Nacci Christophe, Baroncini Massimo, Credi Alberto, Grill Leonhard
Department of Physical Chemistry, University of Graz, Heinrichstrasse 28, 8010, Graz, Austria.
Dipartimento di Scienze e Tecnologie Agro-Alimentari, Università di Bologna, Viale Fanin 50, 40127, Bologna, Italy.
Angew Chem Int Ed Engl. 2018 Nov 12;57(46):15034-15039. doi: 10.1002/anie.201806536. Epub 2018 Oct 8.
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.
偶氮苯是一种典型的分子开关，它可以在近乎平面且无极性的反式结构和扭曲的、有极性的顺式结构之间进行可逆的光异构化。大多数与偶氮苯衍生物相关的研究都集中在平面吸附分子上。我们在此展示了一种由四个呈四面体排列的偶氮苯单元组成的三维形状持久分子结构的研究，该结构吸附在Ag(111)表面。虽然与表面接触的三脚架中的偶氮苯失去了其开关能力，但通过在不同波长下照射，四聚体直立臂的不同异构体能够可逆且高效地获得，其时间常数仅为几分钟。表面扩散取决于直立取向的偶氮苯基团的异构状态——反式或顺式。因此，分子迁移率可以通过其异构状态进行调节，这表明分子生长过程可以由外部刺激控制。
