Hepta-2,4,6-trieniminium cation

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. 

The all-tnms-hepta-2,4,6-trieniminium cation (a longer protonated Schiff base with four conjugated double bonds) has an Sj MEP that is similar to the MEP of Figure 23. However, in contrast to the short protonated Schiff base discussed above, this molecule may undergo trans —> cis isomerization at the double bond in positions 2 and 4 ... 

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