FT-IR SPECTROSCOPIC STUDY OF URACIL DERIVATIVES AND THEIR HYDROGEN-BONDED COMPLEXES WITH MODEL PROTON DONORS .5. COMPLEXES OF URACILS WITH HYDROGEN-CHLORIDE IN ARGON MATRICES

FT-IR spectra are reported for uracils complexed with hydrogen chlorid e in Ar matrices. The spectral characteristics demonstrate that uracil s form a C4=O ... H-Cl hydrogen bond of intermediate strength in Ar ma trices. The large shift of the proton donor mode nu(s) finds support i n the vibration correlation diagram for O-base. HCl complexes. For som e of the bases a small amount of the C2=O ... HCl species is identifie d in matrices containing an excess of HCl. H-bonding of the C=S group plays only a minor role in thiouracils. For all the bases studied here , N-H ... Cl-H structures are also identified from the shifts of the u racil N H modes. The results allow the discussion of particular bondin g trends for the basic groups in uracils, these trends being largely c onsistent with earlier reported results for complexes of uracils with other proton donors.