Search results for "Spectroscopy."
showing 10 items of 9110 documents
Crystallographic, spectroscopic and electrochemical characterization of pyridine adducts of magnesium(II) and zinc(II) porphine complexes
2013
Abstract A new purification method of magnesium(II) and zinc(II) porphine complexes (MgP and ZnP, respectively) by crystallization of their respective pyridine adducts is described. Pure MgP and ZnP can be regenerated by removal of the coordinated pyridine ligands by heating at 200 °C under vacuum. X-ray crystallographic structures of the pyridine adducts are presented for the first time. NMR analyses of the adducts reveal the coordination of two pyridine molecules. Electrochemical as well as UV-vis absorption spectroscopy analyses in DMF of MgP·(Py)2, ZnP·(Py)2, MgP and ZnP indicate that pyridine adducts are totally dissociated. Besides, oxidation peaks of these complexes are totally irrev…
Acidochromism of the luminescence of bis(4-pyridylethenyl)arenes
2004
Abstract A series of C 2 -symmetrical bis[( E )-2-(4-pyridyl)ethenyl]arenes has been synthesised via two-fold PO-activated olefinations. 1,4-Benzene, 1,4-naphthalene, 9,10-anthracene and 2,2′-diphenyl were used as central units. These fluorescent compounds were freely soluble in common solvents. The absorption and the emission were sensitive towards solvent polarity and acid, in solution as well as in the solid state. Depending on the concentration of acid, protonation of the ground state and/or the excited state caused reductions of the fluorescence efficiencies, accompanied by bathochromic shifts of the absorption and the emission spectra of some chromophores. The title compounds, except …
Structural, magnetic and electronic characterization of an isostructural series of dinuclear complexes of 3d metal ions bridged by tpbd
2013
Abstract Dinuclear complexes of the type [{M(H2O)(phen)}2(μ-tpbd)](ClO4)4 with N,N,N′,N′-Tetrakis-(2-pyridylmethyl)-benzene-1,4-diamine (tpbd) as bridging ligand and M = Mn(II) (1), Fe(II) (2), Co(II) (3), Ni(II) (4), Cu(II) (5), Zn(II) (6) were synthesized, structurally analyzed and their magnetic as well as their electrochemical properties are determined. A ligand-centered one-electron oxidation leads to radical complexes for which the lifetimes are strongly dependent on the coordinated metal ion as followed from time-resolved UV–Vis absorption spectroscopy. In addition to the six homometallic dinuclear complexes, one analog heterometallic Mn(II)/Ni(II) compound (7) of the same constituti…
Miscibility of cyanine dyes in two-dimensional aggregates
1995
Mixed aggregates of cyanine dyes at a charged lipid monolayer surface are studied by absorption spectroscopy, fluorescence microscopy and electron diffraction. We show that slight variations of the molecular structure can convert a system from being fully miscible to being immiscible, and also that the concentrations of dyes in the solution and in the crystal may deviate considerably. The different concentration in the solution and crystal was observed for a molecule where force field calculations indicated the existence of two isomers in solution and where probably only one fits into the lattice.
Line intensities of CH3D in the Triad region: 6–10μm
2004
Abstract Line intensities of the three lowest fundamentals of the 12CH3D Triad are modeled with an RMS of 3.2% using over 2100 observed values retrieved by multispectrum fitting of enriched sample spectra recorded with two Fourier transform spectrometers. The band strengths of the Triad in units of 10−18 cm−1/(molecule cm−2) at 296 K are, respectively, 2.33 for ν6 (E) at 1161 cm−1, 1.75 for ν3 (A1) at 1307 cm−1 and 0.571 for ν5 (E) at 1472 cm−1. The total calculated absorption arising from 12CH3D Triad fundamentals is 4.65×10−18 cm−1/(molecule cm−2) at 296 K. In addition, some 740 intensities of nine hotbands are fitted to 8.1%; most of the hotband measurements belong to 2ν6−ν6 and ν3+ν6−ν3…
Spectroscopic and physicochemical properties of rare-earth phthalocyanines entrapped in sol-gel glasses
1997
Abstract The electronic absorption spectra of samarium and neodymium phthalocyanines in DMSO and entrapped in glasses obtained via the sol-gel technique have been obtained. Decrease in concentration of metallophtalocyanines in DMSO leads to observed changes in the relative intensifies of the two bands in the Q-band region. This behavior could be explained by the shifts in equilibrium between the LnPc 2 and LnPc + forms, caused by the dilution. In view of this interpretation, the entrapment of the metallophthalocyanines in the sol-gel glass matrices shifts the diphthalocyanine ⇆ monophthalocyanine equilibrium towards the monophthalocyanine (LnPc + ) form.
Low-temperature optical spectroscopy of cobalt in Cu,Co superoxide dismutase: a structural dynamics study of the solvent-unaccessible metal site.
1995
The temperature dependence (300 to 10 K) of the electronic absorption spectra of the cobalt chromophore in bovine superoxide dismutase (SOD) having the native Zn(II) ion selectivity replaced by Co(II) has been investigated in four different derivatives: Cu(II),Co(II) SOD, N3(-)-Cu(II), Co(II) SOD, Cu(I),Co(II) SOD, and E,Co(II) SOD in which the copper ion has been selectively removed. In the Cu(II),Co(II) SOD, the cobalt spectrum is characterized at room temperature by three bands centered at 18,472, 17,670, and 16,793 cm-1; the low-frequency band is split, at low temperatures, into two components, indicating a lower symmetry contribution to a predominantly tetrahedral crystal field. Additi…
Modifications of optical absorption band of center in silica
2005
Abstract We report an experimental study of the modifications induced by gamma ray irradiation and by thermal treatment of both the electron paramagnetic resonance (EPR) and the optical absorption spectra of the E γ ′ center in silica. Our data show that the main g-values of E γ ′ EPR signal change as a function of the irradiation dose together with a red shift of the peak position of the absorption band around 5.8 eV attributed to the same center. Changes in the opposite direction are observed in both signals after thermal treatments. The peak position change of the optical absorption band is in quantitative agreement with the g-values shift. This strict correlation is evidence for the exi…
Biexciton formation and exciton coherent coupling in layered GaSe.
2015
Nonlinear two-dimensional Fourier transform (2DFT) and linear absorption spectroscopy are used to study the electronic structure and optical properties of excitons in the layered semiconductor GaSe. At the 1s exciton resonance, two peaks are identified in the absorption spectra, which are assigned to splitting of the exciton ground state into the triplet and singlet states. 2DFT spectra acquired for co-linear polarization of the excitation pulses feature an additional peak originating from coherent energy transfer between the singlet and triplet. At cross-linear polarization of the excitation pulses, the 2DFT spectra expose a new peak likely originating from bound biexcitons. The polarizati…
The role of Fe and Cu dopants in electron–hole trapping and relaxation process in congruent LiNbO3
2003
Abstract The transient optical absorption and kinetics of absorption decay is studied in undoped, Fe doped, and Cu doped LiNbO 3 crystals irradiated by pulsed electron beam. The 1.6 eV band of electron polaron trapped at antisite niobium was observed in all crystal samples. The nature of centers responsible for transient absorption is discussed. Electron polarons are shown to be less stable in LiNbO 3 :Fe compared with LiNbO 3 :Cu and undoped LiNbO 3 . It is suggested that a major part of electrons and holes created by irradiation are trapped in the vicinity of dopants.