微量光度滴定法测定咔咯化合物的质子化和去质子化常数

采用微量光度滴定法测定了两种具有不同取代基的新型咔咯化合物,三(4-氯苯基)咔咯(化合物1)和三(2,4-二氯苯基)咔咯(化合物2)在非水溶剂中的质子化和去质子化常数。结果表明:化合物1和化合物2在二氯甲烷中均可以与三氟乙酸反应得到一个质子生成正一价阳离子,其质子化常数(lgKb)分别为4.2和4.0。在甲醇溶液中,化合物1和化合物2与氢氧化钠反应时可以失去一个质子生成负一价阴离子,其去质子化常数(lgKa)分别为3.4和3.5。而在二氯甲烷中与碱反应时,化合物1和化合物2均能够一步失去两个质子生成负二价阴离子,其累积去质子化常数(lgβ2)分别为7.9和11.0。

Determination of Protonation and Deprotonation Constants of 2 New Corroles by Microspectrophotometric Titration

Protonation and deprotonation constants of two novel corroles containing different substituents,i.e.,1 tri(4-chlorophenyl)corrole(ClPh)3CorH3 and 2 tri(2,4-dichlorophenyl)corrole(Cl2Ph)3CorH3,were determined in nonaqueous media by microspectrophotometric titration.It was found that both of the 2 corroles reacted with trifluoroacetic acid in CH2Cl2 medium to form cations by obtaining a proton.The protonation constants(lgKb) found for the corroles 1 and 2 were 4.2 and 4.0 respectively.It was found also that the 2 corroles lost one proton each to form respective anions in CH3OH and NaOH solution.The deprotonation constants(lgKa) were found to be 3.4 for corrole 1 and 3.5 for corrole 2;and both corroles lost 2 protons by reacting with an alkali in CH2Cl2 medium to form dianions with deprotonation constants(lgβ2) of 7.9 and 11.0,respectively.