TY - JOUR
T1 - Characterization of a New Electron Donor-Acceptor Dyad in Conventional Solvents and Ionic Liquids
AU - Saladin, Marissa
AU - Rumble, Christopher A.
AU - Wagle, Durgesh V.
AU - Baker, Gary A.
AU - Maroncelli, Mark
N1 - Funding Information:
We thank Danny Sykes for help with the attempts to quantify impurities in dyad samples using high-performance liquid chromatography. This work was supported by grants from the U.S. Department of Energy, Office of Basic Sciences, Division of Chemical Sciences, Geosciences, and Biosciences under contract nos. DE-SC0008640 and DE-SC0019200 (M.M.) and by the Research Corporation for Science Advancement (G.A.B.).
Publisher Copyright:
© 2019 American Chemical Society.
PY - 2019/11/7
Y1 - 2019/11/7
N2 - Ionic liquids are being tested as potential replacements for current electrolytes in energy-related applications. Electron transfer (ET) plays a central role in these applications, making it essential to understand how ET in ionic liquids differs from ET in conventional organic solvents and how these differences affect reaction kinetics. A new intramolecular electron donor-acceptor probe was synthesized by covalently linking the popular photoacceptor coumarin 152 with the donor dimethylaniline to create the dyad "C152-DMA" for potential use in probing dynamical solvent effects in ionic liquids. Molecular dynamics simulations of this dyad show the considerable conformational flexibility of the linker group but over a range of geometries in which the ET rate parameters vary little and should have minimal effect on reaction times >100 ps. Steady-state and time-resolved fluorescence methods show the spectra of C152-DMA to be highly responsive to solvent polarity, with ET rates varying over the range of 108 to 1012 s-1 between nonpolar and high-polarity conventional solvents. The sensitivity to hydrolysis in the presence of acidic impurities limits the dyad's use to ionic liquids of high purity. The results in the few ionic liquids examined here suggest that in addition to solvent polarity, electron transfer in C152-DMA also depends on solvent fluidity or solvation times.
AB - Ionic liquids are being tested as potential replacements for current electrolytes in energy-related applications. Electron transfer (ET) plays a central role in these applications, making it essential to understand how ET in ionic liquids differs from ET in conventional organic solvents and how these differences affect reaction kinetics. A new intramolecular electron donor-acceptor probe was synthesized by covalently linking the popular photoacceptor coumarin 152 with the donor dimethylaniline to create the dyad "C152-DMA" for potential use in probing dynamical solvent effects in ionic liquids. Molecular dynamics simulations of this dyad show the considerable conformational flexibility of the linker group but over a range of geometries in which the ET rate parameters vary little and should have minimal effect on reaction times >100 ps. Steady-state and time-resolved fluorescence methods show the spectra of C152-DMA to be highly responsive to solvent polarity, with ET rates varying over the range of 108 to 1012 s-1 between nonpolar and high-polarity conventional solvents. The sensitivity to hydrolysis in the presence of acidic impurities limits the dyad's use to ionic liquids of high purity. The results in the few ionic liquids examined here suggest that in addition to solvent polarity, electron transfer in C152-DMA also depends on solvent fluidity or solvation times.
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U2 - 10.1021/acs.jpcb.9b07077
DO - 10.1021/acs.jpcb.9b07077
M3 - Article
C2 - 31596593
AN - SCOPUS:85074397260
SN - 1520-6106
VL - 123
SP - 9395
EP - 9407
JO - Journal of Physical Chemistry B
JF - Journal of Physical Chemistry B
IS - 44
ER -