Retinal protonated Schiff base

The all-tnms-hepta-2,4,6-trieniminium cation (2), a retinal protonated Schiff base model, may undergo trans cis isomerization of the double bond at either position 2 or 4. Thus, the photochemistry is dominated by the structure of the competitive excited state reaction paths leading to distinct conical intersection structures. 

Hendrickx et al. [41 2] have reported the first hyperpolarizabilities of retinal, retinal Schiff base and retinal protonated Schiff base at 1064 nm excitation wavelength. Retinal protonated Schiff base is responsible for the linear and NLO properties of bacteriorhodopsin protein. Their measured hyperpolarizabilities are 3600 X 10 ° esu for retinal protonated Schiff base and 470 x IO" esu for retinal Schiff base. They also investigated theoretical understanding of the first hyperpolarizabilities of retinal derivatives. Results are shown in Table 5. 

Fig. 7.1 Systems under investigation (a) 2,4-Pentadiene-l-iminium cation (protonated Schiff base, PSB5) (b) formal-dimine (c) retinal protonated Schiff base (RPSB, 11-c/sto all-trans isomerization.

As an example of the use of this method, we will describe the computation of the ESRP for the photoisomerization of the minimal retinal protonated Schiff base model tZt-penta-... 

Fig. 3. Resonance Raman spectrum of the all-trani-retinal protonated Schiff base chromo-phore in light-adapted bacteriorhodopsin. The assignments are of the various enhanced vibrational normal modes are indicated. (From Smith el al. )...

Fig. 6 Comparison of retinal protonated Schiff base chemical shifts in rhodopsin different photocycle states. The chemical structure of retinal chromophore in 11-cw (a) and all-trans configuration (b). Chemical shifts of the retinal atoms in ground state, and Batho-, Meta I, and Meta II intermediate states (c) and a schematic drawing of the retinal binding pocket containing all residues within 4 A to the retinal and Lys296 (d). The chemical shifts are adapted from the following references [146-148] (black) [14] (blue) [149-151] (green) and [17, 145] (red), (d) is adapted from [188] with permission from the Elsevier B.V...

Fig. 2 Tunability of the photochemical and photophysical properties of the retinal-protonated Schiff base chromophore in solution. Reprinted with permission from G. Bassolino, T. Sovdat, M. Liebel, C. Schnedermann, B. Odell, T. D. W. Claridge, P. Kukura and S. P. Fletcher, J. Am. Chem. Soc., 2014,136, 2650. Copyright 2014, American Chemical Society.

Szymczak, J. J., Barbatti, M., Lischka, H. (2009). Is the photoinduced isomerization in retinal protonated schiff bases a single- or double-torsional process The Journal of Physical Chemistry A, 113(43), 11907-11918. doi 10.1021/jp903329j. 

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