Electronic Coupling in C-Clamp-Shaped Molecules:  Solvent-Mediated Superexchange Pathways

Kumar, Krishan; Lin, Zhe; Zimmt, Matthew B.

doi:10.1021/ja952999+

Cited by 106 publications

(94 citation statements)

References 47 publications

(29 reference statements)

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“…Since we also want a test independent of the present formulation for quadrupolar solvation, acetonitrile with its small quadrupole moment and large dipole moment presents an ideal choice. Table VIII lists the calculated thermodynamic parameters and rates of charge separation in complex 1 in acetonitrile in the experimental temperature range between 255 and 335 K. 67 The calculations of the free energy gap and the reorganization energy are done by using the recently developed microscopic theory of dipolar solvation. 37,38 The dispersion part of the ET driving force in acetonitrile is calculated according to Eqs.…”

Section: B Et Ratesmentioning

confidence: 99%

Equilibrium solvation in quadrupolar solvents

Milischuk

Matyushov

2005

The Journal of Chemical Physics

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We present a microscopic theory of equilibrium solvation in solvents with zero dipole moment and non-zero quadrupole moment (quadrupolar solvents). The theory is formulated in terms of autocorrelation functions of the quadrupolar polarization (structure factors). It can be therefore applied to an arbitrary dense quadrupolar solvent for which the structure factors are defined. We formulate a simple analytical perturbation treatment for the structure factors. The solute is described by coordinates, radii, and partial charges of constituent atoms. The theory is tested on Monte Carlo simulations of solvation in model quadrupolar solvents. It is also applied to the calculation of the activation barrier of electron transfer reactions in a cleft-shaped donor-acceptor complex dissolved in benzene with the structure factors of quadrupolar polarization obtained from Molecular Dynamics simulations.

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Section: B Et Ratesmentioning

confidence: 99%

Equilibrium solvation in quadrupolar solvents

Milischuk

Matyushov

2005

The Journal of Chemical Physics

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“…Except for some limiting cases, it is virtually not possible to solve equations (4) and (9± 17) analytically . We solved them numerically employing a non-equidistant ® nite-di erence scheme for the space coordinat e r and the implicit Euler scheme with variabl y adjusted timesteps for joint integratio n of equations (12) and (15). Details of the numerical procedures employed may be found elsewhere [71,72].…”

Section: Theoretical Backgroun Dmentioning

confidence: 99%

Magnetic field effect as a probe of distance-dependent electron transfer in systems undergoing free diffusion

KRISSINEL¹

1999

Molecular Physics

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A theoretical analysis is presented of the problem of how distance-dependent electron transf er in photoinduced forward electron transfer followed by geminate backward electron transfer in liquid solution is re¯ected in the viscosity dependence of the magnetic ® eld e ect ( MFE) on the e ciency of free radical formation u ce in such reactions. The stochastic Liouville equation formalism is employed to model the reaction behaviour of distance-distributed, triplet-born radical pairs ( R Ps) undergoing free di usion, distance-and spin-dependent backward electron transfer, coherent and incoherent spin evolution in the ps time domain. In comparison with real systems the spin situation is simpli® ed by reducing it to a two state S , T 0 problem, yet it is parametrized in a way that allows sensible comparison of the results with those of recent experiments. It is predicted that the MFE on u ce exhibits characteristic minima in the MFE versus viscosity curves, and it is veri® ed in detail that this f eature is peculiar to the di usional model with distance-dependent electron transfer, i.e. cannot be reproduced with the simpler (`exponential') R P model employing distance-independent rate constants. Thus, the MFE versus viscosity curves are established as a genuine ® ngerprint of distance-dependent electron transfer. The theoretical results compare f avourably with recent experimental results obtained with R u III complex/methylviologen RPs.

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“…16 In addition, a number of rigidly linked donor-acceptor pairs, in particularly favorable geometries, have also shown evidence of solvent-enhanced electronic coupling. 13,17,18 A number of theoretical studies have also examined the effects of solvent on the electronic coupling. The work of Newton and co-workers on the Fe(H 2 O) 6 +3/+2 self-exchange reaction [19][20][21] (and other similar self-exchange systems) provided convincing evidence that specific interactions between donor(D)/acceptor-(A) and bound solvent (or ligand) could dramatically alter the electronic coupling at a given D-A separation.…”

Section: Introductionmentioning

confidence: 99%

“…15,23 In these two studies it was found that water reduced the rate of decay of H ab with distance and that neither the size nor the decay of H ab with distance were significantly affected by the water orientation between the donor and acceptor. Theoretical studies of solvent effects on H ab for the C-clamp compounds of Zimmt and co-workers 17 have also been performed. 24,25 In studies that focused on individual solvent molecules, 24a, 25 it was shown that solvent molecules can dramatically alter the D-A coupling, via symmetry-breaking and superexchange mechanisms, the latter being by far the larger contributor when solvent is located between D and A.…”

Section: Introductionmentioning

confidence: 99%

A Theoretical Study of the Electronic Coupling Element for Electron Transfer in Water

1999

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The electronic coupling element for electron transfer between a donor and acceptor in water is examined using simulations combining molecular dynamics and semiempirical quantum mechanics. In the first phase of the simulations a model donor and acceptor are solvated in water, using realistic potentials. Following equilibration, molecular dynamics simulations are performed with the donor, acceptor, and water at approximately 300 K, under periodic boundary conditions. In the second phase of the simulation, the electronic coupling element between the donor and acceptor is calculated for a number of time slices, in the presence of the intervening water molecules (those having a nonnegligible effect on the coupling element at the given distance). Finally, a subset of these configurations is used to investigate the donor-acceptor energy dependence of the coupling by varying the model donor and acceptor. It is found, contrary to a number of previous theoretical results, that water significantly increases the electronic coupling element at a given donor-acceptor separation. The value for using INDO wave functions is estimated to be 2.0 Å -1 and is found to depend weakly on the identity of the donor and acceptor. Comparison with ab initio results for a subset of the configurations or using idealized solvent geometries suggests that the ab initio value would be in the range of 1.5-1.8 Å -1 .

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Electronic Coupling in C-Clamp-Shaped Molecules: Solvent-Mediated Superexchange Pathways

Cited by 106 publications

References 47 publications

Equilibrium solvation in quadrupolar solvents

Equilibrium solvation in quadrupolar solvents

Magnetic field effect as a probe of distance-dependent electron transfer in systems undergoing free diffusion

A Theoretical Study of the Electronic Coupling Element for Electron Transfer in Water

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