ASSIGNMENT OF N=N VIBRATIONAL FREQUENCIES AND TAUTOMERIC EFFECTS IN THE VIBRATIONAL-SPECTRA OF 1-ARYL-3-ALKYL-3-HYDROXY-TRIAZENES AND THEIRPLATINUM COMPLEXES

The vibrational frequencies of the N=N stretching mode of 1-aryl-3-alk yl-3-hydroxy-triazenes and their platinum complexes (PtL(4); L = triaz ene) were investigated by FT-IR and FT-Raman spectroscopy. The influen ce of electron-donating or -withdrawing snbstituents on the phenyl rin g and of different alkyl substituents at the N-3 atom on these frequen cies was considered. The N=N vibrational frequency is significantly lo wered (as a result of the delocalization of the N=N bond over three ni trogen atoms) compared to related compounds. The Pt complexes show a r educed intensity and an increased linewidth in the vibrational spectra . Additionally, the NMR spectra of the 1-aryl-3-alkyl-3-hydroxy-triaze nes were recorded in order to short the tautomeric structure of those substances. The hydroxy triazenes preferentially exist in the (NH)-H-1 form. As a consequence, the N=N stretching frequencies of the hydroxy triazenes appear to be influenced by the superposition of two counter acting effects, the delocalization of the N=N bond and tautomerism.