Excited State Twisted Internal Charge Transfer TICT

This phenomenon was found to occur in a number of analogous species, the twisted conformation generally representing the most favourable species. This explanation held for over a decade and as such led to the name of excited state twisted internal charge transfer (TICT). In the early 1970s, new experimental evidence revealed that the TICT model failed to provide a consistent interpretation for empirical data in certain cases, nevertheless the concept of a twisted state still provides a valuable model. For a discussion on the range of hypotheses subsequently postulated regarding the structure of the ICT state and the... 

Bosch LI, Mahon MF, James TD (2004) The B-N bond controls the balance between locally excited (LE) and twisted internal charge transfer (TICT) states observed for aniline based fluorescent saccharide sensors. Tetrahedron Lett 45(13) 2859-2862... 

Z. R. Grabowski, K. Rotkiewicz, W. Rubaszewska, and E. Kirkor-Kaminska, Spectroscopy and kinetic of the twisted internal charge-transfer (TICT) excited state formation in p-substituted dialkylanilines, Acta Phys. Pol. A 54, 767 (1978). 

James and co-workers have prepared 12a, a monoboronic acid fluorescent sensor that shows large shifts in emission wavelength on saccharide binding [50]. The dual fluorescence of 12a, can be ascribed to locally excited (LE) and twisted internal charge transfer (TICT) states of the aniline fluorophore [51]. When saccharides interact with sensor 12a in aqueous solution at pH 8.21 the emission maxima at 404 nm (TICT state) shifts to 362 nm 274 nm, LE state). The band at 404 nm is due to the TICT state of 12a containing a B-N bond i.e. the lone pair is coordinated with the boron and perpendicular to the jt-system. The band at 274 nm (LE state) corresponds to the situation where the B-N bond in 12a has been broken with formation of the boronate (Scheme 12.3). 

Scheme12.3 Locally excited (LE) and twisted internal charge transfer (TICT) states of 12a.

Twisted internal charge transfer TtCT) Intramolecular, photoinduced charge transfer between chromophores interconnected by a single bond leading to an excited state (a TICT state) in which the chromophores interact only weakly because of a considerable twist about the interconnecting bond. 

On the other hand, the fluorescence of ThT has found many applications. In viscous media new emissive species are formed from locally excited states by twisting around the central single C-C bond and their formation correlates with viscosity, thus oflering an opportunity to direct observe the formation of TICT (twisted internal charge transfer) states. ... 

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