Synthesis of novel H-shaped chromophores

A series of H-shaped chromophores with two parallel and non-conjugated D-π-A units have been synthesized, in which a 9,10-dihydroanthracene was employed as molecular backbone. The synthesis of these H-shaped chromophores 9a–11a was accomplished via an eight-step reaction, including double Claisen rearrangement, hydroboration–oxidation, Rieche formylation reaction, Knoevenagel condensation and Corey–Fuchs reaction, with a total yield about 12.5%. The corresponding mono-D-π-A unit compounds 9b–11b were also prepared in a similar procedure for the purpose of comparison. Crystal structures of three intermediates 5a, 7a and 8a were measured, which demonstrate that the two D-π-A units in a single H-shaped chromophore molecule are nearly arranged at the same direction. The studies of UV–vis spectra and the solvatochromic method indicate that the molecular second-order polarizabilities values (μβ) of H-shaped chromophores are remarkably increased compared with the corresponding mono-D-π-A unit reference compounds, without causing a large shift of the absorption band to longer wavelength.