Multiscale Approach to the Study of the Electronic Properties of Two Thiophene Curcuminoid Molecules

Abstract

We studied the electronic and conductance properties of two thiophene-curcuminoid molecules, 2-thphCCM (1) and 3-thphCCM (2), where the only structural difference is the position of the sulfur atoms in the thiophene terminal groups. We used electrochemical techniques as well as UV-vis absorption studies to obtain the values of the HOMO-LUMO band gap energies, showing that molecule 1 has lower values than 2. Theoretical calculations show the same trend. Self-assembled monolayers (SAMs) of these molecules were studied using electrochemistry, showing that the interaction with gold reduces drastically the HOMO-LUMO gap in both molecules to almost the same value. Single-molecule conductance measurements show that molecule 2 has two different conductance values, whereas molecule 1 exhibits only one. Based on theoretical calculations we conclude that the lowest conductance value, similar in both molecules, corresponds to a van der waals interaction between the thiophene ring and the electrodes. The one order of magnitud higher conductance value for molecule 2 corresponds to a covalent interaction between the sulfur atoms and the gold electrodes.

Single-Molecule Transport of Fullerene-Based Curcuminoids

“…Me-S terminated CCM's were chosen because they form stable and well-defined molecular junctions. 22,23 Three systems with the CCM skeleton connected to a C 70 , C 60 and to a C 60 fullerene all-equatorial tetramalonate derivative (CCM-C 70 , CCM-C 60 and CCM-C 60 P, respectively) have been investigated. In the latter, four equatorial diethyl malonate groups were added to the C 60 .…”

Charge Transport through a Single Molecule of trans-1-bis-Diazofluorene [60]fullerene

“…Such interactions can yield additional low-conductance peaks and have been identified in molecular junctions with thiophene anchoring groups. 43 In this way, a second surface scan was performed; this time by elongating the Au−H distance (see Fig. 4b).…”

Origin of the Electron Transport Properties of Aromatic and Antiaromatic Single Molecule Circuits

“…Aromaticity is a key concept which describes the stability and electronic properties of π‐conjugated molecules. Aromatic backbones such as oligoacenes, porphyrins, or polycyclic aromatic hydrocarbons display large stabilization energies and are thus commonly used in many fields of electronics, photovoltaics, and materials science at the molecular scale [1–7] . In other cyclic planar conjugated ‘antiaromatic’ molecules, the arrangement of π electrons is very destabilizing [8] .…”

“…Aromatic backbones such as oligoacenes, porphyrins, or polycyclic aromatic hydrocarbons display large stabilization energies and are thus commonly used in many fields of electronics, photovoltaics, and materials science at the molecular scale. [1][2][3][4][5][6][7] In other cyclic planar conjugated 'antiaromatic' molecules, the arrangement of π electrons is very destabilizing. [8] However, these antiaromatic molecules were long proposed to exhibit increased electron transport properties.…”