Halide ion effect on the chloroform chemical shift in supramolecular complexation studies with tetra-n-butylammonium salts: a ~~1H NMR and X-ray study

摘要

A ~~1H NMR spectroscopic study of tetra-n-butylammonium halides (TBAX: X=Cl~-, Br~- or I~-) in CDCl_3 solutions was conducted. Complexation studies of TBAX salts with different host molecules using ~~1H NMR in CDCl_3 have previously revealed that the reference residual CHCl3 proton signal had been shifted downfield. The aim of the study was to quantify the extent of these chemical shift changes with TBAX salts. Linear concentration-chemical shift relationships in each case were obtained from the resulting titration plots obtained from the addition of the TBAX salts alone to CDCl_3. Interactions in the solid state as determined by X-ray crystallography support the solution-state investigations indicating halide ion-chloroform proton interactions.