RESONANCE RAMAN, SURFACE-ENHANCED RESONANCE RAMAN, INFRARED, AND AB-INITIO VIBRATIONAL SPECTROSCOPIC STUDY OF TETRAAZAANNULENES

The IR and resonance Raman spectra of dibenzo[b,i][1,4,8,11]tetraaza[1 4]annulene (TAA) and ramethyldibenzo[b,i][1,4,8,11]tetraaza[14]annulen e (TMTAA) have been measured and compared to ab initio calculations of the vibrational wavenumbers, using the 3-21G basis set. An excellent fit is found between the experimental and calculated data, enabling pr ecise vibrational assignments to be made. For the CC and CN stretching vibrations there is substantial separation between the vibrational mo tion of the diimine and benzene ring parts of the macrocycles. Surface -enhanced Raman spectra were obtained following adsorption on Ag elect rodes, with potentials in the range -0.1 to -0.6 V vs Ag/AgCl. The dat a indicate that both macrocycles adopt either a perpendicular edge-on or tilted orientation on the Ag electrode surface.