Electrochemistry and Spectroelectrochemistry of meso-Substituted Free-Base Corroles in Nonaqueous Media:  Reactions of (Cor)H₃, [(Cor)H₄]⁺, and [(Cor)H₂]^-

Abstract

Eleven free-base corroles with different electron-donating or electron-withdrawing meso substituents were characterized as to their electrochemistry and UV-visible spectroscopy in benzonitrile (PhCN) or pyridine containing tetra-n-butylammonium perchlorate (0.1 M). Six forms of the compounds with different numbers of protons and/or oxidation states were spectroscopically identified and are represented as (Cor)H3, (.Cor)H2, [(Cor)H2]-, [(.Cor)H2]2-, [(Cor)H4]+, and [(.Cor)H4]2+, where Cor is a trianionic corrole macrocycle. The electrochemistry and UV-visible properties are a function of corrole basicity, solvent basicity, and types or sizes of the meso substituents, and the compounds could be subdivided into one of two different groups, one of which comprises sterically hindered corroles and another that does not. The electroactive species in PhCN is (Cor)H3, whereas in pyridine, one inner proton dissociates, generating a mixture of (Cor)H3, [(Cor)H2]-, and pyH+. The addition of one electron to [(Cor)H2]- reversibly gives the [(.Cor)H2]2- pi-anion radical, whereas a reversible oxidation of the same species gives the neutral radical (.Cor)H2. The first one-electron reduction of (Cor)H3 occurs at the macrocycle in PhCN, but the initial product rapidly converts to [(Cor)H2]-, which undergoes additional reversible redox reactions at the conjugated pi-ring system. The first oxidation of (Cor)H3 in PhCN leads to a mixture of (.Cor)H2 and [(Cor)H4]+, both of which could be further oxidized or reduced. The UV-visible spectra of [(Cor)H4]+ were measured in PhCN after titrations with trifluoroacetic acid, after which selected samples were examined as to their electrochemistry. The HOMO-LUMO gaps of [(Cor)H2]-, (Cor)H3, and [(Cor)H4]+ were also determined.

Ligand Noninnocence in Coinage Metal Corroles: A Silver Knife‐Edge

“…[15] This is seen to be the case in the present study as wella nd is illustrated by the cyclic voltammograms for Ag [TPC] and Ag[Br 8 TPC] in PhCN containing 0.1 m TBAP ( Figure 5). The first two reductions of the TPC derivative at E 1/2 = À0.86 Vand E p = À1.76 Vc orrespond to the Ag III / Ag II and Ag II /Ag I processes, [15] while the third, clearly irreversible reduction at E 1/2 = À2.01 Vi sa ssignedt ot he diproticc orrole demetalation product, [15,36,37] 8 TPC]}C,r espectively,a sp reviously described in the literature for an umber of free-base corrole systems. [15,36,37] Similar demetalation behavior was also found in CH 2 Cl 2 and pyridine.…”

“…The first two reductions of the TPC derivative at E 1/2 = À0.86 Vand E p = À1.76 Vc orrespond to the Ag III / Ag II and Ag II /Ag I processes, [15] while the third, clearly irreversible reduction at E 1/2 = À2.01 Vi sa ssignedt ot he diproticc orrole demetalation product, [15,36,37] 8 TPC]}C,r espectively,a sp reviously described in the literature for an umber of free-base corrole systems. [15,36,37] Similar demetalation behavior was also found in CH 2 Cl 2 and pyridine. In contrast to the silver corroles, one-electron reduction of the coppera nd gold corroles was found to be fully reversible with no indication of demetalation;t hat is, the originals pectra were recovered upon reversal of the voltage.…”

New and Efficient Arrays for Photoinduced Charge Separation Based on Perylene Bisimide and Corroles

“…Model C2 displays a splitting of the Soret band previously discussed [15] and typical of corroles with a deviation from planarity of the macrocycle induced by crowding of substituents and reported for meso aryl groups bearing bulky ortho substituents. [12,11] The dyads C2-PI, C3-PI, and C3-PPI display spectra which are essentially the superimposed absorption spectra of the component models, Figure 1. A very slight bathochro- mic shift (2-3 nm) in the absorption maximum of the dyads with respect to the components can be noticed in C2-PI and C3-PI, but it is completely absent in C3-PPI, where the insertion of a further phenyl group electronically decouples components even more.…”

“…[10,11,12] Free-base corroles can be connected to other units yielding photo-and thermally stable dyads able to undergo interesting photoinduced processes, such as energy [13,14,15] or electron transfer. [15] Herein we address the formation of charge-separated states following photoinduced electron transfer in new free-base corrolebased dyads.…”

Insights into the Tautomerism in meso‐Substituted Corroles: A Variable‐Temperature 1H, 13C, 15N, and 19F NMR Spectroscopy Study

“…[1] Their synthesis, [2] chemical transformations, [3] coordination chemistry, [4] photophysics, [5] non-linear properties, [6] and electrochemistry [7] have recently been studied in great detail. Synthetic advances in corrole chemistry led these macrocycles and the related metal complexes to be applied in oxidation catalysis (Fe, Mn, Cr), [8] reduction catalysis (Cr, Mn, Fe), [8] group transfer catalysis (Rh, Fe), [8] sensors (Co), [9] dye-sensitized solar cells (Ga, Sn), [8] and medicinal applications (free bases, Ga).…”