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Cyclic Voltammetric Studies on [SMo 12 O 40 ] 2– and [SMo 12 O 40 ] 3– at Macrodisk Electrodes in Acetonitrile With and Without Added Supporting Electrolyte
Author(s) -
Bond Alan M.,
Coomber Darren C.,
Harika Rita,
Hultgren Victoria M.,
Rooney Melissa B.,
Vu Truc,
Wedd Anthony G.
Publication year - 2001
Publication title -
electroanalysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.574
H-Index - 128
eISSN - 1521-4109
pISSN - 1040-0397
DOI - 10.1002/1521-4109(200112)13:18<1475::aid-elan1475>3.0.co;2-f
Subject(s) - electrolyte , acetonitrile , cyclic voltammetry , electrochemistry , supporting electrolyte , chemistry , inorganic chemistry , voltammetry , quartz crystal microbalance , precipitation , electrode , diffusion , solvent , chromatography , adsorption , organic chemistry , physics , meteorology , thermodynamics
The polyoxomolybdate [(C 6 H 13 ) 4 N] 2 [SMo 12 O 40 ] while soluble in acetonitrile (>2.5 g L −1 ) precipitates from this solvent when tetraalkylammonium salts are added as the supporting electrolyte at the usual 0.1 M concentration levels used in electrochemical investigations. Although conventional conditions cannot be used, this study demonstrates that application of cyclic voltammetry in the absence of added supporting electrolyte is viable for studies on the [SMo 12 O 40 ] 2–/3– and [SMo 12 O 40 ] 3–/4– reduction processes. Thus, there is excellent agreement between voltammetric experiments and theory based on mass transport by both migration and diffusion, after problems associated with Ohmic drop are overcome by incorporation of the uncompensated resistance into the theory. Unlike the [SMo 12 O 40 ] 2– salts, tetralkylammonium salts of [SMo 12 O 40 ] 3– are soluble in acetonitrile even in the presence of added supporting electrolyte. Consequently, the oxidation of [SMo 12 O 40 ] 3– to [SMo 12 O 40 ] 2– in the presence of 0.1 M (C 6 H 13 ) 4 NClO 4 electrolyte has been examined by both cyclic voltammetry and electrochemical quartz crystal microbalance methods. As a result of the insolubility of [SMo 12 O 40 ] 2– in the presence of added supporting electrolyte, electrolytic production of this species under conventional conditions generates a precipitation process. The resulting complexities are avoided by employing high scan rates that outrun the precipitation process, or by studying the oxidation process in the absence of supporting electrolyte.