A Bis(heptafulvenyl)-dicyanoethylene Thermoswitch with Two Sites for Ring Closure

Broman, Søren Lindbæk; Petersen, Anne Ugleholdt; Tortzen, Christian; Vibenholt, Johan; Bond, Andrew D.; Nielsen, Mogens Brøndsted

doi:10.1021/ol2030586

Cited by 16 publications

(23 citation statements)

References 13 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…All other attempts to perform this step by using oxidants such as DDQ (with or without p TsOH), m ‐ or p ‐chloranil, or tritylium tetrafluoroborate/Et 3 N proved fruitless, giving no reaction or leading to complete decomposition. Also, the previously reported procedure,14a in which two cycloheptatrienyls were incorporated into the structure with one of these functions acting as a leaving group (i.e., tropylium) in the subsequent oxidation step, failed. Thus, although the intermediate 7 was readily obtainable, it could not be converted into 3a .…”

Section: Resultsmentioning

confidence: 99%

Dihydroazulene/Vinylheptafulvene Photoswitch: Ultrafast Back Reaction Induced by Dihydronaphthalene Annulation

et al. 2015

Self Cite

View full text Add to dashboard Cite

The vinylheptafulvene (VHF) to dihydroazulene (DHA) electrocyclization is known to proceed from an s‐cis conformation of VHF and cannot occur from the more stable s‐trans conformation. Locking the VHF in the s‐cis conformation by the introduction of a dihydronaphthalene (DHN) unit has been found to greatly enhance the speed of this reaction. Thus, the half‐life was reduced by more than a factor of 150000 in cyclohexane and by a factor of approximately 950000 in ethanol. In addition, the characteristic absorption of the photoactive DHA isomer, now annulated to DHN, exhibited a desired redshift relative to the parent compound. Here, we present the synthesis and study of these DHN‐DHA/VHFs, including a protocol for the incorporation of a pseudo‐halide to enable the further functionalization of the molecule by metal‐catalyzed cross‐coupling reactions. For proof‐of‐concept, two different sulfur end‐groups were incorporated as anchoring groups for potential molecular electronics applications.

show abstract

Section: Resultsmentioning

confidence: 99%

Dihydroazulene/Vinylheptafulvene Photoswitch: Ultrafast Back Reaction Induced by Dihydronaphthalene Annulation

et al. 2015

Self Cite

View full text Add to dashboard Cite

show abstract

“…To optimize the yield, a different route to the para ‐phenylene‐bridged DHA–DHA 2 was attempted (Scheme ). At this point two cycloheptatriene units were incorporated at each side of the crotononitrile 4 because it has previously been shown that tropylium can act as a leaving group in a subsequent elimination step 18. Treatment with tropylium tetrafluoroborate (5 equiv) gave product 7 in a yield of 74 %.…”

Section: Resultsmentioning

confidence: 99%

Controlling Two‐Step Multimode Switching of Dihydroazulene Photoswitches

Petersen

Broman

Hansen

et al. 2015

Chemistry A European J

View full text Add to dashboard Cite

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-phenylene-bridged 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.

show abstract

“…Acetonitrile and CH 2 Cl 2 were purified and dried using activated Al 2 O 3 (drying-tower). CDCl 3 was purified by passing through activated Al 2 O 3 .T hin-layer chromatography (TLC) was carried out on commercially available pre-coated plates (silica 60) with fluorescence indicator.C hromatographic purifications were performed on silica (SiO 2 )w ith ap ore size of 60 and ap article size of 15-40 mmu sing the dry column vacuum chromatography method, as described previously [15,19] or 40-63 mmu sing flash column chromatography.M ass spectra were recorded with an ESP-MALDI-FT-ICR spectrometer equipped with a7Tm agnet (prior to the experiments, the instrument was calibrated with NaTFAc luster ions) or aM icrOTOF-QII spectrometer using ESP (calibrated with formic acid). All 1 HNMR and 13 CAPT (attached proton test) NMR spectra were recorded with a5 00 MHz instrument equipped with a( non-inverse) cryoprobe (500.1300/125.7578 MHz), with aV arian 300-MHz (300.0787 Hz) instrument with ap enta-probe, or Bruker 500-MHz (499.9731/125.7183 MHz) instrument with ab road bandprobe.…”

Section: Experimental Section General Proceduresmentioning

confidence: 99%

Aromaticity‐Controlled Energy Storage Capacity of the Dihydroazulene‐Vinylheptafulvene Photochromic System

Skov

Broman

Gertsen

et al. 2016

Chemistry A European J

Self Cite

View full text Add to dashboard Cite

Photochemical conversion of molecules into high-energy isomers that, after a stimulus, return to the original isomer presents a closed-cycle of light-harvesting, energy storage, and release. One challenge is to achieve a sufficiently high energy storage capacity. Here, we present efforts to tune the dihydroazulene/vinylheptafulvene (DHA/VHF) couple through loss/gain of aromaticity. Two derivatives were prepared, one with aromatic stabilization of DHA and the second of VHF. The consequences for the switching properties were elucidated. For the first type, sigmatropic rearrangements of DHA occurred upon irradiation. Formation of a VHF complex could be induced by a Lewis acid, but addition of H2 O resulted in immediate regeneration of DHA. For the second type, the VHF was too stable to convert into DHA. Calculations support the results and provide new targets. We predict that by removing one of the two CN groups at C-1 of the aromatic DHA, the heat storage capacity will be further increased, as will the life-time of the VHF. Calculations also reveal that a CN group at the fulvene ring retards the back-reaction, and we show synthetically that it can be introduced regioselectively.

show abstract

A Bis(heptafulvenyl)-dicyanoethylene Thermoswitch with Two Sites for Ring Closure

Cited by 16 publications

References 13 publications

Dihydroazulene/Vinylheptafulvene Photoswitch: Ultrafast Back Reaction Induced by Dihydronaphthalene Annulation

Dihydroazulene/Vinylheptafulvene Photoswitch: Ultrafast Back Reaction Induced by Dihydronaphthalene Annulation

Controlling Two‐Step Multimode Switching of Dihydroazulene Photoswitches

Aromaticity‐Controlled Energy Storage Capacity of the Dihydroazulene‐Vinylheptafulvene Photochromic System

Contact Info

Product

Resources

About