Phase conjugate, third-order effects

In going from benzene to 3-carotene (the second structure), the Y value increases by more than three orders of magnitude showing the importance of increase in the effective conjugation length. The third structure exhibits N-phenyl substitution in the benzimidazole type structures to introduce a two dimensional conjugation. The last structure, an organometallic polymer, has also been measured in the solution phase. Because of the resonance condition encountered, the Y value is.complex. 

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