R. E. Clavijo

Infrared spectrum of the bis-(1,10-phenanthroline) Cu(I) and Cu(II) perchlorate complexes

Abstract FT-IR spectra of the title compounds and derivatives were measured in the range 4000–120 cm −1 . A complete experimental spectral assignment has been performed. A simplified normal coordinate treatment orientates some assignment of frequencies in the low energy region. Bands at ca. 420 and 300 cm −1 are ascribed to the v Cu-N modes. A stability order of the Cu(I) complexes is proposed on the basis of their Cu-N frequency values.

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

Abstract Infrared (middle and far) and Raman spectroscopy were used to study the adsorption of vanadylnaphthalocyanine and vanadylporphine tetraphenyl substituted macrocycles adsorbed onto metallic surfaces. The IR spectra of the compounds deposited onto a KBr monocrystal and onto a smooth copper surface suggest a weak adsorbate–substrate interaction and no significant structural modifications imposed by surface effect. The reflection–absorption IR (IRRAS) spectra allowed to propose a preferential molecular orientation of the molecules deposited onto the copper surface. Surface-enhanced Raman spectral data obtained on colloidal Ag as well as Ag island films suggest a weak macrocycle interaction and small structural modifications of the naphthalocyanine complex on the surface. The whole spectral data indicate that the naphthalocyanine complex is orientated with the naphthalocyanine plane face-on to 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 responsible of the weak adsorbate–substrate interaction. Porphine complex has no interaction with the surface. This different behaviour of the above complexes is related to the different extent of the π-electronic size.

Vibrational and theoretical study of azabipiridyl macrocycle and its Ni(II), Cu(II) and Zn(II) complexes deposited onto a smooth copper surface

Abstract The infrared spectra of the azabipiridyl macrocycle complexes of Ni(II), Cu(II) and Zn(II) were registered between 4000 and 200 cm −1 . The spectral assignment allowed to identify the complex formation and structural differences in the coordination site of the complexes. The Ni complex is coplanar to the coordinating N atoms; the copper ion is slightly out of the coordination site plane and the Zn cation is decidedly out of that plane. The stability order of the complex formation Ni>Cu>Zn, is proposed. Specular reflectance IR spectra indicated that the ligand displays an aleatory orientation onto the smooth copper surface and the Ni and Cu complexes are oriented plane parallel to the surface. The Zn complex–surface interaction is the less energetic in the series. A theoretical study using the INDO/1 semiempirical method and a molecular model for the interacting adsorbate–substrate system support quite well the experimental results and allow an interpretation of the energetic process of the complex–surface interaction; the energy of the complex surface interaction follows the order Ni>Cu>Zn.

Vibrational study of the interaction of dinaphthalenic Ni(II) and Cu(II) azamacrocycle complexes methyl and phenyl substituted with different metal surfaces

Abstract The FT-IR and Raman spectra in the solid state, the reflection–absorption IR spectra (RAIRS) and the surface enhanced IR (SEIR) and surface enhanced Raman spectra (SERS) of the Ni(II) (trans-7,14-dimethyl-5,12,-diphenyl-1,4,8,11-tetra-aza-2,3-9,10-dinaphthyl-cyclotetradeca-5,7,12,14-tetraene) and Cu(II) (5,7,12,14-tetramethyl-1,4,8,11-tetra-aza-2,3-9,10-dinaphthyl-cyclotetradeca-5,7,12,14-tetraene) are reported. The RAIRS analysis and differences observed in the relative intensities of complexes deposited onto KBr and Cu surfaces suggest that the organisation of each macrocycle is different on both surfaces. SERS data allow to propose for both complexes an adsorbate–substrate interaction between the complex and the colloidal Ag surface. Complexes are oriented face-on to the surface being the number of Cu macrocycles oriented face-on to the surface larger than that of the Ni macrocycles. The organisation of the complexes on Au film is different to that found on Ag colloids and rather random. The phenyl groups avoid a better organisation of the Ni complex on the surface. SEIR data analysis of samples deposited on Au film suggests that the Ni complex is less organised than the Cu complex. The dynamic and energetic of the adsorbate–substrate interaction is interpreted by using a simple molecular model and INDO/1 calculations.

Raman Characterization of Pigments in Painted Beams and a Wall Painting Discovered in the San Francisco Church in Santiago, Chile

ABSTRACT A material characterization of two artworks discovered in the San Francisco Church, Santiago, Chile, was performed using micro-Raman spectroscopy. Structural painted beams and a wall painting that belong to the same time period, between the end of the 17th and 19th centuries, were analyzed. The cross-section samples of both artworks were characterized and animal protein was identified in the ground layer in both cases. The supporting material of the beams was identified as cypress wood, and a rag paper layer was used as a base for the paint layer, which is composed mainly of a white ground layer on which the color was subsequently added; the yellow pigments are orpiment and chrome yellow; the green color probably arises from a mixture of orpiment, red lead, ultramarine blue, and calcite. A complete analysis of the materials using complementary techniques such as microchemistry and optical microscopy indicates that the mural was painted using a mixed technique and that organic and inorganic pigments were used. The identification of the synthetic pigment ultramarine blue in some blue areas of the wall revealed a modification of the wall painting in the 19th century; dark blue areas resulted from a mixture of indigo, palygorskite, and lazurite.

Vibrational study of sub-2,3-boronnaphthalocyanine chlorine adsorbed on metal surfaces

Abstract Fourier transform infrared spectroscopy (FTIR), reflection–absorption infrared spectroscopy (RAIRS) and surface-enhanced Raman spectroscopy (SERS) were applied to study the adsorption of the macrocycle sub-2,3-boronnaphthalocyanine chlorine (subBClNPc) on surfaces of different nature. The analysis of the results obtained with the above techniques as well as a semiempirical calculation suggest the existence of a significant although weak adsorbate–substrate interaction and that the compound is oriented with the Cl atom toward the metallic surface. The vibrational study was completed with a normal co-ordinate analysis (NCA).

Surface-enhanced Raman scattering and theoretical study of the bilichromes biliverdin and bilirubin

ABSTRACT The surface-enhanced Raman scattering spectra of biliverdin and bilirubin were obtained and analyzed; a physical silver ligand interaction was inferred. The structural conformation of biliverdin is practically the same when passing from the dry to solution relative to that observed in Raman solid. However, the surface effect induces a different molecular orientation on the surface in dry and in solution. The conformational structure of bilirubin is modified when passing from dry to solution conditions; the orientation of the analyte on the surface is different in both media. The carboxylate groups interact with the surface more closely in bilirubin than in biliverdin. The unsaturated methine bridge in biliverdin confers an additional stability by delocalizing the π-electronic cloud. Both sides of the molecule could be in the same plane. On contrary, bilirubin with a tetrahedric carbon (methylene bridge) confers the whole system a rather free rotation of each side of the whole molecule. Theoretical model calculations of the biliverdin and bilirubin onto the silver surface predict a nearly coplanar orientation of the whole molecules and non-bonded interaction.