Shedding Light on the Photoisomerization Pathway of Donor-Acceptor Stenhouse Adducts

Year: 2017

Authors: Di Donato M., Lerch M.M., Lapini A., Laurent A.D., Iagatti A., Bussotti L., Ihrig S.P., Medved M., Jacquemin D., Szymanski W., Buma W.J., Foggi P., Feringa B.L.

Autors Affiliation: Centre for Systems Chemistry, Stratingh Institute for Chemistry, University of Groningen, Nijenborgh 4, Groningen, 9747 AG, Netherlands; Department of Radiology, University of Groningen, University Medical Center Groningen, Hanzeplein 1, Groningen, 9713 GZ, Netherlands; European Laboratory for Non Linear Spectroscopy (LENS), via N. Carrara 1, Sesto Fiorentino, 50019, Italy; Istituto Nazionale di Ottica, Largo Fermi 6, Firenze, 50125, Italy; Dipartimento di Chimica Ugo Schiff, Università di Firenze, via della Lastruccia 13, Sesto Fiorentino, 50019, Italy; Dipartimento di Chimica, Università di Perugia, via Elce di Sotto 8, Perugia, 06100, Italy; CEISAM, UMR CNRS 6230, BP 92208, 2 Rue de la Houssinière, Nantes Cedex 3, 44322, France; Regional Centre of Advanced Technologies and Materials, Department of Physical Chemistry, Faculty of Science, Palacký University in Olomouc, 17. listopadu 1192/12, Olomouc, CZ-771 46, Czech Republic; Department of Chemistry, Faculty of Natural Sciences, Matej Bel University, Tajovského 40, Banská Bystrica, SK-97400, Slovakia; Institut Universitaire de France, 103 bd St Michael, Paris Cedex 5, 75005, France; Van’t Hoff Institute for Molecular Sciences, University of Amsterdam, Science Park 904, Amsterdam, 1098XH, Netherlands

Abstract: Donor-acceptor Stenhouse adducts (DASAs) are negative photochromes that hold great promise for a variety of applications. Key to optimizing their switching properties is a detailed understanding of the photoswitching mechanism, which, as yet, is absent. Here we characterize the actinic step of DASA-photoswitching and its key intermediate, which was studied using a combination of ultrafast visible and IR pump-probe spectroscopies and TD-DFT calculations. Comparison of the time-resolved IR spectra with DFT computations allowed to unambiguously identify the structure of the intermediate, confirming that light absorption induces a sequential reaction path in which a Z-E photoisomerization of C-2-C-3 is followed by a rotation around C-3-C-4 and a subsequent thermal cyclization step. First and second-generation DASAs share a common photoisomerization mechanism in chlorinated solvents with notable differences in kinetics and lifetimes of the excited states. The photogenerated intermediate of the second-generation DASA was photo-accumulated at low temperature and probed with time-resolved spectroscopy, demonstrating the photoreversibility of the isomerization process. Taken together, these results provide a detailed picture of the DASA isomerization pathway on a molecular level.


Volume: 139 (44)      Pages from: 15596  to: 15599

More Information: The authors gratefully acknowledge financial support from Laserlab-Europe (LENS002289), the Ministry of Education, Culture and Science (Gravitation program 024.001.035), The Netherlands Organization for Scientific Research (NWO-CW, Top grant to B.L.F., VIDI grant no. 723.014.001 for W.S.), the European Research Council (Advanced Investigator Grant, no. 227897 to B.L.F.), and the Royal Netherlands Academy of Arts and Sciences Science (KNAW). A.D.L., D.J., and M.M. thank the Campus France and the Slovak Research and Development Agency for supporting their long-standing collaboration in the framework of Stefanik PHC program (BridgET project, No. 35646SE and SK-FR-2015-0003, respectively), the Czech Science Foundation (project no. 16-01618S), and the Ministry of Education, Youth and Sports of the Czech Republic (grant LO1305). This research used computational resources of the GENCI-CINES/IDRIS, Centre de Calcul Intensif des Pays de Loire (CCIPL), a local Troy cluster, and the HPCC of the Matej Bel University in Banska Bystrica by using the infrastructure acquired in projects ITMS 26230120002 and 26210120002 supported by the Research and Development Operational Programme funded by the ERDF. The Swiss Study Foundation is acknowledged for a fellowship to M.M.L.
KeyWords: Cyclization; Electromagnetic wave absorption; Isomerization; Isomers; Laser spectroscopy; Light absorption; Temperature, Chlorinated solvent; IR pump-probe spectroscopy; Isomerization pathways; Sequential reaction; Switching properties; Td-dft calculations; Thermal cyclization; Time-resolved spectroscopy, Reaction intermediates, solvent, Article; chemical structure; chlorination; cyclization; density functional theory; donor acceptor Stenhouse adduct; infrared spectroscopy; isomerization; light absorption; low temperature; molecular dynamics; photochemistry; photoisomerization; rotation
DOI: 10.1021/jacs.7b09081

Citations: 87
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