Influence of cyclodextrins on the photo-Fries rearrangement of acetanilide

1988 ◽  
Vol 66 (11) ◽  
pp. 2794-2798 ◽  
Author(s):  
Mirtha Nassetta ◽  
Rita H. De Rossi ◽  
Juan J. Cosa
Keyword(s):  
Quantum Yield ◽  
Association Constants ◽  
Para Position ◽  
Quantum Yields ◽  
Fries Rearrangement

The effect of α-, β-, and -γ-cyclodextrins on the quantum yield for the formation of o- and p-aminoacetophenone from the photolysis of acetanilide at 254 nm was determined. There is an increase in the ratio of o/p products when cyclodextrins are added and the total quantum yield is about the same as in water in the presence of γ-CD, higher with β-CD, and lower with α-CD. The association constants between acetanilide and CD were determined and the values are 22.7 M−1 and 30.7 M−1 for α- and β-CD respectively. The quantum yields for the formation of o- and p-aminoacetophenone were measured. The rearrangement occurs in water and in the included acetanilide. The quantum yields for the formation of o-aminoacetophenone and p-aminoacetophenone from the included substrate could be calculated for α- and β-cyclodextrin. Comparing these values with those obtained in water, it is concluded that there is some steric inhibition for rearrangement at the para position when α-cyclodextrin is the host, whereas with β-cyclodextrin the less polar microsolvent effect is responsible for the increase in the total quantum yield relative to water.

Application of 59Co NMR to the investigation of interactions between cobalt sepulchrate and various counterions

1991 ◽  
Vol 69 (3) ◽  
pp. 567-569 ◽  
Author(s):  
João Sotomayor ◽  
Helena Santos ◽  
Fernando Pina
Keyword(s):  
Quantum Yield ◽  
Association Constant ◽  
Chemical Shifts ◽  
Cobalt Complex ◽  
Ion Pairs ◽  
Formation Constants ◽  
Ion Pair ◽  
Association Constants ◽  
Quantum Yields ◽  
True Quantum

Association constants for the ion pairs formed between [Co(Sep)]3+ and the anions fluoride, chloride, bromide, iodide, perchlorate, and oxalate were obtained from the chemical shifts of the 59Co resonance that occur upon addition of such anions to solutions of the cobalt complex. The usefulness of 59Co NMR to obtain formation constants, in order to calculate the "true" quantum yields for the ion pairs, is discussed. Key words: association constant, cobalt sepulchrate, ion pair, 59Co NMR, quantum yield.

scholarly journals Ruthenium-based PACT agents based on bisquinoline chelates: synthesis, photochemistry, and cytotoxicity

2021 ◽  
Author(s):  
Anja Busemann ◽  
Ingrid Flaspohler ◽  
Xue-Quan Zhou ◽  
Claudia Schmidt ◽  
Sina K. Goetzfried ◽  
...  
Keyword(s):  
Quantum Yield ◽  
Singlet Oxygen ◽  
Cancer Cells ◽  
Cellular Uptake ◽  
Ruthenium Complex ◽  
Human Cancer ◽  
Light Irradiation ◽  
Quantum Yields ◽  
Light Activation ◽  
Human Cancer Cells

AbstractThe known ruthenium complex [Ru(tpy)(bpy)(Hmte)](PF6)2 ([1](PF6)2, where tpy = 2,2’:6’,2″-terpyridine, bpy = 2,2’-bipyridine, Hmte = 2-(methylthio)ethanol) is photosubstitutionally active but non-toxic to cancer cells even upon light irradiation. In this work, the two analogs complexes [Ru(tpy)(NN)(Hmte)](PF6)2, where NN = 3,3'-biisoquinoline (i-biq, [2](PF6)2) and di(isoquinolin-3-yl)amine (i-Hdiqa, [3](PF6)2), were synthesized and their photochemistry and phototoxicity evaluated to assess their suitability as photoactivated chemotherapy (PACT) agents. The increase of the aromatic surface of [2](PF6)2 and [3](PF6)2, compared to [1](PF6)2, leads to higher lipophilicity and higher cellular uptake for the former complexes. Such improved uptake is directly correlated to the cytotoxicity of these compounds in the dark: while [2](PF6)2 and [3](PF6)2 showed low EC50 values in human cancer cells, [1](PF6)2 is not cytotoxic due to poor cellular uptake. While stable in the dark, all complexes substituted the protecting thioether ligand upon light irradiation (520 nm), with the highest photosubstitution quantum yield found for [3](PF6)2 (Φ[3] = 0.070). Compounds [2](PF6)2 and [3](PF6)2 were found both more cytotoxic after light activation than in the dark, with a photo index of 4. Considering the very low singlet oxygen quantum yields of these compounds, and the lack of cytotoxicity of the photoreleased Hmte thioether ligand, it can be concluded that the toxicity observed after light activation is due to the photoreleased aqua complexes [Ru(tpy)(NN)(OH2)]2+, and thus that [2](PF6)2 and [3](PF6)2 are promising PACT candidates. Graphic abstract

Quantum yield of solution photolysis of bicyclo[3.1.0]hexan-3-one and derivatives

1981 ◽  
Vol 59 (11) ◽  
pp. 1607-1609 ◽  
Author(s):  
Karl R. Kopecky ◽  
Rodrigo Rico Gomez
Keyword(s):  
Quantum Yield ◽  
Quantum Yields

The quantum yields for photolysis of 0.25 M solutions of bicyclo[3.1.0]hexan-3-one, 1,5-dimethylbicyclo[3.1.0]hexan-3-one, and tricyclo[4.3.1.0]decan-8-one in pentane or cyclohexane with 313 nm light are 0.44, 0.52, and 0.32, respectively.

New soluble 4-(4-formyl-2,6-dimethoxyphenoxy) substituted phthalocyanines: Synthesis, characterization, photophysical and photochemical properties

2021 ◽  
pp. 1-10
Author(s):  
Ibrahim Erden ◽  
Betül Karadoğan ◽  
Fatma Aytan Kılıçarslan ◽  
Göknur Yaşa Atmaca ◽  
Ali Erdoğmuş
Keyword(s):  
Quantum Yield ◽  
Singlet Oxygen ◽  
Fluorescence Quantum Yield ◽  
Metal Ion ◽  
Mass Spectra ◽  
Quantum Yields ◽  
Therapeutic Outcomes ◽  
Ft Ir ◽  
Photochemical Properties ◽  
New Compounds

This work describes the synthesis, spectral and fluorescence properties of bis 4-(4-formyl-2,6-dimethoxyphenoxy) substituted zinc (ZnPc) and magnesium (MgPc) phthalocyanines. The new compounds have been characterized by elemental analysis, UV-Vis, FT-IR, 1H-NMR and mass spectra. Afterward, the effects of including metal ion on the photophysicochemical properties of the complexes were studied in biocompatible solvent DMSO to analyze their potential to use as a photosensitizer in photodynamic therapy (PDT). The fluorescence and singlet oxygen quantum yields were calculated as 0.04–0.15 and 0.70–0.52 for ZnPc and MgPc, respectively. According to the results, MgPc has higher fluorescence quantum yield than ZnPc, while ZnPc has higher singlet oxygen quantum yield than MgPc. The results show that the synthesized complexes can have therapeutic outcomes for cancer treatment.

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 Synthesis of New Antibiotics Derivatives by the Photocatalytic Method: A Screening Research

Catalysts ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 1102
Author(s):  
Wojciech Baran ◽  
Ewa Masternak ◽  
Dominika Sapińska ◽  
Andrzej Sobczak ◽  
Ewa Adamek
Keyword(s):  
Quantum Yield ◽  
Biologically Active ◽  
Quantum Yields ◽  
Photocatalytic Process ◽  
Experimental Conditions ◽  
New Antibiotics ◽  
Photocatalytic Reactions ◽  
Kinetics Of ◽  
Derivatives Of ◽  
Uva Radiation

The aim of our study was to assess the possibility of using the photocatalytic process conducted in the presence of TiO2 to obtain new stable derivatives of antibacterial drugs. The possibility of introducing hydroxyl, chlorine, or bromide groups into antibiotics molecules was investigated. The experiments were conducted in aqueous solutions in the presence of TiO2-P25 as a photocatalyst, Cl− and Br- ions, and antibiotics belonging to eight different chemical classes. All experiments were initiated by UVa radiation. The kinetics of photocatalytic reactions and their quantum yield were determined, and the stable products were identified. All of the antibiotics used in the experiments underwent a photocatalytic transformation, and the quantum yields were in the range from 0.63 to 22.3%. The presence of Br- or FeCl3 significantly increased the efficiency of the photocatalytic process performed in the presence of TiO2, although Br- ion also acted as an inhibitor. Potentially biologically active chlorine derivatives from Trimethoprim, Metronidazole, Chloramphenicol, and bromine derivatives from Trimethoprim, Amoxicillin were obtained under experimental conditions. The potentially inactive halogen derivatives of Sulfamethoxazole and hydroxyl derivatives described in the literature were also identified.

Quantum Yields for the Photodegradation of Pollutants in Dilute Aqueous Solution: Phenol, 4-Chlorophenol and N-Nitrosodimethylamine

1996 ◽  
Vol 1 (2) ◽  
Author(s):  
Te-Fu L. Ho ◽  
James R. Bolton ◽  
Ewa Lipczynska-Kochany
Keyword(s):  
Aqueous Solution ◽  
Hydrogen Peroxide ◽  
Quantum Yield ◽  
High Performance ◽  
Flash Photolysis ◽  
Quantum Yields ◽  
Visible Absorption ◽  
Dilute Aqueous Solution ◽  
Uv Visible ◽  
Photolysis Of Phenol

AbstractA broadband method has been applied to determine the quantum yields for the photochemical removal of three common pollutants: phenol, 4-chlorophenol and N-nitrosodimethylamine (NDMA) in dilute aqueous solution. Flash photolysis (xenon flash lamps) was used to cause a significant amount of photolysis without photolyzing intermediates. The analysis of reactant depletion following a single flash was carried out by high- performance liquid chromatography (HPLC) or UV/visible absorption spectroscopy. The method for determining quantum-yields employed p-benzoquinone as an actinometer and was validated by determining the average (200-400 nm) quantum yield for the generation of hydroxyl radicals from the photolysis of hydrogen peroxide (0.90 ± 0.10) and the quantum yields for the photolysis of phenol (0.13 ± 0.02) and 4-chlorophenol (0.24 ± 0.04). The values determined agree very well with the literature ones obtained with monochromatic radiation. The quantum yield for the direct photolysis of NDMA was found to be 0.11 ± 0.03 at neutral pH and 0.27 ± 0.02 at pH 2-4. Under conditions where hydrogen peroxide is the principal absorber, the NDMA quantum yield is 0.32 ± 0.04, independent of pH in the range 2-8.

MGa2B2O7: Bi3+, Al3+ (M = Sr, Ba) blue phosphors with quantum yield of 99% and negative thermal quenching

2021 ◽  
Author(s):  
Shuai Yang ◽  
Yuning Wu ◽  
Fangyu Yue ◽  
Ruijuan Qi ◽  
Bin Jiang ◽  
...  
Keyword(s):  
Quantum Yield ◽  
Debye Temperature ◽  
Thermal Quenching ◽  
Quantum Yields

By optimizing Debye temperature, we identified two extremely efficient phosphors based on the S-P transition of Bi3+. The quantum yields of Sr0.99Ga1.50B2O7: 0.01Bi3+, 0.50Al3+ and Ba0.995Ga1.60B2O7: 0.005Bi3+, 0.40Al3+ phosphors reach...

scholarly journals Tuning Carbon Dots’ Optoelectronic Properties with Polymers

Polymers ◽  
2018 ◽  
Vol 10 (12) ◽  
pp. 1312 ◽  
Author(s):  
Konstantinos Dimos
Keyword(s):  
Quantum Yield ◽  
Spectral Range ◽  
Carbon Dots ◽  
Surface Passivation ◽  
Low Cost ◽  
Quality Characteristics ◽  
Optoelectronic Properties ◽  
Quantum Yields

Due to their unique properties of photoluminescence, biocompatibility, photostability, ease of preparing, and low cost, carbon dots have been studied extensively over the last decade. Soon after their discovery, it was realized that their main optical attributes may be protected, enhanced, and tuned upon proper surface passivation or functionalization. Therefore, up to date, numerous polymers have been used for these purposes, resulting to higher-quality carbon dots regarding their quantum yield or further emission-related aspects and compared to the primitive, bare ones. Hence, this review aims to clarify the polymers’ role and effect on carbon dots and their features focusing on the quality characteristics of their photoluminescence upon passivation or functionalization. Given in fact the numbers of relevant publications, emphasis is given on recent articles capturing the latest advances for polymers in carbon dots for expanding emission lifetimes, advancing quantum yields, tuning emission wavelengths, enhancing specific spectral range absorption, and tailoring optoelectronic properties in general.

scholarly journals Hybridisation of perovskite nanocrystals with organic molecules for highly efficient liquid scintillators

2020 ◽  
Vol 9 (1) ◽  
Author(s):  
Sangeun Cho ◽  
Sungwoo Kim ◽  
Jongmin Kim ◽  
Yongcheol Jo ◽  
Ilhwan Ryu ◽  
...  
Keyword(s):  
Quantum Yield ◽  
Organic Molecules ◽  
Liquid Scintillator ◽  
Low Cost ◽  
Radiation Detection ◽  
Quantum Yields ◽  
X Ray ◽  
Highly Efficient ◽  
X Ray Imaging ◽  
New Generation

Abstract Compared with solid scintillators, liquid scintillators have limited capability in dosimetry and radiography due to their relatively low light yields. Here, we report a new generation of highly efficient and low-cost liquid scintillators constructed by surface hybridisation of colloidal metal halide perovskite CsPbA3 (A: Cl, Br, I) nanocrystals (NCs) with organic molecules (2,5-diphenyloxazole). The hybrid liquid scintillators, compared to state-of-the-art CsI and Gd2O2S, demonstrate markedly highly competitive radioluminescence quantum yields under X-ray irradiation typically employed in diagnosis and treatment. Experimental and theoretical analyses suggest that the enhanced quantum yield is associated with X-ray photon-induced charge transfer from the organic molecules to the NCs. High-resolution X-ray imaging is demonstrated using a hybrid CsPbBr3 NC-based liquid scintillator. The novel X-ray scintillation mechanism in our hybrid scintillators could be extended to enhance the quantum yield of various types of scintillators, enabling low-dose radiation detection in various fields, including fundamental science and imaging.

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