1 research outputs found
Steric Hindrance of Photoswitching in Self-Assembled Monolayers of Azobenzene and Alkane Thiols
Surface-bound azobenzenes
exhibit reversible photoswitching via
trans–cis photoisomerization and have been proposed for a variety
of applications such as photowritable optical media, liquid crystal
displays, molecular electronics, and smart wetting surfaces. We report
a novel synthetic route using simple protection chemistry to form
azobenzene-functionalized SAMs on gold and present a mechanistic study
of the molecular order, orientation, and conformation in these self-assembled
monolayers (SAMs). We use vibrational sum-frequency generation (VSFG)
to characterize their vibrational modes, molecular orientation, and
photoisomerization kinetics. Trans–cis conformational change
of azobenzene leads to the change in the orientation of the nitrile
marker group detected by VSFG. Mixed SAMs of azobenzene and alkane
thiols are used to investigate the steric hindrance effects. While
100% azobenzene SAMs do not exhibit photoisomerization due to tight
packing, we observe reversible switching (>10 cycles) in mixed
SAMs
with only 34% and 50% of alkane thiol spacers