Dihydroazulene Photoswitch Operating in Sequential Tunneling Regime: Synthesis and Single‐Molecule Junction Studies

Broman, Søren Lindbæk; Lara‐Avila, Samuel; Thisted, Christine Lindbjerg; Bond, Andrew D.; Kubatkin, Sergey; Danilov, Andrey; Nielsen, Mogens Brøndsted

doi:10.1002/adfm.201200897

Cited by 54 publications

(49 citation statements)

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“…15 Other photoswitchable molecules with more complicated structures have also been investigated. 7,18,19 Here, we designed and synthesized a norbornadiene-based photoswitch ( NB-1 ) with embedded oligo(phenylene ethynylene) arms end-capped with thioacetate groups to anchor it to gold electrodes (Scheme 1). …”

Section: Introductionmentioning

confidence: 99%

Effect of Ring Strain on the Charge Transport of a Robust Norbornadiene–Quadricyclane-Based Molecular Photoswitch

Tebikachew

Pirrotta

et al. 2017

J. Phys. Chem. C

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Integrating functional molecules into single-molecule devices is a key step toward the realization of future computing machines based on the smallest possible components. In this context, photoswitching molecules that can make a transition between high and low conductivity in response to light are attractive candidates. Here we present the synthesis and conductance properties of a new type of robust molecular photothermal switch based on the norbornadiene (NB)–quadricyclane (QC) system. The transport through the molecule in the ON state is dominated by a pathway through the π-conjugated system, which is no longer available when the system is switched to the OFF state. Interestingly, in the OFF state we find that the same pathway contributes only 12% to the transport properties. We attribute this observation to the strained tetrahedral geometry of the QC. These results challenge the prevailing assumption that current will simply flow through the shortest through-bond path in a molecule.

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Section: Introductionmentioning

confidence: 99%

Effect of Ring Strain on the Charge Transport of a Robust Norbornadiene–Quadricyclane-Based Molecular Photoswitch

Tebikachew

Pirrotta

et al. 2017

J. Phys. Chem. C

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“…12 Nielsen and coworkers have presented extensive work on dihydroazulene (DHA) photoswitches in recent years. Notably, a new dark switching mechanism was found, 13 where a DHA derivative (DHA4a) see Figure 1, for certain gate voltages, was switching above a bias threshold. Thus, a current-induced excitation replaces the external stimulus from light.…”

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confidence: 98%

Dark Photoswitching Induces Coulomb Blockade Diamond Collapse

Hansen

Mikkelsen

2015

J. Phys. Chem. C

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A derivative of the photochromic molecule dihydroazulene (DHA) undergoes bias-induced switching into its vinylheptafulvene (VHF) conformation when inserted into a silver junction. This dark switching mechanism, which induces a collapse of the Coulomb blockade diamonds, is explained by quantum calculations on the molecular transport junction. Analysis of the nonequilibrium populations of molecular redox states explains the observed bias threshold. Predictions are made that another DHA derivative will not, in future experiments, exhibit bias-induced switching. Thus, the dark switching mechanism depends on the structure of the photoswitch. The methodology applies to any molecular junction and offers a versatile tool for answering mechanistic questions.T he vision of a single-molecule device, the molecular rectifier, was proposed in 1974. 1 Today molecular electronics is a vibrant field studying functionalities of singlemolecule junctions including molecular switches, molecular transistors, and molecular memories. Also, molecular photoswitches comprise a growing field promising applications in harvesting of solar energy, biosensors, and fast and high density data storage. Recently, photoswitches have been placed in molecular transport junctions. 2−10 The complex interplay of the light-induced switching of, and the current passing through, the molecule poses challenging scientific questions and suggest new device functionalities. The most studied photoswitches in molecular junctions are derivatives of dithienylethene, 2−6 which undergo light-induced ring-opening, and azobenzene, 7,8 which experiences cis−trans isomerization upon photoexcitation.The switching behavior of photochromic molecules exposed to light is altered and often quenched in the vicinity of a metal surface. 2 Thus, to obtain reversible and robust photoswitching, the quenching pathway introduced by the strong electronic coupling to the metal surface must be avoided, for example, by inserting a linker group into the molecule. 5,9,10 Feringa and coworkers have presented reversible switching of a diarylethene with a phenyl group spacer in meta position 3,4 and further found that the switching also depends on the tilting of the molecule toward the metal surface. Similar results exist for other derivatives of diarylethene. In all cases, the closed form is found to be the more conducting formthe ON-state. Likewise, the ring-closed form of dimethyldihydropyrene photoswitch is found to be the more conducting form. 11 In addition, Scheer and coworkers showed that the ON−OFF ratio also depends on the side chains of the molecule. 6 Functionalized azobenzenes exhibit strong correlation between reversible switching and electronic coupling to the metal surface. 7 Theoretical investigations predict the trans-isomer to be more conducting than the cis-isomer for most bias voltages. 8 Transport experiments on the E-Z photoisomers of 4,4′-(ethene-1,2-diyl)dibenzoic acid demonstrate a significantly higher conductance for the Z isomer than for the E isomer. 12 Nielsen and...

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“…2‐(1,1′‐Biphenyl‐4‐yl)azulene‐1‐carbonitrile: R f =0.33 (toluene); 1 H NMR (500 MHz, CDCl 3 ): δ =8.63 (d, J= 9.7 Hz, 1 H), 8.40 (d, J= 9.5 Hz, 1 H), 8.16 (d, J= 8.3 Hz, 2 H), 7.79–7.75 (m, 3 H), 7.03–7.67 (m, 2 H), 7.58 (s, 1 H), 7.56–7.45 (m, 4 H), 7.43–7.37 ppm (m, 1 H); HRMS (MALDI +ve) calcd for C 30 H 20 N 2 [ M ] .+ : m / z= 305.1199; found: 305.1208; data in accordance with literature …”

Section: Methodsmentioning

confidence: 99%

Photoswitching of Dihydroazulene Derivatives in Liquid‐Crystalline Host Systems

Petersen

Jevric

Mandle

et al. 2017

Chemistry A European J

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Photoswitches and dyes in the liquid crystalline nematic phase have the potential for use within a wide range of applications. A high order parameter is desirable in order to maximize the change in properties induced by an external stimulus. A set of photochromic and non-photochromic dyes were investigated for these applications. It was found that a bent-shaped 7-substituted dihydroazulene (DHA) photoswitch exhibited liquid crystalline properties. Further investigation demonstrated that this material actually underwent two distinctive reaction pathways upon heating to a deactivated form via a 1,5-sigmatropic shift and to a linear 6-substituted DHA. In addition, elimination of hydrogen cyanide from these photoactive DHAs gave both bent and linear azulene dyes. In a nematic host, which has no absorbance around 350 nm, it was found that only the linearly shaped DHA derivative possessed nematic properties; however, both 6-and 7-substituted DHAs were found to have high order parameters. In the nematic host, ring opening of either DHA to the corresponding vinylheptafulvene (VHF) resulted in a decrease in dichroic order parameter and an unusually fast back reaction to a mixture of both DHAs. Likewise, only the linearly shaped azulene derivative showed mesomorphic properties. In the same nematic host, high order parameters were also observed for these dyes.

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Dihydroazulene Photoswitch Operating in Sequential Tunneling Regime: Synthesis and Single‐Molecule Junction Studies

Cited by 54 publications

References 50 publications

Effect of Ring Strain on the Charge Transport of a Robust Norbornadiene–Quadricyclane-Based Molecular Photoswitch

Effect of Ring Strain on the Charge Transport of a Robust Norbornadiene–Quadricyclane-Based Molecular Photoswitch

Dark Photoswitching Induces Coulomb Blockade Diamond Collapse

Photoswitching of Dihydroazulene Derivatives in Liquid‐Crystalline Host Systems

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