Dual-Channel-Mediated Spin Coupling for One-Electron-Oxidized Cobalt(II)-Saddled Porphyrin

Abstract

Saddle-shaped Co(II)[OET(p-R)PP] (R = CF3, H, CH3) can be readily oxidized with Cl2, Br2, and I2 to the corresponding one-electron-oxidation product Co[OET(p-R)PP]X (X = Cl, Br, I) with the clear character of a ring cation radical. With the series of (1)H and (13)C NMR spectra of these related complexes, both the axial ligand and peripheral substituent of the ring macrocycle are proven to act as a dual channel to tune spin coupling between low-spin Co(II) and a porphyrin π-cation radical. Density functional theory calculations have shown that the antiferromagnetic coupling between spins residing in d(z)(2) and a(2u) are expected to exist as the ground state. The paramagnetic properties are attributed to an a(1u)-type ferromagnetic excited triplet state.

A Highly Oxidized Cobalt Porphyrin Dimer: Spin Coupling and Stabilization of the Four‐Electron Oxidation Product

“…Each Co III center adopts a six‐coordinate octahedral geometry with iodide and triiodide as axial ligands, and the metal is displaced towards I − by 0.08 Å from the least‐squares plane of the C 20 N 4 porphyrinato core. The average Co–N p bond distance was found to be 1.951(7) Å, which falls within the observed range for cobalt(III) porphyrinates, but is longer than that of five‐coordinate 1,2‐bis[iodocobalt(III)‐5‐(2,3,7,8,12,13,17,18‐octaethylporphyrinyl)]ethane . To the best of our knowledge, no structure of a cobalt(III) porphyrin π‐cation radical has been reported previously.…”

“…The treatment of a cobalt(II) porphyrin with iodine is known to generate either a cobalt(III) porphyrin or a cobalt(II) porphyrin π‐cation radical; some of these species have also been structurally characterized ,. However, the oxidation of both the metal and porphyrin centers with iodine has not been reported so far.…”

“…Iodine is known to be a mild oxidant. Saddle‐shaped Co II [OET( p ‐R)PP] (in which R=CF 3 , H, CH 3 and OETPP is the dianion of 2,3,7,8,12,13,17,18‐octaethyl‐5,10,15,20‐tetraphenylporphyrinato) is readily oxidized with I 2 to the corresponding 1e‐oxidized complex Co[OET( p ‐R)PP]I with a clear indication of the formation of a porphyrin π‐cation radical . Also, the oxidation of (tetrabenzoporphyrinato)cobalt(II), Co(tbp), with iodine yielded a cobalt(II) porphyrin π‐cation radical, Co(tbp .…”

Nonplanar porphyrins: synthesis, properties, and unique functionalities

“…A rather simple means, for another classic, the 2,3,7,8, 12,13,17,18-octaethyl-5,10,15,20-tetranitroporphyrin (H 2 147) pioneered by Dolphin is meso-nitration of Zn(II)OEP to yield saddled porphyrins. 166 Metal complexes with the general MO(R)TPP substructure (R = Et, Pr, iPr, iBu) have been structurally characterized with M = 2H, 64b 3H, 167 4H, 155 P V , 168 V IV , 169 Fe III , 170 Co II , 171 Ni III , 172 Cu II , 173 Zn II , 63 Pd II , 66 and Sn IV , 174 each showing the familiar saddle shape. Similarly, crystal structures of OET(Ar)P with Ar: 175 2,6-diF-C 6 H 3 , 66 2,6-diCl-C 6 H 3 , 176 3,5-diMe-C 6 H 3 , 177 3,4,5-tri-MeO-C 6 H 2 , 178 and C 6 F 5 5b aryl units at C m -positions have been reported.…”

“…Metal complexes with the general MO(R)TPP substructure (R = Et, Pr, iPr, iBu) have been structurally characterized with M = 2H, 64 b 3H, 167 4H, 155 P V , 168 V IV , 169 Fe III , 170 Co II , 171 Ni III , 172 Cu II , 173 Zn II , 63 Pd II , 66 and Sn IV , 174 each showing the familiar saddle shape. Similarly, crystal structures of OET(Ar)P with Ar: 2-NH 3 + C 6 H 4 , 67 a 4-HO-C 6 H 4 , 4-Me-C 6 H 4 , 171 4-F 3 C-C 6 H 4 , 171 4-MeO-C 6 H 4 , 175 4-NC-C 6 H 4 , 4-F-C 6 H 4 , 4-Cl-C 6 H 4 , 4-Br-C 6 H 4 , 66 4-MeO 2 C-C 6 H 4 , 175 2,6-diF-C 6 H 3 , 66 2,6-diCl-C 6 H 3 , 176 3,5-diMe-C 6 H 3 , 177 3,4,5-tri-MeO-C 6 H 2 , 178 and C 6 F 5 5 b aryl units at C m -positions have been reported.…”