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Volumn 107, Issue 19, 2003, Pages 3580-3597

Exposing solvent's roles in electron transfer reactions: Tunneling pathway and solvation

Author keywords

[No Author keywords available]

Indexed keywords

COMPOSITION EFFECTS; ELECTRON ENERGY LEVELS; ELECTRON MOBILITY; ELECTRON TUNNELING; FREE ENERGY; MATHEMATICAL MODELS; MOLECULES; REACTION KINETICS; SOLVENTS; THERMAL EFFECTS;

EID: 0037672871     PISSN: 10895639     EISSN: None     Source Type: Journal    
DOI: 10.1021/jp022213b     Document Type: Article
Times cited : (76)

References (152)
  • 24
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    • note
    • (a) The charge-separated state has been observed via charge-transfer fluorescence from shorter spacer systems and by transient absorbance of the anthracene radical cation in 1.
  • 25
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    • (b) N. Segal. Undergraduate Thesis, Brown University, Providence, RI.
    • Segal, N.1
  • 26
    • 0038713040 scopus 로고    scopus 로고
    • note
    • Corroborating evidence for equilibrium between the locally excited and charge transfer states of 1 in benzene was obtained from transient absorption spectroscopy. The formation and decay rate constants of the anthracene radical cation are the same as the two rate constants observed using time-resolved fluorescence spectroscopy.
  • 29
    • 0038036470 scopus 로고    scopus 로고
    • note
    • 1.
  • 49
    • 0037698665 scopus 로고    scopus 로고
    • note
    • Although initial results are encouraging, whether the inclusion of quadrupolar responses is successful at extending continuum treatments to nonpolar and weakly polar solvents remains an open question.
  • 55
    • 0037698663 scopus 로고    scopus 로고
    • PhD Thesis, Brown University, Providence, RI
    • Kumar, K. PhD Thesis, Brown University, Providence, RI, 1996.
    • (1996)
    • Kumar, K.1
  • 56
    • 0038713042 scopus 로고    scopus 로고
    • note
    • This difference on polarizabilities is given more explicitly in refs 20 and 21.
  • 57
    • 0038374687 scopus 로고    scopus 로고
    • note
    • The molecular solvation model assumes that the quadrapole is axial with its major axis along the dipole moment direction. Table S1 in the Supporting Information shows that the quadrupole moments in 2.5-dichlorotoluene and many of the alkylbenzenes are nonaxial; that is, the major axis of the quadrupole moment's principal axis system is not oriented along the dipole moment vectors direction and the other components of the quadrupole moment tensor are not equal in magnitude.
  • 59
    • 0038036469 scopus 로고    scopus 로고
    • note
    • nonaxial> with b an adjustable parameter.
  • 60
    • 0037698667 scopus 로고    scopus 로고
    • note
    • vacG = 0.295 eV, and a radius = 7.8 Å.
  • 61
    • 0037698666 scopus 로고    scopus 로고
    • note
    • A detailed presentation of the predicted reorganization energies for 1 in each of the solvents as a function of temperature is provided in the Supporting Information.
  • 84
    • 0038713038 scopus 로고    scopus 로고
    • See also refs 1 and 2
    • (d) See also refs 1 and 2.
  • 85
    • 0037698664 scopus 로고    scopus 로고
    • note
    • Recent experimental and theoretical studies indicate alternatives to superexchange type mechanisms for long distance electron transfer. The fall off of transfer rates with distance by these mechanisms is much weaker than for superexchange mechanisms. See refs 37 and 41.
  • 123
    • 0037698660 scopus 로고    scopus 로고
    • note
    • (a) There are systems where through bond coupling may exhibit significant fluctuations because of small structural changes. This includes electron-transfer systems involving conformational gating, structural fluctuations of proteins and symmetry breaking.
  • 126
    • 0038036468 scopus 로고    scopus 로고
    • note
    • S1).
  • 128
    • 0037698654 scopus 로고    scopus 로고
    • note
    • The Coulomb term will vary if the separations of D+ and S- change drastically with solvent. The fourth term varies insignificantly with solvent dielectric properties.
  • 129
    • 0037698656 scopus 로고    scopus 로고
    • note
    • These calculations used a nonsymmetric conformation of the spacer and acceptor ester groups to avoid rigorous (mathematical) symmetry constraints on the coupling.
  • 130
    • 0038374686 scopus 로고    scopus 로고
    • note
    • V = -0.9093E(6-31G**) + 2.507, with all values in eV.
  • 132
    • 0038374684 scopus 로고    scopus 로고
    • note
    • The 40-fold drop is premised on a through space decrease of wave function overlap and exchange arising from a β value of -2.6/Å.
  • 133
    • 0038374685 scopus 로고    scopus 로고
    • note
    • 1/2 from 1 to 3 may reflect, in part, the change from symmetry forbidden donor-acceptor topology in 1 to a symmetry allowed donor-acceptor topology in 3. As most in-cleft solvent configurations for both molecules are dissymmetric, the symmetry forbidden nature of the donor-acceptor interaction for 1 should not be heavily expressed in the donor-spacer and spacer-acceptor interactions.
  • 134
    • 0038036465 scopus 로고    scopus 로고
    • note
    • β for the 7.5 and 9.5 Å U-shaped molecules was estimated using rate constants extracted from Figure 3B in ref 66. To one significant figure, the β values are 1 (in TIP, benzene, o-dichlorobenzen, acetonitrile), 0.8 (ethyl acetate), 0.4 (benzylcyanide, tetrahydrofuran), and 0.3(dibutyl ether, diethyl ether).
  • 135
    • 0038036464 scopus 로고    scopus 로고
    • note
    • 2 group eliminates a set of solvent configurations that otherwise might estabilish significant exchange interactions with both the donor and the acceptor. For the purposes of investigating the distance dependence of solvent-mediated coupling, this spacer is inadequate.
  • 136
    • 0038374682 scopus 로고    scopus 로고
    • A molecular mechanics calculation was performed on each of the 78 configurations of benzene within the cleft of 1. These energies were used to calculate the relative probability of each configuration.
  • 137
    • 0037698658 scopus 로고    scopus 로고
    • note
    • This results from the symmetry forbidden topology that causes the average electronic coupling to be near zero. For a system in which the direct interaction was symmetry allowed, the average value would be more comparable to the root-mean-square value.
  • 138
    • 0038036466 scopus 로고    scopus 로고
    • note
    • The rate constants for 1 in mesitylene exhibit similar variations with temperatures but have been measured over a smaller temperature range.
  • 139
    • 0038713043 scopus 로고    scopus 로고
    • note
    • rG decreases from +0.04 eV to 0.0 eV.
  • 140
    • 0038374683 scopus 로고    scopus 로고
    • note
    • rG > 0 eV), the calculated FCWDS are too large. This implies that the actual decrease in |V| at temperatures above 315 K will be steeper than indicated in the present analysis.
  • 141
    • 0037698657 scopus 로고    scopus 로고
    • note
    • Formation of a DSA-solvent "complex" is likely attended by a decrease in entropy. For aromatic solvents with small or no alkyl groups, ΔH for formation of this complex may be negative or close to zero. For aromatic solvents with bulky alkyl groups. ΔH for complex formation will be more positive.
  • 143
    • 0038036467 scopus 로고    scopus 로고
    • manuscript in preparation
    • (b) Troisi, A.; Ratner, M., manuscript in preparation.
    • Troisi, A.1    Ratner, M.2


* 이 정보는 Elsevier사의 SCOPUS DB에서 KISTI가 분석하여 추출한 것입니다.