Synthesis,Crystal Structure and Theoretical Calculation of a Pressure-sensitive Dye Based on Phthalide
With p-dimethylamino-benzaldehyde and m-dimethylamino-benzoic acid as raw materials,the intermediate 6-dimethylamino-2-(4-dimethylamino-benzoyl)-benzoic acid was obtained.Then the target compound 3-(4-dimethylaminobenzyl)-3-(1-butyl-2-methyl-indol-3-yl)-6-dimethylaminophthalide was prepared by condensation reaction between the intermediate and 1-butyl-2-methylindole.The total yield of four steps is 58％.The structure of the target compound was confirmed by 1HNMR spectrum and single crystal test.Based on ultraviolet-visible absorption spectra analysis and theoretical calculations,the discoloration mechanism of the compound was studied.The results showed that the discoloration of the compound could be mainly attributed to the hydrolysis and elimination reactions under acidic condition,leading to the increase of molecular conjugation and the red shift of the absorption spectra.
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