In situ surface-enhanced IR absorption spectroscopy on CO adducts of iron protoporphyrin IX self-assembled on a Au electrode.
The surface coordination chemistry of carbon monoxide with the reduced form (Fe(II)PP) of iron(III) protoporphyrin IX (Fe(III)PP) monolayer self-assembled on a Au electrode in 0.1 M HClO4 was studied for the first time by using in situ ATR-surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS). Both mono- and biscarbonyl adducts [simplified as Fe(II)(CO)PP and Fe(II)(CO)2PP, respectively] were detected, depending on the history of potential control. Initially, the Fe(II)(CO)PP predominates, and the intermediate transition potential for the conversion of Fe(II)(CO)PP to Fe(III)PP and CO was spectrally determined to be ca. 0.09 V (vs SCE). The ratio of Fe(II)(CO)2PP and Fe(II)(CO)PP increases after a potential excursion to a sufficiently positive value. Fe(II)(CO)2PP is much more stable against its electro-oxidation to Fe(III)PP than its counterpart Fe(II)(CO)PP with increasing potential. The observed change of coordination properties may be ascribed to an irreversible structural reorganization of the FePP adlayer caused by the potential excursion.
Ma
Min
M
Shanghai Key Laboratory for Molecular Catalysis and Innovative Materials and Department of Chemistry, Fudan University, Shanghai 200433, China.
Yan
Yan-Gang
YG
Huo
Sheng-Juan
SJ
Xu
Qun-Jie
QJ
Cai
Wen-Bin
WB
D002248:Carbon Monoxide / Q000737:chemistry*; D004566:Electrodes; D006046:Gold / Q000737:chemistry*; D053768:Metal Nanoparticles / Q000737:chemistry*; D011524:Protoporphyrins / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared / Q000379:methods
D011524:Protoporphyrins; C448299:iron protoporphyrin IX; D006046:Gold; D002248:Carbon Monoxide