204 research outputs found
Roy Tarwater, Mayor J. R. Edwards, Sgt P. A. Ziessel
No full textSargeant P. A. Ziessel of the Texas Department of Public Safety points out the operation of equipment of Public Safety points out the operation of equipment to test brake reactions of drivers. Mayor Edwards, center, is taking the test as Roy Tarwater, president of the Riverside Lions Club looks on. Published in Fort Worth Star-Telegram morning edition July 18, 1951.https://mavmatrix.uta.edu/specialcollections_startelegram1950s/13698/thumbnail.jp
-Carborane-Bridged Bipyridine Ligands for Energy Transfer between Two Iridium Centers
No full textTwo iridium(III) complexes displaying for one a high HOMO-LUMO gap and for the other a weaker gap were linked in a controlled and logical manner to closo-p-carborane spacers. The bridging ligand is composed of 5-ethynyl-2,2′-bipyridine units, and the peripherical Ir-ligands are orthometalated 2′,4′-difluoro-2-phenylpyridine (dfppy) (λabs at 400 nm for the "Ir(dfppy)2(bpy′ )") for the energy donor fragment and dibenzo[a,c]phenazine (dbpz) (λabs at 525 nm for "Ir(dbpz)2(bpy′) ") for the energy acceptor fragment.Redox, spectroscopic, and photophysical properties for models and the donor-carborane-acceptor complex were determined. Efficient energy transfer from the "Ir(dfppy)2(bpy′) " moiety to the "Ir(dbpz)2(bpy′)" fragment is occurring with a rate constant of 3.3 × 108 s-1 despite weak electronic coupling through the inert p-carborane spacer. From flash photolysis experiments it is shown that, by excitation of the donor, a low lying triplet state localized on the acceptor bridging ligand side is formed which decays by conversion to the 3MLCT of the acceptor fragment which phosphoresces at 644 nm. © 2013 American Chemical Society
A novel lanthanide chelate tag for ultrasensitive time-resolved fluorescence microscopy imaging of tissues and cells
No full textPyrromethene dialkynyl borane complexes for “cascatelle” energy transfer and protein labeling
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Engineering of Highly Luminescent Lanthanide Tags Suitable for Protein Labeling and Time Resolved Luminescence Imaging.
No full textAbsorption Spectra, Photophysical Properties, and Redox Behavior of Ruthenium(II) Polypyridine Complexes Containing Accessory Dipyrromethene-BF2 Chromophores
No full textThe six multichromophoric species 1-6, containing the potentially luminescent Ru(II) polypyridine subunits and 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene fluorophores (dipyrromethene-BF2 dyes, herein after called bodipy), have been prepared and their absorption spectra, luminescence properties (both at room temperature in fluid solution and at 77 K in rigid matrix), and redox properties have been investigated (for the structural formulas of all the compounds, see Figure 1). For comparison purposes, also the same properties of the bodipy-based free ligands have been examined. Three of the multichromophoric species (1-3) are based on the Ru(bpy)3-type metal subunit, whereas 4-6 are based on the Ru(terpy)2-type metal subunit. Transient absorption spectroscopy at room temperature of all the compounds has also been performed. The absorption spectra of all the metal complexes show features that can be assigned to the Ru(II) polypyridine subunits and to the bodipy centers. In particular, the lowest energy spin-allowed -* transition of the bodipy groups dominates the visible region, peaking at about 530 nm. All the new complexes exhibit a rich redox behavior, with reversible processes attributed to specific sites, indicating a small perturbation of each redox center and therefore highlighting the supramolecular nature of the multichromophoric assemblies. Despite the good luminescence properties of the separated components, 1-6 do not exhibit any luminescence at room temperature; however, transient absorption spectroscopy evidences that for all of them a long-lived (microsecond time scale) excited state is formed, which is identified as the bodipy-based triplet state. Pump-probe transient absorption spectroscopy suggests that such a triplet state is formed from the promptly prepared bodipy-based 1-* state in most cases by the intervention of a charge-separated level. At 77 K, all the complexes except complex 1 exhibit the bodipy-based fluorescence, although with a slightly shortened lifetime compared to the corresponding free ligand(s), and 4-6 also exhibit a phosphorescence assigned to the bodipy subunits. Phosphorescence of bodipy species had never been reported in the literature to the best of our knowledge: in the present cases we propose that it is an effective decay process thanks to the presence of the ruthenium heavy atom and of the closely lying 3MLCT state of the Ru(terpy)2-type subunits
Synthesis and Luminescence of Eu(3+) and Tb(3+) Complexes with Novel Calix[4]arene Ligands Carrying 2,2'-Bipyridine Subunits
No full textEu3+ and Tb3+ complexes with novel branched cali[4]arene ligands incorporating 2,2'-bipyridine subunits functionalized in the 6- or 5,5'-positions have been synthesized and their photophysical properties investigated. High luminescence intensity was obtained for the Eu3+ complex of the calix[4]arene ligand carrying four 5,5'-substituted-2,2'-bipyridines, which has high molar extinction coefficients (epsilon(max) = 39 600 M(-1) cm(-1)) and a high luminescence quantum yield (15%)
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