Reversible photoisomerization of an azobenzene-functionalized self-assembled monolayer probed by sum-frequency generation vibrational spectroscopy

Wagner, Steffen; Leyssner, Felix; Kördel, Christian; Zarwell, Sebastian; Schmidt, Roland; Weinelt, Martin; Rück‐Braun, K.; Wolf, Martin; Tegeder, Petra

doi:10.1039/b823330f

Cited by 78 publications

(106 citation statements)

References 47 publications

(50 reference statements)

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Photoinduced cis-trans isomerization of azobenzene (AB) derivatives is well known from the liquid phase, but has also been applied to adsorbates [211][212][213][214]. The flat-lying trans-isomer switches into a ''helical'' cis-isomer, that is, from an adsorption-induced chiral entity into an intrinsically chiral molecule (Fig.…”

Section: Diastereomers and Diastereomeric Recognitionmentioning

confidence: 99%

Molecular chirality at surfaces

Ernst

2012

Physica Status Solidi (b)

223

264

View full text Add to dashboard Cite

With the adsorption of larger molecules being increasingly tackled by surface scientists, the aspect of chirality often plays a role. This paper gives a topical review of molecular chirality at surfaces and gives a phenomenological overview of different aspects of adsorption and self‐assembly of chiral and prochiral molecules and the principles of mirror‐symmetry breaking at a surface. After a brief introduction into the history of molecular chirality and the important role it played for understanding the spatial structure of molecules, definitions of chirality are presented. Topics treated here are principle ways to create single chiral adsorbates, chiral ensembles, and monolayers by achiral molecules, adsorption of intrinsically chiral molecules at achiral and chiral surfaces, long‐range symmetry breaking in two‐dimensional (2D) crystals due to additional chiral bias, chiral restructuring of solid surfaces under the influence of chiral molecules, switching the handedness of adsorbates, and chirality at the liquid/air interface. An outlook onto further potential research directions and recommendations for further reading, including nonsurface‐related sources of chiral topics completes this paper.

show abstract

Section: Diastereomers and Diastereomeric Recognitionmentioning

confidence: 99%

Molecular chirality at surfaces

Ernst

2012

Physica Status Solidi (b)

223

264

View full text Add to dashboard Cite

show abstract

“…For example, reversible photoisomerization was observed for (tetra)molecular architectures consisting of three adamantane moieties17 or thiols18, 19 anchored to the surface and a fourth branch with an azobenzene group. This approach ensures stable adsorption through the tripod linker and an upright arrangement of the molecular switch unit, and thus electronic decoupling from the surface.…”

mentioning

confidence: 99%

Reversible Photoswitching and Isomer‐Dependent Diffusion of Single Azobenzene Tetramers on a Metal Surface

2018

View full text Add to dashboard Cite

Azobenzene is a prototypical molecular switch that can be reversibly photoisomerized between the nearly planar and apolar trans form, and the distorted, polar cis form. Most studies related to azobenzene derivatives have focused on planar adsorbed molecules. We present herein the study of a three‐dimensional shape‐persistent molecular architecture consisting of four tetrahedrally arranged azobenzene units that is adsorbed on a Ag(111) surface. While the azobenzenes of the tripod in contact with the surface lost their switching ability, different isomers of the upright standing arm of the tetramer were obtained reversibly and efficiently by illumination at different wavelengths, revealing time constants of only a few minutes. Diffusion on the surface was dependent on the isomeric state—trans or cis—of the upright oriented azobenzene group. Hence, molecular mobility can be modulated by its isomeric state, which suggests that molecular growth processes could be controlled by external stimuli.

show abstract

“…These figures of merit indicate an order of magnitude reduction in cross section of surface-bound molecules when compared with the values in solution. 52 Moreover, the cis-trans isomerization cross section of nonconductive-tethered molecules is an order of magnitude larger than that of conductive-tethered molecules indicating the direct effect of tether conductivity on the photoisomerization of surface-bound molecules. Because it is critical to be able to tune the functionality of surface-bound molecular switches to build efficient functional devices, this letter describes the means to gain that ability by tuning the metal−molecule junction properties and to tailor the efficiency of photoisomerization.…”

Section: Sectionmentioning

confidence: 99%

“…22,38−40 Recently, surface-enhanced Raman spectroscopy (SERS) has been shown to be an excellent tool for following photoisomerization of functional molecules on the ensemble scale. 14,37,41 Although, the effects of the surrounding environment, 42,43 the coupling of the functional moiety to the substrate using a tether, 12,18,[20][21][22]44,45 the conductivity of the substrate, 21,39,46 the length and free volume of the tether, 47,48 the structure of the substrate, 37,48−50 and ways to circumvent steric interactions between the azobenzene moieties 22,23,51,52 have been reported previously, the effects of the conductivity of the tethers on photoisomerization have not been reported. To employ such molecular switches in a range of conditions and chemical environments, it is imperative to understand the roles of all the key aspects constituting the photoswitches and their supporting structures.…”

Section: Sectionmentioning

confidence: 99%

Effect of Tether Conductivity on the Efficiency of Photoisomerization of Azobenzene-Functionalized Molecules on Au{111}

Pathem

Yong

Payton

et al. 2012

J. Phys. Chem. Lett.

View full text Add to dashboard Cite

ABSTRACT:We establish the role of tether conductivity on the photoisomerization of azobenzene-functionalized molecules assembled as isolated single molecules in well-defined decanethiolate self-assembled monolayer matrices on Au{111}. We designed the molecules so as to tune the conductivity of the tethers that separate the functional moiety from the underlying Au substrate. By employing surface-enhanced Raman spectroscopy, time-course measurements of surfaces assembled with azobenzene functionalized with different tether conductivities were independently studied under constant UV light illumination. The decay constants from the analyses reveal that photoisomerization on the Au{111} surface is reduced when the conductivity of the tether is increased. Experimental results are compared with density functional theory calculations performed on single molecules attached to Au clusters. SECTION:Physical Processes in Nanomaterials and Nanostructures P recise control over the reversible isomerization of functional molecules when assembled on solid surfaces is of great importance to understand the rules of molecular-and supramolecular-scale action. 1−14 Various kinds of photochromic molecules such as azobenzene, 15−24 diarylethene, 9,25−27 spiropyran, 28−30 and more recently dihydroazulene 31−34 have been investigated as possible candidates for molecular switches. These families of functional molecules have relative advantages and disadvantages due to factors such as their ease of molecular assembly on substrates, quantum yield of photoisomerization, reversibility of isomerization, and quenching of isomerization by the underlying substrate. Of these families of photochromic molecules, azobenzenes have thus far attracted the greatest attention.Azobenzene (henceforth Azo) exists in a near-planar trans conformation in its thermodynamically stable state with nearly zero dipole moment. 35,36 When irradiated with UV light at ∼365 nm, the molecule isomerizes to a nonplanar cis conformation via rotation of a phenyl group out of the plane of the azobenzene moiety, carrying a dipole moment of 3 D. 36 Upon subsequent irradiation with ∼420 nm visible light, the cis conformation reverts back to its original trans conformation, although thermal relaxation from cis to trans has also been shown to be a common pathway for the reverse reaction where relaxation times typically depend on the substituents on the azobenzene moiety ranging from minutes (for alkyl-substituted molecules) to days (for unsubstituted azobenzenes). Because of their difference in planarity, it has been established that trans form is approximately 100 times more conductive than cis, 16 and hence azobenzenes are considered to be a type of molecular switches. 22 Various theoretical and experimental studies have been performed to understand the mechanisms of photoisomerization of azobenezenes in the gas phase, in various solvents, and on solid substrates when isolated as single molecules or in ensembles. For instance, it has been wellestablished that photoisomerization of...

show abstract

Reversible photoisomerization of an azobenzene-functionalized self-assembled monolayer probed by sum-frequency generation vibrational spectroscopy

Cited by 78 publications

References 47 publications

Molecular chirality at surfaces

Molecular chirality at surfaces

Reversible Photoswitching and Isomer‐Dependent Diffusion of Single Azobenzene Tetramers on a Metal Surface

Effect of Tether Conductivity on the Efficiency of Photoisomerization of Azobenzene-Functionalized Molecules on Au{111}

Contact Info

Product

Resources

About