Barnhard Lang, Gonzalo Angulo, and Eric Vauthey Ultrafast Solvation Dynamics of Coumarin 153 in Imidazolium-Based Ionic Liquids Barnhard Lang, Gonzalo Angulo, and Eric Vauthey J.Phys.Chem.A 2006, 110. 7028-7034 300文字/分 Miyasaka Lab. Masayasu Muramatsu

Contents Introduction Experimental Results & discussion Summary Room-Temperature Ionic Liquids Solvation dynamics Experimental Fluorescence up-conversion Three-pulse photon-echo peak-shift Results & discussion Summary [cnpmim]+ [Tf2N]- This slide show then ,after

Room-Temperature Ionic Liquids Room-temperature ionic liquids (RTILs) are organic molten salts Ultralow volatility:揮発性 Flameproof Electrochemical stability High viscosity Application for the Electron Microscope emim（CF3SO2）2N SEM:scanning electron microscope Ionic liquid Star sand SEM image http://www.tuat.ac.jp/~ohno/lab/ionic_liquid/IL.html left:with RTIL right:bulk http://www.chem.eng.osaka-u.ac.jp/~elechem/Research.htm

Solvation dynamics Solvation in conventional liquids Stabilization hν 通常の有機溶媒 hν hν Stabilization Exited state Ground state strongly solvated

Solvation dynamics Solvation in ionic liquids hν emission ○:anion Dynamic Stokes-shift Solvation hν emission Solvation in ionic liquids ○:anion ●:cation

Fluorescence up-conversion sample BBO ωe ωf ωg ωs delay mono chr. PMT ωｓ= ωｆ＋ωｇ Exitation Gate Intensity time delay Excitation pulse : ωe Fluorescence : ωf Gate pulse : ωg Sum frequency : ωs= ωf+ ωg BBO:β-BaB2O4 monochr:モノクロメーター（分光器） PMT:光電子増倍管 Photomultiplier tubes

Three-pulse photon-echo peak-shift ―:-k1+k2+k3 ―: k1-k2+k3 T　→　large pulse1 makes the coherence of polarization. pulse2 interferes with pulse1 indeced polarization. pulse3 is diffracted as the signal. Tが長くなると書き込んだ情報の劣化によってピークシフトが小さくなる τ’　→　small τ=0：Transient Grating 　　　　　→ 　no echo τ≫0：decoherent　　　　　　　　 → 　no echo T≫0：vanish diffraction fringe　 → 　no echo 3PEPS results τ’　vs　T 干渉縞

Fluorescence up-conversion [pmim]+ [cnpmim]+ [Tf2N]- Coumarin153 in[cnpmim+][Tf2N-] and[pmim+][BF4-] Steady-state absorption and emission spectra Excitation : 400nm Response function : 230fs Dynamic red shift Red : rise Blue : decay Fluorescence time profiles

Fluorescence up-conversion Dynamic red shift Missing red shift 4600cm-1 Reconstructed time-dependent emission spectra 600cm-1 500cm-1 Too small peak shift change 　→　ultrafast component? Time dependence of the emission band maximum

Three-pulse photon-echo peak-shift in ionic liquid in ehtanol molecular vibration inertial part 3PEPS results 溶媒の平均自由行程内 分子振動 Indocyanine green in[cnpmim+][Tf2N-] and ethanol Excitation : 800nm Pulse duration : 15fs Differ from Stokes-shift measurements 全体の形は似ている　200fs,400fsあたりに分子振動によるビートが見える　RTIL中 では高いところから始まり、減衰が遅い Inertial part: Signal starts at a higher level and decays slower in ionic liquids

Summary The dynamic Stokes shift of coumarin 153 in Room temperature ionic liquids(RTILs) has been measured using fluorescence up-conversion techniques with a response function of 230fs. Three-pulse photon-echo peak-shift(3PEPS) experiments on indocyanine green in RTILs has been measured. Ultrafast solvation in RTILs which could not be observed by fluorescence up-conversion was suggested from 3PEPS results. Improved 3PEPS may find farther information.

conventional solvents My experiment ―[bmim+][Tf2N-] ―[hmim+][Tf2N-] ―MeOH [bmim+] [Tf2N-] [hmim+] ox4 Cr:F 長時間領域　拡散と関係 Oxazine4 conventional solvents RTILs

Time-zero estimation approximation t t=0 Time-zero Apolar