Intramolecular charge transfer of 4-(dimethylamino)benzonitrile probed by time-resolved fluorescence and transient absorption: No evidence for two ICT states and a {pi}{sigma}{sup *} reaction intermediate

Journal Article · Mon Dec 14 04:00:00 EST 2009 · Journal of Chemical Physics

DOI:https://doi.org/10.1063/1.3270165· OSTI ID:21559815

Zachariasse, Klaas A; Druzhinin, Sergey I; Senyushkina, Tamara ^[1]; Kovalenko, Sergey A ^[2]

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1. Max-Planck-Institut fuer biophysikalische Chemie, Spektroskopie und Photochemische Kinetik, 37070 Goettingen (Germany)
2. Institut fuer Chemie, Humboldt Universitaet zu Berlin, Brook-Taylor Strasse 2, 12489 Berlin (Germany)

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}{sub 1} and {tau}{sub 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}{sub 1}(LE)<{tau}{sub 1}(ICT), is photoproduct formation. By employing a global analysis of the LE and ICT fluorescence response functions with a time resolution of 0.5 ps/channel in 1200 channels reliable kinetic and thermodynamic data can be obtained. The arguments presented in the literature in favor of a {pi}{sigma}* state with a bent CN group as an intermediate in the ICT reaction of DMABN are discussed. From the appearance of an excited state absorption (ESA) band in the spectral region between 700 and 800 nm in MeCN for N,N-dimethylanilines with CN, Br, F, CF{sub 3}, and C(=O)OC{sub 2}H{sub 2} p-substituents, it is concluded that this ESA band cannot be attributed to a {pi}{sigma}{sup *} state, as only the C-C{identical_to}N group can undergo the required 120 deg. bending.

• OSTI ID: 21559815
• Journal Information: Journal of Chemical Physics, Journal Name: Journal of Chemical Physics Journal Issue: 22 Vol. 131; ISSN JCPSA6; ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
74 ATOMIC AND MOLECULAR PHYSICS
ABSORPTION
ACETONITRILE
CARBON COMPOUNDS
CARBON NITRIDES
CHARGE EXCHANGE
EMISSION
ENERGY LEVELS
EXCITED STATES
FLUORESCENCE
FUNCTIONS
GLOBAL ANALYSIS
KINETICS
LUMINESCENCE
MATHEMATICS
MOLECULAR STRUCTURE
NITRIDES
NITRILES
NITROGEN COMPOUNDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PHOTON EMISSION
PNICTIDES
REACTION INTERMEDIATES
REACTION KINETICS
RESOLUTION
RESPONSE FUNCTIONS
SORPTION
TIME RESOLUTION
TIMING PROPERTIES