Porphyrins and Phorphyrin Oligomers

A STM study [108] on vacuum deposited Cu-tetra[3,5 di-t-butylphenyl] porphyrin molecules on Au(llO), Ag(llO) and Cu(lOO) served as example in the discussion previously on differences between AFM and STM. Depending on the substrate the porphyrin molecules took different conformations, however, solely the legs of this porphyrin molecule have been visible in the STM measurements. 

Itaya and co-workers investigated 5,10,15,20-tetrakis(N-methylpyridinium-4-yl)-21H,23H-porphine (TMPyP) on bare Au(lll), lodine-Au(lll) [161] and Sulfur-Au(lll) [162] with STM under potential control. 

68) a-cyclodextrins (CyD) in 0.1 M NaOH were cast dropwise onto freshly cleaved M0S2 substrates and dried in air at room temperature, and then STM was performed under ambient conditions. The concentration of CyD necklaces was sufficiently diluted to enable observation of an isolated chain of a-CyDs. 

69) Also here, the tunnelling tip was prepared from an electrochemically etched W wire with its side wall sealed with transparent nail polish. The tip was previously soaked in the electrolyte solution for several hours to remove soluble contaminants before STM measurements started. 

On bare Au(lll) [161] after injection of a dilute aqueous solution of TMPyP directly into the STM cell under potential control at 0.8 V (versus a reversible hydrogen electrode (RHE)) immediately spots appeared and covered the surface. 

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