Hyperfine structure in the electron spin resonance spectra of reduced porphins

Spectroelectrochemical Investigation of the One‐Electron Reduction of Nonplanar Nickel(II) Porphyrins

“…which indicates that singly reduced 1 does not disproportionate ( F is the Faraday constant, R is the gas constant, T is temperature). The literature also notes that disproportionation of singly reduced metalloporphyrins is typically not observed . This is further explicitly supported by TDDFT calculations that show that the disproportionation reaction of singly reduced 1 (doublet state) to doubly reduced 1 (singlet or triplet state) and parent porphyrin 1 (singlet state) is energetically not favored at room temperature (Δ R G =0.83 and 0.74 eV at 298 K for the formation of the doubly reduced singlet and triplet, respectively; see Table S9).…”

“…The literature also notes that disproportionation of singly reduced metalloporphyrins is typically not observed. [85][86][87] This is furthere xplicitly supported by TDDFT calculations that show that the disproportionation reaction of singly reduced 1 (doublet state) to doubly reduced 1 (singlet or triplet state) and parent porphyrin 1 (singlet state) is energetically not favored at room temperature (D R G = 0.83 and 0.74 eV at 298 K for the formation of the doubly reduced singlet and triplet,r espectively;s ee Table S9). However,s ingly reduced species 1 has an energetically higher lying quartet state and, according to the calculations, the disproportionation of singly reduced 1 (quartet state) to 1 (singlets tate) and doubly reduced 1 (triplet state) is thermodynamically allowed (D R G = À0.01 eV at 298 K; see Ta ble S9).…”

Synthesis and Stereochemistry of Hydroporphyrins

“…The most widely investigated chemical reduction that leads to interrupted systems is the treatment of porphyrins (1) with alkali metals, [46][47][48][49][50] or, better, with aromatic radical anions 26,28 to yield the porphyrin dianions, and the subsequent addition of protic solvent (reductive protonation) or alkylating reagents like alkyliodides (reductive alkylation). The reaction of metalloporphyrins with aromatic radical anions was first investigated by Closs and Closs.…”

“…The first step yields, in a one-electron reduction in aprotic solvents, the radical anion. 29,48,49,119,120,121 In protic solvents, this electron transfer is thought to be followed rapidly by a proton transfer, thus yielding a neutral radical. 48,49 This hypothetical intermediate is unstable, however, and the first detectable reduction product is a phlorin.…”

“…88,120,121 Phlorins can be produced electrochemically in good yield by reduction at a controlled potential. 48,49 They are easily reoxidized to the parent porphyrins, but their structure has been established 48,49 from their characteristic 10,14 uv-vis absorption spectrum, from coulometric studies, and from 1 H/ 2 H exchange experiments. In a similar reaction, chlorinphlorins are produced from chlorins.…”