Fast intramolecular electron transfer and dual fluorescence. Configurational change of the amino nitrogen (pyramidal→planar)

Haar, Th. von der; Hebecker, A.; Il'ichev, Yu.V.; Kühnle, W.; Zachariasse, Klaas A.

doi:10.1063/1.50206

Cited by 11 publications

(49 citation statements)

References 1 publication

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The IC process in 1N4 is clearly slower than in 1N5 and 1DMAN, caused by an increase in the IC activation energy E IC . A similar phenomenon has been observed for the CT reaction of 4-aminobenzonitriles upon replacing the dimethylamino group in DMABN by an azetidinyl (P4C) or a pyrrolidinyl (P5C) substituent, − as mentioned in the Introduction. The reasons for the decrease in reaction efficiency are different, however.…”

Section: Resultssupporting

confidence: 68%

“…The reasons for the decrease in reaction efficiency are different, however. In the present case of the 1-aminonaphthalenes, the relatively large value for E IC of 1N4 is attributed to the smaller amino twist angle θ of 1N4 as compared with 1N5 and 1DMAN, whereas with P4C the increase in the CT activation energy E CT relative to that for P5C and DMABN has been explained by a larger barrier for the latter compounds of the configurational change of the amino group from pyramidal to planar. − …”

Section: Resultsmentioning

confidence: 53%

“…The replacement of the amino substituent in 4-(dimethylamino)benzonitrile (DMABN) by a pyrrolidinyl or an azetidinyl group, giving either 4-( N -azetidinyl)benzonitrile (P4C) or 4-( N -pyrrolidinyl)benzonitrile (P5C), leads to a considerable decrease in the intramolecular charge transfer (ICT) efficiency, especially in the case of P4C. − The difference between P4C and P5C comes from a substantially larger ICT activation energy for the former molecule, determined by the amino nitrogen inversion barrier. , …”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Internal Conversion in 1-Aminonaphthalenes. Influence of Amino Twist Angle

et al. 1999

View full text Add to dashboard Cite

With the 1-aminonaphthalenes 1N5 and 1DMAN a fast radiationless process occurs in n-hexane, diethyl ether, and acetonitrile, which is shown to be internal conversion (IC). The IC reaction is slower with 1N4 and much less efficient with 1MAN and 1AN. This IC process is thermally activated and slows down with increasing solvent polarity, due to a larger IC activation energy. In the ground state S0, the amino twist angle θ relative to the naphthalene plane increases in the order 1MAN, 1AN, 1N4, 1N5, 1DMAN, as derived from absorption and fluorescence spectra, 1H NMR spectra, ground-state dipole moments, and ab initio calculations. For the five 1-aminonaphthalenes in the equilibrated S1 state, the twist angle and the radiative rate constant have similar values. The different IC efficiences of these molecules are therefore determined by the structural differences (amino twist angle) between S1 and S0. A correlation is found between the IC efficiency in these molecules and the twist angle θ. The IC process to S0 starts from the equilibrated S1 state, which is vibronically coupled with S2 due to a small energy gap ΔE(S1,S2). It is therefore concluded that the extent of vibronic coupling and the magnitude of the twist angle θ are the determining factors in the IC process.

show abstract

Section: Resultssupporting

confidence: 68%

Section: Resultsmentioning

confidence: 53%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Internal Conversion in 1-Aminonaphthalenes. Influence of Amino Twist Angle

et al. 1999

View full text Add to dashboard Cite

show abstract

“…Examples are DMABN in toluene, p-dioxane, and diethyl ether. 2,3,8,37,[48][49][50] In all these cases, the same times 2 and 1 are found for the LE as well as the ICT decays, which shows that the two state mechanism scheme 1 is fully applicable for the ICT reaction of DMABN, irrespective of solvent polarity.…”

Section: Extreme Situation With Dmabn In Mecn Different Accuraciesupporting

confidence: 57%

Intramolecular charge transfer of 4-(dimethylamino)benzonitrile probed by time-resolved fluorescence and transient absorption: No evidence for two ICT states and a πσ∗ reaction intermediate

Zachariasse

Druzhinin

Kovalenko

et al. 2009

The Journal of Chemical Physics

View full text Add to dashboard Cite

For the double exponential fluorescence decays of the locally excited (LE) and intramolecular charge transfer (ICT) states of 4-(dimethylamino)benzonitrile (DMABN) in acetonitrile (MeCN) the same times tau(1) and tau(2) are observed. This means that the reversible LE<==>ICT reaction, starting from the initially excited LE state, can be adequately described by a two state mechanism. The most important factor responsible for the sometimes experimentally observed differences in the nanosecond decay time, with tau(1)(LE)

show abstract

“…4-(Dimethylamino)benzonitrile (DMABN) has over the years become the favorite example of a dual fluorescent molecule. − Since the discovery that this molecule emits from two different intramolecular singlet excited states, a locally excited state LE and a charge transfer state CT, several mechanisms have been published to explain this phenomenon. ,− The original hypothesis put forward by Lippert in 1959 was based on a solvent polarity induced reversal of the two directly populated lowest excited states S 1 and S 2 . Although it was pointed out that a small energy gap Δ E ( S 1 , S 2 ) was essential for the appearance of the dual emission, the molecular configuration of the two emitting states was not discussed .…”

Section: Introductionmentioning

confidence: 99%

Intramolecular Charge Transfer in Dual Fluorescent 4-(Dialkylamino)benzonitriles. Reaction Efficiency Enhancement by Increasing the Size of the Amino and Benzonitrile Subunits by Alkyl Substituents

1998

View full text Add to dashboard Cite

The intramolecular charge transfer (ICT) reaction from the locally excited state (LE) to the charge transfer state (CT) in the singlet excited state is investigated for the dual fluorescent 4-(dialkylamino)benzonitriles DRABN and 4-dialkylamino-2,6-dimethyl-benzonitriles RDB (R = methyl, ethyl, n-propyl) in toluene as a function of temperature by photostationary and time-resolved experiments. The efficiency of the ICT reaction, as expressed by the CT/LE fluorescence quantum yield ratio Φ‘(CT)/Φ(LE), is enhanced by the increase in the size of the dialkylamino group as well as by the presence of the two extra methyls in the phenyl ring. This increase is mainly brought about by slowing down the thermal back reaction (k d) due to a larger activation energy E d or a smaller preexponential factor k d o, respectively. The free enthalpy change ΔG becomes more negative (∼6 kJ/mol) for 4-(diethylamino)benzonitrile (DEABN) and 4-(di(n-propyl)amino)benzonitrile (DPrABN) as compared with 4-(dimethylamino)benzonitrile (DMABN) and also for the 4-dialkylamino-2,6-dimethylbenzonitriles EDB (ethyl) and PrDB (n-propyl) relative to MDB (methyl). The ΔG is about 2 kJ/mol more negative for RDB than for DRABN. In both series DRABN and RDB, the ICT stabilization enthalpy, −ΔH, increases from R = methyl to n-propyl. The increase in the ICT rate constant k a for the pairs DEABN/DMABN and EDB/MDB is primarily caused by a larger preexponential factor k a o counteracted but not reversed by a likewise larger activation energy E a. For the dependence of the energy E(CT) of the CT state on the difference between the redox potentials of the dialkylamino and benzonitrile moieties in DRABN and RDB a substantially smaller correlation coefficient (0.29) is found than the value of 1.0 expected for the TICT model, showing that the amino and benzonitrile groups in the CT state are not electronically decoupled. The energy δE rep of the Franck−Condon ground state reached upon CT emission decreases with increasing size of the dialkylamino group in DRABN and RDB.

show abstract

Fast intramolecular electron transfer and dual fluorescence. Configurational change of the amino nitrogen (pyramidal→planar)

Cited by 11 publications

References 1 publication

Internal Conversion in 1-Aminonaphthalenes. Influence of Amino Twist Angle

Internal Conversion in 1-Aminonaphthalenes. Influence of Amino Twist Angle

Intramolecular charge transfer of 4-(dimethylamino)benzonitrile probed by time-resolved fluorescence and transient absorption: No evidence for two ICT states and a πσ∗ reaction intermediate

Intramolecular Charge Transfer in Dual Fluorescent 4-(Dialkylamino)benzonitriles. Reaction Efficiency Enhancement by Increasing the Size of the Amino and Benzonitrile Subunits by Alkyl Substituents

Contact Info

Product

Resources

About