Cyanines, Squaraines and Derivatives

As discussed above, the degree of intramolecular charge transfer is related to the magnitude of the 2PA cross section, and, as such, cyanines and squaraines could also have interesting 2PA properties. 

In the case of the pseudocyanine cy.3, however, the lowest energy 2PA tran- 

Very large cross sections (up to 3.3xl0 GM) have been reported by Chung et al. for a series of squaraines that differ from sq.1-2 in the type of terminal donor and conjugated linker [147]. Two examples are compounds sq.3 and sq.4 in Table 9. The state corresponding to this transition lies about 

Values for Table 2 in the reference cited (the relative intensity between the two peaks is different in Fig. 4 from the same source). 

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