TY - JOUR

T1 - Time-Resolved Electron Paramagnetic Resonance Study of Photoexcited Fullerenes in Ionic Liquids

AU - Kurganskii, Ivan V.

AU - Ivanov, Mikhail Yu

AU - Fedin, Matvey V.

N1 - Publisher Copyright: © 2018 American Chemical Society.

PY - 2018/7/5

Y1 - 2018/7/5

N2 - Molecular-level properties of ionic liquids (ILs) draw an increasing interest. Several informative experimental approaches for investigation of nano/miscrostructuring phenomena and local viscosity/rigidity of ILs use probe molecules sensitive to microenvironment along with suitable detection techniques. In this work, we for the first time investigate capabilities of photoexcited triplet fullerenes to probe local properties of ILs, with time-resolved electron paramagnetic resonance (TR EPR) being a sensitive detection tool. We have selected C60 and its derivative phenyl-C61-butyric acid methyl ester (PCBM) as probes and ILs [Bmim]BF4 and [C10mim]BF4 as solvents. C60 and PCBM demonstrate different sensitivities to microenvironment in ILs. Spin dynamics of photoexcited C60 is strongly contributed by pseudorotation of the Jahn-Teller axis, making its use as a probe for microenvironment challenging. This behavior is strongly suppressed in PCBM, which, in addition, is more soluble in ILs than C60. The in-depth analysis of variableerature two-dimensional TR EPR data shows that spectral shapes are sensitive to the restricted mobility of PCBM in ILs. In this way, the information on local environment and heterogeneities in ILs can be obtained by TR EPR. PCBM usefully complements the other spin probes previously implemented for EPR studies in ILs. It is larger in size and in addition allows high-sensitivity TR EPR measurements up to a room temperature, which is an important improvement for characterization of heterogeneities in roomerature ILs.

AB - Molecular-level properties of ionic liquids (ILs) draw an increasing interest. Several informative experimental approaches for investigation of nano/miscrostructuring phenomena and local viscosity/rigidity of ILs use probe molecules sensitive to microenvironment along with suitable detection techniques. In this work, we for the first time investigate capabilities of photoexcited triplet fullerenes to probe local properties of ILs, with time-resolved electron paramagnetic resonance (TR EPR) being a sensitive detection tool. We have selected C60 and its derivative phenyl-C61-butyric acid methyl ester (PCBM) as probes and ILs [Bmim]BF4 and [C10mim]BF4 as solvents. C60 and PCBM demonstrate different sensitivities to microenvironment in ILs. Spin dynamics of photoexcited C60 is strongly contributed by pseudorotation of the Jahn-Teller axis, making its use as a probe for microenvironment challenging. This behavior is strongly suppressed in PCBM, which, in addition, is more soluble in ILs than C60. The in-depth analysis of variableerature two-dimensional TR EPR data shows that spectral shapes are sensitive to the restricted mobility of PCBM in ILs. In this way, the information on local environment and heterogeneities in ILs can be obtained by TR EPR. PCBM usefully complements the other spin probes previously implemented for EPR studies in ILs. It is larger in size and in addition allows high-sensitivity TR EPR measurements up to a room temperature, which is an important improvement for characterization of heterogeneities in roomerature ILs.

KW - EXCITED TRIPLET-STATE

KW - SPIN PROBES

KW - SPATIAL HETEROGENEITY

KW - EPR

KW - DYNAMICS

KW - C-60

KW - SPECTROSCOPY

KW - MIXTURES

KW - SOLVENTS

KW - PSEUDOROTATION

UR - http://www.scopus.com/inward/record.url?scp=85048516365&partnerID=8YFLogxK

U2 - 10.1021/acs.jpcb.8b04000

DO - 10.1021/acs.jpcb.8b04000

M3 - Article

C2 - 29894190

AN - SCOPUS:85048516365

VL - 122

SP - 6815

EP - 6822

JO - Journal of Physical Chemistry B

JF - Journal of Physical Chemistry B

SN - 1520-6106

IS - 26

ER -