Search results for "Absorption spectra"
showing 10 items of 21 documents
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…
Recognition of oxovanadium(V) species and its separation from other metal species through selective complexation by some acyclic ligands
1998
Acyclic molecules possessing –OH (phenoxo and alkoxo type) groups and imine or amine moieties have been developed to sense the specific preference for VO3+ species. These molecules also showed a capability to quantitatively separate oxovanadium(V) species from a reaction mixture containing metal species of V, Mo, U, Fe, and Mn ions in solution. A cascade quantitative separation of VO3+ followed by cis–MoO2+2 followed by trans –UO2+2 species is demonstrated from their mixture. Synthesis and structural details of oxo-species of vanadium molybdenum and uranium are also discussed. Factors influencing the complexation of these molecules towards oxo metal species of V, Mo and U are also addressed.
Ag11(SG)7 : A New Cluster Identified by Mass Spectrometry and Optical Spectroscopy
2014
We report a one-step and high yield synthesis of a red-luminescent silver cluster with the molecular formula, Ag11(SG)7 (SG: glutathionate) via reduction of silver ions by sodium borohydride in the presence of the tripeptide, glutathione (GSH). The as-prepared cluster shows prominent absorption features at 485 and 625 nm in its UV-vis absorption spectrum. Aging of the as-prepared cluster solution led to the disappearance of the 625 nm peak, followed by broadening of the 485 nm peak to give three maxima at ?487, 437, and 393 nm in its absorption spectrum. These peaks remain unchanged even after polyacrylamide gel electrophoresis (PAGE), where a single band was observed confirming high purity…
Ca impurity in small mixed He-4-He-3 clusters
2009
The structure of small mixed helium clusters doped with one calcium atom has been determined within the diffusion Monte Carlo framework. The results show that the calcium atom sits at the He-4-He-3 interface. This is in agreement with previous studies, both experimental and theoretical, performed for large clusters. A comparison between the results obtained for the largest cluster we have considered for each isotope shows a clear tendency of the Ca atom to reside in a deep dimple at the surface of the cluster for He-4 clusters, and to become fully solvated for He-3 clusters. We have calculated the absorption spectrum of Ca around the 4s4p <- 4s(2) transition and have found that it is bluesh…
X-ray-absorption fine-structure study of ZnSexTe1−x alloys
2004
X-ray-absorption fine-structure experiments at different temperatures in ZnSexTe1−x (x=0, 0.1, 0.2, 0.55, 0.81, 0.93, 0.99, and 1.0) have been performed in order to obtain information about the structural relaxation and disorder effects occurring in the alloys. First and second neighbor distance distributions have been characterized at the Se and Zn K edges, using multiple-edge and multiple-scattering data analysis. The first neighbor distance distribution was found to be bimodal. The static disorder associated with the Zn–Te distance variance did not depend appreciably on composition. On the other hand, the static disorder associated with the Zn–Se distance increased as the Se content dimi…
Neutron irradiation defects in gallium sulfide: Optical absorption measurements
1997
Gallium sulfide single crystals have been irradiated with different thermal neutron doses. Defects introduced by neutron irradiation turn out to be optically active, giving rise to absorption bands with energies ranging from 1.2 to 3.2 eV. Bands lying in the band-gap exhibit Gaussian shape. Their energies and widths are independent of the irradiation dose, but their intensities are proportional to it. Thermal annealing is completed in two stages, ending at around 500 and 720 K, respectively. Centers responsible for the absorption bands are proposed to be gallium-vacancy-galliuminterstitial complexes in which the distance between the vacancy (acceptor) and the interstitial (donor) determines…
Influence of Au, Ag, and Cu Adatoms on Optical Properties of TiO2 (110) Surface: Predictions from RT-TDDFT Calculations
2022
This study was financially supported by Flag-ERA JTC To2Dox project (S.P.) and M-ERA-NET2 project SunToChem (E.A.K.). M.G.B. thanks the support from the Program for the Foreign Experts (Grant No. W2017011) offered by Chongqing University of Posts and Telecommunications and the National Foreign Experts Program for “Belt and Road Initiative” Innovative Talent Exchange (Grant No. DL2021035001L), Estonian Research Council grant PUT PRG111, European Regional Development Fund (TK141), NCN project 2018/31/B/ST4/00924. Institute of Solid State Physics, University of Latvia, as the Center of Excellence, has received funding from the European Union’s Horizon 2020 Framework Program H2020-WIDESPREAD-01…
Structural basis for light control of cell development revealed by crystal structures of a myxobacterial phytochrome
2018
Phytochromes are red-light photoreceptors that were first characterized in plants, with homologs in photosynthetic and non-photosynthetic bacteria known as bacteriophytochromes (BphPs). Upon absorption of light, BphPs interconvert between two states denoted Pr and Pfr with distinct absorption spectra in the red and far-red. They have recently been engineered as enzymatic photoswitches for fluorescent-marker applications in non-invasive tissue imaging of mammals. This article presents cryo- and room-temperature crystal structures of the unusual phytochrome from the non-photosynthetic myxobacterium Stigmatella aurantiaca (SaBphP1) and reveals its role in the fruiting-body formation of this ph…