Search results for "Spectrophotometry"
showing 10 items of 644 documents
Isolated glyoxylic acid-water 1:1 complexes in low temperature argon matrices
2015
Abstract The 1:1 hydrogen bonded complexes between glyoxylic acid (GA) and water are studied in low temperature argon matrices. Four different complex structures were found in deposited matrices. The lowest energy conformer (T1) of GA was found to form complex, where the water molecule was attached to the opposite side of the intramolecular hydrogen bond in the molecule (T1B). Interestingly, this complex was estimated to be +8.0 kJ mol −1 higher in energy than the most stable structure (T1A), where the water is inserted into the internal hydrogen bond, and also found in solid argon but in smaller abundance. For the second-lowest energy conformer of GA (T2), the two lowest-energy complex str…
Theoretical investigations of the IR spectroscopy of Ni(C(2)S(2)H(2))(2). A case study of the P_VMWCI(2) algorithm including anharmonic effects.
2010
The near infrared (NIR) spectra of bis(ethylene-1,2-dithiolato)nickel, Ni(C(2)S(2)H(2))(2) are fully interpreted here by applying a method developed for efficient automatic computation of both the infrared wave numbers and the intensities. The employed procedure uses parallel variational multiple window configuration interaction wave functions, the so-named P_VMWCI(2) algorithm, which incorporates both the mechanical and the electric anharmonic effects. It is shown that inclusion of anharmonicities is crucial for correctly assigning the fundamental, combination, and overtone vibrational frequencies in the infrared spectrum of the target system, for which conflicting assignments are found in…
Magnetic Langmuir-Blodgett films of ferritin with different iron contents.
2006
Magnetic Langmuir-Blodgett films of four ferritin derivatives with different iron contents containing 4220, 3062, 2200, and 1200 iron atoms, respectively, have been prepared by using the adsorption properties of a 6/1 mixed monolayer of methyl stearate (SME) and dioctadecyldimethylammonium bromide (DODA). The molecular organization of the mixed SME/DODA monolayer is strongly affected by the presence of the water-soluble protein in the subphase as shown by pi-A isotherms, BAM images, and imaging ellipsometry at the water-air interface. BAM images reveal the heterogeneity of this mixed monolayer at the air-water interface. We propose that the ferritin is located under the mixed matrix in thos…
Green direct determination of mineral elements in artichokes by infrared spectroscopy and X-ray fluorescence.
2015
Near infrared (NIR) and X-ray fluorescence (XRF) spectroscopy were investigated to predict the concentration of calcium, potassium, iron, magnesium, manganese and zinc in artichoke samples. Sixty artichokes were purchased from different Spanish areas (Benicarlo, Valencia and Murcia). NIR and XRF spectra, combined with partial least squares (PLS) data treatment, were used to develop chemometric models for the prediction of mineral concentration. To obtain reference data, samples were mineralised and analysed by inductively coupled plasma optical emission spectrometry (ICP-OES). Coefficients of determination obtained for the regression between predicted values and reference ones for calcium, …
Rhenium(I) and platinum(II) complexes with diimine ligands bearing acidic phenol substituents: hydrogen-bonding, acid-base chemistry and optical prop…
2010
Tricarbonylchloro-rhenium(i) (1-4) and catecholato-platinum(ii) complexes (6, 7) of diimine ligands bearing phenol and O-protected phenol substituents have been prepared and fully characterised including single crystal structure analyses of 1, 4 and 7. The redox behaviour of the catecholato platinum(ii) complexes 6 and 7 has been probed by cyclic voltammetry, preparative oxidation and EPR spectroscopy (6˙(+), 7˙(+)). Reversible deprotonation of the hydroxy substituted complexes 1, 3 and 6 to 1(-), 3(-) and 6(-) resulted in significant changes in their electronic spectra. The luminescence properties of the diamagnetic complexes have been investigated using emission spectroscopy. DFT and TD-D…
Azo-Sulforhodamine Dyes: A Novel Class of Broad Spectrum Dark Quenchers
2014
A rapid access to a novel class of water-soluble dark quencher dyes was achieved using an azo-coupling reaction between a fluorescent primary arylamine derived from a sulforhodamine 101 scaffold and a tertiary aniline equipped with different bioconjugatable groups. The thus obtained nonfluorescent azo-sulforhodamine hybrids display a broad quenching range spanning the visible to NIR regions. This was demonstrated through the preparation and enzymatic activation of FRET-based fluorogenic substrates of urokinase.
Synthesis, characterization, and crystal structure of [Cu(cinoxacinate)2] · 2H2O complex: A square-planar CuO4 chromophore. Antibacterial studies
1995
The structural and spectroscopic properties of a new copper (II) complex of cinoxacin (HCx) have been investigated. The complex [Cu(Cx)2].2H2O crystallizes in the monoclinic system, space group P2(1)/c. The cell dimensions are: a = 7.998(2), b = 7.622(1), c = 18.955(6) A, beta = 94.38(2) degree, V = 1154.6(6) A3, Z = 2. The structure was refined to R = 0.051. The crystal is composed of [Cu(Cx)2] units and uncoordinated water molecules. The Cu(II) ion, at a center of symmetry, is coordinated to two cinoxacinate (Cx) ligands related by the inversion center. Each cinoxacinate acts as bidentate ligand bonded to the cation through its carboxylate oxygen atom and through its exocyclic carbonyl ox…
Syntheses, X-ray structures, and physicochemical properties of phenoxo-bridged dinuclear nickel(II) complexes: kinetics of transesterification of 2-h…
2009
Four dinuclear nickel(II) complexes [Ni(II)(2)(L(1))(O(2)CMe)(2)(H(2)O)(2)][PF(6)].MeOH.3H(2)O (1), [Ni(II)(2)(L(1))(O(2)CMe)(2)(NCS)] (2), [Ni(II)(2)(L(2))(O(2)CMe)(2)(MeOH)(H(2)O)][ClO(4)] (3), and [Ni(II)(2)(L(2))(O(2)CMe)(2)(MeOH)(H(2)O)][BPh(4)].3MeOH.H(2)O (4) have been synthesized [HL(1): 2,6-bis[N-methyl-N-(2-pyridylethyl)amino]-4-methylphenol; HL(2): 2,6-bis[3-(pyridin-2-yl)pyrazol-1-ylmethyl]-4-methylphenol]. Complexes 1, 3, and 4 are new while complex 2 was reported previously by Fenton and co-workers (the structure of 2 was presented but no physicochemical properties of this complex were reported; in this work such studies have been completed). X-ray crystallographic analyses of…
Host−Guest Interactions between β-Cyclodextrin and the (Z)-Phenylhydrazone of 3-Benzoyl-5-phenyl-1,2,4-oxadiazole: The First Kinetic Study of a Ring…
2002
The effect of beta-cyclodextrin (beta-CD) on the mononuclear heterocyclic rearrangement of the (Z)-phenylhydrazone of 3-benzoyl-5-phenyl-1,2,4-oxadiazole (1) in aqueous borate buffer at pH = 9.6 has been analyzed at temperatures ranging from 293.15 to 313.15 K. The trend of the absorption spectra of 1 as a function of time has been accounted for with the formation of two different 1:1 complexes between beta-CD and 1, the first, "unreactive" complex being formed faster than the "reactive" one. The occurrence of negative activation enthalpy values for the studied interconversion evidences the kinetic relevance of inclusion processes. Computational models elaborated using the MM2 molecular mec…
Synthesis of platinum complexes with 2-(5-perfluoroalkyl-1,2,4-oxadiazol-3yl)-pyridine and 2-(3-perfluoroalkyl-1-methyl-1,2,4-triazole-5yl)-pyridine …
2016
Five new mononuclear Pt(II) complexes with 5-perfluoroalkyl-1,2,4-oxadiazolyl-pyridine and 3-perfluoroalkyl-1,2,4-triazolyl-pyridine ligands are reported. The ligands 2-(5-perfluoroheptyl-1,2,4-oxadiazole-3yl)-pyridine (pfhop), 2-(5-perfluoropropyl)-1,2,4-oxadiazole-3yl)-pyridine (pfpop), 2-(3-perfluoroheptyl-1-methyl-1,2,4-triazole-5yl)-pyridine (pfhtp), 2-(3-perfluoropropyl-1-methyl-1,2,4-triazole-5yl)-pyridine (pfptp) and their complexes [PtCl2(pfhop)(2)]center dot 1.5 DMSO (2a), [PtCl2(pfpop)(2)]center dot 1.5 DMSO (3a), [PtCl2(pfhtp)(2)]center dot 1.5 DMSO (4a), PtCl2(pfhtp) (4b), [PtCl2(PfPtP)(2)]center dot 1.5 DMSO (5a) have been synthesized and structurally characterized. The comple…