Abstract
Molecular conformational reorganization following photon absorption is a fundamental process driving reactions such as the cis–trans isomerization at the heart of the primary step of vision and can be exploited for switching in artificial systems using photochromics. In general, conformational change occurs on a timescale defined by the energy of the main vibrational mode and the rate of energy dissipation. Typically, for a conformational change such as a twist around the backbone of a conjugated molecule, this occurs on the tens of picoseconds timescale. However, here we demonstrate experimentally that in certain circumstances the molecule, in this case an oligofluorene, can change conformation over two orders of magnitude faster (that is sub-100 fs) in a manner analogous to inertial solvent reorganization demonstrated in the 1990s. Theoretical simulations demonstrate that non-adiabatic transitions during internal conversion can efficiently convert electronic potential energy into torsional kinetic energy, providing the ‘kick’ that prompts sub-100 fs torsional reorganization.
This is a preview of subscription content, access via your institution
Access options
Subscribe to this journal
Receive 12 print issues and online access
$209.00 per year
only $17.42 per issue
Buy this article
- Purchase on Springer Link
- Instant access to full article PDF
Prices may be subject to local taxes which are calculated during checkout
Similar content being viewed by others
References
Clark, J. & Lanzani, G. Organic photonics for communications. Nature Photon. 4, 438–446 (2010.).
Yap, B. K., Xia, R. D., Campoy-Quiles, M., Stavrinou, P. N. & Bradley, D. D. C. Simultaneous optimization of charge-carrier mobility and optical gain in semiconducting polymer films. Nature Mater. 7, 376–380 (2008).
Virgili, T., Marinotto, D., Manzoni, C., Cerullo, G. & Lanzani, G. Ultrafast intrachain photoexcitation of polymeric semiconductors. Phys. Rev. Lett. 94, 117402 (2005).
Vishnubhatla, K. C., Clark, J., Lanzani, G., Ramponi, R., Osellame, R. & Virgili, T. Ultrafast optofluidic gain switch based on conjugated polymer in femtosecond laser fabricated microchannels. Appl. Phys. Lett. 94, 041123 (2009).
Virgili, T. et al. Ultrafast optical gain switch in organic photonic devices. J. Mater. Chem. 20, 519–523 (2010).
Kabra, D., Lu, L. P., Song, M. H., Snaith, H. J. & Friend, R. H. Efficient single-layer polymer light-emitting diodes. Adv. Mater. 22, 3194–3198 (2010).
Barlow, I. A., Kreouzis, T. & Lidzey, D. G. High-speed electroluminescence modulation of a conjugated-polymer light emitting diode. Appl. Phys. Lett. 94, 243301 (2009).
McNeill, C. R. & Greenham, N. C. Conjugated-polymer blends for optoelectronics. Adv. Mater. 21, 3840–3850 (2009).
Clarke, T. M. & Durrant, J. R. Charge photogeneration in organic solar cells. Chem. Rev. 110, 6736–6767 (2010).
Sakanoue, T. & Sirringhaus, H. Band-like temperature dependence of mobility in a solution-processed organic semiconductor. Nature Mater. 9, 736–740 (2010).
Spano, F. C. & Silvestri, L. Multiple mode exciton-vibrational coupling in h-aggregates: synergistic enhancement of the quantum yield. J. Chem. Phys. 132, 094704 (2010).
Kukura, P., McCamant, D. W., Yoon, S., Wandschneider, D. B. & Mathies, R. A. Structural observation of the primary isomerization in vision with femtosecond-stimulated Raman. Science 310, 1006–1009 (2005).
Tamai, N. & Miyasaka, H. Ultrafast dynamics of photochromic systems. Chem. Rev. 100, 1875–1890 (2000).
Franck, J. Elementary processes of photochemical reactions. Trans. Faraday Soc. 21, 536–542 (1926).
Condon, E. A theory of intensity distribution in band systems. Phys. Rev. 28, 1182–1201 (1926).
Lanzani, G., Nisoli, M., DeSilvestri, S. & Tubino, R. Femtosecond vibrational and torsional energy redistribution in photoexcited oligothiophenes. Chem. Phys. Lett. 251, 339–345 (1996).
Hintschich, S. I., Dias, F. B. & Monkman, A. P. Dynamics of conformational relaxation in photoexcited oligofluorenes and polyfluorene. Phys. Rev. B 74, 045210 (2006).
Justino, L. L. G. et al. Conformational studies of poly(9,9-dialkylfluorene)s in solution using NMR spectroscopy and density functional theory calculations. J. Phys. Chem. B 113, 11808–11821 (2009).
Chen, H. L. Excited-state backbone twisting of polyfluorene as detected from photothermal after-effects. J. Phys. Chem. B 113, 8527–8531 (2009).
Parkinson, P., Muller, C., Stingelin, N., Johnston, M. B. & Herz, L. M. Role of ultrafast torsional relaxation in the emission from polythiophene aggregates. J. Phys. Chem. Lett. 1, 2788–2792 (2010).
Prokhorenko, V. I. Coherent control of retinal isomerization in bacteriorhodopsin. Science 313, 1257–1261 (2006).
Tretiak, S., Saxena, A., Martin, R. L. & Bishop, A. R. Conformational dynamics of photoexcited conjugated molecules. Phys. Rev. Lett. 89, 097407 (2002).
Wu, C., Malinin, S. V., Tretiak, S. & Chernyak, V. Y. Exciton scattering and localization in branched dendrimeric structures. Nature Phys. 2, 631–635 (2006).
Karabunarliev, S., Bittner, E. R. & Baumgarten, M. Franck–Condon spectra and electron-libration coupling in para-polyphenyls. J. Chem. Phys. 114, 5863–5870 (2001).
Karabunarliev, S., Baumgarten, M., Bittner, E. R. & Mullen, K. Rigorous Franck-Condon absorption and emission spectra of conjugated oligomers from quantum chemistry. J. Chem. Phys. 113, 11372–11381 (2000).
Clark, J. et al. Blue polymer optical fiber amplifiers based on conjugated fluorene oligomers. J. Nanophoton. 2, 023504 (2008.).
Hayes, S. C. & Silva, C. Analysis of the excited-state absorption spectral bandshape of oligofluorenes. J. Chem. Phys. 132, 214510 (2010).
Franco, I. & Tretiak, S. Electron-vibrational dynamics of photoexcited polyfluorenes. J. Am. Chem. Soc. 126, 12130–12140 (2004).
Westenhoff, S. et al. Anomalous energy transfer dynamics due to torsional relaxation in a conjugated polymer. Phys. Rev. Lett. 97, 166804 (2006).
Fratiloiu, S. et al. Electronic structure and optical properties of charged oligofluorenes studied by VIS/NIR spectroscopy and time-dependent density functional theory. J. Phys. Chem. B 110, 5984–5993 (2006).
Virgili, T., Marinotto, D., Lanzani, G. & Bradley, D. D. C. Ultrafast resonant optical switching in isolated polyfluorenes chains. Appl. Phys. Lett. 86, 091113 (2005).
Tong, M., Sheng, C. X. & Vardeny, Z. V. Nonlinear optical spectroscopy of excited states in polyfluorene. Phys. Rev. B 75, 125207 (2007).
Zhang, X. P., Xia, Y. J. & Friend, R. H. Multiphoton excited photoconductivity in polyfluorene. Phys. Rev. B 75, 245128 (2007).
Kohler, A. et al. Charge separation in localized and delocalized electronic states in polymeric semiconductors. Nature 392, 903–906 (1998).
Nelson, T., Fernandez-Alberti, S., Chernyak, V., Roitberg, A. E. & Tretiak, S. Nonadiabatic excited-state molecular dynamics modeling of photoinduced dynamics in conjugated molecules. J. Phys. Chem. B 115, 5402–5414 (2011).
Fernandez-Alberti, S., Kleiman, V. D., Tretiak, S. & Roitberg, A. E. Unidirectional energy transfer in conjugated molecules: The crucial role of high-frequency C≡C bonds. J. Phys. Chem. Lett. 1, 2699–2704 (2010).
Tully, J. C. & Preston, R. K. Trajectory surface hopping approach to nonadiabatic molecular collisions—reaction of H+ with D2 . J. Chem. Phys. 55, 562–572 (1971).
Tully, J. C. Molecular-dynamics with electronic-transitions. J. Chem. Phys. 93, 1061–1071 (1990).
Rosenthal, S. J., Xie, X. & Fleming, G. R. Femtosecond solvation dynamics in acetonitrile: Observation of the inertial contribution to the solvent response. J. Chem. Phys. 95, 4715–4718 (1991).
Stratt, M. R. & Cho, M. The short-time dynamics of solvation. J. Chem. Phys. 9, 6700–6708 (1994).
Jimenez, R., Fleming, G. R., Kumar, P. V. & Maroncelli, M. Femtosecond solvation dynamics of water. Nature 369, 471–473 (1994).
Elich, K., Kitazawa, M., Okada, T. & Wortmann, R. Effect of s-1 torsional dynamics on the time-resolved fluorescence spectra of 9,9’-bianthryl in solution. J. Phys. Chem. A 101, 2010–2015 (1997).
Jurczok, M., Plaza, P., Martin, M. M., Meyer, Y. H. & Rettig, W. Excited state relaxation paths in 9,9’-bianthryl and 9-carbazolyl-anthracene: A sub-ps transient absorption study. Chem. Phys. 253, 339–349 (2000).
Miller, R. J. D. ‘Making the molecular movie’: First frames. Acta Crystallogr. A 66, 137–156 (2010).
Shoenlein, R. W., Peteanu, L. A., Mathies, R. A. & Shank, C. V. The 1st step in vision—femtosecond isomerization of rhodopsin. Science 254, 412–415 (1991).
Polli, D. et al. Conical intersection dynamics of the primary photoisomerization event in vision. Nature 467, 440–U88 (2010).
Brida, D. et al. Few-optical-cycle pulses tunable from the visible to the mid-infrared by optical parametric amplifiers. J. Opt. 12, 013001 (2010).
Allen, M. P. & Tildesley, D. J. Computer Simulation of Liquids (Oxford Univ. Press, 1990).
Acknowledgements
We thank S. Fernandez-Alberti for stimulating discussions and for help with the code for the non-adiabatic simulations. J.C. acknowledges the Royal Society for a Dorothy Hodgkin Fellowship. We also acknowledge support of the Center for Integrated Nanotechnology (CINT), the Center for Nonlinear Studies (CNLS) and the LDRD programme at Los Alamos National Laboratory, operated by Los Alamos National Security, LLC, for the National Nuclear Security Administration of the US Department of Energy under contract DE-AC52-06NA25396, as well as the European Union for financial support through FP6-026365.
Author information
Authors and Affiliations
Contributions
J.C. and G.L. devised the experiments, J.C. and G.C. carried out the experiments and J.C. and G.L. analysed the data. S.T. and T.N. carried out the calculations that were devised by S.T. J.C., G.L., S.T. and T.N. wrote the paper.
Corresponding author
Ethics declarations
Competing interests
The authors declare no competing financial interests.
Supplementary information
Supplementary Information
Supplementary Information (PDF 884 kb)
Rights and permissions
About this article
Cite this article
Clark, J., Nelson, T., Tretiak, S. et al. Femtosecond torsional relaxation. Nature Phys 8, 225–231 (2012). https://doi.org/10.1038/nphys2210
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1038/nphys2210
This article is cited by
-
Sub-10-fs observation of bound exciton formation in organic optoelectronic devices
Nature Communications (2022)
-
Structural distortion and electron redistribution in dual-emitting gold nanoclusters
Nature Communications (2020)
-
Coherent exciton-vibrational dynamics and energy transfer in conjugated organics
Nature Communications (2018)
-
Ultraslow isomerization in photoexcited gas-phase carbon cluster \({{\rm C}}_{10}^ -\)
Nature Communications (2018)
-
Restoring electronic coherence/decoherence for a trajectory-based nonadiabatic molecular dynamics
Scientific Reports (2016)