THE REACTION OF ISOPROPANOL VAPOR WITH Hg 6 (3P1) ATOMS: PART I. PURE SUBSTRATE

1962 ◽  
Vol 40 (6) ◽  
pp. 1134-1139 ◽  
Author(s):  
Arthur R. Knight ◽  
Harry E. Gunning
Keyword(s):  
Quantum Yield ◽  
Hydrogen Production ◽  
Exposure Time ◽  
Resonance Line ◽  
Light Period ◽  
Inert Gas ◽  
Quantum Yields ◽  
Volatile Product ◽  
Intermittent Illumination ◽  
Static Conditions

The reaction of isopropanol vapor with Hg 6(3P1) atoms has been investigated under static conditions at 25 °C under continuous and intermittent illumination. The effect of added inert gas and isolation of the 2537 Å Hg resonance line were also studied.The products of the reaction are H2 (0.72), CH3COCH3 (0.25), CO, CH4, C2H6, CH3CHO, and H2O, with the numbers in parentheses representing the quantum yields at zero exposure time. The non-volatile product remaining in the cell was a mixture of C6-glycols, containing 98.6% pinacol, 1.2% 2-methyl-2,4-pentanediol, and ca. 0.2% or less of 2,5-hexanediol.Under intermittent illumination, the quantum yield of hydrogen production, measured as a function of light period, tL, rose linearly with log tL, and had a constant value of unity for tL < 0.45 msec. A mechanism is proposed involving the primary formation with perfect efficiency of isopropoxy radicals and H atoms.

Collisional deactivation of singlet methylene in the photolysis of ketene

1969 ◽  
Vol 47 (18) ◽  
pp. 3345-3353 ◽  
Author(s):  
R. A. Cox ◽  
K. F. Preston
Keyword(s):  
Carbon Monoxide ◽  
Quantum Yield ◽  
Ground State ◽  
Inert Gases ◽  
Inert Gas ◽  
Quantum Yields ◽  
Electronic Relaxation ◽  
Excited Singlet ◽  
State Formula ◽  
Singlet Methylene

An investigation has been made into the effect of inert gas additions on product quantum yields for the photolysis at 2800 and 2490 Å of mixtures of ketene and oxygen and for the photolysis at 2800 Å of mixtures of ketene and carbon monoxide. Concentration ratios of O2 (or CO) to CH2CO were chosen so that the reaction of CH2(3Σg−) with CH2CO could be ignored and C2H4 formation could be attributed entirely to the reaction[Formula: see text]Quenching of the C2H4 quantum yield by inert gases was interpreted in terms of collisional deactivation of CH2(1A1) to the ground state[Formula: see text]and rate constant ratios k2/k1 have been determined for a number of gases: He (0.018), Ar (0.014), Kr (0.033), Xe (0.074), N2 (0.052), N2O (0.10), CF4 (0.047), C2F6 (0.11), and SF6 (0.045). It has been assumed that collision-induced intersystem crossover in excited singlet ketene makes an insignificant contribution to the observed quenching effects, but it has not been possible to verify this assumption experimentally. The mechanism of collision-induced electronic relaxation of singlet methylene is discussed in the light of the results.

Direct Photolysis of 2-Propanol Vapor

1972 ◽  
Vol 50 (14) ◽  
pp. 2217-2223 ◽  
Author(s):  
O. S. Herasymowych ◽  
A. R. Knight
Keyword(s):  
Quantum Yield ◽  
Wavelength Range ◽  
Exposure Time ◽  
Yield Enhancement ◽  
Quantum Yields ◽  
Unimolecular Decomposition ◽  
Direct Photolysis ◽  
Volatile Products ◽  
Temperature And Pressure

The photolysis of 2-propanol vapor in the 1800–2000 Å wavelength range has been investigated. The volatile products of the reaction and their quantum yields at 80 °C and 200 Torr substrate pressure are H2 (0.64), CH3COCH3 (0.34), CH4 (0.39), CH3CHO (0.29), CO (0.15), and C2H6 (0.08). A mechanism is proposed that accounts for the observed rate variations with substrate pressure, exposure time, temperature, and pressure of inert addend. Acetone and acetaldehyde undergo significant secondary decomposition and this is the source of CO, CH4, and C2H6. Acetaldehyde is formed in the unimolecular decomposition of C3H7O radicals produced in the primary process.The effects of CO2 and CF4 as inert addends have been examined and it has been established that the quantum yield enhancement through collision induced predissociation that has been reported to occur in methanol is not a characteristic of the 2-propanol photolysis.

scholarly journals PRIMARY QUANTUM EFFICIENCIES IN THE REACTION OF CYCLOPENTANE WITH MERCURY 6(3P1) ATOMS

1960 ◽  
Vol 38 (12) ◽  
pp. 2295-2302 ◽  
Author(s):  
Richard L. Stock ◽  
Harry E. Gunning
Keyword(s):  
Nitric Oxide ◽  
Steady State ◽  
Quantum Yield ◽  
Prolonged Exposure ◽  
Product Formation ◽  
Quantum Yields ◽  
Gas Liquid Chromatography ◽  
Low Light ◽  
Yield Data ◽  
Static Conditions

An investigation has been made of the reaction of cyclopentane with Hg 6(3P1) atoms at a substrate pressure of 107 mm, under static conditions at 24 °C. Low light intensities were used in order to minimize secondary reactions.The products of the reaction, for small extents of decomposition, have been shown to be exclusively hydrogen, bicyclopentyl, and cyclopentene. With increasing duration of exposure, the cyclopentene-to-cyclopentane ratio achieves a steady-state value of 5.7 × 10−3. Furthermore, it has been found that the same ratio is ultimately reached, upon prolonged exposure of a substrate initially containing cyclopentene at a concentration higher than the steady-state value. In the runs with added cyclopentene, a fourth product appeared in measurable quantities. Its molecular weight corresponded to the formula, C10H16, and it was assumed to be a cyclopentyl cyclopentene. The same compound appears in extensive decomposition of the pure substrate.The addition of small amounts of nitric oxide was found to have a marked inhibiting effect on the reaction. Bicyclopentyl formation was completely suppressed when 0.7 mole% of nitric oxide was present; and the cyclopentene yield was reduced to one-fifth of its value for the pure substrate, by adding 0.98 mole% of nitric oxide.In order to obtain primary quantum yields for the reaction, a series of runs were performed of 1 to 33 minutes in duration, with a cyclopentane which had been purified by gas–liquid chromatography. By a short extrapolation of the mean quantum yields of product formation to zero extent of reaction, it was found that the primary quantum yields for hydrogen, bicyclopentyl, and cyclopentene were respectively 0.8, 0.4, and 0.4.On the basis of a simple four-step paraffinic mechanism, taken in conjunction with the primary quantum yield data, it is concluded that the reaction has a primary quantum yield of substrate decomposition of 0.8, and that cyclopentyl radicals have the same rates for disproportionation and recombination at 24 °C.

THE REACTION OF ETHANOL VAPOR WITH Hg 6(3P1) ATOMS

1961 ◽  
Vol 39 (12) ◽  
pp. 2466-2473 ◽  
Author(s):  
Arthur R. Knight ◽  
Harry E. Gunning
Keyword(s):  
Dark Period ◽  
Hydrogen Abstraction ◽  
Ethanol Vapor ◽  
Continuous Illumination ◽  
Quantum Yields ◽  
Maximum Value ◽  
Volatile Products ◽  
Intermittent Illumination ◽  
Heavy Product ◽  
Static Conditions

The reaction of ethanol vapor with Hg 6(3P1) atoms has been investigated under static conditions at 25 °C. To determine the nature and efficiency of the primary process, the reaction has been studied in the presence of nitric oxide, and also under conditions of inter mittent illumination. For the pure substrate the volatile products were H2 (0.53), CH3CHO (0.08), CO (0.025), C2H6 (0.006), and CH4 (0.002), with the bracketed numbers representing the quantum yields at zero exposure time. The heavy product was a mixture of butanediols containing 90% 2,3-, 8% 1,3-, and 2% 1,4-butanediol. With 20% added NO, the products were EtONO (0.25), N2O (0.14), H2O, and H2 (0.017). Under intermittent illumination, the quantum yield (Φ) of H2 formation for pure substrate was measured as a function of the light period (tL) and the dark period (tD). For maximum values of Φ(H2), it was found that tD had to exceed ca. 120 msec. Under these conditions, Φ(H2) rose linearly with decreasing log tL, to a maximum value of 0.96 at tL less than 0.4 msec.From the study it is concluded that ethanol reacts with Hg 6(3P1) atoms to form ethoxy radicals and H atoms with at least 96% efficiency. The primary ethoxy radicals disappear by hydrogen abstraction from the substrate to form mainly CH3CHOH radicals. Under continuous illumination the low value (0.53) for Φ(H2) is caused principally by the addition of H atoms to the CH3CHOH radicals.

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.

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