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Electronic decoupling approach to quantitative photoswitching in linear multiazobenzene architectures

  • A strategy to optimize the photoswitching efficiency of rigid, linear multiazobenzene constructs is presented. It consists of introducing large dihedral angles between azobenzene moieties linked via aryl-aryl connections in their para positions. Four bisazobenzenes exhibiting different dihedral angles as well as three single azobenzene reference compounds have been synthesized, and their switching behavior has been studied as well as experimentally and theoretically analyzed. As the dihedral angle between the two azobenzene units increases and consequently the electronic conjugation decreases, the photochromic characteristics improve, finally leading to individual azobenzene switches operating independently in the case of the perpendicular ortho,ortho,ortho',ortho'-tetramethyl biphenyl linker. The electronic decoupling leads to efficient separation of the absorption spectra of the involved switching states and hence by choosing the appropriate irradiation wavelength, an almost quantitative E -> Z photoisomerization up to 97% overallA strategy to optimize the photoswitching efficiency of rigid, linear multiazobenzene constructs is presented. It consists of introducing large dihedral angles between azobenzene moieties linked via aryl-aryl connections in their para positions. Four bisazobenzenes exhibiting different dihedral angles as well as three single azobenzene reference compounds have been synthesized, and their switching behavior has been studied as well as experimentally and theoretically analyzed. As the dihedral angle between the two azobenzene units increases and consequently the electronic conjugation decreases, the photochromic characteristics improve, finally leading to individual azobenzene switches operating independently in the case of the perpendicular ortho,ortho,ortho',ortho'-tetramethyl biphenyl linker. The electronic decoupling leads to efficient separation of the absorption spectra of the involved switching states and hence by choosing the appropriate irradiation wavelength, an almost quantitative E -> Z photoisomerization up to 97% overall Z-content can be achieved. In addition, thermal Z -> E isomerization processes become independent of each other with increasing decoupling. The electronic decoupling could furthermore be proven by electrochemistry. The experimental data are supported by theory, and calculations additionally provide mechanistic insight into the preferred pathway for the thermal Z,Z -> Z,E -> E,E isomerization via inversion on the inner N-atoms. Our decoupling approach outlined herein provides the basis for constructing rigid rod architectures composed of multiple azobenzene photochromes, which display practically quantitative photoswitching properties, a necessary prerequisite to achieve highly efficient transduction of light energy directly into motion.show moreshow less

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Metadaten
Author:David BlegerORCiD, Jadranka Dokic, Maike V. Peters, Lutz Grubert, Peter SaalfrankORCiDGND, Stefan Hecht
DOI:https://doi.org/10.1021/jp2044114
ISSN:1520-6106 (print)
Parent Title (English):The journal of physical chemistry : B, Condensed matter, materials, surfaces, interfaces & biophysical chemistry
Publisher:American Chemical Society
Place of publication:Washington
Document Type:Article
Language:English
Year of first Publication:2011
Year of Completion:2011
Release Date:2017/03/26
Volume:115
Issue:33
Pagenumber:11
First Page:9930
Last Page:9940
Funder:German Research Foundation (DFG) [SFB 658, B8, C2]
Organizational units:Mathematisch-Naturwissenschaftliche Fakultät / Institut für Chemie
Peer Review:Referiert