Cooperative intramolecularly hydrogen-bonded motif in the structure of 2:2 complex of TBD with 4-nitrocatechol

In the crystal of the 2:2 complex of 1,5,7-triazabicyclo[4.4.0]dec-5-ene with 4nitrocatechol the proton from 1-hydroxyl group of 4-nitrocatechol moiety is transferred to TBD to form ion-pair; two adjacent ion-pairs are linked across a center of inversion. The structure exhibits a cooperative, intramolecularly hydrogen-bonded motif. The hydrogen bonds are relatively long and, and they display only minor proton polarizability. The structure of the complex is retained in chloroform solution, as shown by FT-IR and 1H NMR measurement; in acetonitrile, the compound partially dissociates. The partial dissociation is implied by the presence of free cations, and also by that of the (O···H···O)- hydrogen bonds formed between two mono-deprotonated 4nitrocatechol molecules.