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 wi th 4-nitrocatechol the proton from 1-hydroxyl group of 4-nitrocatechol moie ty is transferred to TBD to form ion-pair; two adjacent ion-pairs are linke d across a center of inversion. The structure exhibits a cooperative, intra molecularly hydrogen-bonded motif. The hydrogen bonds are relatively long a nd, and they display only minor proton polarizability. The structure of the complex is retained in chloroform solution, as shown by Fr-IR and H-1 NMR measurement; in acetonitrile, the compound partially dissociates. The parti al dissociation is implied by the presence of free cations, and also by tha t of the (O . . .H . . .O)(-) hydrogen bonds formed between two mono-deprot onated 4-nitrocatechol molecules. (C) 2001 Elsevier Science B.V. All rights reserved.