STRUCTURES OF SELF-ASSEMBLED MONOLAYERS OF AROMATIC-DERIVATIZED THIOLS ON EVAPORATED GOLD AND SILVER SURFACES - IMPLICATION ON PACKING MECHANISM
STRUCTURES OF SELF-ASSEMBLED MONOLAYERS OF AROMATIC-DERIVATIZED THIOLS ON EVAPORATED GOLD AND SILVER SURFACES - IMPLICATION ON PACKING MECHANISM
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DOI：
10.1021/ja00094a038
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发表时间：
1994-07-27
影响因子：
15
通讯作者：
TAO, YT
中科院分区：
文献类型：
--
作者：
CHANG, SC;CHAO, I;TAO, YT
4 '-烷氧基联苯基-4-甲烷乙炔基，4'-CH 3（CH 2）（m）OC 6 H 4C 6 H 4 -4-CH 2SH（I），（6-烷氧基萘-2-基）甲烷硫醇，6-CH 3（CH 2）（m）OC 10 H6 -2-CH 2SH（II），和4 ′-烷氧基联苯-4-硫醇，4 ′-CH 3（CH 2）（m）OC 6 H4 C6 H4 -4-SH（III）（m = 15，16）的结构，并与正烷基硫醇CH_3（CH_2）（m）SH（TV）（m = 15，16）的相应结构进行了比较。结果表明，化合物I、II和III在Au和Ag上形成了有序的单分子膜，具有几乎相同的烃尾结构，这可能是因为在几乎相同的Au和Ag基底晶格上的芳香族发色团具有相同的人字形堆积。由分子力学计算支持的芳族发色团的人字形堆积反过来决定了烃链的晶格和间距。化合物I和III似乎具有相同的结构，这表明硫的结合几何形状可以是sp（3）（表面-S-C键角类似于109度）或sp杂化（表面-S-C键角类似于180度），这取决于分子其他部分中的堆积相互作用。空间要求最低的正烷基乙氧基化物（IV）允许在Ag上而不是在Au上具有更大的堆积密度，导致硫与表面的结合几何形状在两种金属上不同。IV在Ag上的紧密堆积使得具有短链的硫醇的单层比Au的单层在构象上更有序。
Structures of self-assembled monolayers of 4'-alkoxybiphenyl-4-methanethiol, 4'-CH3(CH2)(m)OC6H4C6H4-4-CH2SH (I), (6-alkoxynaphth-2-yl)methanethiol, 6-CH3(CH2)(m)OC10H6-2-CH2SH (II), and 4'-alkoxybiphenyl-4-thiol, 4'-CH3(CH2)(m)OC6H4C6H4-4-SH (III) (m = 15, 16) on surfaces of evaporated Au and Ag were characterized and compared with the corresponding structures of n-alkanethiol, CH3(CH2)(m)SH (TV) (m = 15, 16). The results revealed that compounds I, II, and III form well-ordered monolayers on Au and Ag, with nearly identical structure of the hydrocarbon tail, presumably because of the same herringbone packing of the aromatic chromophores on nearly identical lattices of Au and Ag substrates. The herringbone packing of the aromatic chromophores, supported by molecular mechanics calculations, in turn determines the lattice and the spacing of the hydrocarbon chains. That compounds I and III appear to have the same structure indicates that the binding geometry of sulfur can be either sp(3) (surface-S-C bond angle of similar to 109 degrees) or sp hybridized (surface-S-C bond angle of similar to 180 degrees), depending on packing interactions in other parts of the molecules. The least sterically demanding n-alkanethiol (IV) allows a greater density of packing on Ag but not on Au, causing the binding geometry of sulfur to the surface to differ on the two metals. The tighter packing of IV on Ag makes monolayers of thiols with short chains more ordered conformationally than those of Au.