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PubMed2006

Highly phosphorescent iridium complexes containing both tridentate bis(benzimidazolyl)-benzene or -pyridine and bidentate phenylpyridine: synthesis, photophysical properties, and theoretical study of Ir-bis(benzimidazolyl)benzene complex.

Novel mixed-ligand Ir(III) complexes, [Ir(L)(NwedgeC)X]n+ (L = N/\C/\N or N/\N/\N; X = Cl, Br, I, CN, CH3CN, or -CCPh; n = 0 or 1), were synthesized, where N/\CwedgeN = bis(N-methylbenzimidazolyl)benzene (Mebib) and bis(N-phenylbenzimidazolyl)benzene (Phbib), N/\N/\N = bis(N-methylbenzimidazolyl)pyridine (Mebip), and N/\C = phenylpyridine (ppy) derivatives. The X-ray crystal structures of [Ir(Phbib)(ppy)Cl] and [Ir(Mebib)(mppy)Cl] [mppy = 5-methyl-2-(2'-pyridyl)phenyl] indicate that the nitrogen atom of the ppy ligand is located trans to the coordinating carbon atom in Me- or Phbib, while the coordinating carbon atom in ppy occupies the trans position of Cl. [Ir(Mebip)(ppy)Cl]+ showed a quasireversible Ir(III/IV) oxidation wave at +1.05 V, while the Ir complexes, [Ir(Mebib)(ppy)Cl], were oxidized at +0.42 V versus Fc/Fc+. The introduction of an Ir-C bond in [Ir(Mebib)(ppy)Cl] induces a large potential shift of 0.63 V in a negative direction. Further, the oxidation potential of [Ir(Mebib)(Rppy)X] was altered by the substitution of R, R', and X groups. Compared to the oxidation potential, the first reduction potential revealed an almost constant value at -2.36 to -2.46 V for [Ir(L)(ppy)Cl] (L = Mebib and Phbib) and -1.52 V for [Ir(Mebip)(ppy)Cl. The UV-vis spectra of [Ir(Mebib)(R-ppy)X] show a clear singlet metal-to-ligand charge-transfer transition around 407 approximately 425 nm and a triplet metal-to-ligand charge-transfer transition at 498 approximately 523 nm. [Ir(Mebip)(ppy)Cl]+ emits at 610 nm with a luminescent quantum yield of Phi = 0.16 at room temperature. The phosphorescence of [Ir(Mebib)(ppy)X] was observed at 526 nm for X = CN and 555 nm for X = Cl with the high luminescent quantum yields, Phi = 0.77 approximately 0.86, at room temperature. [Ir(Phbib)(ppy)Cl] shows the emission at 559 nm with a luminescent quantum yield of Phi = 0.95, which is an unprecedentedly high value compared to those of other emissive metal complexes. Compared to the luminescent quantum yields of the Ir(ppy)2(L) derivatives and [Ir(Mebip)(ppy)Cl]+, the neutral Ir complexes, [Ir(L)(R-ppy)X] (L = Me- or Phbib), reveal very high quantum yields and large radiative rate constants (kr) ranging from 3.4 x 10(5) to 5.5 x 10(5) s(-1). The density functional theory calculation suggests that these Ir complexes possess dominantly metal-to-ligand charge-transfer and halide-to-ligand charge-transfer excited states. The mechanism for a high phosphorescence yield in [Ir(bib)(ppy)X] is discussed herein from the perspective of the theoretical consideration of radiative rate constants using perturbation theory and a one-center spin-orbit coupling approximation.

Journal Article↗

PubMed2006

En route to the formation of high-efficiency, osmium(II)-based phosphorescent materials.

Triosmium cluster complexes [Os3(CO)8(fppz)2] (2a) and [Os3(CO)8(fptz)2] (2b) bearing two 2-pyridyl azolate ligands were synthesized in an attempt to establish the reaction mechanism that gives rise to the blue-emitting phosphorescent complexes [Os(CO)2(fppz)2] (1a) and [Os(CO)2(fptz)2] (1b) [(fppz)H = 3-(trifluoromethyl)-5-(2-pyridyl)pyrazole; (fptz)H = 3-(trifluoromethyl)-5-(2-pyridyl)triazole]. X-ray structural analysis of 2b showed an open triangular metal framework incorporating multisite-coordinated 2-pyridyltriazolate ligands. Treatment of 2 with the respective 2-pyridylazolate ligand led to the formation of blue-emitting complex 1b, confirming their intermediacy, while the reaction of 2b with phosphine ligand PPh2Me afforded two hitherto novel hydride complexes 3 and 4, for which the reversible interconversion was clearly established at higher temperatures (> 180 degrees C). The single-crystal X-ray diffraction analyses of 3 and 4 confirmed their monometallic and isomeric nature, together with the coordination of two phosphine ligands located in the trans-disposition and one CO and one hydride located opposite to the pyridyl triazolate chelate. Subtle differences in photophysical properties were examined for isomers 3 and 4 on the basis of steady state absorption and emission, the relaxation dynamics, and temperature-dependent luminescent studies. The results, in combination with time-dependent density function theory (TDDFT) calculations, provide fundamental insights into the future design and preparation of highly efficient phosphorescent emitters.

Journal Article↗

PubMed1998

Electronic Absorption Spectra and Phosphorescence of Oxygen-Containing Molybdenum(IV) Complexes.

Electronic absorption and emission spectra are reported for salts of two oxomolybdenum(IV) cations, [MoOCl(CN-t-Bu)(4)](+) and [MoOCl(Ph(2)PCH(2)CH(2)PPh(2))(2)](+), and for the new Mo(IV) complex [trans-Mo(OCH(3))(2)(CN-t-Bu)(4)](2+). All three ions show absorption bands (lambda(max,abs) 550-570 nm; epsilon 45-120 M(-)(1) cm(-)(1)) attributable to the (1)A(1)[(d(xy)())(2)] --> (1)E[(d(xy)())(1)(d(xz)()(,)(yz)())(1)] (C(4)(v)()) transition, and the last two show weak shoulders in the 700-750 nm range due to the analogous spin-forbidden ((1)A(1) --> (3)E) transition. Phosphorescence (lambda(max,em) 850-960 nm) occurs in the solid state for all three compounds at both room temperature and 77 K, and for [MoOCl(CN-t-Bu)(4)](+) in CH(2)Cl(2) at room temperature. These are the first phosphorescences recorded for molybdenum(IV) complexes. [MoOCl(CN-t-Bu)(4)](BPh(4)) precipitates quickly if NaBPh(4) is added to the Mo(IV) solution prepared from MoCl(5) and tert-butyl isocyanide in CH(3)OH. However, if NaPF(6) is used instead, [trans-Mo(OCH(3))(2)(CN-t-Bu)(4)](PF(6))(2) (formed by reaction of [MoOCl(CN-t-Bu)(4)](+) with methanol) crystallizes over a period of ca. 24 h. The crystal structure of [trans-Mo(OCH(3))(2)(CN-t-Bu)(4)](PF(6))(2) has been determined: C(22)H(42)F(12)MoN(4)O(2)P(2), monoclinic; space group P2(1)/c; a = 9.1538(8) Å, b = 15.709(2) Å, c = 13.456(2) Å; beta = 103.31(1) degrees; Z = 2; R(F) = 0.063, R(w)(F) = 0.056 for 2719 reflections with I > sigma(I).

Journal Article↗

PubMed1998

Phosphorescence and Structure of a Tetrameric Copper(I)-Amide Cluster.

The colorless copper(I) cluster [CuN(Si(CH(3))(3))(2)](4), which contains a square-planar Cu(4)N(4) core, phosphoresces in CH(2)Cl(2) solution (lambda(max), 512 nm; lifetime, 30 &mgr;s) and in the solid state at room temperature. Its electronic absorption spectrum in CH(2)Cl(2) consists of two intense bands at 283 and 246 nm; these transitions, as well as the phosphorescence, are likely to involve population of MOs reflecting substantial Cu.Cu interactions. Solid [CuN(Si(CH(3))(3))(2)](4) luminesces with approximately the same spectrum as that of the CH(2)Cl(2) solutions. At 77 K, the solid-state luminescence red-shifts slightly (lambda(max), 524 nm) and narrows substantially (fwhm, 2400 cm(-)(1); vs 3500 cm(-)(1) at 300 K); the emission lifetime in glassy Et(2)O solution is 690 &mgr;s. X-ray analysis of crystals of [CuN(Si(CH(3))(3))(2)](4) at 130 and 296 K shows that, although the previously reported structure solution (in space group I2/m, with the molecules on 2/m sites; Eur. J. Solid State Inorg. Chem. 1992, 29, 573-583) is approximately correct, the lattice is actually primitive, P2/n, and the only crystallographically required symmetry element for the molecule is a 2-fold axis. C(24)H(72)Cu(4)N(4)Si(8): monoclinic, space group P2/n, Z = 2. At 130 K, a = 9.285(3) Å, b = 13.393(3) Å, c = 17.752(5) Å, and beta = 90.53(2) degrees. [At 296 K, a = 9.3773(4) Å, b = 13.5836(7) Å, c = 17.814(2) Å, and beta = 90.207(7) degrees.] At 130 K, the Cu and N atoms in the cluster are planar within 0.007 Å, and the Cu-N and Cu.Cu distances are 1.917(4)-1.925(4) and 2.6770(7)-2.6937(7) Å, respectively. Despite the low volatility of the compound, it can be used as a precursor for chemical vapor deposition (CVD) of copper metal, under H(2) carrier gas, with both source and substrate at ca. 200 degrees C. Smaller amounts of Cu metal films are also deposited when the substrate temperature is as low as 145 degrees C (in the dark) or 136-138 degrees C (under Pyrex-filtered Xe arc lamp illumination). Thus, Cu CVD with this precursor shows slight photochemical enhancement.

Journal Article↗

PubMed2001

Highly phosphorescent bis-cyclometalated iridium complexes: synthesis, photophysical characterization, and use in organic light emitting diodes.

The synthesis and photophysical study of a family of cyclometalated iridium(III) complexes are reported. The iridium complexes have two cyclometalated (C(**)N) ligands and a single monoanionic, bidentate ancillary ligand (LX), i.e., C(**)N2Ir(LX). The C(**)N ligands can be any of a wide variety of organometallic ligands. The LX ligands used for this study were all beta-diketonates, with the major emphasis placed on acetylacetonate (acac) complexes. The majority of the C(**)N2Ir(acac) complexes phosphoresce with high quantum efficiencies (solution quantum yields, 0.1-0.6), and microsecond lifetimes (e.g., 1-14 micros). The strongly allowed phosphorescence in these complexes is the result of significant spin-orbit coupling of the Ir center. The lowest energy (emissive) excited state in these C(**)N2Ir(acac) complexes is a mixture of (3)MLCT and (3)(pi-pi) states. By choosing the appropriate C(**)N ligand, C(**)N2Ir(acac) complexes can be prepared which emit in any color from green to red. Simple, systematic changes in the C(**)N ligands, which lead to bathochromic shifts of the free ligands, lead to similar bathochromic shifts in the Ir complexes of the same ligands, consistent with "C(**)N2Ir"-centered emission. Three of the C(**)N2Ir(acac) complexes were used as dopants for organic light emitting diodes (OLEDs). The three Ir complexes, i.e., bis(2-phenylpyridinato-N,C2')iridium(acetylacetonate) [ppy2Ir(acac)], bis(2-phenyl benzothiozolato-N,C2')iridium(acetylacetonate) [bt2Ir(acac)], and bis(2-(2'-benzothienyl)pyridinato-N,C3')iridium(acetylacetonate) [btp2Ir(acac)], were doped into the emissive region of multilayer, vapor-deposited OLEDs. The ppy2Ir(acac)-, bt2Ir(acac)-, and btp2Ir(acac)-based OLEDs give green, yellow, and red electroluminescence, respectively, with very similar current-voltage characteristics. The OLEDs give high external quantum efficiencies, ranging from 6 to 12.3%, with the ppy2Ir(acac) giving the highest efficiency (12.3%, 38 lm/W, >50 Cd/A). The btp2Ir(acac)-based device gives saturated red emission with a quantum efficiency of 6.5% and a luminance efficiency of 2.2 lm/W. These C(**)N2Ir(acac)-doped OLEDs show some of the highest efficiencies reported for organic light emitting diodes. The high efficiencies result from efficient trapping and radiative relaxation of the singlet and triplet excitons formed in the electroluminescent process.

Journal Article↗

PubMed2002

Divalent osmium complexes: synthesis, characterization, strong red phosphorescence, and electrophosphorescence.

We report new divalent osmium complexes that feature strong red metal-to-ligand-charge-transfer (MLCT) phosphorescence and electrophosphorescence. The general formula of the complexes is Os(II)(N-N)(2)L-L, where N-N is either a bipyridine or a phenanthroline and L-L is either a phosphine or an arsine. New polypyridyl ligands synthesized are 4,4'-di(biphenyl)-2,2'-bipyridine (15) and 4,4'-di(diphenyl ether)-2,2'-bipyridine (16), and the 1,10-phenanthroline derivatives synthesized are 4,7-bis(p-methoxyphenyl)-1,10-phenanthroline (17), 4,7-bis(p-bromophenyl)-1,10-phenanthroline (18), 4,7-bis(4'-phenoxybiphen-4-yl)-1,10-phenanthroline (19), and 4,7-bis(4-naphth-2-ylphenyl)-1,10-phenanthroline (20). 4,4'-Diphenyl-2,2'-bipyridine (21) and 4,7-diphenyl-1,10-phenanthroline (22) were also used in these studies. Strong pi-acid ligands used were 1,2-bis(diphenylarseno)ethane (23), cis-1,2-bis(diphenylphosphino)ethylene (24), and cis-1,2-vinylenebis(diphenylarsine) (25). Ligand 25 is used for the first time in these types of luminescent osmium complexes. These compounds feature strong MLCT absorption bands in the visible region and strong red phosphorescent emission ranging from 611 to 651 nm, with quantum efficiency up to 45% in ethanol solution at room temperature. Red organic light-emitting diodes (OLEDs) were successfully fabricated by doping the Os(II) complexes into blend of poly(N-vinylcarbazole) (PVK) and 2-tert-butylphenyl-5-biphenyl-1,3,4-oxadiazole (PBD). Brightness over 1400 cd/m(2) for a double-layer device has been reached, with a turn-on voltage of 8 V. The maximum external quantum efficiency was 0.64%. Commission Internationale de l'Eclairage (CIE) chromaticity coordinates (x, y) of the red electrophosphorescence from the complexes are (0.65, 0.34), which indicates pure red emission.

Journal Article↗

PubMed2003

Direct observation of triplet state emission of single molecules: single molecule phosphorescence quenching of metalloporphyrin and organometallic complexes by molecular oxygen and their quenching rate distributions.

Single molecules are detected through the phosphorescence emission of their triplet states. Emission of the triplet states of single molecules of Pt octabutoxycarbonyl porphyrin (PtOBCP) and ruthenium(II)-tris-4,7-diphenyl-1,10-phenanthroline dichloride (Ru(dpp)(3)Cl(2)) is reported. The single molecule phosphorescence is very sensitive to molecular oxygen. Each molecule has its own characteristic quenching rate by oxygen, and the distribution of these rates is measured for (Ru(dpp)(3)Cl(2)) on a quartz surface. The large variance of this distribution is presumed to be caused by fluctuations in the pseudobimolecular rate coefficient and the local oxygen concentration. The possibility of creating a quantitative single oxygen molecule sensor is suggested.

Luminescent Measurements↗

PubMed2005

Brightly phosphorescent trinuclear copper(I) complexes of pyrazolates: substituent effects on the supramolecular structure and photophysics.

Synthetic details, solid-state structures, and photophysical properties of a group of trimeric copper(I) complexes containing pyrazolate ligands are described. The reaction of copper(I) oxide and the fluorinated pyrazoles [3-(CF(3))Pz]H, [3-(CF(3)),5-(Me)Pz]H, and [3-(CF(3)),5-(Ph)Pz]H leads to the corresponding trinuclear copper(I) pyrazolates, {[3-(CF(3))Pz]Cu}(3), {[3-(CF(3)),5-(Me)Pz]Cu}(3), and {[3-(CF(3)),5-(Ph)Pz]Cu}(3), respectively, in high yield. The {[3,5-(i-Pr)(2)Pz]Cu}(3) compound was obtained by a reaction between [Cu(CH(3)CN)(4)][BF(4)], [3,5-(i-Pr)(2)Pz]H, and NEt(3). These compounds as well as {[3,5-(Me)(2)Pz]Cu}(3) and {[3,5-(CF(3))(2)Pz]Cu}(3) adopt trimeric structures with nine-membered Cu(3)N(6) metallacycles. There are varying degrees and types of intertrimer Cu...Cu interactions. These contacts give rise to zigzag chains in the fluorinated complexes, {[3-(CF(3))Pz]Cu}(3), {[3-(CF(3)),5-(Me)Pz]Cu}(3), {[3-(CF(3)),5-(Ph)Pz]Cu}(3), and {[3,5-(CF(3))(2)Pz]Cu}(3), whereas the nonfluorinated complexes, {[3,5-(Me)(2)Pz]Cu}(3) and {[3,5-(i-Pr)(2)Pz]Cu}(3) form dimers of trimers. Out of all the compounds examined in this study, {[3-(CF(3)),5-(Ph)Pz]Cu}(3) has the longest (3.848 Angstroms) and {[3,5-(Me)(2)Pz]Cu}(3) has the shortest (2.946 Angstroms) next-neighbor intertrimer Cu...Cu distance. The Cu...Cu separations within the trimer units do not vary significantly (typically 3.20-3.26 Angstroms). All of these trinuclear copper(I) pyrazolates show bright luminescence upon exposure to UV radiation. The luminescence bands are hugely red-shifted from the corresponding lowest-energy excitations, rather broad, and unstructured even at low temperatures, suggesting metal-centered emissions owing to intertrimer Cu...Cu interactions that are strengthened in the phosphorescent state. The {[3-(CF(3)),5-(Ph)Pz]Cu}(3) compound exhibits an additional highly structured phosphorescence with a vibronic structure corresponding to the pyrazolyl (Pz) ring. The luminescence properties of solids and solutions of the trimeric compounds in this study show fascinating trends with dramatic sensitivities to temperature, solvent, concentration, and excitation wavelengths.

Journal Article↗

PubMed2005

Enhancement of platinum octaethyl porphyrin phosphorescence near nanotextured silver surfaces.

We observe more than a 200-fold increase in the photoexcited phosphorescent emission of PtOEP (2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphyrin platinum II) in a polystyrene film on nanotextured silver surfaces, coincident with a reduction in the triplet state lifetime by a factor of 5. The large enhancement results in films with apparent luminescence quantum yields much greater than unity and can be understood in terms of increased radiative rates due to interactions between the molecules and the electron plasma in nearby silver nanoparticles. We study the photoluminescence efficiency, excitation spectrum, and decay dynamics as a function of film thickness and silver density. We use a model of the photophysics to decompose the phosphorescent enhancement into contributions from increases in absorption, emissive rate, and quenching. Quenching increases in importance for very thin films, and we conclude that approximately 3 nm spacing between metal and chromophore leads to the largest photoluminescence enhancement.

Journal Article↗

PubMed2005

Phosphorescent excited state of [Au2[(Ph2Sb)2O]3]2+: Jahn-Teller distortion at only one gold(I) center.

Dinuclear three-coordinate Au(I) complex [Au2{(Ph2Sb)2O}3](ClO4)2 1 displays an interesting phosphorescent behavior in which a large Stokes' shift is observed. Ab initio calculations show that the main distortion for the first triplet excited state, which is responsible for the luminescence behavior of complex 1, is a Jahn-Teller distortion for only one of the Au(I) centers together with a gold-gold distance shortening. This behavior could be extrapolated to other phosphorescent dinuclear three-coordinate Au(I) complexes.

Antimony↗

PubMed2006

Functionalized gold nanoparticles as phosphorescent nanomaterials and sensors.

Ligand-capped gold nanoparticles were synthesized by capping monothiol derivatives of 2,2'-dipyridyl onto the surface of Au nanoparticles (Au-BT). The average size of the metal core is around 4 nm, with a shell of approximately 340 bipyridine ligands around the Au nanoparticle. The high local concentration of the chelating ligands ( approximately 5 M) around the Au nanoparticle makes these particles excellent ion sponges, and their complexation with Eu(III)/Tb(III) ions yields phosphorescent nanomaterials. Absorption spectral studies confirm a 1:3 complexation between Eu(III)/Tb(III) ions and bipyridines, functionalized on the surface of Au nanoparticles. The red-emitting Au-BT:Eu(III) complex exhibits a long lifetime of 0.36 ms with six line-like emission peaks, whereas the green-emitting Au-BT:Tb(III) complex exhibits a lifetime of 0.7 ms with four line-like emission peaks. These phosphorescent nanomaterials, designed by linking BT:Eu(III) complexes to Au nanoparticles, were further utilized as sensors for metal cations. A dramatic decrease in the luminescence was observed upon addition of alkaline earth metal ions (Ca(2+), Mg(2+)) and transition metal ions (Cu(2+), Zn(2+), Ni(2+)), resulting from an isomorphous substitution of Eu(III) ions, whereas the luminescence intensity was not influenced by the addition of Na(+) and K(+) ions. Direct interaction of bipyridine-capped Au nanoparticles with Cu(2+) ions brings the nanohybrid systems closer, leading to the formation of three-dimensional superstructures. Strong interparticle plasmon interactions were observed in these closely spaced Au nanoparticles.

2,2'-Dipyridyl↗

PubMed2006

Simultaneous two-photon excited fluorescence and one-photon excited phosphorescence from single molecules of an organometallic complex Ir(ppy)3.

We report a study of excited-state lifetimes of the phosphorescent organometallic complex Ir(ppy)3 on ensemble and a single-molecule level. With decreasing concentration, an increasingly intense fast component of 3 ns lifetime appears next to the 1.1 mus phosphorescence. Experimental evidence suggests that strong two-photon absorption followed by fluorescence is responsible for the fast lifetime component.

Journal Article↗

PubMed2007

The unusual electrochemical and photophysical behavior of 2,2'-bis(1,3,4-oxadiazol-2-yl)biphenyls, effective electron transport hosts for phosphorescent organic light emitting diodes.

The fluorescence and phosphorescence of 2,2'-bis(5-phenyl-1,3,4-oxadiazol-2-yl)biphenyl shows good spectral matching with the absorption spectra of the MLCT1 and MLCT3 transitions of Ir(ppy)3. The red-shift of the 0-0 band in the phosphorescence at 77 K is due to the intramolecular pi-pi interactions between the oxadiazole side chains. Maximum brightness of 43,000 cd/m2 with an efficiency of 26 cd/A at 200 cd/m2 was achieved when BOBP was used as the host material for Ir(ppy)3 in the PHOLED study. [structure: see text].

Biphenyl Compounds↗

PubMed1997

Binding of the activating ion Co(II) to myo-inositol monophosphatase monitored by fluorescence and phosphorescence spectroscopy.

Two extrinsic probes, pyrene-maleimide and eosin-maleimide, were used to label specific SH groups of the enzyme myo-inositol monophosphatase. The fluorescence of pyrene-monophosphatase is enhanced upon addition of the activating metal ions Co(II) and Mg(II). Co(II) ions bind with a dissociation constant of 4 microM, whereas the apparent activation constant Ka is 0.4 mM. Energy transfer measurements demonstrated that the pyrene chromophore, covalently linked to Cys-218, is within 9 A of the metal ion Tb(III) coordinated to the metal-binding site. The phosphorescence emitted by eosin covalently linked to the protein is quenched by the addition of the activating cations Co(II) and Mg(II). Phosphorescence titrations conducted under anaerobic conditions were used to determine a dissociation constant of approximately 3 microM for the binding of Co(II) ions. The results are consistent with the hypothesis that two activating ions per monomeric subunit participate in the catalytic mechanism. The affinity of the tightly bound ion is at least 100-fold greater than the affinity of the weakly bound ion.

Animals↗

PubMed2002

Interstitial PO(2) determination by phosphorescence quenching microscopy.

OBJECTIVE: This study introduces the technique of microinjection of phosphor probe into skeletal muscle tissue to determine oxygen tension (PO(2)) in the interstitium by phosphorescence quenching microscopy. METHOD: The spinotrapezius muscle of Wistar-Kyoto rats weighing 240-280 g was surgically isolated and underwent the microinjection procedure. We measured the spatial distribution of phosphor probe 10, 30, and 80 minutes after injection; the tissue PO(2) at sites adjacent to arteriolar and venular microvessels; and the decline in tissue PO(2) during a 3-minute period of 8-Hz contraction. RESULTS: The phosphorescence signal from the probe was undetectable outside a 2.5-mm radius from the site of injection at the 10-minute time point, increased to measurable values after 30 minutes, and was double the 30-minute intensity value after 80 minutes. When used to measure periarteriolar PO(2), the tissue microinjection technique demonstrated a nonlinear fall in tissue PO(2) with distance away from secondary arterioles (30-40 microm diameter). Conversely, perivenular tissue PO(2) increased in a nonlinear manner with distance away from secondary venules (60-70 microm diameter). The tissue PO(2) at distances of 16 microm and greater from both types of secondary microvessels was significantly different from values taken directly over the centerline of these microvessels. During muscle contraction, the PO(2) fell from a mean precontraction value of 28.3 +/- 4.9 mmHg to 8.2 +/- 0.9 mmHg at the end of the contraction period. CONCLUSIONS: These observations indicate that the microinjection technique yields values for tissue PO(2) that are in good agreement with previously published results using oxygen microelectrodes.

Animals↗

PubMed2001

Determination of naproxen in pharmaceutical preparations by room-temperature phosphorescence. A comparative study of several organized media.

Different methods for the determination of naproxen by room-temperature phosphorescence (RTP) using organized media such as cyclodextrins (beta-CD and gamma-CD) and micelles (Triton X-100 and sodium dodecyl sulfate) are reported. The inclusion complexes formed between both beta- and gamma-cyclodextrins and naproxen were previously investigated at both acid and basic pH by spectrofluorimetry. In both cases, 1:1 guest-host stoichiometries were established and the corresponding association constants were calculated. Different systems were examined with the purpose of obtaining phosphorescent emission from naproxen solutions, and the best signals were obtained when naproxen was in the presence of beta-CD-cyclohexane-Tl(I), gamma-CD-1,3-dibromopropane, Triton X-100-Tl(I) and SDS-Tl(I), respectively. In all cases, sodium sulfite was used as deoxygenator. The use of an inorganic compound (thallium nitrate) as a heavy-atom source in a cyclodextrin system represents a novel finding. Surface response optimization approaches were carried out to optimize the chemical variables which have an influence on the RTP emission of naproxen. Based on the results obtained, univariate RTP calibration methods for the determination of the analyte in pharmaceutical preparations were satisfactorily developed. In one case, the standard additions method was applied to a mixture of naproxen and the antibiotic tetracycline.

Anti-Inflammatory Agents, Non-Steroidal↗

PubMed2003

Determination of the amino acid tryptophan and the biogenic amine tryptamine in foods by the heavy atom induced-room temperature phosphorescence methodology.

Very simple and selective methods are presented to determine the amino acid tryptophan (Trp) and the biogenic amine tryptamine (Tryp), both compounds with an indole-type molecular structure by the methodology named Heavy Atom Induced-Room Temperature Phosphorescence (HAI-RTP) which constitutes the first time that HAI-RTP has been used to detect compounds with non-naphthalenic structures in their molecules. Different variables affecting the phosphorescence signal (heavy atom perturber and sodium sulfite concentration) were carefully studied. The analytical curves give a linear dynamic range of 15-100 ng ml(-1) and a detection limit of 4 ng ml(-1) for Trp and 94-400 ng ml(-1) and 28 ng ml(-1) for Tryp. The methods have been successfully applied to the analysis of complex food matrices such as the presence of tryptophan in yoghurt and tryptamine in bottled beer. A single alkaline hydrolysis to release Trp from yoghurt proteins and two methods for extracting Tryp from beer samples are proposed and optimised. A total Trp content of 374 mg of Trp per kg of yoghurt was quantified by the standard addition method of calibration and a recovery of 90% was obtained for 250 ng ml(-1) of Tryp in spiked non-alcoholic beer samples.

Beer↗

PubMed1983

Segmental motion and rotational diffusion of the Ca2+-translocating adenosine triphosphatase of sarcoplasmic reticulum, measured by time-resolved phosphorescence depolarization.

We studied the rotational mobility of the Ca2+ + Mg2+-activated ATPase in skeletal-muscle sarcoplasmic-reticulum vesicles, using time-resolved measurements of the depolarization of laser-flash-excited phosphorescence of the extrinsic triplet probe erythrosin. Our results are in general agreement with those of others [Bürkli & Cherry (1981) Biochemistry 20, 138-145] obtained by linear dichroism methods. In addition, we directly observed fast depolarization in the 1-5 microseconds time range that can be attributed to limited motion of part of the protein (segmental motion). Temperature-dependent changes in phosphorescence anisotropy indicated the onset of a conformational change in structure of the Ca2+ + Mg2+-activated ATPase at 11-13 degrees C. We also describe the synthesis of 5-iodoacetamidoerythrosin.

Adenosine Triphosphatases↗