Adlayers of 5,10,15,20-tetraphenyl-21H,23H-porphine cobalt(II) and copper(II) (CoTPP and CuTPP) formed on a Au(111) electrode by immersion into a benzene solution containing either CoTPP or CuTPP were investigated in 0.1 M HClO4 by cyclic voltammetry and in situ scanning tunneling microscopy (STM). Highly ordered arrays of CoTPP and CuTPP molecules were observed on the Au(111) surface. Highresolution STM images revealed the characteristic shape, internal molecular structure, and molecular orientation of individual CoTPP and CuTPP molecules in ordered arrays. The adlayers of CoTPP and CuTPP formed on Au(111) were in an identical packing arrangement with the same orientation. The center cobalt ion in CoTPP appeared as the brightest spot in the STM image, whereas the copper ion in CuTPP was dark. On the adlayers of highly ordered CoTPP and CuTPP molecules, O 2 reduction was carried out in 0.1 M HClO4 saturated with O2. Voltammetric results indicated that CuTPP did not catalyze the reaction, whereas the highly ordered CoTPP adlayer on Au(111) enhanced the two-electron reduction of O2 to H2O2.
Two-component adlayers consisting of zinc(II) phthalocyanine (ZnPc) and a metalloporphyrin, such as zinc(II) octaethylporphyrin (ZnOEP) or zinc(II) tetraphenylporphyrin (ZnTPP), were prepared by immersing either an Au(111) or Au(100) substrate in a benzene solution containing those molecules. The bimolecular adlayers thus prepared were investigated in 0.1 M HClO4 by cyclic voltammetry (CV) and electrochemical scanning tunneling microscopy (EC-STM). A supramolecularly organized "chessboard" structure was formed for the ZnPc and ZnOEP bimolecular array on Au(111), while characteristic nanohexagons were found in the ZnTPP and ZnOEP bimolecular adlayer. EC-STM revealed that the surface mobility and the molecular re-organization of ZnPc and ZnOEP on Au(111) were tunable by manipulating the electrode potential, whereas the ZnTPP and ZnOEP bimolecular array was independent of the electrode potential. A "bottom-up" hybrid assembly of fullerene molecules was formed successfully on an alternate array of bimolecular ZnPc and ZnOEP molecules. The bimolecular "chessboard" served as a template to form the supramolecular assembly of C60 by selective trapping in the open spaces. A supramolecular organization of ZnPc and ZnOEP was also found on the reconstructed Au(100)-(hex) surface. A highly ordered, compositionally disordered but alternate array of ZnPc and ZnOEP was formed on the reconstructed Au(100)-(hex) surface, indicating that the bimolecular adlayer structure is dependent on the atomic arrangement of underlying Au in the formation of supramolecular nanostructures composed of those molecules. On the bimolecular array consisting of ZnPc and ZnOEP on the Au(100)-(hex), no highly ordered supramolecular assembly of C60 was found, suggesting that the supramolecular assembly of C60 molecules is strongly dependent upon the bimolecular packing arrangement of ZnPc and ZnOEP.
Adlayers of cobalt(II) porphine (CoP) and [2,3,7,8,12,13,17,18-octaethyl-21H,23-H-porphine]cobalt(II)
(CoOEP) were formed on Au(111) by immersing the substrate in a benzene solution containing either CoP
or CoOEP molecules and investigated in 0.1 M HClO4 by using in situ scanning tunneling microscopy. Highly
ordered arrays of CoP were observed on the Au(111)-(1×1) surface under controlled potential conditions.
The adlayer of CoOEP molecules was also highly ordered, whereas the Au(111) substrate was found to
become reconstructed upon adsorption of CoOEP. Both CoP and CoOEP molecules were closely packed on
Au(111). On the adlayers of CoP and CoOEP, the electrochemical reduction of O2 was examined in 0.1 M
HClO4 saturated with O2. The adlayers of both CoP and CoOEP on Au(111) enhanced the reduction of O2.
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