Photochemistry of Complex Ions. III. Absolute Quantum Yields for the Photolysis of Some Aqueous Chromium(III) Complexes. Chemical Actinometry in the Long Wavelength Visible Region

1966 ◽  
Vol 88 (3) ◽  
pp. 394-404 ◽  
Author(s):  
Ernst E. Wegner ◽  
Arthur W. Adamson
Keyword(s):  
Visible Region ◽  
Quantum Yields ◽  
Complex Ions ◽  
Long Wavelength ◽  
Absolute Quantum

scholarly journals Single-Ion Magnet and Photoluminescence Properties of Lanthanide(III) Coordination Polymers Based on Pyrimidine-4,6-Dicarboxylate

2021 ◽  
Vol 7 (1) ◽  
pp. 8
Author(s):  
Oier Pajuelo-Corral ◽  
Jose Angel García ◽  
Oscar Castillo ◽  
Antonio Luque ◽  
Antonio Rodríguez-Diéguez ◽  
...  
Keyword(s):  
Coordination Polymers ◽  
Single Molecule ◽  
Visible Region ◽  
Emission Spectra ◽  
Lanthanide Ions ◽  
Quantum Yields ◽  
Nitrate Anion ◽  
Absolute Quantum

Herein, we report the magnetic and photoluminescence characterization of coordination polymers (CP) built from the combination of lanthanide(III) ions, pyrimidine-4,6-dicarboxylate (pmdc) ligand and a co-ligand with formula {[Dy(μ-pmdc)(μ-ox)0.5(H2O)3]·2H2O}n (1-Dy), {[Dy(μ3-pmdc)(μ-ox)0.5(H2O)2] ~2.33H2O}n (2-Dy), {[Dy2(μ3-pmdc)(μ4-pmdc)(μ-ox)(H2O)3]·5H2O}n (3-Dy), {[Ln(μ3-pmdc)(μ-ox)0.5(H2O)2]·H2O}n (where Ln(III) = Nd (4-Nd), Sm (4-Sm), Eu (4-Eu) and Dy (4-Dy)) and {[Dy(μ4-pmdc)(NO3)(H2O)]·H2O}n (5-Dy). It must be noted the presence of oxalate anion acting as ditopic co-ligand in compounds 1-Dy, 2-Dy, 3-Dy and 4-Ln, whereas in 5-Dy the nitrate anion plays the role of terminal co-ligand. Direct current measurements carried out for the dysprosium-based CPs reveal almost negligible interactions between Dy3+ ions within the crystal structure, which is confirmed by computed values of the exchange parameters J. In addition, alternating current measurements show field-induced single-molecule magnet (SMM) behavior in compounds 1-Dy, 2-Dy, 4-Dy and 5-Dy, whereas slight-frequency dependence is also observed in 3-Dy. Solid state emission spectra performed at room temperature for those compounds emitting in visible region confirm the occurrence of significant ligand-to-lanthanide charge transfer in view of the strong characteristic emissions for all lanthanide ions. Emission decay curves were also recorded to estimate the emission lifetimes for the reported compounds, in addition to the absolute quantum yields. Among them, the high quantum yield of 25.0% measured for 4-Eu is to be highlighted as a representative example of the good emissive properties of the materials.

Photooxidation effect of cupric complexes on aliphatic alcohols in nonaqueous solutions

1982 ◽  
Vol 47 (8) ◽  
pp. 2061-2068 ◽  
Author(s):  
Jan Sýkora ◽  
Mária Jakubcová ◽  
Zuzana Cvengrošová
Keyword(s):  
Coordination Sphere ◽  
Alcohol Oxidation ◽  
Aliphatic Alcohols ◽  
Oxidation Products ◽  
Molar Ratio ◽  
Quantum Yields ◽  
Nonaqueous Solutions ◽  
The Absolute ◽  
Absolute Quantum

In the photolysis of copper(II)-chloride-alcohol-acetonitrile systems (cCu = 1 mmol l-1, copper(II)-to-chloride molar ratio 1 : 2 to 1 : 8, 10% (v/v) alcohol), Cu(II) is reduced to Cu(I), and methanol, ethanol, 1-propanol, or 1-butanol is oxidized to the corresponding aldehyde, 2-propanol to acetone. In the case of 1-propanol and 1-butanol, chlorinated aldehydes are formed in addition too. The measured quantum yields of the photoreduction of Cu(II) to Cu(I) lay in the range of ΦCu(I) = 4.5 to 40 mmol einstein-1, the absolute quantum yields of the alcohol oxidation products were 2.3 to 47 mmol einstein-1. The photoactive components are chlorocupric complexes [CuClx](2-x)+ (x = 1-4). The presence of complexes with a higher number of chloroligands in the coordination sphere (x = 3, 4) brings about a decrease in the Cu(II) photoreduction rate. The decrease in the photoreduction rate observed in the presence of dioxygen is explained in terms of re-oxidation of copper(I) by the latter, resulting in an increase in the concentration of the photochemically active cupric complexes. The catalytic aspects of the systems in question are discussed with respect to this effect.

Photoelectromotive Force (PEMF) Studies of [Fe(CN)5SCN]3- Complex Ions Adsorbed on Pb(SCN)2 Semiconductor Surfaces

2001 ◽  
Vol 66 (1) ◽  
pp. 81-88 ◽  
Author(s):  
Horst Hennig ◽  
Athanasios Kokorakis ◽  
Stefan Fränzle ◽  
Cornelia Damm ◽  
Franz W. Müller ◽  
...  
Keyword(s):  
Redox Reactions ◽  
Visible Region ◽  
Laser Flash ◽  
Semiconductor Surfaces ◽  
Spectral Sensitization ◽  
Complex Ions ◽  
Hole Trapping ◽  
Photoelectromotive Force

Adsorbates of [Fe(CN)5SCN]3- complex ions on semiconducting Pb(SCN)2 surfaces were subject to photoelectromotive force (PEMF) investigations. Laser flash excitation of the adsorbates at 560 nm yields a weak PEMF signal due to spectral sensitization of the semiconductor Pb(SCN)2, not absorbing in the visible region. PEMF signals observed with laser flash excitation at 337 nm are explained by hole trapping accompanied with photoinduced redox reactions of the complex, when the number of flashes is increased.

Terminology, relative photonic efficiencies and quantum yields in heterogeneous photocatalysis. Part II: Experimental determination of quantum yields

1999 ◽  
Vol 71 (2) ◽  
pp. 321-335 ◽  
Author(s):  
Angela Salinaro ◽  
Alexei V. Emeline ◽  
Jincai Zhao ◽  
Hisao Hidaka ◽  
Vladimir K. Ryabchuk ◽  
...  
Keyword(s):  
Quantum Yield ◽  
Visible Region ◽  
Heterogeneous Photocatalysis ◽  
Quantum Yields ◽  
Yield Data ◽  
Normal Absorption ◽  
The One ◽  
Solid Liquid ◽  
Photonic Efficiency

In the preceding article [Serpone and Salinaro, Pure Appl. Chem., 71(2), 303-320 (1999)] we examined two principal features of heterogeneous photocatalysis that demanded scrutiny: (i) description of photocatalysis and (ii) description of process efficiencies. For the latter we proposed a protocol relative photonic efficiency which could subsequently be converted to quantum yields. A difficulty in expressing a quantum yield in heterogeneous photochemistry is the very nature of the system, either solid/liquid or solid/gas, which places severe restrictions on measurement of the photon flow absorbed by the light harvesting component, herein the photocatalyst TiO2, owing to non-negligible scattering by the particulates. It was imperative therefore to examine the extent of this problem. Extinction and absorption spectra of TiO2 dispersions were determined at low titania loadings by normal absorption spectroscopy and by an integrated sphere method, respectively, to assess the extent of light scattering. The method is compared to the one reported by Grela et al. [J. Phys. Chem., 100, 16940 (1996)] who used a polynomial extrapolation of the light scattered in the visible region into the UV region where TiO2 absorbs significantly. This extrapolation underestimates the scattering component present in the extinction spectra, and will no doubt affect the accuracy of the quantum yield data. Further, we report additional details in assessing limiting photonic efficiencies and quantum yields in heterogeneous photocatalysis.

scholarly journals Bis[Pyrrolyl Ru(II)] Triads: a New Class of Photosensitizers for Metal-Organic Photodynamic Therapy

2020 ◽  
Author(s):  
Deborah A. Smithen ◽  
Susan Monro ◽  
Mitch Pinto ◽  
John A. Roque III ◽  
Roberto M. Diaz-Rodriguez ◽  
...  
Keyword(s):  
Photodynamic Therapy ◽  
Visible Light ◽  
Red Light ◽  
Visible Region ◽  
Hl60 Cell ◽  
Quantum Yields ◽  
Human Leukemia ◽  
New Family ◽  
Hl60 Cell Line

A new family of ten dinuclear Ru(II) complexes based on the bis[pyrrolyl Ru(II)] triad scaffold, where two Ru(bpy)<sub>2</sub> centers are separated by a variety of organic linkers, was prepared to evaluate the influence of the organic chromophore on the spectroscopic and in vitro photodynamic therapy (PDT) properties of the compounds. The bis[pyrrolyl Ru(II)] triads absorbed strongly throughout the visible region, with several members having molar extinction coefficients (e) ≥10<sup>4</sup> at 600–620 nm and longer. Phosphorescence quantum yields were generally less than 0.1% and in some cases undetectable. The singlet oxygen quantum yields ranged from 5% to 77% and generally correlated with their photocytotoxicities toward human leukemia (HL-60) cells regardless of the wavelength of light used. Dark cytotoxicities varied ten-fold, with EC<sub>50</sub> values in the range of 10–100 µM and phototherapeutic indices (PIs) as large as 5,400 and 260 with broadband visible (28 J cm<sup>-2</sup>, 7.8 mW cm<sup>-2</sup>) and 625-nm red (100 J cm<sup>-2</sup>, 42 mW cm<sup>-2</sup>) light, respectively. The bis[pyrrolyl Ru(II)] triad with a pyrenyl linker (5h) was especially potent, with an EC50 value of 1 nM and PI >27,000 with visible light and subnanomolar activity with 625-nm light (100 J cm<sup>-2</sup>, 28 mW cm<sup>-2</sup>). The lead compound 5h was also tested in a tumor spheroid assay using the HL60 cell line and exhibited greater photocytotoxcicity in this more resistant model (EC<sub>50</sub>=60 nM and PI>1,200 with 625-nm light) despite a lower dark cytotoxicity. The in vitro PDT effects of 5h extended to bacteria, where submicromolar EC<sub>50</sub> values and PIs >300 against <i>S. mutans</i> and <i>S. aureus </i>were obtained with visible light. This activity was attenuated with 625-nm red light, but PIs were still near 50. The ligand-localized <sup>3</sup>ππ* state contributed by the pyrenyl linker of 5h likely plays a key role in its phototoxic effects toward cancer cells and bacteria.<br><br>

Tb2(bpdc)3 and Eu2(bpdc)3 Nanoparticles (bpdc: 2,2ʹ-Bipyridine-4,4ʹ- dicarboxylate) and Their Luminescence

2014 ◽  
Vol 69 (2) ◽  
pp. 248-254 ◽  
Author(s):  
Ana Kuzmanoski ◽  
Claus Feldmann
Keyword(s):  
Colloidal Stability ◽  
Aqueous Suspension ◽  
Earth Metal ◽  
Quantum Yields ◽  
X Ray Diffraction ◽  
Antenna Effect ◽  
Metal Centers ◽  
X Ray ◽  
Suspension Particle ◽  
Absolute Quantum

Tb2(bpdc)3 and Eu2(bpdc)3 nanoparticles (bpdc: 2,2ʹ-bipyridine-4,4ʹ-dicarboxylate) have been prepared via straightforward precipitation from aqueous solution. The nanoparticles exhibit mean diameters of 41(5) nm (Tb2(bpdc)3) and 56(4) nm (Eu2(bpdc)3) and show a very good colloidal stability in aqueous suspension. Particle size and chemical composition have been characterized based on electron microscopy, X-ray diffraction, infrared spectroscopy and thermogravimetry. Photoluminescence validates an efficient excitation of Tb3+/Eu3+ via the bpdc ligand as an antenna that leads to intense characteristic green and red emissions. The absolute quantum yields of Tb2(bpdc)3 and Eu2(bpdc)3 have been determined at 28 and 12%, respectively. Although rare-earth metal-based photoluminescence is typically quenched in water due to vibronic loss processes (v(O-H)), here, the antenna effect and the shielding of the metal centers via the bpdc ligand are very efficient, allowing for an intense green and red emission of the Tb2(bpdc)3 and Eu2(bpdc)3 nanoparticles even in aqueous suspension.

scholarly journals One-Step Hydrothermal Synthesis of Yellow and Green Emitting Silicon Quantum Dots with Synergistic Effect

Nanomaterials ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 466
Author(s):  
Zhixia Zhang ◽  
Chunjin Wei ◽  
Wenting Ma ◽  
Jun Li ◽  
Xincai Xiao ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Synergistic Effect ◽  
High Efficiency ◽  
Synergistic Effects ◽  
Biomedical Science ◽  
Future Application ◽  
Quantum Yields ◽  
Silicon Quantum Dots ◽  
Long Wavelength ◽  
One Step

The concept of synergistic effects has been widely applied in many scientific fields such as in biomedical science and material chemistry, and has further attracted interest in the fields of both synthesis and application of nanomaterials. In this paper, we report the synthesis of long-wavelength emitting silicon quantum dots based on a one-step hydrothermal route with catechol (CC) and sodium citrate (Na-citrate) as a reducing agent pair, and N-[3-(trimethoxysilyl)propyl]ethylenediamine (DAMO) as silicon source. By controlling the reaction time, yellow-emitting silicon quantum dots and green-emitting silicon quantum dots were synthesized with quantum yields (QYs) of 29.4% and 38.3% respectively. The as-prepared silicon quantum dots were characterized by fluorescence (PL) spectrum, UV–visible spectrum, high resolution transmission electron microscope (HRTEM), Fourier transform infrared (FT-IR) spectrometry energy dispersive spectroscopy (EDS), and Zeta potential. With the aid of these methods, this paper further discussed how the optical performance and surface characteristics of the prepared quantum dots (QDs) influence the fluorescence mechanism. Meanwhile, the cell toxicity of the silicon quantum dots was tested by the 3-(4,5-dimethylthiazolyl-2)-2,5-diphenyltetrazolium (MTT) bromide method, and its potential as a fluorescence ink explored. The silicon quantum dots exhibit a red-shift phenomenon in their fluorescence peak due to the participation of the carbonyl group during the synthesis. The high-efficiency and stable photoluminescence of the long-wavelength emitting silicon quantum dots prepared through a synergistic effect is of great value in their future application as novel optical materials in bioimaging, LED, and materials detection.

The Photolysis in Acidic Aqueous Solutions of the Monooxalato-bisethylenediamine Chromium(III) Cation and the Bisoxalatomonoethylenediamine Chromate(III) Anion: Photolysis Modes and Quantum Yields

1971 ◽  
Vol 49 (3) ◽  
pp. 375-383 ◽  
Author(s):  
A. D. Kirk ◽  
K. C. Moss ◽  
J. G. Valentin
Keyword(s):  
Quantum Yield ◽  
Aqueous Solutions ◽  
Quantum Yields ◽  
Ligand Field ◽  
Intersystem Crossing ◽  
Empirical Correlations ◽  
Complex Ions ◽  
Ethylenediamine Complex ◽  
Ethylenediamine Ligand ◽  
Ph Range

The photolysis reactions of the complex ions [Cr(en)2ox]+ and [Cren(ox)2]− have been studied in the pH range 1 → 3 and at temperatures from 0 to 25 °C. It has been found that both ions photoaquate to a monodentate protonated ethylenediamine complex which then undergoes further aquation thermally with loss of the ethylenediamine ligand. Quantum yields for these aquations were measured for irradiation into the ligand field bands, the values obtained being 0.18 and 0.02, respectively. The results are discussed in terms of known empirical correlations for Cr(III) complexes. Assuming these reactions may occur from the 4T2g state as precursor, arguments are presented that the correlation between quantum yield and ΔE may depend on mixing of the 4T2g and 2Eg states, and its effect on the intersystem crossing rate constant.

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