Adsorbed structures of 4,4′-bipyridine on Cu(111) in acid studied by STM and IR
Adsorbed structures of 4,4′-bipyridine on Cu(111) in acid studied by STM and IR
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DOI：
10.1021/la052765w
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发表时间：
2006-04-11
期刊：
影响因子：
3.9
通讯作者：
Osawa, M
中科院分区：
文献类型：
--
作者：
Diao, YX;Han, MJ;Osawa, M
用循环伏安法、电化学扫描隧道显微镜（STM）和表面增强红外吸收光谱（SEIRAS）研究了4，4 '-联吡啶（BiPy）在0.1M HClO_4溶液中在Cu（111）表面的吸附行为.循环伏安法显示双电层区在-0.2 ~0.26V之间，在较负的电位下，有一对氧化还原波叠加在析氢波上。双质子化的BiPy（BiPyH 22+）在Cu（111）（1 x 1）表面上被平坦吸附，并在双层势区形成具有（3 x 4）对称性的有序单分子层。在更负的电势下，BiPyH 22+被还原成其一价阳离子自由基，BiPyH 2中心点+，并形成另一种有序结构，其中自由基以分子行堆叠，面对面的自二聚体作为构建单元。BiPyH_（22+）和BiPyH_（22+）的SEIRA光谱都是由gerade模式主导的，对于中心对称的物种来说，gerade模式应该是IR惰性的。红外吸收的选择规则的故障归因于电子振动耦合与BiPyH 22+和表面之间的电荷转移和自由基之间。
The adsorption of 4,4'-bipyridine (BiPy) on Cu(111) has been investigated in 0.1 M HClO4 by cyclic voltammetry, electrochemical scanning tunneling microscopy (STM), and surface-enhanced infrared adsorption spectroscopy (SEIRAS). Cyclic voltammetry showed the double layer region extending from -0.2 to 0.26 V and a pair of redox waves superposing on hydrogen evolution wave at more negative potentials. Diprotonated BiPy, BiPyH22+, is adsorbed flat on the Cu(111) (1 x 1) surface and forms a well-ordered monolayer with a (3 x 4) symmetry in the double-layer potential region. At more negative potential, BiPyH22+ is reduced to its monocation radical, BiPyH2 center dot+, and forms another well-ordered structure in which the radicals are stacked in molecular rows with a face-to-face self-dimer as the building unit. The SEIRA spectra of both BiPyH22+ and BiPyH2 center dot+ are dominated by gerade modes which should be IR-inactive for the centrosymmetric species. The breakdown of the selection rule of IR absorption is ascribed to the vibronic coupling associated with charge transfer between BiPyH22+ and the surface and between the radicals.