Reviews in Computational Chemistry Volume 18
Reviews in Computational Chemistry Volume 18
Reviews in Computational Chemistry Volume 18
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206 Charge-Transfer Reactions <strong>in</strong> Condensed Phases<br />
of the ET free energy surfaces to the solvent-<strong>in</strong>duced component of the optical<br />
Franck–Condon provides a unique possibility to apply the statistical mechanical<br />
analysis of ET and CT energetics and to test it on experiment. The band<br />
shape analysis of optical profiles is thus the key factor <strong>in</strong> a successful <strong>in</strong>terplay<br />
between theory and experiment.<br />
This chapter outl<strong>in</strong>es some recent advances <strong>in</strong> the statistical mechanical<br />
analysis of the CT energetics. The basic strategy used <strong>in</strong> this approach is to<br />
<strong>in</strong>troduce new physical features of CT activation <strong>in</strong>to the system Hamiltonian<br />
used to build the free energy surfaces. These are then applied to calculate the<br />
Franck–Condon factors and determ<strong>in</strong>e how the changes <strong>in</strong> the physics of the<br />
problem affect the optical observables. This development highlights two fundamental<br />
results. First, the MH model of fixed charges solvated <strong>in</strong> a dense,<br />
condensed-phase environment leads to a very accurate representation of the<br />
ET energetics <strong>in</strong> terms of two <strong>in</strong>tersect<strong>in</strong>g parabolas. The static nonl<strong>in</strong>ear solvation<br />
effects are generally weak and do not substantially distort the parabolas.<br />
There is, however, ample room to modify the free energy surfaces when<br />
changes <strong>in</strong> the electronic density of the donor–acceptor complex are allowed<br />
either through polarizability or electronic delocalization. The CT free energies<br />
then <strong>in</strong>herit nonl<strong>in</strong>ear features, and a number of <strong>in</strong>terest<strong>in</strong>g consequences for<br />
optical observables can be anticipated. These fasc<strong>in</strong>at<strong>in</strong>g phenomena will be<br />
the subject of future research.<br />
ACKNOWLEDGMENTS<br />
D.V.M. acknowledges the support by the Department of <strong>Chemistry</strong> and Biochemistry at<br />
ASU and partial support by the Petroleum Research Fund, adm<strong>in</strong>istered by the American Chemical<br />
Society, (36404-G6). G.A.V. acknowledges support from the Department of Energy, Basic Energy<br />
Sciences Program.<br />
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