Twisting and Charge Transfer The TICT Mechanism

The TICT model was put forward to account for the observation that the dual fluorescence of DMABN with its normal band (B band) at around 350 nm and its anomalous one (A band, around 450 nm in medium polar solvents) depends on the 

Equations (5.1) and (5.2) can be used to predict possible new TICT systems/9,35 Whether or not the energetic minimum of the A (TICT) state is lower than that of the precursors state (inequality Eq. (5.1) fulfilled) sensitively depends on the electron donor-acceptor properties of the subsystems which can be quantified by ionization (or Oxydation) potential and electron affinity (or reduction potential) of donor D and acceptor A (Eq. (5.2)). 

The B state responds much less to changes in donor and acceptor properties than the TICT state, and Eq. (5.1) can often be easily fulfilled by increasing donor and/or acceptor strength. In addition to these two factors which deliver the decisive part of the reaction driving force, polar solvent stabilization SOiv and the mutual Coulombic attraction C of the linked donor and acceptor radical anion/cation also help to preferentially stabilize the TICT state with respect to the precursor B state. 

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