Imine Derivatives on Au(111): Evidence for “Inverted” Thermal Isomerization
详细信息 查看全文
- 作者：Johannes Mielke ; Felix Leyssner ; Matthias Koch ; Stephan Meyer ; Ying Luo ; Sofia Selvanathan ; Rainer Haag ; Petra Tegeder ; Leonhard Grill
- 刊名：ACS Nano
- 出版年：2011
- 出版时间：March 22, 2011
- 年：2011
- 卷：5
- 期：3
- 页码：2090-2097
- 全文大小：972K
- 年卷期：0
- ISSN：1936-086X
文摘
Molecules that undergo reversible isomerization between trans and cis states, typically upon illumination with light at appropriate wavelengths, represent an important class of molecular switches. In this combined scanning tunneling microscopy (STM) and high-resolution electron energy loss spectroscopy (HREELS) study, we report on self-assembled arrays of imine derivatives on a Au(111) surface. Most of the molecules are found in the trans state after deposition at room temperature, but many of them change their conformation upon heating, which we assign to switching to the cis state. As for many molecular switches, the trans isomer is the energetically more stable compound in solution, resulting in thermal cis to trans relaxation upon sufficient heating. On the surface, however, the number of cis isomers increases with temperature, pointing toward an “inverted” thermal isomerization behavior. The reason for this surface-mediated effect could be a stronger coupling, as compared to the trans state, of the central imine part of the molecule to the gold surface, which is sterically only possible in the cis state.