Vanadyl naphthalocyanine and vanadyl porphine phenyl substituted macrocycles: SERS and thin film organisation studies

Infrared (middle and far) and Raman spectroscopy were used to study the ads orption of vanadylnaphthalocyanine and vanadylporphine tetraphenyl substitu ted macrocycles adsorbed onto metallic surfaces. The IR spectra of the comp ounds deposited onto a KBr monocrystal and onto a smooth copper surface sug gest a weak adsorbate-substrate interaction and no significant structural m odifications imposed by surface effect. The reflection-absorption IR (IRRAS ) spectra allowed to propose a preferential molecular orientation of the mo lecules deposited onto the copper surface. Surface-enhanced Raman spectral data obtained on colloidal Ag as well as Ag island films suggest a weak mac rocycle interaction and small structural modifications of the naphthalocyan ine complex on the surface. The whole spectral data indicate that the napht halocyanine complex is orientated with the naphthalocyanine plane face-on t o the surface. In both complexes the vanadyl group is perpendicular to the coordination site and opposed to the surface. In both molecular systems the phenyl substituents, oriented perpendicular to the macrocycle plane, are r esponsible of the weak adsorbate-substrate interaction. Porphine complex ha s no interaction with the surface. This different behaviour of the above co mplexes is related to the different extent of the pi -electronic size. (C) 2001 Elsevier Science B.V. All rights reserved.