Hydrogen bonds and a hydrogen-bonded chain in Mannich bases of 5,5'-dinitro-2,2'-biphenol-FT-IR and H-1 NMR studies

5,5'-Dinitro-3-diethylaminomethyl-2,2'-biphenol (1) and 5,5'-dinitro-3,3' bis(diethylaminomethyl)-2,2'-biphenol (2) as well as 5,5'-dinitro-2,2'-biphenol (3) were synthesized and studied by FT-IR and H-1 NMR spectroscopy in acetonitrile or acetonitrile-d(3) solutions, respectively, With compound 1 a hydrogen-bonded system with large proton polarizability is found. In the hydrogen bonds in compound 2 the protons are localized at the N atoms. These hydrogen bonds show no proton polarizability. In the protonated compound 2 a very strong homoconjugated O- ... H+... O- hydrogen bond with large proton polarizability is found, whereas two other protons are localized at the N atoms. The deviation of the results obtained with other derivatives of 2,2'-biphenols are caused by the larger acidity of the nitro groups. (C) 1997 Elsevier Science B.V.