Theoretical investigations of the hydrogen bond in a tetraamido/diamino quaternized macrocycle

ABSTRACT

We present theoretical investigations on the nature and persistence of the strong central hydrogen bond of a tetraamido/diamino quaternized macrocycle. Our theoretical study of the NMR properties of the central hydrogen bond proved difficult to reconcile with the available experimental results, suggesting the possibility of the non-persistence of the central hydrogen bond of the macrocycle in solution. We demonstrate alternative scenarios, in which a tautomerization of the macrocycle in solution gives rise to the experimentally observed NMR shifts.