Picosecond dynamics of contact ion pairs and solvent-separated ion pairs in the photosolvolysis of diphenylmethyl chloride

Peters, Kevin S.; Li, Bulang

doi:10.1021/j100053a009

Cited by 42 publications

(64 citation statements)

References 1 publication

(1 reference statement)

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“…10 The laser system, based upon a Continuum (PY61C-10) Nd:YAG (30 ps fwhm), produces the pump beam at 266 nm. The diphenylmethyl radical was monitored at 334 nm, and the diphenylmethyl cation was monitored at 440 nm.…”

Section: Methodsmentioning

confidence: 99%

Picosecond Kinetic Study of the Photoinduced Homolysis and Heterolysis of Diphenymethyl Bromide. 1. The Nature of the Conversion from Radical Pairs to Ion Pairs

Dreyer

Peters

1996

J. Phys. Chem.

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Picosecond absorption spectroscopy is used to study the dynamics of bond homolysis and heterolysis of diphenylmethyl bromide and bis(4-methoxyphenyl)methyl bromide in acetonitrile. Combining these kinetics results with our previous study of diphenylmethyl chlorides, the nature of the conversion of the geminate radical pair into contact ion pairs is addressed. Also a qualitative potential energy diagram, based upon a valence bond description, that accounts for the factors that determine the partitioning between geminate radical pair and contact ion pair subsequent to the decay of the first excited singlet state is presented.

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Section: Methodsmentioning

confidence: 99%

Picosecond Kinetic Study of the Photoinduced Homolysis and Heterolysis of Diphenymethyl Bromide. 1. The Nature of the Conversion from Radical Pairs to Ion Pairs

Dreyer

Peters

1996

J. Phys. Chem.

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“…In previous studies, ion-pair dynamics of small organic compounds were characterized experimentally using time-resolved absorption spectroscopy, infrared (IR) spectroscopy, and Raman spectroscopy. 5–8 The transitions between the CIP and SIP states were found to occur on a ps – ns timescale for the ion pairs of these small organic compounds, and the free energy differences between their CIP and SIP states were found to be ~1–2 kcal/mol. 5–9 Despite the wealth of information available for small organic compounds, very little is currently known about the dynamics of ion pairs tethered to biological macromolecules because their complexity renders application of the above-mentioned methods impractical.…”

Section: Introductionmentioning

confidence: 98%

Direct Observation of the Ion-Pair Dynamics at a Protein–DNA Interface by NMR Spectroscopy

et al. 2013

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Ion pairing is one of the most fundamental chemical interactions and is essential for molecular recognition by biological macromolecules. From an experimental standpoint, very little is known to date about ion-pair dynamics in biological macromolecular systems. Absorption, infrared, and Raman spectroscopic methods were previously used to characterize dynamic properties of ion pairs, but these methods can be applied only to small compounds. Here, using NMR 15N relaxation and hydrogen-bond scalar 15N-31P J-couplings (h3JNP), we have investigated the dynamics of the ion pairs between lysine side-chain NH3+ amino groups and DNA phosphate groups at the molecular interface of the HoxD9 homeodomain-DNA complex. We have determined the order parameters and the correlation times for C-N bond rotation and reorientation of the lysine NH3+ groups. Our data indicate that the NH3+ groups in the intermolecular ion pairs are highly dynamic at the protein-DNA interface, which should lower the entropic costs for protein-DNA association. Judging from the C-N bond-rotation correlation times along with experimental and quantum-chemically derived h3JNP hydrogen-bond scalar couplings, it seems that breakage of hydrogen bonds in the ion pairs occurs on a sub-nanosecond timescale. Interestingly, the oxygen-to-sulfur substitution in a DNA phosphate group was found to enhance the mobility of the NH3+ group in the intermolecular ion pair. This can partially account for the affinity enhancement of the protein-DNA association by the oxygen-to-sulfur substitution, which is a previously observed but poorly understood phenomenon.

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“…The dynamics of these processes involving the carbocations in nonviscous liquids was observed in the picosecond time scale. 28 The resulting second order rate constant is much lower than the diffusion limit, being of the same order as the known bimolecular reaction rate constants of the ethylphenyl and aryltropyl radicals with MeO -and other nucleophilic ions, 29 as well as the rate constant of the reaction of the CC generated from 1,2,2,4,6 pentamethyl 1,2 dihydro quinoline with azide ions. 30 An increase in the stability of the CC upon the introduction of electron donor substitu ents decreases the rate constants of their reactions.…”

Section: Resultsmentioning

confidence: 71%

Laser flash photolysis study of the decay kinetics of carbocations of 1,2,2,4-tetramethyl-1,2-dihydroquinoline in the porous glass in the presence of methanol

2005

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The efficiency of formation and the decay kinetics of carbocations formed under the photolysis of 1,2,2,4 tetramethyl 1,2 dihydroquinoline in methanol and in a porous glass filled with methanol or dried in air or in vacuo were studied by the laser flash photolysis techniques. In MeOH, the carbocations recombine via the second order law in the reaction with the MeOanion formed in an equimolar amount and decay via the first order law in the reaction with the solvent with rate constants of 3•10 8 L mol -1 s -1 and 1.4•10 3 s -1 , respectively. When the solution is placed into the porous glass, no recombination of the carbocations with MeO -is observed, and the reaction with the solvent is somewhat inhibited (rate constant 8•10 2 s -1 ). More than tenfold inhibition of the reaction of the carbocations with methanol is observed on going to a monolayer of MeOH on the surface. The main route of carbocation decay in the porous glass dried in vacuo is the geminate recombination with the SiO groups. The corre sponding kinetics is described in terms of the model of freely diffusing reactants.

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Picosecond dynamics of contact ion pairs and solvent-separated ion pairs in the photosolvolysis of diphenylmethyl chloride

Cited by 42 publications

References 1 publication

Picosecond Kinetic Study of the Photoinduced Homolysis and Heterolysis of Diphenymethyl Bromide. 1. The Nature of the Conversion from Radical Pairs to Ion Pairs

Picosecond Kinetic Study of the Photoinduced Homolysis and Heterolysis of Diphenymethyl Bromide. 1. The Nature of the Conversion from Radical Pairs to Ion Pairs

Direct Observation of the Ion-Pair Dynamics at a Protein–DNA Interface by NMR Spectroscopy

Laser flash photolysis study of the decay kinetics of carbocations of 1,2,2,4-tetramethyl-1,2-dihydroquinoline in the porous glass in the presence of methanol

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