Eisuke Takeuchi Miyasaka Lab. Photoinduced Electron Transfer in Bianthryl and derivatives in Ionic Liquid

Contents I.Introduction What is ionic liquid (IL)? Charge transfer (CT) of bianthryl derivatives. II.Motivation Effect of pre-solvation on CT dynamics. III.Experimental method Femtosecond transient absorption (TA) spectroscopy. IV.My work Comparison of symmetric and asymmetric bianthryl derivatives. V.Summary

What is ionic liquid (IL)? Ionic LiquidInorganic salt ex. NaCl Deme BF 4 m.p 9 ℃ m.p 800 ℃ Bmim TFSI m.p -4 ℃ Ionic Liquid :Molten organic salt at room temperature, which consists of organic cations and inorganic anions

Science 302, 792 (2003) S. Kuwabata, et al., Chem. Lett. 35, 600 (2006) SEM image of IL. IL does not vaporize even in vacuum. What is ionic liquid (IL)?  Electric conductivity  Vapor pressure: nearly 0  Hard to burn (fire resistant)  Heat-resistant  High viscosity etc… Application in various fields. Safe and sustainable solvent （ Green solvent ） Electrochemical device （ Electrolyte ） Lubricant

Organic solventIonic Liquid hυhυ : cation : anion CH 3 CN hυhυ δ+δ+δ-δ- Solvation Dynamics （溶媒和ダイナミク ス）

Charge transfer (CT) of bianthryl derivatives hυhυ Locally Excited (LE) state Charge Transfer (CT) state 9,9’-Bianthryl (BA)

LE emission 10-Cyano-9,9’-Bianthryl (CNBA) Solute of this experiment Electron withdrawing group According to quantum chemical calculations lowering CT state 0.25eV in comparison with BA M. Jurczok et al. Chemical Physics.. 256, (2000) 137- LE state hυhυ CT emission CT state energy solvation coordinate CNBA Charge transfer (CT) of bianthryl derivatives BA 0.25eV

Motivation Peculiarity of solvation coordinate and dynamics effect reactivity of solute polar molecule nonpolar molecule with a symmetric Pre - solvation different ? : cation : anion

Femtosecond transient absorption (TA) spectroscopy Transient Absorption ( 過渡吸収 )  t Sample Detector delay time pulse2 pulse1 delay time  t : several fs ~ 1 fs = s = seconds distance that light travels in 1s30 fs globe 7.5 times ( 300,000 km ) pylori bacteria 3 times ( 9 μm ) pulse-duration : 30 fs

My work Delay time Time constant: 0.063ps 672nm

My work Delay time - + δ-δ- δ+δ+ 720nm Time constant : 60ps

Compare BA BA 680nm Time constant CNBA : 0.063ps BA : 1.25ps

Time constant : 60ps Time constant: 0.063ps hυhυ * δ-δ- δ+δ+ - + My work LE state Grand state CT state Solvation (1.5ns)

Summary  Charge transfer in CNBA / Deme BF 4 is more faster than charge transfer by solvation and unaffected by solvation The ultrafast CT kinetics could be arising from the pre- solvation state caused by the polar nature of asymmetric CNBA, while for nonpolar symmetric BA, much drastic solvent reorganization is required.  LE state CT state LE state CT state CNBABA 0.5 kcal / mol K. Tominaga et al. J. Phys. Chem. 95, (1991) ≈ 0