Circular dichroism of ketones at 185–195 nm

Kirk, D. N.; Klyne, W.; Mose, W. P.; Otto, E.

doi:10.1039/c39720000035

Cited by 12 publications

(7 citation statements)

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“…The signs of the 195 and the 300 nm Cotton effects are generally tfie same for substituents placed in the -Z hemisphere of the chromophore coordinate frame, i.e. in the four rear octants of the -XYZ octant rule for the 300 nm carbonyl CD bands [23], but a number of chiral cyclopentanones are exceptional [30], e.g. the molecule (I) which gives CD bands of opposite sign at 195 and 300 nm (Fig.…”

Section: Chemical Spectroscopymentioning

confidence: 93%

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Linear and Circular Dichroism in the Vacuum Ultraviolet Region

Drake

Mason

1978

J. Phys. Colloques

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Section: Chemical Spectroscopymentioning

confidence: 93%

“…The.signs of the CD bands near 195 nm of a series of steroidal ketones in hexane solution have been fitted to a stereochemical quadrant rule [30]. The sign follows that of the product XY of.…”

Section: Chemical Spectroscopymentioning

confidence: 99%

Linear and Circular Dichroism in the Vacuum Ultraviolet Region

Drake

Mason

1978

J. Phys. Colloques

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“…The quencher, also dissolved in 0.01 M HClO 4 , was delivered into the Pt 2 (pop) 4 4- solution in 7−12 aliquots, 5−20 μL in volume, and each lifetime was determined at 22 ± 1 °C using an average value of five measurements. Excitation was with a 20 ns pulse using a nitrogen laser exciting a solution of quinine sulfate to shift the irradiation to 370 nm as described in the literature . The quenching rate constants, k q , for the quenching reaction of 3 Pt 2 (pop) 4 4- with each of the nickel complexes were obtained from the slopes of Stern−Volmer plots of τ 0 /τ versus quencher concentration.…”

Section: Methodsmentioning

confidence: 99%

Quenching of Triplet State Tetrakis(μ-pyrophosphito-PP‘)diplatinate(II) by Nickel(II) Macrocyclic and Tris-diimine Complexes

1999

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The excited state of tetrakis(&mgr;-pyrophosphito-PP')diplatinate(II), Pt(2)(pop)(4)(4)(-), has been shown to be reductively quenched by a series of Ni(II) complexes. Steady-state photolysis of Pt(2)(pop)(4)(4)(-) in the presence of Ni(cyclam)(2+) and SO(4)(2)(-) ions was followed by absorption spectroscopy and showed the production of the Ni(III) complex with low efficiency. The Ni(III) yield was enhanced in the presence of oxygen presumably because of scavenging of Pt(2)(pop)(4)(5)(-) from the solvent-caged {Pt(2)(II,I).Ni(III)} primary product pair resulting from electron transfer. Cage escape yields of 0.028 in N(2) saturated solution and 0.054 in aerated solutions were estimated from the data. For a series of complexes with decreasing redox potential, the rate constants for their (3)Pt(2)(pop)(4)(4)(-) phosphorescence lifetime quenching decreased with driving force DeltaG, consistent with Rehm-Weller behavior and leading to a reorganization energy of approximately 60 kJ mol(-)(1). The diffusional rate constant calculated from the Debye-Smoluchowski equation was 1.6 x 10(10) M(-)(1) s(-)(1), in excellent agreement with the observed value of 1.6 x 10(10) M(-)(1) s(-)(1) based on the Rehm-Weller equation. The transmission factor for the electron transfer was estimated at 10(-)(4), in the weakly adiabatic region. Although the Rehm-Weller treatment has been used successfully in reactions involving mainly uncharged organic reactants, in this investigation it leads to an unrealistic ratio for the rate constants for the diffusive separation of the charged reactants and products. An alternative interpretation of the results based on an approach by Meyer and Nagle removes this problem and the observed linear dependence of ln k(q) on the square root of E degrees (Ni(II)/Ni(III)) in the endergonic region shows that the dominant back electron transfer produces ground-state species. The analysis also leads to an estimate of the (3)Pt(2)(pop)(4)(4)(-)/Pt(2)(pop)(4)(5)(-) potential of 1.29 +/- 0.05 V(vs NHE), in excellent agreement with the previous literature value of 1.34 V.

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“…Two systems were used. First, a PTI PL 2300 nitrogen laser of pulse energy 1.5 mJ at 337 nm, filtered through a Corning CS 7−54 filter, was wavelength-shifted to 370 nm using a 1 cm cell containing quinine sulfate in ethanol, as previously described …”

Section: Methodsmentioning

confidence: 99%

“…The results for different Co(CN) 5 X 3- implied that there were some differences in the mechanism of the quenching for different X, and the present work was undertaken to try to establish the primary quenching process for the four complexes with X = I, Br, Cl, N 3 . In an earlier communication, we presented our finding that Co(CN) 5 I 3- represents the first metal complex showing an atom-transfer quenching mechanism in its reaction with 3 Pt 2 (pop) 4 4- . Here we present additional evidence for this process and our findings for the remaining complexes.…”

Section: Introductionmentioning

confidence: 94%

Atom Transfer Processes in Oxidative Quenching of Triplet State Tetrakis(μ-pyrophosphite-P,P‘)diplatinate(II) by Acidopentacyanocobaltate(III) Anions

Kirk

Cai

1998

Inorg. Chem.

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In the presence of high electrolyte concentration to screen the Coulomb repulsion, the emission of 3Pt2(pop)4 4- (where pop = μ-pyrophosphite-P,P‘) can be quenched by the complexes Co(CN)5X3- (where X = I, Br, Cl, N3). In acidic aqueous solutions the quenching involves the eventual reduction of the cobalt complexes to Co2+ aq and gives the oxidative quenching products Pt2 III(pop)4X2 4- (X = I, Br, Cl). For the reaction of 3Pt2(pop)4 4- with Co(CN)5I3- and Co(CN)5Br3- in 0.5 M KCl/pH 2 solution, the product yields per quenching event are 0.34 and 0.21, respectively. Steady-state photolysis using the Co(CN)5I3- quencher in 0.5 M KCl medium gave predominantly Pt2(pop)4I2 4- as product with only small amounts of Pt2(pop)4ICl4-, pointing to a direct iodine atom-transfer process. In contrast, Co(CN)5Br3- quencher gave Pt2(pop)4Cl2 4- under the same conditions, possibly indicative of electron transfer. However, study of the mixed-valence platinum dimer intermediates formed by laser flash transient spectroscopy provides conclusive evidence for atom transfer as the dominant primary reactive quenching step for all three halopentacyanocobaltates. The steady-state results for Co(CN)5Br3- quencher arose via the interconversion of the monobromo mixed-valence platinum dimer intermediate to its chloro analogue in chloride solutions. Co(CN)5N3 3- gave a mixture of oxidation products and no intermediate corresponding to electron transfer, indicating a complex interaction with 3Pt2(pop)4 4-.

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Circular dichroism of ketones at 185–195 nm

Cited by 12 publications

References 0 publications

Linear and Circular Dichroism in the Vacuum Ultraviolet Region

Linear and Circular Dichroism in the Vacuum Ultraviolet Region

Quenching of Triplet State Tetrakis(μ-pyrophosphito-PP‘)diplatinate(II) by Nickel(II) Macrocyclic and Tris-diimine Complexes

Atom Transfer Processes in Oxidative Quenching of Triplet State Tetrakis(μ-pyrophosphite-P,P‘)diplatinate(II) by Acidopentacyanocobaltate(III) Anions

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