplexes Studied Using Diffusion-Ordered NMR Spectroscopy (DOSY)

Luis Escobar, Yong Sheng Li, Yoram Cohen, Yang Yu, Julius Rebek, Pablo Ballester

Research output: Contribution to journalArticlepeer-review

Abstract

A deep cavitand binds long-chain trans,trans- and trans,cis-bis-formamide isomers in water solution giving a pair of caviplexes in a ca. 60:40 ratio. Both caviplexes display in/out guest exchange dynamics that are slow on the 1H NMR chemical shift timescale, but fast on the EXSY timescale. We apply diffusion-ordered NMR spectroscopy (DOSY) to characterize the caviplexes. On the diffusion timescale, the guest in/out exchange processes feature intermediate dynamics allowing the assessment of their kinetic stabilities. We found that the trans,cis-bis-formamide isomers form kinetically more stable caviplexes than the trans,trans-counterparts. We also show that the kinetic stabilities of the bis-formamide caviplexes relate well with their relative thermodynamic stabilities. Fortunately, the tuning of the DOSY parameters allowed the observation of the exchange dynamics as slow processes on the experiment timescale.

Original languageEnglish
Pages (from-to)8220-8225
Number of pages6
JournalChemistry - A European Journal
Volume26
Issue number37
DOIs
StatePublished - 2 Jul 2020

Keywords

  • DOSY
  • cavitands
  • diffusion
  • exchange
  • inclusion complexes

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