Synthesis and characterization of polyene chromophores with hydroxyl functionalization

Eight hydroxyl functionalized donor–acceptor polyene chromophores 3–10 were synthesized and characterized. Knoevenagel condensation reaction of aromatic polyenals with 2-cyanoacetamide derivatives was utilized to synthesize chromophores with all-E configuration. Chromophores of this kind can be attached covalently to polymers or functionalized with dendrons in order to tune the properties. The structures of the molecules were verified by 1H NMR, 13C NMR, ESI-TOF mass spectrometry and UV–vis measurements. Reduced bond-length alternation of the molecules in DMSO-d6 solution were observed by calculating the average difference of the vicinal coupling constants between adjacent CHCH and CH–CH bonds of the conjugated bridge. Thermal stability of the molecules was determined by thermogravimetric analysis (TG). The decomposition temperatures varied between 190 and 256 °C. All measured compounds displayed absorption maximum in visible region, and found to exhibit positive solvatochromic behavior.