Effect of NO₂ substitution and solvent on UV-visible spectra, redox potentials and electron transfer mechanisms of copper β-nitrotriarylcorroles. Proposed electrogeneration of a Cu(I) oxidation state

Abstract

Three copper triarylcorroles containing a [Formula: see text]-pyrrole nitro substituent were synthesized and characterized as to their spectral and electrochemical properties in nonaqueous media. The examined compounds are represented as [Formula: see text]-NO2(YPh)3CorCu, where Cor is the trianion of a triphenylcorrole and Y is a Cl, H or CH3 substituent at the para-position of the three meso-phenyl rings of the compound. The data from absorption spectra, electrochemistry and thin-layer spectroelectrochemistry are consistent with an initial assignment of Cu[Formula: see text]-Cor[Formula: see text] in CH2Cl2, DMF and pyridine and electrogeneration of a formal Cu(II) corrole with an unreduced macrocycle, represented as Cu[Formula: see text]-Cor[Formula: see text], after the first one-electron reduction in these solvents. The doubly reduced [Formula: see text]-nitrocorrole has a sharp Soret band at 439 nm and a well-defined Q-band at 611 nm in CH2Cl2. Similar absorption spectra are seen for the three examined doubly reduced nitrocorroles in DMF and pyridine, suggesting formation of a Cu(I) species with an unreduced macrocycle which is represented as Cu[Formula: see text]-Cor[Formula: see text]. Changes in redox potentials and absorption spectra of the nitrocorroles are examined as a function of solvent and substituents on the meso-phenyl rings of the compounds and comparisons are made between spectral and electrochemical data of the newly synthesized corroles and that of structurally related tetraarylcorroles lacking a [Formula: see text]-nitro group.

The Difficult Marriage of Triarylcorroles with Zinc and Nickel Ions

“…The one-electron oxidation of Zn­(3,17-Br 2 TTCorr) (Figure b) also results in quite similar spectral changes as those seen for the nonbrominated derivative (Figure b) in that a decreased intensity of the major Soret band at 448 nm is observed and shifted to 453 nm while two weak absorptions appear in the visible region at 656 and 871 nm. Again, the decreased Soret band of singly oxidized Zn­(3,17-Br 2 TTCorr) is blue-shifted as compared to the neutral complex, similar to the spectral changes observed during the oxidation of other non-innocent triarylcorroles ( vide supra ). ,− ,− …”

“…It is worth noting that the spectrum of the singly reduced species, [Zn II (TTCorr 3– )] − , is strikingly similar to other M­(II) corrole 3– systems such as singly reduced copper − ,− or nickel corroles, all of which display a red-shifted Soret band and at least one well-defined Q-band as compared to their non-innocent, neutral M II (TTCorr 2–• ) counterparts. Moreover, non-innocent cobalt corroles also display similar spectral changes upon reduction ( i.e.…”

“…These Δ E H‑L values for the Zn­(II) corrole radicals are notably smaller than other non-innocent corroles with electroinactive metal centers such as copper corroles, which typically exhibit Δ E H‑L values of 0.90 ± 0.07 V. ,− On the other hand, the HOMO–LUMO gap of structurally analogous nickel corrole was shown to exist as a dimer in solution and exhibit Δ E H‑L ∼ 0.70 V when measured in CH 2 Cl 2 /0.1 M TBAP …”

Grafting Copper and Gallium Corroles onto Zinc Oxide Nanoparticles

“…In addition, both compounds retain a peak at 374 nm, corresponding to the typical NO 2 functionality at corrole βposition. [29,30] Further evidence of this functionalization was obtained by X-ray analysis, confirming the position of the formyl group at the pyrrole α position ( Figure 3).…”

“…In addition, both compounds retain a peak at 374 nm, corresponding to the typical NO 2 functionality at corrole β ‐position ,…”