TY - JOUR
T1 - Scanning tunneling microscopy with chemically modified tips
T2 - Discrimination of porphyrin centers based on metal coordination and hydrogen bond interactions
AU - Ohshiro, T.
AU - Ito, T.
AU - Bühlmann, P.
AU - Umezawa, Y.
PY - 2001/3/1
Y1 - 2001/3/1
N2 - STM gold tips chemically modified with 4-mercaptopyridine (4MP) were found capable of discriminating zinc(II) 5,15-bis(4-octadecyloxyphenyl)porphyrin (Por-Zn) from its metal-free porphyrin (Por-2H) and nickel(II) complexes (Por-Ni) in the mixed monolayers of these compounds, spontaneously formed at the solution/graphite interface. The porphyrin centers in STM images observed with 4MP-modified tips exhibited bright spots, while those measured with unmodified tips exhibited the porphyrin centers as dark depressions. The centers of Por-Zn were brighter than those of Por-2H and Por-Ni, thereby allowing the discrimination of Por-Zn from Por-2H or Por-Ni in mixed monolayers. The changes in the contrasts of porphyrin centers of Por-2H and Por-Zn/Por-Ni were explained by facilitated electron tunneling due to hydrogen bond and metal coordination interactions, respectively, between porphyrin centers and the pyridyl group of 4MP on the tip.
AB - STM gold tips chemically modified with 4-mercaptopyridine (4MP) were found capable of discriminating zinc(II) 5,15-bis(4-octadecyloxyphenyl)porphyrin (Por-Zn) from its metal-free porphyrin (Por-2H) and nickel(II) complexes (Por-Ni) in the mixed monolayers of these compounds, spontaneously formed at the solution/graphite interface. The porphyrin centers in STM images observed with 4MP-modified tips exhibited bright spots, while those measured with unmodified tips exhibited the porphyrin centers as dark depressions. The centers of Por-Zn were brighter than those of Por-2H and Por-Ni, thereby allowing the discrimination of Por-Zn from Por-2H or Por-Ni in mixed monolayers. The changes in the contrasts of porphyrin centers of Por-2H and Por-Zn/Por-Ni were explained by facilitated electron tunneling due to hydrogen bond and metal coordination interactions, respectively, between porphyrin centers and the pyridyl group of 4MP on the tip.
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U2 - 10.1021/ac001056e
DO - 10.1021/ac001056e
M3 - Article
C2 - 11289431
AN - SCOPUS:0035282349
SN - 0003-2700
VL - 73
SP - 878
EP - 883
JO - Analytical Chemistry
JF - Analytical Chemistry
IS - 5
ER -