Structural, theoretical and spectroscopic studies of the 1 : 2 complex of 1,5,7-triazabicyclo[4.4.0]dec-5-ene-4-nitrophenol

In the crystal of the 1:2 complex of 1,5.7-triazabicyclo[4.4.0]dec-5-ene wi th 4-nitrophenol one hydrogen atom of the phenolic group is transferred to the TBD molecule and two NH protons form hydrogen bonds with one nitro grou p [(NO)-O-... distances are 2.968(5), 2.985(4) Angstrom]. This hydrogen-bon ded segment is linked to another molecule of 4 -nitrophenol by a short ((OH O)-H-...-O-...)(-) hydrogen bond [(OO)-O-... = 2.512(3) Angstrom]. The stru cture of the cation is investigated theoretically by geometry-optimization calculations. The structure of the complex is very well reflected in its FT IR spectrum in the solid. The complex dissolution in acetonitrile causes it s dissociation and its FTIR and H-1 NMR spectra prove the presence of the p rotonated TBD and ((OHO)-H-...-O-...)(-) hydrogen-bonded 4-nitrophenol-4-ni trophenolate species. In chloroform a new structure of the complex is found and discussed. (C) 2001 Elsevier Science B,V, All rights reserved.