Search

Six-coordinate iridium(III) triarylcorrole derivatives, Ir[TpXPC)]L2, where TpXPC = tris(para-X-phenyl)corrole (X = CF3, H, Me, and OCH3) and L = pyridine (py), trimethylamine (tma), isoquinoline (isoq), 4-dimethylaminopyridine (dmap), and 4-picolinic acid (4pa), have been examined, with a view to identifying axial ligands most conducive to near-infrared phosphorescence. Disappointingly, the phosphorescence quantum yield invariably turned out to be very low, about 0.02 – 0.04% at ambient temperature, with about a two-fold increase at 77 K. Phosphorescence decay times were found to be around ~5 µs at 295 K and ~10 µs at 77 K. Fortunately, two of the Ir[TpCF3PC)]L2 derivatives, which were tested for their ability to sensitize singlet oxygen formation, were found to do so efficiently with quantum yields Φ(1O2) = 0.71 and 0.38 for L = py and 4pa, respectively. Iridium corroles thus may hold promise as photosensitizers in photodynamic therapy (PDT). The possibility of varying the axial ligand and of attaching biotargeting groups at the axial positions makes iridium corroles particularly exciting as PDT drug candidates. [ABSTRACT FROM AUTHOR]

Temperature is an essential parameter for reliable assessment of oxygen concentration by optical sensors. This can be done by a conventional sensor such as a resistance thermometer or by adding an optical temperature probe to the sensing material. A sensor that relies on a single emitter capable of simultaneous sensing of oxygen and temperature would be highly advantageous. Unfortunately, such materials are extremely rare and moreover poorly suitable for measurement at ambient temperatures and physiological conditions. To cover this gap, we systematically investigated 15 Pd(II) and 6 Pt(II) complexes of π-extended porphyrins that simultaneously emit thermally activated delayed fluorescence (TADF) and phosphorescence. The class of quinone-extended benzoporphyrins was found to feature especially high ratios of TADF to phosphorescence (1.4–2.7 and 0.10–0.21, for Pd(II) and Pt(II) complexes, respectively, at 25 °C) which represents approximately a sixteen-fold improvement compared to the benchmark octasulfone-substituted porphyrins. Interconversion of phosphorescence into TADF with increasing temperature enables ratiometric measurement of this parameter in the range from 0 to about 65 °C whereas the oxygen concentration is accessed through the decay time of either TADF or phosphorescence. Simultaneous sensing of both temperature and oxygen is demonstrated for a naphthoquinone-extended Pt(II) benzoporphyrin embedded in polystyrene that shows dual emission with maxima at 677 and 789 nm. The sensor is characterized for temperatures from 5° to 55 °C and oxygen partial pressure from 0 to 202 hPa, corresponding to the conditions found in the majority of applications. As an application example temperature compensated imaging of oxygen distribution is demonstrated. [Display omitted] • Dual emission of Pd(II) and Pt(II) porphyrins is systematically investigated. • Quinone-extended porphyrins show the highest TADF/phosphorescence ratio. • Temperature increase promotes conversion of phosphorescence into TADF. • Simultaneous monitoring of O 2 and temperature is achieved with a single indicator. [ABSTRACT FROM AUTHOR]

Presented herein is a first photophysical investigation of a series of rhenium(v)-oxo tris(p-X-phenyl)corroles, Re[TpXPC](O), where X = CF3, F, H, CH3, and OCH3. The complexes all exhibit near-IR phosphorescence in anoxic toluene at room temperature, with emission maxima at 780 ± 10 nm, phosphorescence decay times of 56–74 μs and quantum yields of 1.07–1.52%, the highest reported to date for phosphorescent corrole derivatives. We have also demonstrated that the dyes may serve as indicators in optical oxygen sensors and as sensitizers in triplet–triplet-annihilation-based upconversion. Although the ReO corroles are not superior to benchmark benzoporphyrin complexes that are currently used in these applications, they may prove useful in certain areas such as optical multianalyte sensing owing to improved flexibility in the available spectral properties of the dyes. The high thermal and photochemical stability of the complexes also bodes well for their deployment as new, phosphorescent sensitizers in photodynamic therapy. [ABSTRACT FROM AUTHOR]

The highly sensitive optical detection of oxygen including dissolved oxygen (DO) is of great interest in various applications. We devised a novel room-temperature-phosphorescence (RTP)-based oxygen detection platform by constructing core-shell nanoparticles with water-soluble polymethyloxazoline shells and oxygen-permeable polystyrene cores crosslinked with metal-free purely organic phosphors. The resulting nanoparticles show a very high sensitivity for DO with a limit of detection (LOD) of 60 n m and can be readily used for oxygen quantification in aqueous environments as well as the gaseous phase. [ABSTRACT FROM AUTHOR]

A series of bis(phenylacetylido)(porphyrinato) E(IV) (E = Si, Ge, Sn) derivatives were obtained by reacting lithium phenylacetylide with the corresponding bis(chlorido)(porphyrinato) E(IV) precursors. Crystal structure determinations demonstrated that the transcoordinated acetylide ligands deviate from their expected ideal geometry. Density functional theory calculations and comparison of the packing of the molecules among the homologous series of Si(IV), Ge(IV) and Sn(IV) revealed causes for the deviation from the simple valence shell electron pair repulsion model. Fluorescence and phosphorescence of these organometallic group 14 derivatives were studied and the results are compared to the literature-known properties of the related bis(chlorido) (porphyrinato) E(IV) compounds (E = Si, Ge, Sn). The first crystal structure of a porphyrinato Ge(IV) compound with σ-bonded acetylide ligands is reported. [ABSTRACT FROM AUTHOR]

Optical oxygen sensing is of broad interest in many areas of research, such as medicine, food processing, and micro- and marine biology. The operation principle of optical oxygen sensors is well established and these sensors are routinely employed in lab and field experiments. Ultra-trace oxygen sensors, which enable measurements in the sub-nanomolar region (dissolved oxygen), are becoming increasingly important. Such sensors prominently exhibit phenomena that complicate calibration and measurements. However, these phenomena are not constrained to ultratrace sensors; rather, these effects are inherent to the way optical oxygen sensors work and may influence any optical oxygen measurement when certain conditions are met. This scenario is especially true for applications that deal with high-excitation light intensities, such as microscopy and microfluidic applications. Herein, we present various effects that we could observe in our studies with ultratrace oxygen sensors and discuss the reasons for their appearance, the mechanism by which they influence measurements, and how to best reduce their impact. The phenomena discussed are oxygen photoconsumption in the sensor material; depletion of the dye ground state by high-excitation photon-flux values, which can compromise both intensity and ratiometric-based measurements; triplet-triplet annihilation; and singlet-oxygen accumulation, which affects measurements at very low oxygen concentrations. [ABSTRACT FROM AUTHOR]

New Pt(II) and Pd(II) complexes with donor–acceptor Schiff bases are conveniently prepared in only two steps. The complexes efficiently absorb in the red part of the spectrum (ε > 105 M-1 cm-1) and show moderate to strong room-temperature phosphorescence in the near-infrared (NIR) region. Particularly, Pt(II) complexes possess phosphorescence quantum yields (Φ) of ∼10%, but the emission of the respective Pd(II) complexes is less efficient (Φ ≈ 1%-2%). The complexes exhibit solvatochromic behavior, in which the absorption and emission spectra shift bathochromically in polar solvents. The Pt(II) complexes are embedded in polystyrene to produce oxygen-sensing materials. The Pd(II) and Pt(II) complexes are demonstrated to be efficient sensitizers in triplet–triplet annihilation-based upconversion systems. [ABSTRACT FROM AUTHOR]

Abstract: Nucleophilic substitution of the labile para-fluorine atoms of 2,3,4,5,6-pentafluorophenyl groups enables a click-based covalent linkage of an oxygen indicator (platinum(II) or palladium(II) 5,10,15,20-meso-tetrakis-(2,3,4,5,6-pentafluorophenyl)-porphyrin) to the sensor matrix. Copolymers of styrene and pentafluorostyrene are chosen as polymeric materials. Depending on the reaction conditions either soluble sensor materials or cross-linked microparticles are obtained. Additionally, we prepared Ormosil-based sensors with linked indicator, which showed very high sensitivity toward oxygen. The effect of covalent coupling on sensor characteristics, stability and photophysical properties is studied. It is demonstrated that leaching and migration of the dye are eliminated in the new materials but excellent photophysical properties of the indicators are preserved. [Copyright &y& Elsevier]

Abstract: New optical sensors for trace amounts of oxygen are based on platinum(II) and palladium(II) complexes of 5,10,15,20-meso-tetrakis-(2,3,4,5,6-pentafluorphenyl)-porphyrin covalently attached to the surface of amino-modified silica-gel particles. The dye-doped silica-gel particles are dispersed in silicone rubber. The Stern–Volmer plots show linear response and are virtually identical for either luminescence intensity and decay time. Other features include high photostability and rapid response times (∼150ms in gas phase). The sensors based on the palladium(II) complex show significantly higher sensitivity (K SV about 67kPa−1 at 25°C) with the dynamic range from 0.02 to 100Pa. The sensitivity of the platinum(II) complexes is significantly lower (K SV =3.7–4.2kPa−1, dynamic range 0.3–1000Pa). The sensors can be suitable for application in breweries, water boilers and for marine research (monitoring of oxygen minimum zones). [Copyright &y& Elsevier]

New robust optical sensors for measurement of low oxygen concentrations are presented. The simple synthesis of a new Pt(II) and Pd(II)-benzoporphyrin indicator and the subsequent modification via Suzuki-coupling to introduce reactive styrene groups are shown. These indicators have excellent photophysical properties like high brightness, good photostability and NIR emission. A highly mechanically and chemically stable oxygen-permeable silicon rubber matrix was prepared by curing polysiloxane pre-polymers using the catalytic hydrosilylation reaction. The new indicator dyes act as crosslinkers in this reaction and are covalently immobilised into the matrix which prevents aggregation and leaching of the dye. Differently substituted polysiloxane pre-polymers were used in order to fine-tune the sensitivity of the sensor. In contrast to most state-of-the-art oxygen sensors the Stern–Volmer plots are ideally linear in the relevant measurement range which ensures simple (re)calibration. The sensors show very fast response <1 and K SV values between 0.082 and 0.141 hPa −1 when using Pt(II)-benzoporphyrin and 0.921 hPa −1 when using Pd(II)-benzoporphyrin. To illustrate potential applications of these oxygen sensors, the measurement of oxygen diffusion through cork-sealed colored glass bottles is demonstrated. [ABSTRACT FROM AUTHOR]

• Three Pd(II) (benzo)porphyrins are cyclometalated. • All molecular hybrids show decreased luminescence decay times in solution. • Cym1 shows strong bathochromic shift of spectra and 20-fold decreased lifetime. • All the dyes are efficient photosensitizers of singlet oxygen. Cyclometalation is investigated as a method to modulate the photophysical properties of phosphorescent (benzo)porphyrins. For cyclometalation with Pt(II), 2-pyridyl groups were incorporated into three Pd(II) porphyrin complexes. Integration of the freely rotating cyclometalated 2-phenylpyridyl based motif in meso -position does not lead to notable spectral changes and only affects the luminescence decay time (about 2-fold decrease) in solution at room temperature. The decay times, however, are not affected in frozen glass at 77 K or immobilized into a rigid polystyrene matrix. In contrast, cyclometalation involving a 2-pyridyl unit in meso -position and the β-H of the porphyrin results in a large bathochromic shift (∼ 1900 cm−1) of Q-bands in the absorption spectrum and the phosphorescence peak. A drastic decrease of the phosphorescence lifetime (about 20-fold) also is observed. Cyclometalation is accompanied by an increase of the singlet oxygen quantum yield to 85 % making the new dye a powerful red-light excitable 1O 2 photosensitizer. [ABSTRACT FROM AUTHOR]

Complexes of benzoporphyrins are highly promising for application in optical oxygen sensors, as triplet sensitizers for generation of singlet oxygen and upconversion based on triplet-triplet annihilation (TTA). Particularly, they benefit from efficient absorption in red part of the spectrum and strong NIR phosphorescence. In this contribution, we investigate different strategies of tuning the photophysical properties of these readily available complexes via 1-step modification. The new π-extended derivatives are obtained via Friedel-Crafts acylation of tetraphenyltetrabenzoporphyrin (TPTBP) complexes and by Suzuki or Sonogashira cross-coupling reaction of the tetrabromo-substituted benzoporphyrins. The Soret and Q absorption bands of the tetra-substituted dyes shift bathochromically by about 15 nm compared to the parent TPTBP compounds. The modified dyes retain their NIR phosphorescent properties and feature slight improvement of the quantum yield. Application in optical oxygen sensing materials and triplet-triplet annihilation-based upconversion systems is demonstrated. [ABSTRACT FROM AUTHOR]

A glucose optode measuring the internal oxygen gradient is presented. The multilayer biosensor is composed of (i) analyte-impermeable transparent support, (ii) first oxygen-sensing layer combined with an enzymatic layer, (iii) diffusion barrier, and (iv) second oxygen-sensing layer. To make this design suitable for measurement in subcutaneous tissue, a pair of NIR phosphorescent indicators with very different spectral properties is chosen. Combination of a conventional Pt(II) tetrabenzoporphyrin dye (absorption and emission maxima at 617 and 772 nm, respectively) used in the first layer and a new intramolecularly bridged Pt(II) complex (absorption and emission maxima at 673 and 872 nm, respectively) in the second layer enables efficient separation of both emission signals. This specially designed dye class is accessible via Scholl-reaction from tetraphenyltetrabenzoporphyrin complexes. For the first time, the new optode allows simultaneous glucose and oxygen measurement in a single spot and therefore accurate compensation of oxygen heterogeneities resulting from fluctuations in the tissue. The presented material covers the dynamic ranges from 0 to 150 hPa O2 and from 0 to 360 mg/dL (20 mM) glucose (at 37 °C). [ABSTRACT FROM AUTHOR]

Abstract: There is currently a need for a method capable of measuring the activity and inhibition of biologically relevant oxygenases in a format that enables the convenient, fast, and cost-efficient generation of dose–response information. Here we describe a low-volume luminescence-based assay for the measurement of such oxygen-dependent enzymes. The assay employs a photoluminescent oxygen-sensitive probe and glass capillary microcuvettes measured on the Roche LightCycler detection platform. Three discrete types of oxygen probe were evaluated for this application: (i) solid-state coatings, (ii) soluble macromolecular MitoXpress probe, both phosphorescent porphyrin-based, and (iii) a luminescent Ir(III)-based nanoparticle probe. Measurement parameters were optimised and subsequently applied to the analysis of three biologically relevant oxygenases, namely cytochrome P450 (CYP), monoamine oxygenase (MAO), and cyclooxygenase (COX). CYP enzymes are central players in drug detoxification while specific inhibitors of MAO and COX are important for therapeutic intervention and treatment of neurological and inflammatory diseases, respectively. To determine assay utility, oxygen consumption catalysed by all three enzyme types was measured and the effect of specific inhibitors determined. The panel included the MAO-A/B inhibitors clorgyline, toloxatone, deprenyl, and the COX-1/2 inhibitors niflumic acid, nimesulide, SC-560, ketoprofen, and phenylbutazone. IC50 values were then compared with literature values. The measurement methodology described allows the low-volume analysis of biologically relevant oxygenases and displays the requisite sensitivity and throughput to facilitate routine analysis. It is also applicable to other O2-dependent enzymes and enzymatic systems. [Copyright &y& Elsevier]