Oxygen In Organic Solvents Research Articles

Encapsulation of Hydrophobic Porphyrins into Biocompatible Nanoparticles: An Easy Way to Benefit of Their Two-Photon Phototherapeutic Effect without Hydrophilic Functionalization.

Simple SummaryEfficient photosensitizers for photodyanmic therapy (PDT) need to be soluble in physiologic media. This requirement often complicates significantly the chemical access to such compounds, resulting in lower availability and higher production costs for the best representatives. Given that their screening and selection is often initially conducted in organic media from series of hydrophobic model compounds, the possibility to use directly such hydrophobic photosensitizers in real PDT studies was highly desirable to speed up their definitive identification but also to alleviate their cost. In this respect, PMLABe polymeric nanoparticles (NPs) were presently probed as nanocarriers to water-solubilize hydophobic star-shaped porphyrin-based which turned out to be promising oxygen photosensitizers for theranostic approaches. We show here that PDT conducted using such NPs loaded with these compounds is as efficient than when functional hydrosoluble analogues of these photosensitiers are tested alone and that tracking of the photosensitizer by fluorescence imaging is even easier.Star-shaped hydrophobic porphyrins, acting as powerful fluorescent two-photon photosensitizers for oxygen in organic solvents, can easily be loaded into PMLABe polymeric nanoparticles at various concentrations. In this contribution, the performance of these porphyrin-containing nanoparticles in terms of photodynamic therapy (PDT) is compared to those of the corresponding water-soluble porphyrin analogues when irradiated in MCF-7 cancer cells. While quite promising results are obtained for performing PDT with these nanoparticles, validating this approach as a mean for using more easily accessible and less expensive photosensitizers, from a synthetic perspective, we also show that their luminescence can still be used for bioimaging purposes in spite of their confinement in the nanoparticles, validating also the use of these nano-objects for theranostic purposes.

A hypervalent iodine secondary oxidant synthesized by photosensitized singlet oxygen: Synthesis, characterization and oxidative reactivity

Chemical scavenging of singlet oxygen by iodobenzene in the presence of (triethyleneglycol)monomethyl ether led to the formation of almost spherical nano-structured iodosylbenzene in water, water/acetonitrile and acetonitrile. To our knowledge, it is the first report on the direct aerobic photooxidative synthesis of iodosylbenzene. A polymer supported cationic porphyrin, nanoAmbSO3@H2TMPyP, was used as the photosensitizer. The nanoparticles, were characterized by various spectrophotometric and microscopic methods. The reactivity of the secondary oxidant for the oxidation of organic substrates was studied in the oxidation of methyl phenyl sulfide catalyzed by manganese meso-tetrakis(2-methylphenyl)porphyrin.The synthesis of the reactive secondary oxidant, PhIO, is suggested as anapplicablestrategy to overcome the problem of very short lifetime of singlet oxygen in organic solvents and water, which decreases the efficiency of singlet oxygen due to the involvement of the oxidant in unwanted physicalandchemicalquenchingpathways.It is noteworthy that due to very short lifetime of singlet oxygen, most of the singlet oxygen produced in the presence of different photosensitizers is deactivated by other species to return to its triplet ground state by physical or non-productive chemical quenching.

Oxygen sensors for flow reactors – measuring dissolved oxygen in organic solvents

We are demonstrating a solvent resistant optical sensor for measuring dissolved oxygen in pressurized micro flow reactors.

Photophysical properties and photocytotoxicity of free and liposome-entrapped diazepinoporphyrazines on LNCaP cells under normoxic and hypoxic conditions

5,7-Diaryl-substituted symmetrical diazepinoporphyrazine and tribenzodiazepinoporphyrazine were synthesized and characterized using UV–Vis, MS MALDI, and various NMR techniques. The expected photosensitizing potentials of these porphyrazines were evaluated by measuring their abilities to generate singlet oxygen in organic solvents and by comparing them with that of the recently obtained dendrimeric G1-type diazepinoporhyrazine. Absorbance and fluorescence measurements were performed to study the aggregation properties of the novel macrocycles. The photocytotoxicity of tribenzodiazepinoporphyrazine towards LNCaP cells in its free form and after its incorporation into liposomes was examined using MTT assay under normoxic and hypoxic conditions. It is interesting that all tested liposome formulations maintained their phototoxic activity in hypoxia. Also, tribenzodiazepinoporphyrazine incorporated into liposomes revealed better photocytotoxic effect (IC50 values of 0.600 ± 0.357 μM and 0.378 ± 0.002 μM) than its free form (IC50 values of 3.135 ± 0.156 μM). Following the in vitro experiments, the most promising liposomal formulation containing l-α-phosphatidyl-DL-glycerol for tribenzodiazepinoporphyrazine was found. Moreover, tribenzodiazepinoporphyrazine incorporated into liposomes containing 1,2-dioleoyl-3-trimethylammonium-propane (chloride salt) revealed moderate phototoxicity at 5 × 10−5 μM for antibacterial photodynamic therapy. It was established that an irradiation of planktonic bacterial strains significantly reduced CFUs of Staphylococcus aureus ATCC 25923 in comparison to tribenzodiazepinoporphyrazine containing l-α-phosphatidyl-DL-glycerol liposomes.

Solubility of Oxygen in Organic Solvents and Calculation of the Hansen Solubility Parameters of Oxygen

The solubility of oxygen in 21 pure organic solvents was measured at 298.2 K and 101.33 kPa using the static method. The Hansen solubility parameters (HSPs) of oxygen were determined from the measured solubilities in the pure solvents. The HSPs of oxygen were δd = 6.7 MPa1/2, δp = 0.0 MPa1/2, and δh = 3.8 MPa1/2, where d, p, and h stand for dispersion forces, dipole interaction, and hydrogen bonding, respectively. A linear relationship between the log of the gas solubility (log xG) in pure solvents and the difference between the HSP values of oxygen and the pure solvents was obtained with a high correlation coefficient of 0.944. In addition, the solubilities of oxygen in mixed solvents were measured, and these were compared with the oxygen gas solubility calculated from the HSPs of oxygen.

Direct optical excitation of singlet oxygen in organic solvents

Efficient excitation of singlet oxygen is demonstrated for several organic solvents (CS2, CCl4, and C6F14) that are irradiated using LED in the visible spectral range in the absorption bands of the O2-O2 collision complexes at the corresponding cooperative transitions. It is shown that the two-photon interaction of the pumping radiation in the Herzberg I band of molecular oxygen with its excitation to the 3Σu+ state and the subsequent collisional relaxation to the 1Σg and 1Δg singlet states contributes to the excitation of singlet oxygen.

Electrochemical Reduction of Oxygen in Organic Solvents With and Without Li+ Cation – Effect of Oxygen Supply

not Available.

Kinetics and mechanism of formyl- and acetylferrocene oxidation with molecular oxygen in organic solvents

Kinetic laws and the products of autoxidation of formyl- and acetylferrocene in organic solvents in the presence of strong and weak Bronsted acids were investigated. The special feature of the studied reactions is the extreme dependence of the metal complex oxidation rate on the strong acid concentration. This is explained by protonation of the metal complex at high concentrations of the acids leading to the formation of stable to oxidation α-ferrocenylcarbenium complexes C5H5FeC5H4C+(OH)R.

Conditions for manifestation of approachment and orientation effect at the oxidation of ferrocenylacetic acid and its methyl ester by molecular oxygen in organic Solvents

By comparison of reactivity of the ferrocene derivatives differing in the nature of the substituents the conditions were revealed of their participation as Bronstedt and Lewis acidic centers in the process of the metallocomplex molecular oxidation with oxygen in terms of manifestations of the effects of rapproachment and orientation. From this standpoint were analyzed the experimental data obtained in the oxidation of methyl ferrocenylacetate. A probable mechanism of the process is proposed that includes the molecular and radicalchain macro steps.

Features of the oxidation of certain hydroxy derivatives of ferrocene with molecular oxygen in organic solvents

Features of the oxidation of hydroxymethylferrocene with molecular oxygen in organic solvent in the presence of weak and strong Broensted acids were studied. The resulting data were compared with published data on ferrocene and hydroxyferrocene oxidation, which made it possible to assess the trend in the oxidation mechanism in going from ferrocene π complexes to their hydroxyferrocene and hydroxymethylferrocene analogs. A conclusion was drawn that each of the ferrocenes reacts with oxygen in quite a specific way.

Electrocatalytic reduction of oxygen with phenanthroline-strapped porphyrins

The electrochemical behavior of three cytochrome c oxidase models has been investigated. All the models are derived from a phenanthroline-strapped, porphyrin framework that binds zinc(II) or iron(III) chloride in the porphyrin subunit, and copper(I) in the phenanthroline site. The iron complex and the bimetallic zinc(II) copper(I) complex of the parent ligand have been characterized by X-ray diffraction. One model consists of the parent structure on which C 12 alkyl chains have been added. This soluble model achieves electrochemical 2-electron reduction of oxygen in organic solvents without the addition of an exogenous axial base, and in the presence of an organic or inorganic source of protons. The two other models comprise the parent phenanthroline-strapped porphyrin framework, on which two pendant imidazoles have been incorporated. These models adsorbed on ring-disk electrodes with an edge-oriented, pyrolytic graphite (EOPG) disk and a platinum ring, efficiently catalyze the 4-electron reduction of oxygen in dioxygen saturated water at neutral pH.

Quantitative Structure-Property Relationship: XXIII. Solubility of Oxygen in Organic Solvents

The solubility of oxygen in organic solvents was estimated from property-property correlations.

Specific Features of the Oxidation of Ferrocenylacetic Acid and 1,1'-Diethylferrocene with Molecular Oxygen in Organic Solvents

Specific Features of the Oxidation of Ferrocenylacetic Acid and 1,1'-Diethylferrocene with Molecular Oxygen in Organic Solvents

Oxygen-sensitive reverse-phase optode membrane using silica gel-adsorbed ruthenium(II) complex embedded in gelatin film

An oxygen-sensitive reverse-phase optode membrane consisting of tris(4,7-diphenyl-1,10-phenanthroline)ruthenium(II) ditetrakis(4-chlorophenyl)borate adsorbed on silica gel and embedded in a gelatin film has been successfully fabricated and used to continuously monitor dissolved oxygen in organic solvents. The optode membrane shows a very strong and stable pink emission when excited by blue light and it is efficiently quenched by molecular oxygen. The response of the sensor displays typical nonlinear Stern–Volmer behaviour when the dissolved oxygen concentration in organic solvents is at high levels. But the sensor is most sensitive at lower oxygen levels and is linear in the range 0–1.14, 0–2.10 and 0–0.53 mM for dissolved oxygen in acetone, dimethyl formamide and toluene, respectively. The t 95 response times of the sensor are 10 s on going from nitrogen-saturated toluene to air-saturated toluene and 22 s on going from air-saturated toluene to nitrogen-saturated toluene. The sensor has good reproducibility, high photostability, no hysteresis, good precision and long lifetime.

Oxidation studies of phenols with cobalt(II) ion-modified silica in a liquid chromatographic reactor

The activity of cobalt(II) ion-modified silica, a new catalyst for the oxidation of phenols with dissolved oxygen in organic solvents, has been studied in liquid chromatographic reactors using several approaches. In this reactor mode, catalyst activity can be maintained over months of repeated use while phenols are oxidized to p-benzoquinones at or below 45 °C. This approach eliminates problems of catalyst separations. Using the ideal liquid chromatographic reactor model with inert standard methods, the reaction is found to be first-order with respect to the phenolic reactants. Some pseudo-first-order rate constants have also been measured. The cobalt(II) ions bonded to silica probably function through reaction pathways similar to those of homogeneous cobalt complex catalysts for phenol oxidations. However, they are stable for long periods of time under the mild reaction conditions used here and can provide separation with concerted reaction.

In vivo measurement of oxygen concentration using sonochemically synthesized microspheres

Proteinaceous microspheres filled with nitroxides dissolved in an organic liquid have been synthesized for the first time using high intensity ultrasound; these were used to measure oxygen concentrations in living biological systems. The microspheres have an average size of 2.5 microns, and the proteinaceous shell is permeable to oxygen. Encapsulation of the nitroxides into the microsphere greatly increased the sensitivity of the electron paramagnetic resonance signal line width to oxygen because of the higher solubility of oxygen in organic solvents. The encapsulation also protected the nitroxide from bioreduction. No decrease in intensity of the electron paramagnetic resonance signal was observed during 70 min after intravenous injection of the microspheres into a mouse. Measurement of the changes in oxygen concentration in vivo by means of restriction of blood flow, anesthesia, and change of oxygen content in the respired gas were made using these microspheres.

N,N'-dibromo-5,5-dimethylhydantoin and N-bromosuccinimide, chemical sources of singlet molecular oxygen: Observation of singlet oxygen with ultra-sensitive near-infrared chemiluminescence spectroscopy.

N,N′-Dibromo-5,5-dimethylhydantoin and N-bromosuccinimide were found to be versatile and commercially available synthetic reagents for generating singlet molecular oxygen in organic solvents under mild conditions. Detection was by an ultra-sensitive near-IR chemiluminescence spectrometer designed and constructed in our laboratory.

Photosensitization with α-terthienyl: The formation of superoxide ion in aqueous media

It is well known that α-terthienyl generates singlet oxygen in organic solvents with high quantum yields. In an aqueous medium, the production of superoxide radical-anion is readily detected by comparing the reduction of ferricytochrome c or nitro blue tetrazolium in the presence and in the absence of superoxide dismutase. Electron transfer reactions from the electronically excited sensitizer are also detected in an argon atmosphere.

On the Determination of Oxygen in Organic Solvents Using an Inductively Coupled Plasma

The application of an inductively coupled plasma spectrometer, equipped with a linear photodiode array detector, to the determination of total oxygen in compounds dissolved in xylene has been investigated. Sample introduction was achieved with the use of a concentric nebulizer, and nonresonant, near-infrared emission lines were used for detection. A torch that prevents the entrainment of atmospheric oxygen and that is not susceptible to the buildup of carbon deposits was developed for this application. It was found that the measured emission intensity is dependent on both the concentration of oxygen and the boiling point of the oxygen-containing compound that is dissolved in the xylene. The detection limit for oxygen determination was found to be 0.070% total oxygen.

Peroxo-, Oxo-, and catena-Oxo-Manganese Complexes with N,N′-Ethylenebis(salicylideneimine) Analogues

Abstract By the reaction of MnII(salen) (salen=N,N′-ethylenebis(salicylideneiminato) dianion) and its analogues with molecular oxygen in organic solvents, three types of complexes including as structural units the MnIII–O2–MnIII,–(–MnIV–O–)–n, and MnIV=O bonds respectively, have been obtained, and characterized by means of their electronic and infrared spectra, by thermogravimetric analysis, and in terms of their magnetic properties. The lower magnetic moments for [MnIII(salen)]2O2 and –[–MnIV(salen)–O–]–n than those expected have been interpreted in terms of antiferromagnetic interactions. The oxo complex was found to give the catena-oxo complex quantitatively in a DMF, DMSO, or Py solution. The effects of the oxygen partial pressure and the nature of the substituent in the organic part on the complex formation were investigated. A lower partial pressure of oxygen has the advantage of yielding the μ-peroxo complex in a higher yield. A discussion of the reaction mechanism is also included.