Remarkable Discrimination in the Triplet Lifetimes of the Diastereomers of 1,4-Bis(<i>p</i>-methoxyphenyl)- 2,3-diphenylbutan-1,4-dione

Moorthy, Jarugu Narasimha; Patterson, W. S.; Bohne, Cornelia

doi:10.1021/ja971296k

Cited by 16 publications

(18 citation statements)

References 29 publications

(50 reference statements)

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“…Select organic compounds containing phenone or benzophenone moieties have been reported to display diastereomeric transient lifetime discrimination in the literature. − In these cases, the difference was attributed to the ability of one diastereomer to adopt a conformation that led to either an additional quenching pathway or a lower energy transition state for the quenching mechanism. Our data suggests that the diastereomeric lifetime differentiation observed in the diruthenium complexes 1a , b may be caused by a similar phenomenon.…”

Section: Discussionmentioning

confidence: 99%

Diastereomerically Differentiated Excited State Behavior in Ruthenium(II) Hexafluoroacetylacetonate Complexes of Diphenyl Thioindigo Diimine

et al. 2018

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Mono- and diruthenium hexafluoroacetylacetonate (hfac) complexes of the thioindigo-N,N'-diphenyldiimine chelating ligand 3 have been prepared. The thioindigo diimine ligand binds to ruthenium in a bidentate fashion in the mononuclear compound 2 and serves as a bidentate chelating bridging ligand in the diruthenium complexes 1a and 1b. Compound 2 was isolated as a racemic mixture while the diruthenium complexes were isolated as the meso (ΔΛ) 1a and rac (ΔΔ and ΛΛ) 1b diastereomers. In-depth structural characterization of the compounds was performed, including X-ray crystallography, H,C, and F nuclear magnetic resonance (NMR) spectroscopy, and 2D NMR correlation experiments. Electrochemical properties were evaluated utilizing cyclic voltammetry. Ground state optical properties of the complexes were examined using UV-visible spectroscopy and spectroelectrochemistry. The excited state dynamics of the series were investigated by ultrafast transient absorption spectroscopy. Variable temperature NMR experiments demonstrated that the rac diruthenium compound 1b undergoes conformational exchange with a rate constant of 8700 s at 298 K, a behavior that is not observed in the meso diastereomer 1a. The series of complexes possess metal-to-ligand charge transfer (MLCT) absorption bands in the near-infrared (λ 689-783 nm). The compounds do not display photoluminescence in room temperature solution-phase experiments or in experiments at 77 K. Transient absorption spectroscopy measurements revealed excited states with picosecond lifetimes for 1a, 1b, and 2, and spectroelectrochemical experiments confirmed assignment of the transient species as arising from MLCT transitions. Unexpectedly, the transient absorption measurements revealed disparate time constants for the excited state decay of diastereomers 1a and 1b.

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Section: Discussionmentioning

confidence: 99%

Diastereomerically Differentiated Excited State Behavior in Ruthenium(II) Hexafluoroacetylacetonate Complexes of Diphenyl Thioindigo Diimine

et al. 2018

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“…Recent work aimed at producing naphthoxanthenyl, a remarkably stable radical, led us to propose that the transient species could in fact be a 1H-2-6aH-naphtho[2,1,8-mna]xanthene (hereafter naphthoxanthene), 8 which could be formed in a formal 6-p electrocyclic intramolecular photocyclisation of 1 through the b-phenyl quenching (BPQ) mechanism. [9][10][11][12][13][14][15][16][17] In this contribution, we report a comprehensive theoretical and experimental investigation of the role of BPQ in the photochemistry of 1. The new results confirm the production of naphthoxanthenes and uncover their reactivity.…”

Section: Introductionmentioning

confidence: 99%

β-Phenyl quenching of 9-phenylphenalenones: a novel photocyclisation reaction with biological implications

Bucher

Bresolí‐Obach

Brosa

et al. 2014

Phys. Chem. Chem. Phys.

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The singlet and triplet excited states of 9-phenylphenalenones undergo β-phenyl quenching (BPQ) via addition of the carbonyl oxygen to the ortho position of the phenyl substituent. This reaction leads to the formation of naphthoxanthenes , which, in the absence of quenchers, undergo a very rapid electrocyclic ring opening reaction reverting to within a few microseconds. Naphthoxanthene contains a remarkably weak C-H bond, which enables efficient hydrogen transfer reactions to suitable acceptors, giving rise to the production of the naphthoxanthenyl radical or the naphthoxanthenium cation, depending on the solvent polarity. The study uncovers a number of new aspects of BPQ and suggests an excited state-mediated metabolic pathway in the biosynthesis of plant fluorones.

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“…Interestingly, the ketone chromophores in 1 and 2 have a β-phenyl group; the triplet excited state of β-phenyl aryl ketones with (n, π*) configuration are generally unusually short-lived because they are efficiently quenched by an intramolecular process. [11][12][13][14][15][16][17][18][19][20] The mechanism for β-quenching, however, has not been fully elucidated until recently. [21,22] Bucher has proposed that the intramolecular quenching of these β-phenyl aryl ketones takes place through addition of the carboxyl oxygen to the ipso carbon atom in the β-phenyl ring to form a triplet biradical that intersystem crosses to reform the starting material (Scheme 3).…”

Section: Introductionmentioning

confidence: 99%

“…Interestingly, the ketone chromophores in 1 and 2 have a β‐phenyl group; the triplet excited state of β‐phenyl aryl ketones with (n, π*) configuration are generally unusually short‐lived because they are efficiently quenched by an intramolecular process . The mechanism for β‐quenching, however, has not been fully elucidated until recently .…”

Section: Introductionmentioning

confidence: 99%

Photolysis of acetophenone derivatives with α‐cyclopropyl substituents

Ranaweera

Weragoda

Bain

et al. 2014

J of Physical Organic Chem

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Laser flash photolysis of cyclopropyl(phenyl)methanone 6 in argon-saturated methanol yields the triplet ketone (T 1K ) of 6 that is formed with a rate constant of~1.7 × 10 7 s À1 (λ max = 360 nm) and has a lifetime of~1.4 μs. T 1K of 6 decays to form ketyl radical 7 (λ max~3 00 nm), which dimerizes to form photoproducts, pinacol derivatives 8 and 9. In comparison, photolysis of trans-phenyl(2-phenylcyclopropyl)methanone 1 in argon-saturated chloroform-d results in cis-phenyl (2-phenylcyclopropyl)methanone 2 and a smaller amount of 3, presumably through 1,3-biradical 11. Nanosecond laser flash photolysis of 1 does not reveal significant transient absorption, although the T 1K of 1 is detected with phosphorescence at 77 K. Density functional theory calculations were used to elucidate the triplet reactivity of 1, 2 and 6 by comparing the feasibility of H atom abstraction, cyclopropyl cleavage and β-quenching of their triplet ketones.

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Remarkable Discrimination in the Triplet Lifetimes of the Diastereomers of 1,4-Bis(p-methoxyphenyl)- 2,3-diphenylbutan-1,4-dione

Cited by 16 publications

References 29 publications

Diastereomerically Differentiated Excited State Behavior in Ruthenium(II) Hexafluoroacetylacetonate Complexes of Diphenyl Thioindigo Diimine

Diastereomerically Differentiated Excited State Behavior in Ruthenium(II) Hexafluoroacetylacetonate Complexes of Diphenyl Thioindigo Diimine

β-Phenyl quenching of 9-phenylphenalenones: a novel photocyclisation reaction with biological implications

Photolysis of acetophenone derivatives with α‐cyclopropyl substituents

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