Modulation of trans-to-cis photoisomerization and photoluminescence of 1,2-bis(4-pyridyl)ethylene or 4-styrylpyridine coordinated to fac-tricarbonyl(5-chloro-1,10-phenathroline)rhenium(I)

Photochemical and photophysical properties of fac-[Re(CO)(3)(Clphen)(trans-L)](+) complexes, Clphen = 5-chloro-1,10-phenathroline and L = 1,2-bis(4-pyridyl)ethylene, bpe, or 4-styrylpyridine, stpy, were investigated to complement the understanding of intramolecular energy transfer process in tricarbonyl rhenium(I) complexes having an electron withdrawing group attached to polypyridyl ligands. These new compounds were synthesized, characterized and the photoisomerization quantum yields were accurately determined by (1)H NMR spectroscopy. The true quantum yields for fac-[Re(CO)(3)(Clphen) (trans-bpe)](+) were constant (Phi = 0.55) at all investigated irradiation wavelengths. However, for fac-[Re(CO)(3)(Clphen)(trans-stpy)](+), similar true quantum yields were observed only at higher energy irradiation (Phi(313 nm) = 0.53 and Phi(365 nm) = 0.57), but it decreased significantly at 404 nm (Phi = 0.41). These results indicated different deactivation pathways for the trans-stpy complex photoisomerization. Quantum yields decreased as the (3)IL(trans-L) and (3)MLCT(Re -> NN) excited states become closer and the behavior was discussed in terms of the excited state energy gaps. Additionally, luminescence properties of photoproducts, fac-[Re(CO)(3)(Clphen)(cis-L)](+), were also investigated in different environments to analyze the relative energy of the (3)MLCT(Re -> Clphen) excited state for each compound. (C) 2011 Elsevier B.V. All rights reserved.

On the energy transfer from a polymer host to the rhenium(I) complex in OLEDs

Photoluminescence and electroluminescence of PVK films doped with fac-[ClRe(CO)(3)(bpy)], bpy=2,2`-bipyridine, are investigated. Photoluminescence spectra of spin-coated PVK films (lambda(exc)=290 nm) exhibit a broad band centered at 405 nm. As the concentration of dopant increases, the polymer emission is quenched and a band at 555 nm appears (isosbestic point at 475 nm). In OLEDs with ITO/PEDOT:PSS/PVK/butylPBD/Al architecture doped with fac-[ClRe(CO)(3)(bpy)], the polymer host emission is completely quenched even at the lowest concentration of dopant. The electroluminescence spectra of the devices show that there is an efficient energy transfer from the host to the dopant, which exhibits a very intense emission at 580 nm. (C) 2009 Elsevier B.V. All rights reserved.

(1)H NMR spectroscopy as a tool to determine accurate photoisomerization quantum yields of stilbene-like ligands coordinated to rhenium(I) polypyridyl complexes

In this work, the use of proton nuclear magnetic resonance, (1)H NMR, was fully described as a powerful tool to follow a photoreaction and to determine accurate quantum yields, so called true quantum yields (Phi(true)), when a reactant and photoproduct absorption overlap. For this, Phi(true) for the trans-cis photoisomerization process were determined for rhenium(I) polypyridyl complexes, fac-[Re(CO)(3)(NN)(trans-L)](+) (NN = 1,10-phenanthroline, phen, or 4,7-diphenyl-1,10-phenanthroline, ph(2)phen, and L = 1,2-bis(4-pyridyl) ethylene, bpe, or 4-styrylpyridine, stpy). The true values determined at 365 nm irradiation (e. g. Phi(NMR) = 0.80 for fac-[Re(CO)(3)(phen)(trans-bpe)](+)) were much higher than those determined by absorption spectral changes (Phi(UV-Vis) = 0.39 for fac-[Re(CO)(3)(phen)(trans-bpe)](+)). Phi(NMR) are more accurate in these cases due to the distinct proton signals of trans and cis-isomers, which allow the actual determination of each component concentration under given irradiation time. Nevertheless when the photoproduct or reactant contribution at the probe wavelength is negligible, one can determine Phi(true) by regular absorption spectral changes. For instance, Phi(313) nm for free ligand photoisomerization determined both by absorption and (1)H NMR variation are equal within the experimental error (bpe: Phi(UV-Vis) = 0.27, Phi(NMR) = 0.26; stpy: Phi(UV-Vis) = 0.49, Phi(NMR) = 0.49). Moreover, (1)H NMR data combined with electronic spectra allowed molar absorptivity determination of difficult to isolate cis-complexes. (C) 2009 Elsevier B. V. All rights reserved.

Study of the phenanthroline-Mn-imidazole bonding in Mn(I) triscarbonyl complex: A X-ray and DFT computational analysis

355 nm light irradiation of fac-[Mn(CO)(3)(phen)(imH)](+) (fac-1) produces the mer-1 isomer and a long lived radical which can be efficiently trapped by electron acceptor molecules. EPR experiments shows that when excited, the manganese(I) complex can be readily oxidized by one-electron process to produce Mn(II) and phen(.-). In the present study, DFT calculations have been used to investigated the photochemical isomerization of the parent Mn(I) complex and to characterize the electronic structures of the long lived radical. The theoretical calculations have been performed on both the fac-1 and mer-1 species as well as on their one electron oxidized species fac-1+ and mer-1+ for the lowest spin configurations (S = 1/2) and fac-6 and mer-6 (S = 5/2) for the highest one to characterize these complexes. In particular, we used a charge decomposition analysis (CDA) and a natural bonding orbital (NBO) to have a better understanding of the chemical bonding in terms of the nature of electronic interactions. The observed variations in geometry and bond energies with an increasing oxidation state in the central metal ion are interpreted in terms of changes in the nature of metal-ligand bonding interactions. The X-ray structure of fac-1 is also described. (C) 2011 Elsevier B.V. All rights reserved.

A multicommuted flow-system for spectrophotometric determination of tannin exploiting the Cu(I)/BCA complex formation

A flow system exploiting the multicommutation approach is proposed for spectrophotometric determination of tannin in beverages. The procedure is based on the reduction of Cu(II) in the presence of 4,4`-dicarboxy-2,2`-biquinoline, yielding a complex with maximum absorption at 558 nm. Calibration graph was linear (r=0.999) for tannic acid concentrations up to 5.00 mu mol L-1. The detection limit and coefficient of variation were estimated as 10 nmol L-1 (99.7% confidence level) and 1% (1.78 mu mol L-1 tannic acid, n=10), respectively. The sampling rate was 50 determinations per hour. The proposed procedure is more sensitive and selective than the official Folin-Denis method, also minimizing drastically waste generation. Recoveries within 91.8 and 115% were estimated for total tannin determination in tea and wine samples. (C) 2007 Elsevier B.V. All rights reserved.

Excited-State Dynamics in fac-[Re(CO)(3)(Me(4)phen)(L)](+)

Excited-state dynamics in fac-[Re(CO)(3)(Me(4)phen)(cis-L)](+) (Me(4)phen = 3,4,7,8-tetramethyl-1,10-phenanthroline, L = 4-styrylpyridine (stpy) or 1,2-bis(4-pyridyl)ethylene (bpe)) were investigated by steady-state and time-resolved techniques. A complex equilibrium among three closely lying excited states, 3IL(cis-L), (3)MLCT(Re -> me4phen), and (3)IL(Me4phen), has been established. Under UV irradiation, cis-to-trans isomerization of coordinated cis-L is observed with a quantum yield of 0.15 in acetonitrile solutions. This photoreaction competes with radiative decay from (3)MLCT(Re -> Me4phen) and (3)IL(Me4phen) excited states, leading to a decrease in the emission quantum yield relative to the nonisomerizable complex fac-[Re(CO)(3)(Me(4)phen)(bpa)](+) (bpa = 1,2-bis(4-pyridyl)ethane). From temperature-dependent time-resolved emission measurements in solution and in poly(methyl methacrylate) (PMMA) films, energy barriers (Delta E(a)) for interconversion between (3)MLCT(Re -> me4Phen) and (3)IL(Me4phen) emitting states were determined. For L = cis-stpy, Delta E(a) = 11 (920 cm(-1)) and 15 kJ mol(-1) (1254 cm(-1)) in 5:4 propionitrile/butyronitrile and PMMA, respectively. For L = cis-bpe, Delta E(a) = 13 kJ mol(-1) (1087 cm(-1)) in 5:4 propionitrile/butyronitrile. These energy barriers are sufficient to decrease the rate constant for internal conversion from higher-lying (3)IL(me4phen) state to (3)MLCT(Re -> Me4phen), k(i) congruent to 10(6) s(-1). The decrease in rate allows for the observation of intraligand phosphorescence, even in fluid medium at room temperature. Our results provide additional insight into the role of energy gap and excited-state dynamics on the photochemical and photophysical properties of Re(I) polypyridyl complexes.

Photoswitches and Luminescent Rigidity Sensors Based on fac-[Re(CO)(3)(Me(4)phen)(L)](+)

The fac-[Re(CO)(3)(Me(4)phen)(trans-L)](+) complexes, Me(4)phen = 3,4,7,8-tetramethyl-1,10-phenanthroline and L = 4-styrylpyridine, stpy, or 1,2-bis(4-pyridyl)ethylene, bpe, were synthesized and characterized by their spectroscopic, photochemical, and photophysical properties. The complexes exhibit trans-to-cis isomerization upon 313, 334, 365, and 404 nm irradiation, and the true quantum yields can be efficiently determined by absorption changes combined with (1)H NMR data. For fac-[Re(CO)(3)(Me(4)phen)(trans-bpe)](+) similar quantum yields were determined at all wavelengths investigated. However, a lower value (phi(true) = 0.35) was determined for fac-[Re(CO)(3)(Me(4)phen)(trans-stpy)](+) at 404 nm irradiation, which indicates different pathways for the photoisomerization process. The photoproducts, fac-[Re(CO)(3)(Me(4)phen)(cis-L)](+), exhibit luminescence at room temperature with two maxima ascribed to the (3)IL(Me4phen) and (3)MLCT(Re -> Me4phen) excited states. The luminescence properties were investigated in different media, and the behavior in glassy EPA at 77 K showed that the contribution of each emissive state is dependent on the excitation wavelength. The photochemical and photophysical behavior of the complexes were rationalized in terms of the energy gap of excited states and can be exploited in photoswitchable luminescent rigidity sensors.

Quantification of some nonsteroidal anti-inflammatory drugs as reducing agents of Cu(II)/4,4 '-dicarboxy-2,2 '-biquinoline complexes in cationic micellar medium

A simple method was developed for spectrophotometric determination of some nonsteroidal anti-inflammatory drugs (meloxicam, piroxicam and tenoxicam) based on the reduction of copper(II) in buffered solution (pH 7.0) and micellar medium containing 4,4'-dicarboxy-2,2'-buffered solution (pH 7.0) and micellar medium containing 4,4'-dicarboxy-2,2'-biquinoline acid. The-biquinoline acid. The absorbance values at 558 nm, characteristic of the formed Cu(I)/4,4'-dicarboxy-2,2'-biquinoline complexes, are linear with the concentrations (5.7-40 mmol L(-1), n = 5) of these oxicams (meloxicam r = 0.998; piroxicam and tenoxicam r = 0.999). The limit of detection values, in mmol L(-1), calculated for meloxicam (2.7), piroxicam (1.2) and tenoxicam (1.3) was obtained with 99% confidence level and the relative standard deviations for meloxicam (3.1%), piroxicam (5.1%) and tenoxicam (1.2%) were calculated using a 25 mmol L(-1) solution (n = 7). Mean recovery values for meloxicam, piroxicam and tenoxicam forms were 100 +/- 6.9, 98.6 +/- 3.6 and 99.4 +/- 2.5%, respectively. The conditional potential of Cu(II)/Cu(I) in complex medium of 7.5 mmol L(-1) BCA was determined to be 629 +/- 11 mV vs. NHE.

Characterization of the stimulus for reactive oxygen species generation in calcium-overloaded mitochondria

We have used two different probes with distinct detection properties, dichlorodihydrofluorescein diacetate and Amplex Red/horseradish peroxidase, as well as different respiratory substrates and electron transport chain inhibitors, to characterize the reactive oxygen species (ROS) generation by the respiratory chain in calcium-overloaded mitochondria. Regardless of the respiratory substrate, calcium stimulated the mitochondrial generation of ROS, which were released at both the mitochondrial-matrix side and the extramitochondrial space, in a way insensitive to the mitochondrial permeability transition pores inhibitor cyclosporine A. In glutamate/malate-energized mitochondria, inhibition at complex I or complex III (ubiquinone cycle) similarly modulated ROS generation at either mitochondrial-matrix side or extramitochondrial space; this also occurred when the backflow of electrons to complex I in succinate-energized mitochondria was inhibited. On the other hand, in succinate-energized mitochondria the modulation of ROS generation at mitochondrial-matrix side or extra-mitochondrial space depends on the site of complex III which was inhibited. These results allow a straight comparison between the effects of different respiratory substrates and electron transport chain inhibitors on ROS generation at either mitochondrial-matrix side or extra-mitochondrial space in calcium-overloaded mitochondria.

Cubebin and derivatives as inhibitors of mitochondrial complex I. Proposed interaction with subunit B8

The effects on mitochondrial respiration and complex I NADH oxidase activity of cubebin and derivatives were evaluated. The compounds inhibited the state 3 glutamate/malate-supported respiration of hamster liver mitochondria with IC50 values ranging from 12.16 to 83.96M. NADH oxidase reaction was evaluated in submitochondrial particles. The compounds also inhibited this activity, showing the same order of potency observed for effects on state 3 respiration, as well as a tendency towards a non-competitive type of inhibition (KI values ranging from 0.62 to 16.1M). A potential binding mode of these compounds with complex I subunit B8, assessed by docking calculations, is proposed.

Repetitive Transcranial Magnetic Stimulation Is Efficacious as an Add-On to Pharmacological Therapy in Complex Regional Pain Syndrome (CRPS) Type I

Single session repetitive transcranial magnetic stimulation (rTMS) of the motor cortex (M1) is effective in the treatment of chronic pain patients but the analgesic effect of repeated sessions is still unknown We evaluated the effects of rTMS in patients with refractory pain due to complex regional pain syndrome (CRPS) type I Twenty three patients presenting CRPS type I of 1 upper limb were treated with the best medical treatment (analgesics and adjuvant medications physical therapy) plus 10 daily sessions of either real (r) or sham (s) 10Hz rTMS to the motor cortex (M1) Patients were assessed daily and after 1 week and 3 months after the last session using the Visual Analogical Scale (VAS) the McGill Pain Questionnaire (MPQ) the Health Survey 36 (SF 36) and the Hamilton Depression (HDRS) During treatment there was a significant reduction in the VAS scores favoring the r rTMS group mean reduction of 4 65 cm (50 9%) against 2 18 cm (24 7%) in the s rTMS group The highest reduction occurred at the tenth session and correlated to improvement in the affective and emotional subscores of the MPQ and SF 36 Real rTMS to the M1 produced analgesic effects and positive changes in affective aspects of pain in CRPS patients during the period of stimulation Perspective This study shows an efficacy of repetitive sessions of high frequency rTMS as an add on therapy to refractory CAPS type I patients It had a positive effect in different aspects of pain (sensory discriminative and emotional affective) It opens the perspective for the clinical use of this technique (C) 2010 by the American Pain Society

Cationic technetium and rhenium complexes with pendant carbohydrates

Three carbohydrate conjugated dipicolylamine chelators, 2-bis(2-pyridinylmethyl)amino)ethyl 1-deoxy-1-thio-beta-D-glucopyranoside (L(1)), 2-bis(2-pyridinylmethyl)amino)ethyl-beta-D-glucopyranoside (L(2)), and 2-bis(2-pyridinylmethyl)amino)carboxamide-N-(2-amino-2-deoxy-D-glucopyranose) (L(3)) were complexed to the [M(Co)(3)](+) core (M=Tc, Re) and the properties of the resulting complexes were investigated. Synthesis and characterization of the chelator 2-bis(2-pyridinylmethyl)amino)ethyl 1-deoxy-1-thio-beta-D-glucopyranoside (L(1)) and the corresponding Re complex are reported. All chelators were radiolabeled in high yield with [(99)mTc(CO)(3)(H(2)O)(3)](+) ( > 98%) and [(186)Re(CO)(3)(H(2)O)(3)](+) ( > 80%). The chelators and Re-complexes were determined to not be substrates for the glucose metabolism enzyme hexokinase. However, the biodistribution of each of the (99m)Tc complexes demonstrated fast clearance from most background tissue, including >75% clearance of the activity in the kidneys and the liver within 2 h post-injection. (C) 2010 Elsevier Ltd. All rights reserved.

Synthesis, spectroscopic characterization, DFT studies and biological assays of a novel gold(I) complex with 2-mercaptothiazoline

A new gold(I) complex with 2-mercaptothiazoline (MTZ) with the coordination formula [AuCN(C(3)H(5)NS(2))] was synthesized and characterized by chemical and spectroscopic measurements, OFT studies and biological assays. Infrared (IR) and (1)H, (13)C and (15)N nuclear magnetic resonance (NMR) spectroscopic measurements indicate coordination of the ligand to gold(I) through the nitrogen atom. Studies based on OFT confirmed nitrogen coordination to gold(I) as a minimum of the potential energy surface with calculations of the hessians showing no imaginary frequencies. Thermal decomposition starts at temperatures near 160 degrees C, leading to the formation of Au as the final residue at 1000 degrees C. The gold(I) complex with 2-mercaptothiazoline (Au-MTZ) is soluble in dimethyl sulfoxide (DMSO), and is insoluble in water, methanol, ethanol, acetonitrile and hexane. The antibacterial activities of the Au-MTZ complex were evaluated by an antibiogram assay using the disc diffusion method. The compound showed an effective antibacterial activity against Staphylococcus aureus (Gram-positive) and Escherichia coli and Pseudomonas aeruginosa (Gram-negative) bacterial cells. Biological analysis for evaluation of the cytotoxic effect of the Au-MTZ complex was performed using HeLa cells derived from human cervical adenocarcinoma. The complex presented a potent cytotoxic activity, inducing 85% of cell death at a concentration of 2.0 mu mol L(-1). (C) 2011 Elsevier Ltd. All rights reserved.

Major histocompatibility complex (MHC) class II but not MHC class I molecules are required for efficient control of Strongyloides venezuelensis infection in mice

P>Strongyloides stercoralis is an intestinal nematode capable of chronic, persistent infection and hyperinfection of the host; this can lead to dissemination, mainly in immunosuppressive states, in which the infection can become severe and result in the death of the host. In this study, we investigated the immune response against Strongyloides venezuelensis infection in major histocompatibility complex (MHC) class I or class II deficient mice. We found that MHC II(-/-) animals were more susceptible to S. venezuelensis infection as a result of the presence of an elevated number of eggs in the faeces and a delay in the elimination of adult worms compared with wild-type (WT) and MHC I(-/-) mice. Histopathological analysis revealed that MHC II(-/-) mice had a mild inflammatory infiltration in the small intestine with a reduction in tissue eosinophilia. These mice also presented a significantly lower frequency of eosinophils and mononuclear cells in the blood, together with reduced T helper type 2 (Th2) cytokines in small intestine homogenates and sera compared with WT and MHC I(-/-) animals. Additionally, levels of parasite-specific immunoglobulin M (IgM), IgA, IgE, total IgG and IgG1 were also significantly reduced in the sera of MHC II(-/-) infected mice, while a non-significant increase in the level of IgG2a was found in comparison to WT or MHC I(-/-) infected mice. Together, these data demonstrate that expression of MHC class II but not class I molecules is required to induce a predominantly Th2 response and to achieve efficient control of S. venezuelensis infection in mice.

Rhenium chelate complexes with maltolate or kojate

Novel rhenium complexes containing the maltolate (mal) or kojate (koj) anions as chelating ligands have been synthesized: [ReOCl(mal)(2)] (1), [ReOCl(2)(mal)(PPh(3))] (2), [ReOBr(2)(mal)(PPh(3))] (3), [ReOCl2(koj)(PPh(3))] (4) and [ReOBr(2)(koj)(PPh(3))] (5). The products have been characterized by MR, (1)H, (13)C, and (31)P NMR spectroscopies and elemental analysis. The crystal and molecular structures of all complexes were determined. Complex I crystallizes monoclinic, space group C2/c, Z = 8. It contains two O, O`-bidentate maltolate ligands and one chloro ligand at the (ReO)(3+) unit, so that a distorted octahedral geometry is adopted by the six-coordinated rhenium(V) center. The chloro ligand occupies a cis position to the oxo ligand. Complexes 2 and 3 are isostructural and crystallize orthorhombic, space group Pbca and Z = 8. The isostructural complexes 4 and 5 crystallize monoclinic, space group P2(1)/n and Z = 4. In complexes 2-5, the (ReO)(3+) unit is coordinated by a monoanionic O,O-bidentate unit of the maltolate (2 and 3) or kojate (41 and 5) ligand, one triphenylphosphine and two halogeno ligands (Cl in 2 and 4; Br in 3 and 5), with the rhenium(V) center in a distorted octahedral environment. The halide ligands are in cis positions to each other. (c) 2008 Elsevier Ltd. All rights reserved.