Nafion‐supported metal complexes: a resonance Raman and UV–visible spectroscopic study

Abstract

Resonance Raman and UV-visible spectra of cobalt tetraphenylporphyrin and cobalt phthalocyanine in Nafion were recorded. The spectroscopic measurements show that the porphyrin is incorporated into the hydrophobic regions of the polymer whilst the phthalocyanine is associated with the ionic domains. The macrocycles undergo a change in geometry in Nsfion, the porphyrins exhibiting a decreased core size in the membrane.

Molecular catalysis of the oxygen reduction reaction by iron porphyrin catalysts tethered into Nafion layers: An electrochemical study in solution and a membrane-electrode-assembly study in fuel cells

“…6 shows the UVeVis spectral changes observed for Fe(III) TMPyP in the absence and presence of Nafion. Upon the addition of two drops of Nafion there was a red-shift of the Soret band from 396 nm to 402 nm, and this shift was accompanied by a decrease in absorbance and band broadening [58,59]. The pep* transitions in metalloporphyrins are known to be affected by the complex coordination environment or by the distortion of the ring [58,59].…”

“…Upon the addition of two drops of Nafion there was a red-shift of the Soret band from 396 nm to 402 nm, and this shift was accompanied by a decrease in absorbance and band broadening [58,59]. The pep* transitions in metalloporphyrins are known to be affected by the complex coordination environment or by the distortion of the ring [58,59]. This red-shift could therefore be explained in terms of the interaction between Nafion with the central metal ion or with the ring, though the latter is strongly accepted [58e60].…”

Reactions of Hydroxylamine with Metal Porphyrins

“…The resonance Raman spectra were also consistent with a cobalt(III) porphyrin complex. In acetonitrile, the ν 2 band for the hydroxylamine complex (Co II (TPP) bands in parentheses occurred at 1569 cm -1 (1563 cm -1 ) and the ν 4 band at 1373 cm -1 (1363 cm -1 ). Overall, the spectroscopic evidence was consistent with the formation of a Co III (TPP)(NH 2 OH) 2 + complex.…”

Chemically Modulated Microwave-Assisted Synthesis of MOF-74(Ni) and Preparation of Metal–Organic Framework-Matrix Based Membranes for Removal of Metal Ions from Aqueous Media

“…In Figure B Raman spectra from Nafion is shown where four distinct vibrational bands at 731, 1216, 1297, and 1377 cm –1 are observed, which correspond to [-(CF 2 CF 2 )-] groups present in the polymer backbone. Side chains in Nafion result in the five other vibrational bands observed at 805, 971, 1060, 1180, and 1360 cm –1 . − Prior studies have paid special attention to the two peaks located at 971 and 1060 cm –1 due to their sensitivity to cation exchange in Nafion. − These peaks correspond to symmetric stretch modes of the ether group and the S–O bonds in the Nafion structure and change when dehydration or cation exchange processes occur. After exposure to an aqueous solution of silver nitrate the Raman spectra of composite films significantly changes, where two intense peaks at 1358 and 1585 cm –1 are observed.…”