Singlet and Triplet State Back Electron Transfer from Photogenerated Radical Ion Pairs Studied by Time-Resolved CIDNP

Schaffner, Erik; Fischer, Hanns

doi:10.1021/jp951999t

Cited by 21 publications

(4 citation statements)

References 60 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The triplet state of the excited 1,4dimethoxynaphthalene molecule is lower in energy than the radical-ion pair; therefore, by changing the concentration of fumaronitrile, one can change the multiplicity of the radical pair. 53 The measurement of the DEE rate constants can be markedly simplified by proceeding from the dependence of the DNP kinetics on the concentration of the diamagnetic product. This method has advantages over investigation of the concentration dependence of the half-with of the DNP spectra because the half-width of the spectra depends appreciably on the amplitude of the RF field B 1 , whereas the DNP kinetics do not.…”

Section: Dynamic Nuclear Polarisation In Radical Ionsmentioning

confidence: 99%

Dynamic and stimulated nuclear polarisation in photochemical radical reactions

Bagryanskaya¹,

Sagdeev²

2000

Russ. Chem. Rev.

View full text Add to dashboard Cite

Section: Dynamic Nuclear Polarisation In Radical Ionsmentioning

confidence: 99%

Dynamic and stimulated nuclear polarisation in photochemical radical reactions

Bagryanskaya¹,

Sagdeev²

2000

Russ. Chem. Rev.

View full text Add to dashboard Cite

“…Quenching of singlet aromatic amines by ground state acceptors can also result in electron transfer. − In comparison to the quenching of singlet acceptors by aromatic amines, quenching of singlet aromatic amines by ground state acceptors has received limited attention. Beens and Weller 1a noted the failure of dimethylaniline and benzene to form an exciplex and suggested that it might be a consequence of limited orbital overlap.…”

mentioning

confidence: 99%

Formation and Anomalous Behavior of Aminonaphthalene−Cinnamonitrile Exciplexes

2000

View full text Add to dashboard Cite

The solvent dependence of the electronic spectra of several 1-aminonaphthalenes and 2-aminonaphthalenes in the absence and presence of two styrene derivatives, cinnamonitrile and 1-phenylpropene, has been investigated. The absorption maxima of the aminonaphthalenes are dependent upon both the polarity and hydrogen-bond donor and acceptor properties of the solvent and display both red and blue solvent shifts. The fluorescence maxima are more sensitive to solvent polarity than are the absorption maxima and display red shifts in both non-hydroxylic and hydroxylic solvents. The excited state dipole moments of the 1-aminonaphthalenes are larger than those of the 2-aminonaphthalenes. Quenching of the aminonaphthalene fluorescence by cinnamonitrile occurs with diffusion-controlled rates in all solvents, in accord with the occurrence of exergonic electron transfer. Exciplex fluorescence is observed only for the tertiary aminonaphthalenes in nonpolar solvents. The exciplex fluorescence displays anomalous temperature dependence in hexane solution, an increase in temperature resulting in blue-shifted exciplex fluorescence and an increase in the exciplex decay time. Quenching of the aminonaphthalene fluorescence by 1-phenylpropene is slower than diffusioncontrolled and is not accompanied by exciplex fluorescence.Aromatic amines are strong electron donors that have been widely employed in investigations of exciplex formation and photoinduced electron transfer. [1][2][3][4][5] In most such studies, ground state N,N-dialkylanilines have been used to quench relatively nonpolar singlet acceptors. Since the exciplex or contact ion pair formed in such reactions is more polar than the locally excited singlet state, solvent polarity has a pronounced effect on exciplex formation and behavior. Increasing solvent polarity has little effect on the fluorescence of the locally excited singlet but causes a red shift in the exciplex emission and a decrease in the exciplex fluorescence intensity and lifetime due increased rates of nonradiative decay or ionic dissociation. The formation of fluorescent exciplexes has been observed for N,N-dialkylanilines but not for primary or secondary anilines. 2 The absence of exciplex fluorescence from exciplexes formed by secondary and tertiary anilines has been attributed to proton transfer processes and enhanced intersystem crossing. 2,5 Quenching of singlet aromatic amines by ground state acceptors can also result in electron transfer. [6][7][8][9][10][11] In comparison to the quenching of singlet acceptors by aromatic amines, quenching of singlet aromatic amines by ground state acceptors has received limited attention. Beens and Weller 1a noted the failure of dimethylaniline and benzene to form an exciplex and suggested that it might be a consequence of limited orbital overlap. Intermolecular exciplex formation upon quenching of 2-dimethylaminonaphthalene by dimethylphthalates in nonpolar solvents was observed by Kaneta and Kiozumi. 6 Fluorescence

show abstract

“…At the initial stages, we could see only the characteristic absorptions of 3 (ZnP(TPA) 3 )* at 480 and 820 nm, suggesting that the intersystem crossing (ISC) process from 1 (ZnP(TPA) 3 )* occurs after the fast charge-separation and charge-recombination processes in the picoseconds time region. Such fast intersystem crossing (ISC) processes were reported in compact donor−acceptor molecules, especially when the donor is placed to be nearly in perpendicular orientation to that of the acceptor. − With the decay of 3 (ZnP(TPA) 3 )*, the absorption bands appeared at 480, 770, and 1310 nm as seen in the transient spectra in the microsecond region (inset of Figure ). This observation demonstrates the generation of (ZnP(TPA) 3 ) •+ −(SubPc(F) 12 ) •− via 3 (ZnP(TPA) 3 )* in benzonitrile.…”

Section: Resultsmentioning

confidence: 85%

Long-Lived Charge Separation in a Dyad of Closely-Linked Subphthalocyanine-Zinc Porphyrin Bearing Multiple Triphenylamines

et al. 2009

View full text Add to dashboard Cite

Photoinduced intramolecular events of the newly synthesized multimodular system composed of three triphenylamine (TPA) entities covalently substituted at the meso positions of the zinc porphyrin ring (ZnP), which is linked with the dodecafluorosubphthalocyanine SubPc(F)12 at its axial position with the B−O bond have been examined. Appreciable electronic interactions between the meso-substituted TPA entities and the ZnP π-system were observed, and as a consequence, ZnP(TPA)3 acts as an electron-donor, whereas the SubPc(F)12 moiety acts as an excellent electron-acceptor unit in the multimodular conjugate, ZnP(TPA)3−SubPc(F)12. The computational studies performed by the DFT-B3LYP at the 6-31G level revealed delocalization of the highest occupied molecular orbital (HOMO) over the (TPA)3 entities and the porphyrin macrocycle, while the lowest unoccupied molecular orbital (LUMO) is localized on SubPc(F)12. Free-energy calculations suggested that the light-induced processes from the excited states of ZnP(TPA)3 are exothermic in both polar benzonitrile and nonpolar toluene and benzene. The occurrence of fast and efficient charge-separation processes (∼1012 s−1) via the singlet excited state of ZnP(TPA)3 was confirmed by the femtosecond transient absorption spectral measurements in polar and nonpolar solvents. The delocalization of the π-cation radical species over the donor ZnP(TPA)3, the lower energy of the radical-ion pair, the particular characteristics of the axial B−O bond, and the triplet radical-ion pair character rationalize the charge stabilization of (ZnP(TPA)3)•+−(SubPc(F)12)•− with extremely long lifetime (370 μs) compared with the reported phthalocyanine-based compounds.

show abstract

Singlet and Triplet State Back Electron Transfer from Photogenerated Radical Ion Pairs Studied by Time-Resolved CIDNP

Cited by 21 publications

References 60 publications

Dynamic and stimulated nuclear polarisation in photochemical radical reactions

Dynamic and stimulated nuclear polarisation in photochemical radical reactions

Formation and Anomalous Behavior of Aminonaphthalene−Cinnamonitrile Exciplexes

Long-Lived Charge Separation in a Dyad of Closely-Linked Subphthalocyanine-Zinc Porphyrin Bearing Multiple Triphenylamines

Contact Info

Product

Resources

About