Synthesis, optical and electrochemical properties of substituted 2-cinnamoyl-1, 3-indandione O-methyl ethers

• Differently substituted 2-cinnamoyl-1,3-indandione O-methyl ethers were synthesized.
• Methylation occurred at the exocyclic enol group of cinnamoyl fragment.
• Some obtained compounds have high molar absorptivity and intensive luminescence.
• Compound with julolidyl substituent showed relatively high quantum yield.

Seven new 2-cinnamoyl-1,3-indandione (2CID) O-methyl ethers with different substituents (R = –H, –CH3, –OCH3, –N(C6H5)2, –N(CH2CH2CN)2, julolidyl, –N(CH3)2) in 4-position of the cinnamoyl moiety were synthesized. The methylation with dimethylsulfate occurred at the oxygen atom of the exocyclic enol group with high selectivity.The synthesized compounds were characterized by 1H, 13C NMR, IR, UV–Vis and luminescence spectroscopy, their electrochemical properties were investigated by cyclic voltammetry. The obtained results indicates that introducing an electron donating substituents in the 4-position of cinnamoyl moiety facilitates electrochemical oxidation, remarkably shifts absorption and emission bands to longer wavelengths, simultaneously increases extinction coefficient (ε). O-methyl ethers with strong electron donating groups (R = –N(C6H5)2, –N(CH2CH2CN)2, julolidyl, –N(CH3)2) in molecule are characterized by luminescence with maximum in range from 547 to 647 nm and absolute photoluminescence quantum yields from 0.02 to 0.32. Quantum yield (QY) of chromophore containing julolidyl fragment is solvent dependent. It was 0.32 in chloroform and decreased in other polar (ethanol, acetone) solvents.