Phase Switching of a Single Isomeric Molecule and Associated Characteristic Rectification

Abstract

Variations in molecular electronic structures related to conformational change are exceedingly attractive because of their key role in the understanding and development of functional processes in molecular electronics and biology. We observed, for the first time, the novel phase switching of a photoactive isomeric molecule, N-(2-mercaptoethyl)-4-phenylazobenzamide (Azo molecule) at a single-molecule level, which exhibits a distinctive change in the conductive characteristic under scanning tunneling microscope (STM) measurement. In comparison with the results obtained by the measurement of photoactive isomerization of the isolated Azo molecule, which was performed also for the first time, the observed characteristics are attributed to the results of the trans and cis phase transformation of the Azo molecule, under the condition of an external electric field and current flow. A specific point is that the potential landscape of the system is controllable by the electric field and provides a conformational stability with asymmetric bias dependence resulting in rectification.

Light Switching of Molecules on Surfaces

“…One of the earliest reported studies correlating photochromic switching to changes in the conductance of individual molecules employed azobenzene derivatives embedded in n-dodecanethiol SAMs assembled on Au(111) (41). Azobenzenes undergo a cis-trans isomerization that alters the physical height of the molecules (Figure 8), albeit without significant change to molecular conductance.…”

Optical properties of azobenzene-functionalized self-assembled monolayers: Intermolecular coupling and many-body interactions

“…[1][2][3][4][5][6] Azobenzene-functionalized selfassembled monolayers (SAMs) of alkyl chains have been successfully synthesized in the last two decades. [7][8][9][10][11][12] Unfortunately, such systems come with a substantial drawback: The photo-isomerization rate is drastically suppressed due to steric hindrance or excitonic coupling. 13,14 A number of experimental strategies have been suggested to overcome this problem, such as replacing the aliphatic linker by an aromatic one 15 or even bulkier groups, [16][17][18] or diluting the azobenzene moieties in densely-packed alkanethiolate SAMs.…”

Self-assembly of triazatriangulenium-based functional adlayers on Au(111) surfaces

“…7 This is most commonly accomplished by employing mixed monolayers with short-chain spacer molecules. 5,6,[8][9][10][11][12][13][14][15][16][17] More modern approaches to enforce a sufficient free volume employ specially designed molecules, which feature additional bulky spacer groups 6,[18][19][20][21] or molecular tripods [22][23][24][25] as basis. Nevertheless, these types of adlayers also exhibit intrinsic disadvantages such as a comparable low structural order or lack of temporal stability due to phase separation.…”