Solvation of Copper(II) Sulfate in Binary Water/N,N-Dimethylformamide Mixtures: From the Solution to the Gas Phase
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- 作者：Nikos G. Tsierkezos ; Jana Roithová ; Detlef Schrö ; der ; Ioanna E. Molinou ; Helmut Schwarz
- 刊名：Journal of Physical Chemistry B
- 出版年：2008
- 出版时间：April 10, 2008
- 年：2008
- 卷：112
- 期：14
- 页码：4365 - 4371
- 全文大小：136K
- 年卷期：v.112,no.14(April 10, 2008)
- ISSN：1520-5207
文摘
The solvation of copper(II) sulfate in binary mixtures of water and N,N-dimethylformamide (DMF) is studiedby a combined approach using electrochemical studies in solution and a mass spectrometric assay of thesolvated ions formed from these solutions upon electrospray ionization (ESI). In the condensed phase, thelimiting transference numbers (t±o) and the apparent ion association constants (KA's) of CuSO4 have beendetermined in water/DMF solutions at 20 
C. The t+o values decrease with increasing DMF content,demonstrating a gradual solvation of Cu2+ by DMF molecules. The association constants indicate thataggregation becomes more pronounced as the DMF content increases. In order to achieve complementaryinsight, the intrinsic interactions among the ions and solvent molecules are investigated in gas-phase experimentsof the CuSO4/water/DMF system using ESI mass spectrometry. Under the conditions used, the dications[Cu(DMF)n]2+ (n = 3-6), [Cu2(DMF)nSO4]2+ (n = 2-7), and [Cu3(DMF)n(SO4)2]2+ (n = 2-7), and themonocations [Cu(OH)(DMF)n]+, [Cu(DMF)n(HSO4)]+ (both, n = 1-3), and [Cu(DMF)n]+ (n = 1, 2), areformed as the leading copper-containing cations. Likewise, polynuclear copper clusters observed in the anionESI spectra support partial aggregation occurring in solution. The gas-phase studies clearly support theconclusions that (i) DMF is a highly preferred ligand for CuII in comparison to water and that (ii) DMFsupports ion association for which the mass spectrometric data suggest the formation of polynuclear copperclusters.
C. The t+o values decrease with increasing DMF content,demonstrating a gradual solvation of Cu2+ by DMF molecules. The association constants indicate thataggregation becomes more pronounced as the DMF content increases. In order to achieve complementaryinsight, the intrinsic interactions among the ions and solvent molecules are investigated in gas-phase experimentsof the CuSO4/water/DMF system using ESI mass spectrometry. Under the conditions used, the dications[Cu(DMF)n]2+ (n = 3-6), [Cu2(DMF)nSO4]2+ (n = 2-7), and [Cu3(DMF)n(SO4)2]2+ (n = 2-7), and themonocations [Cu(OH)(DMF)n]+, [Cu(DMF)n(HSO4)]+ (both, n = 1-3), and [Cu(DMF)n]+ (n = 1, 2), areformed as the leading copper-containing cations. Likewise, polynuclear copper clusters observed in the anionESI spectra support partial aggregation occurring in solution. The gas-phase studies clearly support theconclusions that (i) DMF is a highly preferred ligand for CuII in comparison to water and that (ii) DMFsupports ion association for which the mass spectrometric data suggest the formation of polynuclear copperclusters.