Abstract
Many H-1 NMR spectroscopic studies involving supramolecular binding of tetra-n-butylammonium halides (TBAX) with a variety of molecular receptors have been reported to date. Previously we demonstrated that the reference residual proton signal of the deuterochloroform solvent itself in TBAX solutions shifted downfield in a linear TBAX concentration-dependent relationship. We now report that a similar downfield chemical shift behaviour of the residual protons of other commonly employed deuterated solvents with TBACl can be seen for dichloromethane-d(2) and acetonitrile-d(3), but in acetone-d(6), methanol-d(4) and DMSO-d(6), upfield shifts are observed. A hypothesis based on Density Functional Theory (DFT) modelling is presented to account for this behaviour.