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Energy and Electron Transfer in Ethynylene Bridged Perylene Diimide Multichromophores

Energy and Electron Transfer in Ethynylene Bridged Perylene Diimide Multichromophores. Cristina Flors, Ingo Oesterling, Tobias Schnitzler, Eduard Fron, Gerd Schweitzer, Michel Sliwa, Andreas Herrmann, Mark van der Auweraer, Frans C. de Schryver, Klaus Mullen, and Johan Hofkens

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Energy and Electron Transfer in Ethynylene Bridged Perylene Diimide Multichromophores

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  1. Energy and Electron Transfer in Ethynylene Bridged Perylene Diimide Multichromophores Cristina Flors, Ingo Oesterling, Tobias Schnitzler, Eduard Fron, Gerd Schweitzer, Michel Sliwa, Andreas Herrmann, Mark van der Auweraer, Frans C. de Schryver, Klaus Mullen, and Johan Hofkens J.Phys.Chem.C. 2007, 111, 4861-4870 Kou ITOHMIYASAKA Lab.

  2. Contents ● Background ● Method– explanation of measurement technique time-resolved spectroscopy (ensemble) single-molecule spectroscopy ● Results and discussion Steady-state measurement Florescence decay measurement Femtosecond transient absorption spectroscopy Single-Molecule detection ● Conclusion

  3. light light pulse Background Novel photonic devices consisting of molecular systems ● single photon source ● artificial light-harvesting system etc. single photon source artificial light-harvesting system Single photon energy Chromophore : J.P.C.B.2004,108,16686-16696 J.A.C.S.2007,129,3539-3544

  4. Evaluation and understanding of the molecular photonic devices Ensemble measurements Single molecule measurements Dynamics, Efficiency of • Emission dynamics of individual molecular systems • Photon antibunching • Energy transfer • Electron transfer • Emission lifetime etc. • Ultra-high temporal resolution • Reliable average values Enables us to evaluate single nanoscale photonic devices Complementary use of bothmeasuring methods can give us comprehensive understanding of the nanoscale-molecular devices

  5. Method 1): ensemble time-resolved measurement S1 Charge separation count ① hν time/ns fluorescence Fluorescence decay S0 ② Pump light Delta A detector T Probe light sample Wavelength/nm Transient absorption spectra T: delay time

  6. Method 2): single-molecule spectroscopy imaging counts Time/ns Fluorescence decay Events Delay/ns coincidence counts Time/s Fluorescence intensity trajectory

  7. Molecular structure of PDI derivatives Ａ Perylene-3,4,9,10-tetracarboxdiimide (PDI) :bay area C ＰＤＩ０ B

  8. : Diphenylacetylene group(electron donor) Steady-state measurement in toluene Summery of the photophysical properties of Ａ－Ｃ in solution A: black B: red C: blue (in toluene) A in THF scheme Charge Separation S1 B S0

  9. Fluorescence decay measurement C(THF) A(THF) B(THF) C B nitrogen oxygen Ａ Fluorescence decay (time constant) Time-resolved fluorescence depolarization tF: 1.0 ns Electron transfer from a diphenylacetylene group tF ~ 2.8 ns Through-space electron transfer

  10. Femtosecond transient absorption spectroscopy ① PDI0 Lifetime Compound B 185ps S1 Radical anion 1.1ns (Slide 9) 1ns S0 Transient absorption spectra in THF of PDI0(A) And B(B) at 2(black),10(red),50(green),100(blue) 200(purple),and 400ps(brown).

  11. Summary of the ensemble measurements Electron Transfer ●Femtosecond transient absorptionmeasurement The dynamics of generation and decay about PDI radicalanion was revealed. (in more polar solvent)

  12. Single-Molecule measurement : Results① Beam splitter APD1 Channel A fluorescence Off time APD2 Channel B Single-molecule intensity trace of Ａ in PMMA Channel A (gray) and B (black) correspond to Polarization directions perpendicular in each other. 1:stepwise change→the emitting chromophoric site is changing with time. 2:fluctuating trace→intersystem crossing from singlet to triplet by oxygen 3:off time →　influence of charge separation

  13. ：Photon APD1 NL NL APD2 NC NC/NL~0.2 J.P.C.B2004,108,16686-16696 Jpn.J.Appl.Phys2007,46,268-270 Single-Molecule measurement(Coincidence) Fluorescence from the sample Repetition period~ 125ns sample APD1 APD2 Interphoton arrival time Single-photon emitting source 1 pulse → 1 photon Coincidence NC/NL = 1－( 1 / M ) Antibunching NC : number of central position NL : number of lateral positions M : number of photons / 1 pulse

  14. S1-S1 annihilation S1*+S1*→So+S1* Sｎ S１ S１ S０ S０ Single-Molecule measurement : results② Compound A Fluorescence trajectory of single-molecule (A) and fluctuation of Nc/NL ratio J.Phys,:.Condens.Matter.2007,19,445004

  15. Conclusion The authors synthesized a multichromophoric system as a candidate for single photon source and measured the property of the emission. Steady state and time-resolved ensemble measurement revealed that charge transfer can take place in the multi-chromophoric compound in relatively polar environment; polarity affects the emission property of compound A. The time-resolved measurement also suggested that energy-migration as well as the charge transfer. The efficient energy migration was confirmed by measuring the photon-antibunching of compound; the compound worked as “single photon emitter”.

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