Molecular Conductance through a Quadruple‐Hydrogen‐Bond‐Bridged Supramolecular Junction

Abstract

As eries of self-complementary ureido pyrimidinedione (UPy) derivatives modified with different aurophilic anchoring groups were synthesized. Their electron transport properties through the quadruple hydrogen bonds in apolar solvent were probed employing the scanning tunneling microscopyb reak junction (STMBJ) technique.T he molecule terminated with at hiol shows the optimal electron transport properties,with astatistical conductance value that approaches 10 À3 G 0 .T he 1 HNMR spectra and control experiments verify the formation of quadruple hydrogen bonds,w hich can be effectively modulated by the polarity of the solvent environment. These findings provide an ew design strategy for supramolecular circuit elements in molecular electronics.

Detecting Mechanochemical Atropisomerization within an STM Break Junction

“…Molecular electronics is an extremely exciting area of nanotechnology, which aims to develop new electronic devices operating at the single molecule level. − Understanding and controlling the conformation of molecules in single molecule junctions (SMJs) is a key challenge on the road to functional electronic devices based on individual molecules. It is an important consideration for 'rigid' molecules, such as those based on conjugated π-systems , and also for biomolecules with weaker internal hydrogen bonds such as DNA . Here, by studying a family of porphyrin compounds in which we specifically vary the anchor groups and conduct a detailed plateau-length analysis, we show it is possible to probe the conformation of the molecules between a pair of nanoelectrodes and moreover show that atropisomerization takes place due to the strain imposed on the molecules during tip retraction.…”

Characterization and Application of Supramolecular Junctions

“…Beyond the conductance difference, the reported formation probability of H‐bonded junction is relatively low (3 %≈15 %), [10b,c] in comparison to single‐molecule [8a, 65] and other supramolecular junctions [13, 31] . This low formation probability may arise from the following reasons.…”

“…Quantitative extraction and discrimination of hidden events from large datasets is a prerequisite for gaining more insight into the electronic properties of intermolecular interactions. In general, molecular junctions that differ considerably in conductance, [33] stretching distance, [10c, 34] or flicker noise [35] can be identified by analyzing their statistical distributions to estimate the proportion quantitatively. For example, Figure 5a shows a supramolecular junction based on the quadruple hydrogen bonds.…”

Solvent-molecule interaction induced gating of charge transport through single-molecule junctions

“…Wiring functional molecules into electrical circuits has been found to have significant potential for miniaturization of electronic devices [1][2][3][4][5][6]. Various intrinsic molecular factors have been investigated to advance the understanding on their effect on singlemolecule junction conductance, such as conformation [7][8][9], anchor groups [10,11], electrodes [12], hybridization [13], and quantum interference [14][15][16]. By altering these parameters, molecular switching can be achieved due to changing redox states [17][18][19], protonation [20,21], and connectivity [3]; however, the molecular states have been restricted to be less than three.…”