Surface enhancement Raman scattering of tautomeric thiobarbituric acid. Natural bond orbitals and B3LYP/6-311+G (d, p) assignments of the Fourier Infrared and Fourier Raman Spectra.

Surface enhancement Raman scattering (SERS) of two tautomer of thiobarbituric acid was obtained using silver and gold nanoparticles. Large band enhancement in the region of the ν(C=S), ν(C=C), δ(CH2), and δ(CNH) vibrational modes was found. Natural bond analysis of the tautomer species revealed expressive values of charge transfer, principally from lone pair electron orbitals of the S, N, and O atoms. Complete vibrational assignment was done for the two tautomers using the B3LYP/6-311+G (d, p) procedure, band deconvolution analysis, and from a rigorous interpretation of the normal modes matrix. The calculated spectra agree well with the experimental ones.

FT-IR vibrational spectrum and DFT:B3LYP/6-31G and B3LYP/6-311G structure and vibrational analysis of glycinate-guanidoacetate nickel (II) complex: [Ni(Gly)(Gaa)].

The glycinate-guanidoacetate nickel (II) complex was synthesized and obtained as a crystalline powder. The characterization of this complex was performed by means of the experimental methods: CHN-O elemental analysis, atomic absorption spectrometry, thermo-gravimetric analysis and infrared spectrum. Density functional theory calculations, DFT:B3LYP/6-31G and B3LYP/6-311G, were performed for the determination of geometrical structure and vibrational assignment for the glycinate-guanidoacetate nickel (II) complex. A full discussion of the framework vibrational modes was done using as criteria the study of the distorted geometric structures generated for each one of the vibrational modes in the low energy region. As results of this research we have obtained and characterized a novel complex, glycinate-guanidoacetate nickel (II), [Ni(Gly)(Gaa)], and we deduced the most probable structure using the experimental data of the infrared spectrum in conjunction with the theoretical DFT procedures. The calculated DFT spectra in the high and low energy regions agree well with the observed ones.

Fourier transform infrared spectrum, vibrational analysis and structural determinations of the trans-bis(glycine)nickel(II) complex by means of the RHF/6-311G and DFT:B3LYP/6-31G and 6-311G methods.

The trans-bis(glycine)nickel(II) complex was synthesized, and the Fourier transform infrared spectra in the regions 4000-370 cm(-1) and 700-30 cm(-1) were measured. Band deconvolution analysis and the second derivative of the infrared spectrum were also performed. The determination of the geometrical structure in the trans position of the glycine ligands around Ni(II) for the trans-bis(glycine)nickel(II) complex as well as the vibrational assignment were assisted by RHF/6-311G and by Density Functional Theory calculations, DFT:B3LYP/6-31G and 6-311G basis sets. A full discussion of the framework vibrational modes was done using as criteria the geometry study of distorted structures generated for the vibrational modes. Incidentally, Normal Coordinate Analysis was carried out for the Ni(N)(2)(O)(2) structural fragment. The calculated DFT spectra in the high- and low-energy regions agree with the observed ones.

FT-IR vibrational spectrum and DFT:B3LYP/6-311G structure and vibrational analysis of bis-serinenickel(II) complex: [Ni(Ser)2].

The bis-serinenickel(II) complex was synthesized, and the Fourier-transforms infrared spectra in the regions 4000-370 and 700-30 cm(-1) was measured. The second derivative spectra and band deconvolution analysis was also obtained. Density functional theory calculations, DFT:B3LYP/6-311G, were performed for the determination of geometrical structure and vibrational assignment for the bis-serinenickel(II) complex. A full discussion of the framework vibrational modes was done using as criteria the geometry study of distorted structures generated for the vibrational modes. Incidentally, the normal coordinate analysis was carried out for the Ni(N)2(O)2 structural fragment. The calculated DFT spectra in the high and low energy regions agree well with the observed ones.

FT-IR vibrational spectrum and DFT:B3LYP/6-31G structure and vibrational analysis of guanidinoaceticserinenickel(II) complex: [Ni(GAA)(Ser)].

Vibrational assignment and structural determination for the guanidinoaceticserinenickel(II) complex have been made through DFT:B3LYP/6-31G calculations. A full discussion of the framework vibrational modes was done using as criteria the geometry study of distorted structures generated for the vibrational modes. Incidentally, the normal co-ordinate treatments have been made in order to clarify the assignments for the Ni(N)(2)(O)(2) structural fragment. The calculated DFT spectra in the high and low energy regions agree well with the observed ones.