Quadrupolar pattern chromophores

Comparison of the energies for TPA and OPA shows a higher energy for the TP excited state compared to the lowest allowed OP excited state (Si) for all chromophores (99-107) examined in this section. Hence, the amplitude of TPA can be described by Eq. (27). There are no dipolar contributions, no matter that solvatochromism occurs for the samples 99-104. The influence of the quadrupolar pattern is reflected in M12. Application of models of the symmetry break are not likely to provide clarification of the relation between TPA properties and the distinct quadrupolar substitution of the chromophores 99-107. 

D-7i-A)3-D chromophores exhibit large TPA, as shown for chromophore 122 [490]. This compound can be considered a propeller-shaped molecule consisting of three quadrupolar arms. This study demonstrates that addition of each individual arm results in a twofold increase of 8 as shown for the TPA of 122 (5 = 5030 GM) in comparison with the quadrupolar chromophore 100c (7) = 1370 GM). The latter comprises one arm of 122. Substitution of one arm by a methyl group results in a twin chromophore exhibiting a 8 of 3130 GM. Thus, one can conclude that TPA depends on the number of arms (na), na > 2, incorporated in both (D-rc- A)na-D and (D-7i)na-D chromophores. The structural pattern of 122 comprises three quadrupolar arms. Thus, Eqs. (59) and (60) cannot be applied to describe TPA of 122 because A/(m 0 due to the quadrupolar pattern of each arm. Therefore, the enhacement of 8 is better explained by the increase of the transition dipole moments Mqi and M 2 because... 

Fig. 8 Schematics of various linear (one-dimensional) chromophores classified based on the substitution pattern. I-IV quadrupolar molecules V dipolar molecules (D = donor group 7T = 7T-conjugated bridge A = acceptor group)...

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