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Download fileContinuous-Wave and Pulse EPR Study of the Copper(II) Complex of N-Confused Tetraphenylporphyrin: Direct Observation of a σ Metal−Carbon Bond
journal contribution
posted on 05.03.2007, 00:00 authored by Carlos Calle, Arthur Schweiger, George MitrikasN-confused or inverted porphyrins, a family of porphyrin isomers that contain a confused pyrrole ring connected
through its α and β‘ positions in the macrocycle, exhibit unique physical and chemical properties, like, for instance,
the ability to stabilize unusual oxidation states of metals due to the reactivity of the inverted pyrrole. In this Article,
a combined multifrequency continuous-wave and pulse electron paramagnetic resonance (EPR) study of the copper(II) complex of N-confused tetraphenylporphyrin (TPP) is presented. By use of pulse EPR methods like ENDOR
and HYSCORE, the magnetic interactions between the unpaired electron of the compound and the surrounding
nitrogen nuclei were revealed. Through 13C labeling of the macrocycle, a detailed study of the carbon hyperfine
interaction became possible and provided further insight into the character of the metal−carbon bond. The observed
hyperfine couplings of the ligand atoms in the first coordination sphere showed the presence of a remarkably
strong σ Cu−C bond and allowed for a detailed analysis of the spin delocalization over the porphyrin macrocycle.
Interestingly, it was found that the observed delocalization is approximately 11% larger than the corresponding one
for CuTPP.