Search results for " Spectroscopy"

Polypyrrole films functionalized with pendant titanocene dichloride complexes: Ellipsometric study of the electropolymerization process

2007

Electrochemical and ellipsometric methods have been used to study the electropolymerization process of a functionalized monomer, Tc3Py (in which pyrrole is covalently bonded with titanocene dichloride complex) on platinum electrode from a dilute monomer solution in acetonitrile. The deposition has been performed in the potentiodynamic regime. A new method for the acquisition and treatment of ellipsometric data has been proposed which allowed us to analyze the evolution of the film properties at each potential. The model of a single uniform layer was unable to describe the ellipsometric experimental observations with the necessary precision. A proper fitting of the data has been achieved con…

FTIR spectroscopy studies of high pressure-induced changes in pork macromolecular structure

2019

Abstract High pressure processing (HPP) allows to extend the shelf life of meat and meat products by pressurization of microorganisms. At the same time, HPP can induce changes of the protein structure. Vacuum-packed pork chops were HPP-treated at 300, 600 MPa for 1 or 15 min. Samples of raw, cooked and HPP-treated meat muscles and juice were analysed to evaluate the structure of macromolecules. HPP caused visible discolouration of pork chops; hence, the colour of pork meat surface was tested. The lightness (colour component L*) was directly proportional to the applied pressure, probably due to the increased protein denaturation by high pressure. Pork meat muscle and juice samples were analy…

Electronic structure of phthalocyanines : Theoretical investigation of the optical properties of phthalocyanine monomers, dimers, and crystals

1990

We present valence effective Hamiltonian (VEH) calculations on the optical absorptions of a series of phthalocyanine compounds: the metal‐free phthalocyanine molecule, a model system for the lithium phthalocyanine molecule, the metal‐free phthalocyanine dimer, and model systems for the lutetium diphthalocyanine and the lithium phthalocyanine crystal. For these compounds, it is found that the major factor influencing the evolution of the optical transitions is not the electronic structure of the metal but rather the geometric structure: phthalocyanine intraring geometry and, in the dimers and crystals, interring separation and staggering angle. The origin of the so‐called Soret or B absorpti…

Synthesis, structural diversity, inter-conversion and reactivity of Cu(II) complexes of hydroxy-rich molecules

2002

Tetranuclear Cu(II) complexes having linear, cubane and pseudodouble-cubane cores were synthesized using hydroxy-rich molecules possessing amine and imine groups. The products were structurally characterized and were studied for their ability to oxidize catechol as well as for their inter-conversion between mono- and tetra-nuclear complexes.

Lanthanide–saccharide chemistry: synthesis and characterisation of Ce(III)–saccharide complexes

2000

A series of nine Ce(III) complexes has been synthesised with seven different monosaccharides (D-glucose, D-fructose, D-galactose, D-mannose, L-sorbose, D-ribose and D-xylose) and two different disaccharides (D-maltose and L-lactose), and these have been characterised with various analytical, spectral, magnetic and electrochemical techniques. The NMR studies have highlighted some interesting features about the metal-ion-binding pattern of the saccharides. Some additional coordination has been proposed along with the chelating groups in the saccharide molecules, based on the shifts in 13C NMR spectra. On the other hand, solution absorption studies and solid-state magnetic susceptibilities hav…

Pressure dependence of the optical properties of wurtzite and rock-salt Zn1–xCoxO thin films

2007

In this paper we investigate the electronic structure of Zn 1-x Co x O by means of optical absorption measurements under pressure. Thin films of Zn 1-x Co x O with different Co content (from 1 to 30%) were prepared by pulsed laser deposition on mica substrates. Absorption spectra exhibit three main features that are clearly correlated to the Co content in the films: (i) absorption peaks in the infrared associated to crystal-field-split internal transitions in the Co 3d shell, with very small pressure coefficients due to their atomic character; (ii) a broad absorption band below the fundamental edge associated to charge transfer transitions, that exhibit relatively large pressure coefficient…

Huge shift of fundamental electronic absorption edge in Sr1−xBaxNb2O6 crystals at elevated temperatures

1995

The vibrational levels of methane obtained from analyses of high-resolution spectra

2006

International audience; Methane and its tetrahedral isotopologues are spherical-top molecules whose high-resolution rovibrational spectra can only be analyzed in detail, thanks to sophisticated symmetry-adapted tensorial models. However, the effective Hamiltonian parameters of such models do not give direct access to the positions of the vibrational sublevels. In this paper, we present a calculation of the vibrational level positions for 12CH4, 13CH4, 12CD4 and 13CD4 performed using the effective Hamiltonian parameters obtained through recent analyses. We also include the results of a re-analysis of the octad system of 12CH4 performed with a higher order of the development which slightly im…

A five-coordinate manganese(iii) complex of a salen type ligand with a positive axial anisotropy parameter D.

2017

A new high-spin d4 roughly trigonal–bipyramidal (TBP) manganese(III) complex with a salen type ligand (H2L), namely MnL(NCS)·0.4H2O, has been synthesised and characterised by elemental analysis, ESI mass spectrometry, IR and UV-vis spectroscopy, and spectroelectrochemistry. X-ray diffraction analysis revealed an axial compression of the approximate TBP. Temperature dependent magnetic susceptibility and variable-temperature variable-field (VTVH) magnetisation measurements, as well as high-frequency and -field EPR (HFEPR) spectroscopy, were used to accurately describe the magnetic properties of this complex and, in particular, determine the spin Hamiltonian parameters: g-values and the zero-f…

Mechanochemical Synthesis, Photophysical Properties, and X-ray Structures of N-Heteroacenes

2016

The described mechanochemical methodology is an example of a proof-of-concept in which solution-based tedious, poor yielding, and difficult syntheses of pyrazaacenes are achieved under solvent-free ball-milling conditions; the method is easy, high yielding, time-efficient, and environmentally benign. The synthesized compounds also include pyrazaacenes (N-heteroacenes) that are octacene analogues containing pyrene building blocks. The compounds were sparingly soluble in common solvents, and column chromatographic purifications could be avoided after the solvent-free syntheses. The UV/Vis absorption spectra of the pyrazaacenes show intense absorption bands in the near-IR region. The single-cr…