Ion association and solvation in aqueous and non aqueous solutions of some metal(II) and metal(III) nitrates : a spectroscopic study

Collins, Bradley Mark (1992). Ion association and solvation in aqueous and non aqueous solutions of some metal(II) and metal(III) nitrates : a spectroscopic study PhD Thesis, School of Molecular and Microbial Sciences, The University of Queensland. doi:10.14264/uql.2015.642

       
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Author Collins, Bradley Mark
Thesis Title Ion association and solvation in aqueous and non aqueous solutions of some metal(II) and metal(III) nitrates : a spectroscopic study
School, Centre or Institute School of Molecular and Microbial Sciences
Institution The University of Queensland
DOI 10.14264/uql.2015.642
Publication date 1992
Thesis type PhD Thesis
Supervisor David W. James
John R. Hall
Rob Stranger
Total pages 192
Language eng
Subjects 03 Chemical Sciences
Formatted abstract
Ion association and solvation in the following systems has been probed using vibrational and multi nuclear magnetic resonance spectroscopies:
aqueous solutions of cadmium(II) nitrate, aqueous solutions of mercury(II) nitrate,
anhydrous ethanol solutions of cadmium(II) nitrate,
anhydrous N,N-Klimethyformamide solutions of cadmium(II) nitrate and
anhydrous N,N-dimethyformamide solutions of indium(III) nitrate.

Aqueous Solutions of Cadmium(II) Nitrate
Extensive and increasing ion association has been postulated for cadmium nitrate over the concentration range 0.5 to 6.4 m. The presence of two nitrate species, the "free" solvated nitrate and the contact ion pair, were suggested by the presence and behaviour of two bands under the non degenerate nitrate v1 profile in the Raman spectra. The presence and separation of four maxima in the degenerate nitrate v3 vibration profile were consistent with the postulated species. Two bands, corresponding to the nitrate v4 vibration, were observed in the Raman spectrum which are also consistent with ion association. NMR data was also consistent with the proposed association. Association quotients are reported.

From changes in the shape and position of the water vs vibration, an overall increase in solution structure, due to the presence of the cation, was observed with increasing salt concentration.

Aqueous Solutions of Mercury(II) Nitrate
Aqueous mercuric nitrate solutions exhibited ion association over the concentrations range 0.14 to 1.35 m. The amount of association increased with increasing salt concentration. Component band analysis of the Raman spectra of the nitrate v1, yielded two bands at 1033 and 1047 cm-1 The behaviour of these bands suggested the assignment of the 1033 and 1047 cm-1 bands to the contact ion pair and the "free" solvated nitrate, respectively. The assignments of these bands were assisted by consideration of the splitting of the nitrate v1, into two components and the presence and separation of four maxima in the nitrate v3 vibration profile. The behaviour of the NMR data was consistent with the proposed model. An association quotient is reported.

An overall increase in solution structure due to the cation with increasing salt concentration was indicated by the changes in the water vs vibration.

Anhydrous Ethanol Solutions of Cadmium(II) Nitrate
Over the concentration range 0.5 to 7.0 m, anhydrous ethanolic solutions of cadmium nitrate exhibited extensive ion association in solution. The presence of three nitrate species, the "free" solvated nitrate, the contact ion pair and the ion aggregate, were suggested by the presence and behaviour of three bands under the non degenerate nitrate v1 profile in the Raman spectra. Three bands appear in the infrared spectra of the nitrate v2 profile also suggesting the presence of the three nitrate species. The nitrate v3 and v4 profiles and the NMR data were supportive of the proposed species.

The changes in the vibration spectra and NMR spectra of ethanol were consistent with solvation of the cation through the oxygen of the alcohol group. The changes in the OH vs of ethanol implied an overall increase in solution structure with increasing salt concentration. The increase in structure has been attributed to the presence of the cation.

Anhydrous N.N-dimethyformamide Solutions of Cadmium(II) Nitrate
Extensive ion association was found for cadmium nitrate in DMF solution over the concentration range 0.5 to 4.0 m. Analysis of the nitrate v1 profile of the Raman spectra revealed the presence of three bands. These bands have been assigned to the "free" unsolvated nitrate, the monodentate contact ion pair and the bidentate contact ion pair. The splitting and position of the nitrate v3 and v4 vibrations supported ion association occurring. The presence of three nitrate species was reflected in the infrared spectra by the nitrate v2 profile possessing three maxima. The NMR data was consistent with ion association occurring. An association quotient is reported.

The nitrate ion was found to be unsolvated by DMF. All experimental evidence pointed to solvation of the cation through the oxygen of the carbonyl group. Two different types of solvation molecules were found. A solvation number of 5.7 was found for the cadmium(II) ion.

Anhydrous N.N-dimethyformamide Solutions of Indiumf(II) Nitrate
Indium nitrate exhibited considerable ion association in DMF solutions over a concentration range of 0.25 to 3.0 m. The extent of the ion association was moderated by the strong solvation of the cation by DMF. Component band analysis of the Raman spectra of the nitrate v1, showed the presence of two bands. These bands were assigned to the "free" unsolvated nitrate and the bidentate contact ion pair. At higher salt concentration the band assigned to the "free" nitrate broadened significantly suggesting the anion coming under the influence of the cation similar to that involved in a loose ion pair.

The rest of the vibrational data for the nitrate ion is consistent with ion association although there is the need for further studies to interpret the observed changes fully. The NMR data is consistent with ion association occurring. Association quotients are reported.

Solvation of the anion was not observed from the data. The cation was strongly solvated by DMF through the oxygen of the carbonyl group. All experimental evidence pointed toward this mode of solvation. A total solvation number of 7.0 was calculated for the indium(III) ion in the absence of ion pairing.
Keyword Nitrates -- Spectra
Solvation

Document type: Thesis
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