Hexakis(2, 3, 6-tri-O-methyl)-α-cyclodextrin–I5− complex in aqueous I−/I3− thermocells and enhancement in the Seebeck coefficient. Issue 3 (6th November 2018)

• Record Type: Journal Article
• Authors: Liang, Yimin; Yamada, Teppei; Zhou, Hongyao; Kimizuka, Nobuo
• Is Part Of: Chemical science. Volume 10:Issue 3(2019)
• Page Start: 773
• Page End: 780
• Publication Date: 2018-11-06
• Subjects: Chemistry -- Periodicals; 540.5
• DOI: 10.1039/c8sc03821j
• Languages: English
• ISSNs: 2041-6520

Abstract

Abstract : Supramolecular thermocell composed of I − (yellow balls), I3 − (trio of red balls), I5 − (five connected dark red balls) and Me18 -α-CD (gray cone-shaped cylinder). Abstract : A large Seebeck coefficient ( S e ) of 1.9 mV K −1 was recorded for the I − /I3 − thermocell by utilizing the host-guest complexation of hexakis(2, 3, 6-tri- O -methyl)-α-cyclodextrin (Me18 -α-CD) with the oxidized iodide species. The thermocell measurement and UV-vis spectroscopy unveiled the formation of an Me18 -α-CD–pentaiodide (I5 − ) complex, which is in remarkable contrast to the triiodide complex α-CD–I3 − previously reported. Although the precipitation of the α-CD–I3 − complex in the presence of an electrolyte such as potassium chloride is a problem in thermocells, this issue was solved by using Me18 -α-CD as a host compound. The absence of precipitation in the Me18 -α-CD and I − /I3 − system containing potassium chloride not only improved the S e of the I − /I3 − thermocell, but also significantly enhanced the temporal stability of its power output. This is the first observation that I5 − species is formed in aqueous solution in a thermocell. Furthermore, the solution equilibrium of the redox couples was controlled by tuning the chemical structure of the host compounds. Thus, the integration of host-guest chemistry with redox couples extends the application of thermocells.