Miyasaka laboratory Satoe Morishima

1. Measurements of the Complete Solvation Response in Ionic LiquidSergei Arzhantsev, Hui Jin, Gary A. Baker, and Mark MaroncelliJ. phys. Chem. B 2007,111, 4978-4989 Miyasaka laboratory Satoe Morishima

2. Contents Introduction -Ionic liquid as a solvent - Photo-induced solvation dynamics Femtosecond~nanosecond - Dynamic Stokes shift Results and Discussion -Kerr-gated emission (KGE) -Time-correlated single photon counting (TCSPC) -Results of time-resolved spectroscopy -Solvation “Mechanism” Conclusion -Bi-phasic solvation dynamics was observed.

3. Introduction Experiment Results & Discussion Conclusion 1-ethyl-3-methylimidazolium （emim+） bis(trifluoromethylsulfonyl)imide （TFSI-） Ionic Liquid A molten salt at room temperature constituted from anion and cation. Ionic liquid is spotlighted as a new type of solvent. Example emimTFSI (m.p. -16℃) NaCl (m.p. 800℃) S. Hayashi & h.Hamaguchi, Chem. Lett. 33, 1590-1591 (2004)

4. Introduction Experiment Results & Discussion Conclusion Electric conductivity Vapor pressure nearly 0 Hard to burn High viscosity Biochemistry application Energy device material Green chemistry rotation diffusion : dipole Solvent Influence The solvation (溶媒和) structure and molecular dynamics of ILs can be different from that of ordinary solvent.

5. Introduction Experiment Results & Discussion Conclusion Wavelength (m) 10-10 10-8 10-6 10-5 10-2 Photo-Excitation at UV-Vis Region Electro magnetic spectrum LUMO X-rays HOMO Ultraviolet Rays electronic excitation Ground state Excited state visible infrared IR spectroscopy vibration Micro waves Rotation

6. Introduction Experiment Results & Discussion Conclusion Excited state time Blue Red hn Energy relaxation time Ground state Detection of Dynamic Stokes Shift Time-resolved spectroscopycan directly observesolvationdynamics ! Time-scale of solvation in IL: Femtosecond~nanosecond

7. Introduction Experiment Results & Discussion Conclusion (ps) 0.1 1 10 100 1000 KGE TCSPC Instrumental Time-Resoluton Time-correlated single photon counting (TCSPC) : >20 ps Picosecond: Roughly 50% of the solvation response is too rapid to be observed by TCSPC　･･･ Femtosecond: Kerr-gated emission (KEG) ~450 fs KGE + TCSPC technique may give us complete solvation

8. Experiment Introduction Results & Discussion Conclusion Counts time Time-correlated single photon countingTCSPC Laser pulse t t’ photon 125 ns Light source: Ti: Sapphire laser(SHG) Exciting λ: 390 nm System response time： ~36 ps （FWHM） Step size: 4 ps temperature： 295K

9. Experiment Introduction Results & Discussion Conclusion Kerr-gated emissionKGE KGE set up

10. Experiment Introduction Results & Discussion Conclusion benzene benzene Kerr-gated emissionKGE 2 Kerr-Gate

11. Experiment Introduction Results & Discussion Conclusion Sample Solvatochromic probe : Trans-4-dimethylamino-4’-cyanostilbene

12. Results & discussion Introduction Experiment Conclusion Time-resolved emission spectra of DCS in [Im41+] [BF4-] hn time Results of KGE+TCSPC time Peak shift ☞ solvation Fast (fs) and slow (ps~ns)

13. Results & discussion Introduction Experiment Conclusion Emission peak shift Bi-phasic Solvation Function Sub-ps component: t1：100 ~ 700 fs (~20 %) Dominant slower component t2：80 ps ~ 3.0 ns (~80 %) b ： 0.3~0.5

14. Results & discussion Introduction Experiment Conclusion Sub-picosecond component m : Reduced mass(換算質量) (R+ + R- ) : Sum of van der Waals radii There is a reasonable correlation of both f1 and t1 with 1/{m±(R++ R-)}1/2

15. Results & discussion Introduction Experiment Conclusion pico~nanosecond component Time scale of slower component is not directly proportional to viscosity h but rather to hp (p≈1.2 – 1.3) D=kT / 6phr Slow components associate with diffusion??

16. conclusion Introduction Experiment Results & Discussion Conclusion Author have presented KGE+TCSPC measurements of the complete solvation response in six ionic liquids using the probe DCS Observed response functions were found to be biphasic, consisting of a sub-picosecond component associated with inertial solvent motion And a dominant “slow” component which is correlated to the solvent viscosity.