Altering the Static Dipole on Surfaces through Chemistry: Molecular Films of Zwitterionic Quinonoids

详细信息    查看全文

• 作者：Lucie Routaboul ; Pierre Braunstein ; Jie Xiao ; Zhengzheng Zhang ; Peter A. Dowben ; Guillaume Dalmas ; Victor Da Costa ; Olivier F茅lix ; Gero Decher ; Luis G. Rosa ; Bernard Doudin
• 刊名：The Journal of the American Chemical Society
• 出版年：2012
• 出版时间：May 23, 2012
• 年：2012
• 卷：134
• 期：20
• 页码：8494-8506
• 全文大小：714K
• 年卷期：v.134,no.20(May 23, 2012)
• ISSN：1520-5126

文摘

The adsorption of molecular films made of small molecules with a large intrinsic electrical dipole has been explored. The data indicate that such dipolar molecules may be used for altering the interface dipole screening at the metal electrode interface in organic electronics. More specifically, we have investigated the surface electronic spectroscopic properties of zwitterionic molecules containing 12蟺 electrons of the p-benzoquinonemonoimine type, C₆H₂(路路路NHR)₂(路路路O)₂(R = H (1), n-C₄H₉ (2), C₃H₆鈥揝鈥揅H₃ (3), C₃H₆鈥揙鈥揅H₃ (4), CH₂鈥揅₆H₅ (5)), adsorbed on Au. These molecules are stable zwitterions by virtue of the meta positions occupied by the nitrogen and oxygen substituents on the central ring, respectively. The structures of 2鈥?b>4 have been determined by single crystal X-ray diffraction and indicate that in these molecules, two chemically connected but electronically not conjugated 6蟺 electron subunits are present, which explains their strong dipolar character. We systematically observed that homogeneous molecular films with thickness as small as 1 nm were formed on Au, which fully cover the surface, even for a variety of R substituents. Preferential adsorption toward the patterned gold areas on SiO₂ substrates was found with 4. Optimum self-assembling of 2 and 5 results in ordered close packed films, which exhibit n-type character, based on the position of the Fermi level close to the conduction band minimum, suggesting high conductivity properties. This new type of self-assembled molecular films offers interesting possibilities for engineering metal鈥搊rganic interfaces, of critical importance for organic electronics.