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Effect of Ring Strain on the Charge Transport of aRobust Norbornadiene – Quadricyclane-Based Molecular Photoswitch
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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. |
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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 |
View Article: PubMed Central - PubMed
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.
