Charge transfer between triphenyl phosphine and colloidal silver: A SERS study combined with DFT calculations
Charge transfer between triphenyl phosphine and colloidal silver: A SERS study combined with DFT calculations
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DOI：
10.1021/jp0703915
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发表时间：
2007-06-21
影响因子：
3.7
通讯作者：
Li, Can
中科院分区：
文献类型：
--
作者：
Hu, Gengshen;Feng, Zhaochi;Li, Can
用表面增强拉曼光谱（Sers）研究了三苯基膦（PPh 3）在胶体银上的吸附。根据表面选择规则，从Sers结果推断PPh 3是通过其三个苯环上的P原子相对于银表面倾斜吸附在银表面上的。PPh 3的给电子效应可被共吸附的SCN-灵敏地探测。当PPh 3与SCN-共吸附时，吸附SCN-的nu（CN）的拉曼频率向低频移动，CN伸缩振动频率的红移随PPh 3表面覆盖度的增加而增加.这可以用PPh 3的给电子效应来解释：吸附在银表面的PPh 3将其孤对电子给银表面，然后银表面的负电荷通过S-Ag键转移到CN键的π * 轨道上。因此，CN键被削弱，并且nu（CN）的频率向较低频率移动。密度泛函理论（DFT）计算进一步证实了实验结果，电荷转移是从PPh 3到银表面而不是银表面. PPh 3在银表面吸附的SERS信息有助于理解膦配体在过渡金属表面配位的多相催化机理。
The adsorption of triphenyl phosphine (PPh3) on colloidal silver has been investigated by means of surface-enhanced Raman spectroscopy (SERS). On the basis of surface selection rule, it is deduced from SERS results that PPh3 adsorbs on silver surface via its P atom with three phenyl rings tilted with respect to the silver surface. The electron-donor effect of PPh3 can be sensitively probed by the coadsorbed SCN-. The Raman frequency of nu(CN) of the adsorbed SCN- shifts to lower frequencies when PPh3 is coadsorbed with SCN-, and the red shift of CN stretching frequency is found to increase with increasing the surface coverage of PPh3. This could be explained in terms of the electron-donor effect of PPh3: PPh3 adsorbed on silver surface donates its lone pair of electrons to silver surface, and then the negative charge of silver surface transfers to the pi* orbital of CN bond via S-Ag bond. Consequently, the CN bond is weakened, and the frequency of nu(CN) shifts to lower frequencies. Density functional theory (DFT) calculations further confirm the experimental results that the charge transfer is from PPh3 to silver surface rather than reversely. The information obtained from the adsorption of PPh3 on silver by SERS may be helpful to understand the mechanism of heterogeneous catalysis involving phosphine ligands coordinated on transition-metal surfaces.