Controlling two-step multimode switching of Dihydroazulene photoswitches

Anne Ugleholdt Petersen; Søren Lindbæk Broman; Stine Tetzschner Olsen; Anne Schou Hansen; Lin Du; Anders Kadziola; Thorsten Hansen; Henrik Grum Kjærgaard; Kurt Valentin Mikkelsen; Mogens Brøndsted Nielsen

doi:10.1002/chem.201405457

Controlling two-step multimode switching of Dihydroazulene photoswitches

Anne Ugleholdt Petersen, Søren Lindbæk Broman, Stine Tetzschner Olsen, Anne Schou Hansen, Lin Du, Anders Kadziola, Thorsten Hansen, Henrik Grum Kjærgaard, Kurt Valentin Mikkelsen, Mogens Brøndsted Nielsen

Department of Chemistry

24 Citations (Scopus)

Abstract

We present the synthesis and switching studies of systems with two photochromic dihydroazulene (DHA) units connected by a phenylene bridge at either para or meta positions, which correspond to a linear or cross-conjugated pathway between the photochromes. According to UV/Vis absorption and NMR spectroscopic measurements, the meta-phenylene-bridged DHA-DHA exhibited sequential light-induced ring openings of the two DHA units to their corresponding vinylheptafulvenes (VHFs). Initially, the VHF-DHA species was generated, and, ultimately, after continued irradiation, the VHF-VHF species. Studies in different solvents and quantum chemical calculations indicate that the excitation of DHA-VHF is no longer a local DHA excitation but a charge-transfer transition that involves the neighboring VHF unit. For the linearly conjugated para-phenylenebridged dimer, electronic communication between the two units is so efficient that the photoactivity is reduced for both the DHA-DHA and DHA-VHF species, and DHA-DHA, DHA-VHF, and VHF-VHF were all present during irradiation. In all, by changing the bridging unit, we can control the degree of stepwise photoswitching.

Original language	English
Journal	Chemistry: A European Journal
Volume	21
Issue number	10
Pages (from-to)	3968-3977
Number of pages	10
ISSN	0947-6539
DOIs	https://doi.org/10.1002/chem.201405457
Publication status	Published - 7 Oct 2014

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title = "Controlling two-step multimode switching of Dihydroazulene photoswitches",

abstract = "We present the synthesis and switching studies of systems with two photochromic dihydroazulene (DHA) units connected by a phenylene bridge at either para or meta positions, which correspond to a linear or cross-conjugated pathway between the photochromes. According to UV/Vis absorption and NMR spectroscopic measurements, the meta-phenylene-bridged DHA-DHA exhibited sequential light-induced ring openings of the two DHA units to their corresponding vinylheptafulvenes (VHFs). Initially, the VHF-DHA species was generated, and, ultimately, after continued irradiation, the VHF-VHF species. Studies in different solvents and quantum chemical calculations indicate that the excitation of DHA-VHF is no longer a local DHA excitation but a charge-transfer transition that involves the neighboring VHF unit. For the linearly conjugated para-phenylenebridged dimer, electronic communication between the two units is so efficient that the photoactivity is reduced for both the DHA-DHA and DHA-VHF species, and DHA-DHA, DHA-VHF, and VHF-VHF were all present during irradiation. In all, by changing the bridging unit, we can control the degree of stepwise photoswitching.",

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AU - Petersen, Anne Ugleholdt

AU - Broman, Søren Lindbæk

AU - Olsen, Stine Tetzschner

AU - Hansen, Anne Schou

AU - Du, Lin

AU - Kadziola, Anders

AU - Hansen, Thorsten

AU - Kjærgaard, Henrik Grum

AU - Mikkelsen, Kurt Valentin

AU - Nielsen, Mogens Brøndsted

N1 - The paper has received the Back Cover illustration

PY - 2014/10/7

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N2 - We present the synthesis and switching studies of systems with two photochromic dihydroazulene (DHA) units connected by a phenylene bridge at either para or meta positions, which correspond to a linear or cross-conjugated pathway between the photochromes. According to UV/Vis absorption and NMR spectroscopic measurements, the meta-phenylene-bridged DHA-DHA exhibited sequential light-induced ring openings of the two DHA units to their corresponding vinylheptafulvenes (VHFs). Initially, the VHF-DHA species was generated, and, ultimately, after continued irradiation, the VHF-VHF species. Studies in different solvents and quantum chemical calculations indicate that the excitation of DHA-VHF is no longer a local DHA excitation but a charge-transfer transition that involves the neighboring VHF unit. For the linearly conjugated para-phenylenebridged dimer, electronic communication between the two units is so efficient that the photoactivity is reduced for both the DHA-DHA and DHA-VHF species, and DHA-DHA, DHA-VHF, and VHF-VHF were all present during irradiation. In all, by changing the bridging unit, we can control the degree of stepwise photoswitching.

AB - We present the synthesis and switching studies of systems with two photochromic dihydroazulene (DHA) units connected by a phenylene bridge at either para or meta positions, which correspond to a linear or cross-conjugated pathway between the photochromes. According to UV/Vis absorption and NMR spectroscopic measurements, the meta-phenylene-bridged DHA-DHA exhibited sequential light-induced ring openings of the two DHA units to their corresponding vinylheptafulvenes (VHFs). Initially, the VHF-DHA species was generated, and, ultimately, after continued irradiation, the VHF-VHF species. Studies in different solvents and quantum chemical calculations indicate that the excitation of DHA-VHF is no longer a local DHA excitation but a charge-transfer transition that involves the neighboring VHF unit. For the linearly conjugated para-phenylenebridged dimer, electronic communication between the two units is so efficient that the photoactivity is reduced for both the DHA-DHA and DHA-VHF species, and DHA-DHA, DHA-VHF, and VHF-VHF were all present during irradiation. In all, by changing the bridging unit, we can control the degree of stepwise photoswitching.

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JO - Chemistry: A European Journal

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Controlling two-step multimode switching of Dihydroazulene photoswitches

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