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

View Article: PubMed Central - PubMed

ABSTRACT

Integratingfunctional molecules into single-molecule devices isa key step toward the realization of future computing machines basedon the smallest possible components. In this context, photoswitchingmolecules that can make a transition between high and low conductivityin response to light are attractive candidates. Here we present thesynthesis and conductance properties of a new type of robust molecularphotothermal switch based on the norbornadiene (NB)–quadricyclane(QC) system. The transport through the molecule in the ON state isdominated by a pathway through the π-conjugated system, whichis no longer available when the system is switched to the OFF state.Interestingly, in the OFF state we find that the same pathway contributesonly 12% to the transport properties. We attribute this observationto the strained tetrahedral geometry of the QC. These results challengethe prevailing assumption that current will simply flow through theshortest through-bond path in a molecule.

No MeSH data available.


(a)Transmission calculated with DFTB+ and the auorg parametersfor the molecules NB-1 and QC-2 sandwichedbetween the gold electrodes. (b) Local currents calculated with DFTB+at the Fermi level energy with a symmetric bias of 0.1 eV. The redarrows indicate a positive contribution to the current density, whilethe (small) blue arrows indicate a negative contribution (vide zoomed out front and back insets Figure 4(b)). The photochemically active region affectsthe electron transport properties: a fully conjugated path in NB-1 is replaced by a saturated ring, which reduces the electrontransmission. Moreover, the saturated region in QC-2 perturbsthe current pathway: only 12% of the current goes through the shortestσ path, while the 88% goes through three σ bonds.
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fig4: (a)Transmission calculated with DFTB+ and the auorg parametersfor the molecules NB-1 and QC-2 sandwichedbetween the gold electrodes. (b) Local currents calculated with DFTB+at the Fermi level energy with a symmetric bias of 0.1 eV. The redarrows indicate a positive contribution to the current density, whilethe (small) blue arrows indicate a negative contribution (vide zoomed out front and back insets Figure 4(b)). The photochemically active region affectsthe electron transport properties: a fully conjugated path in NB-1 is replaced by a saturated ring, which reduces the electrontransmission. Moreover, the saturated region in QC-2 perturbsthe current pathway: only 12% of the current goes through the shortestσ path, while the 88% goes through three σ bonds.

Mentions: The calculated transmissionfor the two molecular junctions usingDFTB+ is shown in Figure 4(a). The transmission through molecules terminated with thiolsis usually dominated by a transmission resonance associated with thehighest occupied molecular orbital (HOMO), whose energy lies closeto the Fermi energy of the gold electrodes.38,39


Effect of Ring Strain on the Charge Transport of aRobust Norbornadiene – Quadricyclane-Based Molecular Photoswitch
(a)Transmission calculated with DFTB+ and the auorg parametersfor the molecules NB-1 and QC-2 sandwichedbetween the gold electrodes. (b) Local currents calculated with DFTB+at the Fermi level energy with a symmetric bias of 0.1 eV. The redarrows indicate a positive contribution to the current density, whilethe (small) blue arrows indicate a negative contribution (vide zoomed out front and back insets Figure 4(b)). The photochemically active region affectsthe electron transport properties: a fully conjugated path in NB-1 is replaced by a saturated ring, which reduces the electrontransmission. Moreover, the saturated region in QC-2 perturbsthe current pathway: only 12% of the current goes through the shortestσ path, while the 88% goes through three σ bonds.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5385524&req=5

fig4: (a)Transmission calculated with DFTB+ and the auorg parametersfor the molecules NB-1 and QC-2 sandwichedbetween the gold electrodes. (b) Local currents calculated with DFTB+at the Fermi level energy with a symmetric bias of 0.1 eV. The redarrows indicate a positive contribution to the current density, whilethe (small) blue arrows indicate a negative contribution (vide zoomed out front and back insets Figure 4(b)). The photochemically active region affectsthe electron transport properties: a fully conjugated path in NB-1 is replaced by a saturated ring, which reduces the electrontransmission. Moreover, the saturated region in QC-2 perturbsthe current pathway: only 12% of the current goes through the shortestσ path, while the 88% goes through three σ bonds.
Mentions: The calculated transmissionfor the two molecular junctions usingDFTB+ is shown in Figure 4(a). The transmission through molecules terminated with thiolsis usually dominated by a transmission resonance associated with thehighest occupied molecular orbital (HOMO), whose energy lies closeto the Fermi energy of the gold electrodes.38,39

View Article: PubMed Central - PubMed

ABSTRACT

Integratingfunctional molecules into single-molecule devices isa key step toward the realization of future computing machines basedon the smallest possible components. In this context, photoswitchingmolecules that can make a transition between high and low conductivityin response to light are attractive candidates. Here we present thesynthesis and conductance properties of a new type of robust molecularphotothermal switch based on the norbornadiene (NB)–quadricyclane(QC) system. The transport through the molecule in the ON state isdominated by a pathway through the π-conjugated system, whichis no longer available when the system is switched to the OFF state.Interestingly, in the OFF state we find that the same pathway contributesonly 12% to the transport properties. We attribute this observationto the strained tetrahedral geometry of the QC. These results challengethe prevailing assumption that current will simply flow through theshortest through-bond path in a molecule.

No MeSH data available.