Computation of pKa Values of Substituted Aniline Radical Cations in Dimethylsulfoxide Solution
详细信息 查看全文
- 作者：Ao Yu ; Yuanhai Liu ; Zucheng Li ; Jin-Pei Cheng
- 刊名：Journal of Physical Chemistry A
- 出版年：2007
- 出版时间：October 4, 2007
- 年：2007
- 卷：111
- 期：39
- 页码：9978 - 9987
- 全文大小：242K
- 年卷期：v.111,no.39(October 4, 2007)
- ISSN：1520-5215
文摘
A newly developed computation strategy was used to calculate the absolute pKa values of 18 substitutedaniline radical cations in dimethylsulfoxide (DMSO) solution with the error origin elucidated and deviationminimized. The B3LYP/6-311++G(2df,2p) method was applied and was found to be capable of reproducingthe gas-phase proton-transfer free energies of substituted anilines with a precision of 0.83 kcal/mol. TheIEF-PCM solvation model with gas-phase optimized structures was adopted in calculating the pKa values ofthe substituted neutral anilines in DMSO, regenerating the experimental results within a standard deviationof 0.4 pKa unit. When the IEF-PCM solvation model was applied to calculate the standard redox potentialsof anilide anions, it showed that the computed values agreed well with experiment, but the redox potentialsof substituted anilines were systematically overestimated by 0.304 eV. The cause of this deviation was foundto be related to the inaccuracy of the calculated solvation free energies of aniline radical cations. By adjustingthe size of the cavity in the IEF-PCM method, we derived a reliable procedure that can reproduce theexperimental pKa values of aniline radical cations within 1.2 pKa units to those from experiment.