Intramolecular charge transfer and thermal exciplex dissociation with p-aminobenzonitriles in toluene

Journal Article · Thu Mar 07 04:00:00 UTC 1991 · Journal of Physical Chemistry; (USA)

DOI:https://doi.org/10.1021/j100158a024· OSTI ID:5740970

Leinhos, U; Kuehnle, W; Zachariasse, K A ^[1]

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1. Max-Planck-Institut fuer biophysikalische Chemie, Goettingen (West Germany)

The rate constants of the reversible intramolecular excited-state charge-transfer (CT) reaction of 4-(dimethylamino)benzonitrile (DMABN;I) in toluene were determined as a function of temperature, from double-exponential fluorescence decays measured by time-correlated single-photon counting. The same decay times were found for the locally excited (LE) and the CT state, as shown by global analysis. For the CT state, the stabilization enthalpy {Delta}H ({minus}6 kJ mol{sup {minus}1}) and the change in entropy {Delta}S ({minus}24 J K{sup {minus}1} M{sup {minus}1}) were determined. A correlation of the charge-transfer time of DMABN with the longitudinal dielectric relaxation time was not observed. The presence of dimers or solute/solvent complexes in the ground state was excluded by {sup 1}H NMR experiments. A reversible excited-state reaction was shown to occur in toluene for the planar molecules 1-methyl-5-cyanoindoline (NMCI; II) and 1-methyl-6-cyano-1,2,3,4-tetrahydroquinoline (NMCQ;III) as well as for 3,5-dimethyl-4-(dimethylamino)benzonitrile (DMADBN;IV), based on the wavelength dependence of the double-exponential fluorescence decays. Such a dependence was not found for N-methyl-4-aminobenzonitrile (MABN; IH), 4-aminobenzonitrile (ABN; IHH), and 3,5-dimethyl-4-aminobenzonitrile (ADBN; IVHH), which is attributed to an increase in energy of the CT state relative to the LE state in these secondary and primary aromatic amines.

• OSTI ID: 5740970
• Journal Information: Journal of Physical Chemistry; (USA), Journal Name: Journal of Physical Chemistry; (USA) Vol. 95:5; ISSN JPCHA; ISSN 0022-3654
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
ALKYLATED AROMATICS
AROMATICS
DATA
DATA ANALYSIS
ELECTRON TRANSFER
EMISSION SPECTROSCOPY
EXPERIMENTAL DATA
FLUORESCENCE SPECTROSCOPY
HYDROCARBONS
INFORMATION
MAGNETIC RESONANCE
NITRILES
NUCLEAR MAGNETIC RESONANCE
NUMERICAL DATA
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
RESONANCE
SPECTROSCOPY
TEMPERATURE DEPENDENCE
TOLUENE