We report the successful fabrication of azobenzene-functionalized self-assembled monolayers (SAMs) exhibiting high and reversible photoswitching between trans and cis states on a flat gold surface. Azobenzene thiols (MeSH and EtSH) containing meta and/or ortho substituents were chosen based on the occupied area per molecule as well as intermolecular interactions between the azobenzene aromatic rings (formation of H-aggregates). Theoretical predictions of the geometrical structures were performed to clarify the correlation between the molecular structure and photoisomerization characteristics in monolayer systems. The striking difference in absorption spectra of a trans-EtSH SAM and a cis-EtSH SAM by alternating UV and visible light irradiation was in good agreement with that in their contact angles for water, strongly indicating that the structural changes were controlled by light wavelength. By contrast, despite there being sufficient free space for each MeSH molecule, the strong tendency of the planar azobenzene units to generate H-aggregates even during cis-MeSH SAM formation lessened the trans-to-cisphotoisomerization yield in a monolayer.
                                    我们报告了
偶氮苯官能化自组装单分子层(S
AM)的成功制备,该S
AM在平面
金表面上表现出反式和顺式状态之间的高度可逆光开关。根据每分子的占用面积以及
偶氮苯芳香环之间的分子间相互作用(氢聚集体的形成),我们选择了含有间位和/或邻位取代基的
偶氮苯硫醇(MeSH和EtSH)。我们对几何结构进行了理论预测,以阐明单分子层系统中分子结构与光异构化特性之间的相关性。通过交替的紫外和可见光照射,反式-EtSH S
AM和顺式-EtSH S
AM在吸收光谱上的显着差异与它们的
水接触角非常一致,这有力地表明结构变化是由光波长控制的。相比之下,尽管每个MeSH分子都有足够的自由空间,但平面
偶氮苯单元即使在顺式-MeSH S
AM形成过程中也倾向于产生氢聚集体,这降低了单分子层中反式到顺式的光异构化产率。