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

Abstract

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.

Fast Data Sorting with Modified Principal Component Analysis to Distinguish Unique Single Molecular Break Junction Trajectories

“…Next, we showed that PC sorting can perform a very useful task: it can distinguish groups with a change in conductance of about half an order of magnitude and an associated change in plateau length of about 0.15 nm. Changes in conductance like this are common in optically [22] and electrochemically [23] switched SMBJs. Furthermore, 0.15 nm represents the radius of a gold atom and the bottom limit of measurable differences between groups.…”

Electronic Communication across Porphyrin Hexabenzocoronene Isomers

“…With an increasing core-to-core distance of the porphyrins from 10.7 to 18.3 and 21.3 for the ortho-, meta-, and para-conjugates,r espectively,t hroughspace communication has only minor impact on the spectral features.H owever,t he situation is more distinct upon inspecting the molecular orbitals.A lthough most of the electron distribution of the highest occupied molecular orbital (HOMO) is located on the porphyrins,p art is also based on the HBC core.H ereby,t he conjugation pathway is found to go always across the middle ring of the HBC core.Inthe ortho case,t he communication takes an angular pathway through the HBC'sc entral ring, rather than through the biphenyl fragment. [23] Less pronounced, this indirect pathway is also true for the meta conjugate.O nt he other hand, para structures find their most direct communication through the middle of the HBC.…”

Theoretical study on the reaction mechanism of the thermal cis–trans isomerization of fluorine-substituted azobenzene derivatives

“…Molecular photoswitches have aroused widespread interest in recent years. [1][2][3][4][5] Because of their unique photochromic characteristics, 6 they have been widely used in molecular data storage, 7-9 photopharmacology, 10 optochemical genetics, 11 materials science, 12 and biomolecules 13,14 among other areas. Over the past few decades, most research has been focused on azobenzenes, 15 spiropyrans, 16 diarylethenes, 17 and stilbenes 18 which are all characterized by photoisomerization.…”