Monitoring the reversible photoisomerization of an azobenzene-functionalized molecular triazatriangulene platform on Au(111) by IRRAS

Abstract

Spectroscopic evidence of a reversible, photoinduced trans ↔ cis photoisomerization is provided for an azobenzene-functionalized triazatriangulene (TATA) platform on Au(111). As shown by scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS), these molecules form a well-ordered self-assembled monolayer (SAM) on Au(111). The surface-adsorbed azo-TATA platforms are also investigated by infrared reflection absorption spectroscopy (IRRAS); a methoxy marker group at the upper phenyl ring of the azo moiety is employed to monitor the switching state. The IRRAS data are analyzed by comparison with theoretical and transmission IR spectra as well as bulk and surface-enhanced Raman spectroscopic (SERS) data. IRRAS shows that the methoxy group is oriented perpendicular to the surface in trans- and tilted with respect to the surface normal in cis-configuration. This indicates that the photoswitching capability of the azobenzene moieties is retained on the gold surface. The lifetime of the cis-configuration is, however, reduced by a factor of ∼10(3) with respect to the homogeneous solution.

Imine‐Functionalized Triazatriangulenium Platforms: Towards an Artificial Ciliated Epithelium

“…[11] In the hexagonal packing, the platforms have ad istance of 12.5 t ot heir next neighbors on the Au(111)s urface.T his provides sufficient free volumef or the switching of azobenzenes, [15] and should also be sufficient for the very similar imines tructures.E thynyl groups were used as spacers or pillars to electronically decouple the switches from the metal surface, and to provide an upright orientation fort he imines attached on top. [11] In the hexagonal packing, the platforms have ad istance of 12.5 t ot heir next neighbors on the Au(111)s urface.T his provides sufficient free volumef or the switching of azobenzenes, [15] and should also be sufficient for the very similar imines tructures.E thynyl groups were used as spacers or pillars to electronically decouple the switches from the metal surface, and to provide an upright orientation fort he imines attached on top.…”

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

“…[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. 14,[19][20][21][22] From a theoretical viewpoint the issue of hindered photo-isomerization in densely-packed azobenzenefunctionalized SAMs has been addressed by a few works, mainly focused on the excitonic coupling between the chromophores, 23,24 as well as on the effects of a metal substrate.…”

High azobenzene functionalization enhances stability of the cis isomer: Periodic mesoporous organosilica network on the way to new light triggered applicable materials

“…Comparing these values to the values reported in literature, the half life time of the cis isomer of azobenzene derivatives is quite long for both cases (half life time in the literature: 1 min -56 h [60,102,[105][106][107][108][109][110]) and shows that the π electron rich environment inside the bz-PMO could stabilize the cis configuration of the azobenzene switch.…”