Wei Lingyun, Tiznado Hugo, Liu Guangming, Padmaja Kisari, Lindsey Jonathan S, Zaera Francisco, Bocian David F
Department of Chemistry, University of California, Riverside, California 92521-0403, USA.
J Phys Chem B. 2005 Dec 22;109(50):23963-71. doi: 10.1021/jp0537005.
X-ray photoelectron and Fourier transform infrared spectroscopy studies are reported for self-assembled monolayers (SAMs) of two tripodal thiol-functionalized metalloporphyrins (Zn and Cu) and three benchmark tripods on gold substrates. The tripodal unit common to all five molecules is 1-(phenyl)-1,1,1-tris(4-mercaptomethylphenyl)methane (Tpd). Both porphyrins contain S-acetyl-protected thiols and are linked to the 4-position of the phenyl ring of Tpd via a phenylethyne group. The benchmark molecules include (1) two tripods containing a bromine atom at the 4-position of the apical phenyl ring, one a free thiol and the other its S-acetyl-protected analogue, and (2) a S-acetyl-protected tripod containing a phenylethyne unit at the 4-position of the apical phenyl group. Together, the spectroscopic studies reveal that none of the five tripodal molecules bond to the gold surface via all three sulfur atoms. Instead, the average number of bound thiols ranges from 1.5 to 2, with the porphyrinic molecules generally falling at the middle to upper end of the range and the smallest benchmark tripods falling at the lower end. Similar surface binding is found for the S-acetyl-protected and free benchmark tripods, indicating that the presence of the protecting group does not influence binding. Furthermore, the surface binding characteristics of the SAMs are not sensitive to deposition conditions such as solvent type, deposition time, or temperature of the solution.
本文报道了两种三脚架状硫醇功能化金属卟啉（锌和铜）以及三种基准三脚架在金基底上自组装单分子层（SAMs）的X射线光电子能谱和傅里叶变换红外光谱研究。所有五个分子共有的三脚架单元是1-(苯基)-1,1,1-三(4-巯基甲基苯基)甲烷（Tpd）。两种卟啉都含有S-乙酰基保护的硫醇，并通过苯乙炔基连接到Tpd苯环的4-位。基准分子包括：(1) 两种在顶端苯环的4-位含有溴原子的三脚架，一种是游离硫醇，另一种是其S-乙酰基保护的类似物；(2) 一种在顶端苯基的4-位含有苯乙炔单元的S-乙酰基保护的三脚架。光谱研究共同表明，五个三脚架状分子中没有一个通过所有三个硫原子与金表面结合。相反，结合硫醇的平均数量在1.5到2之间，卟啉分子通常处于该范围的中高端，最小的基准三脚架处于低端。对于S-乙酰基保护的和游离的基准三脚架，发现了类似的表面结合，表明保护基团的存在不影响结合。此外，SAMs的表面结合特性对沉积条件（如溶剂类型、沉积时间或溶液温度）不敏感。
