Experimental and Theoretical Investigation of a Series of Novel Dimanganese(III) μ‑Hydroxo Bisporphyrins: Magneto–Structural Correlation and Effect of Metal Spin on Porphyrin Core Deformation

The synthesis, structure, and properties of a new family of five ethane-bridged dimanganese­(III) μ-hydroxo bisporphyrins with the same core structure but different counteranions are reported here. Additions of 10% Brønsted acids such as HI, HBF₄, HSbF₆, HPF₆, and HClO₄ to a dichloromethane solution of the dichloro dimanganese­(III) bisporphyrin produces complexes having a remarkably bent μ-hydroxo group with I₃^–, BF₄^–, SbF₆^–, PF₆^–, and ClO₄^– as counteranions, respectively. The X-ray structures of all complexes have been determined, which have revealed the presence of two equivalent high-spin manganese­(III) centers with equally distorted porphyrin rings in the complexes, in sharp contrast with the case for the diiron­(III) μ-hydroxo bisporphyrin analogues. ¹H NMR spectra have shown highly deshielded <i>meso</i> resonances, unlike the case for the diiron­(III) analogues, where the <i>meso</i> resonances are highly shielded. The variable-temperature magnetic data have been subjected to a least-squares fit which provides a moderate antiferromagnetic coupling through the hydroxo bridge between two zero-field split Mn­(III) centers with coupling constant (<i>J</i>) values ranging from −29.5 to −38.6 cm^–1. Fairly good correlations are observed for <i>J</i> with Mn–O­(H) distances and Mn–O­(H)–Mn angles for all the complexes except for that having an I₃^– counteranion. DFT calculations support the stabilization of two equivalent high-spin Mn­(III) porphyrin cores in the complexes and have also explored the role of metal spin in controlling porphyrin ring deformation. Unlike diiron­(III) μ-hydroxo bisporphyrin complexes, the dimanganese­(III) analogues do not have easily accessible spin states of the metal attainable by subtle environmental perturbations and, therefore, can only stabilize the high-spin state with a variety of counteranions

Experimental and Theoretical Investigation of a Series of Novel Dimanganese(III) μ‑Hydroxo Bisporphyrins: Magneto–Structural Correlation and Effect of Metal Spin on Porphyrin Core Deformation

The synthesis, structure, and properties of a new family of five ethane-bridged dimanganese­(III) μ-hydroxo bisporphyrins with the same core structure but different counteranions are reported here. Additions of 10% Brønsted acids such as HI, HBF₄, HSbF₆, HPF₆, and HClO₄ to a dichloromethane solution of the dichloro dimanganese­(III) bisporphyrin produces complexes having a remarkably bent μ-hydroxo group with I₃^–, BF₄^–, SbF₆^–, PF₆^–, and ClO₄^– as counteranions, respectively. The X-ray structures of all complexes have been determined, which have revealed the presence of two equivalent high-spin manganese­(III) centers with equally distorted porphyrin rings in the complexes, in sharp contrast with the case for the diiron­(III) μ-hydroxo bisporphyrin analogues. ¹H NMR spectra have shown highly deshielded <i>meso</i> resonances, unlike the case for the diiron­(III) analogues, where the <i>meso</i> resonances are highly shielded. The variable-temperature magnetic data have been subjected to a least-squares fit which provides a moderate antiferromagnetic coupling through the hydroxo bridge between two zero-field split Mn­(III) centers with coupling constant (<i>J</i>) values ranging from −29.5 to −38.6 cm^–1. Fairly good correlations are observed for <i>J</i> with Mn–O­(H) distances and Mn–O­(H)–Mn angles for all the complexes except for that having an I₃^– counteranion. DFT calculations support the stabilization of two equivalent high-spin Mn­(III) porphyrin cores in the complexes and have also explored the role of metal spin in controlling porphyrin ring deformation. Unlike diiron­(III) μ-hydroxo bisporphyrin complexes, the dimanganese­(III) analogues do not have easily accessible spin states of the metal attainable by subtle environmental perturbations and, therefore, can only stabilize the high-spin state with a variety of counteranions

Experimental and Theoretical Investigation of a Series of Novel Dimanganese(III) μ‑Hydroxo Bisporphyrins: Magneto–Structural Correlation and Effect of Metal Spin on Porphyrin Core Deformation

The synthesis, structure, and properties of a new family of five ethane-bridged dimanganese­(III) μ-hydroxo bisporphyrins with the same core structure but different counteranions are reported here. Additions of 10% Brønsted acids such as HI, HBF₄, HSbF₆, HPF₆, and HClO₄ to a dichloromethane solution of the dichloro dimanganese­(III) bisporphyrin produces complexes having a remarkably bent μ-hydroxo group with I₃^–, BF₄^–, SbF₆^–, PF₆^–, and ClO₄^– as counteranions, respectively. The X-ray structures of all complexes have been determined, which have revealed the presence of two equivalent high-spin manganese­(III) centers with equally distorted porphyrin rings in the complexes, in sharp contrast with the case for the diiron­(III) μ-hydroxo bisporphyrin analogues. ¹H NMR spectra have shown highly deshielded <i>meso</i> resonances, unlike the case for the diiron­(III) analogues, where the <i>meso</i> resonances are highly shielded. The variable-temperature magnetic data have been subjected to a least-squares fit which provides a moderate antiferromagnetic coupling through the hydroxo bridge between two zero-field split Mn­(III) centers with coupling constant (<i>J</i>) values ranging from −29.5 to −38.6 cm^–1. Fairly good correlations are observed for <i>J</i> with Mn–O­(H) distances and Mn–O­(H)–Mn angles for all the complexes except for that having an I₃^– counteranion. DFT calculations support the stabilization of two equivalent high-spin Mn­(III) porphyrin cores in the complexes and have also explored the role of metal spin in controlling porphyrin ring deformation. Unlike diiron­(III) μ-hydroxo bisporphyrin complexes, the dimanganese­(III) analogues do not have easily accessible spin states of the metal attainable by subtle environmental perturbations and, therefore, can only stabilize the high-spin state with a variety of counteranions

Experimental and Theoretical Investigation of a Series of Novel Dimanganese(III) μ‑Hydroxo Bisporphyrins: Magneto–Structural Correlation and Effect of Metal Spin on Porphyrin Core Deformation

The synthesis, structure, and properties of a new family of five ethane-bridged dimanganese­(III) μ-hydroxo bisporphyrins with the same core structure but different counteranions are reported here. Additions of 10% Brønsted acids such as HI, HBF₄, HSbF₆, HPF₆, and HClO₄ to a dichloromethane solution of the dichloro dimanganese­(III) bisporphyrin produces complexes having a remarkably bent μ-hydroxo group with I₃^–, BF₄^–, SbF₆^–, PF₆^–, and ClO₄^– as counteranions, respectively. The X-ray structures of all complexes have been determined, which have revealed the presence of two equivalent high-spin manganese­(III) centers with equally distorted porphyrin rings in the complexes, in sharp contrast with the case for the diiron­(III) μ-hydroxo bisporphyrin analogues. ¹H NMR spectra have shown highly deshielded <i>meso</i> resonances, unlike the case for the diiron­(III) analogues, where the <i>meso</i> resonances are highly shielded. The variable-temperature magnetic data have been subjected to a least-squares fit which provides a moderate antiferromagnetic coupling through the hydroxo bridge between two zero-field split Mn­(III) centers with coupling constant (<i>J</i>) values ranging from −29.5 to −38.6 cm^–1. Fairly good correlations are observed for <i>J</i> with Mn–O­(H) distances and Mn–O­(H)–Mn angles for all the complexes except for that having an I₃^– counteranion. DFT calculations support the stabilization of two equivalent high-spin Mn­(III) porphyrin cores in the complexes and have also explored the role of metal spin in controlling porphyrin ring deformation. Unlike diiron­(III) μ-hydroxo bisporphyrin complexes, the dimanganese­(III) analogues do not have easily accessible spin states of the metal attainable by subtle environmental perturbations and, therefore, can only stabilize the high-spin state with a variety of counteranions

The Planar Cyclooctatetraene Bridge in Bis-Metallic Macrocycles: Isolating or Conjugating?

A minor modification of the reported procedure for the synthesis of a corrole dimer that is fused by the cyclooctatetraene (COT) unit, (H₃tpfc)₂COT, allowed for its isolation in 18% yield. Of the two redox isomers that this interesting macrocycle does form, the current focus is on the reduced form, in which each subunit resembles that of monomeric corroles with a trianionic N₄ coordination core. The corresponding bis-gallium­(III) complex was prepared as an entry into the potentially rich coordination chemistry of (H₃tpfc)₂COT. Both X-ray crystallography and DFT calculations disclosed that the COT moiety is essentially planar with very unusual nonalternating C–C bonds. The same holds true for the bis-gallium­(III) complexes [(Ga-tpfc)₂]­COT­(py)₂ and [(Ga-tpfc)₂]­COT­(py)₄, obtained with one and two pyridine molecules coordinated to each metal ion, respectively. The electronic spectra of both the free base and the gallium­(III) complexes display an extremely low energy band (λ_max at 720–724 nm), which points toward extensive π delocalization through the COT bridge. This aspect was fully addressed by examining the interactions between the two corrole subunits in terms of electrochemistry and DFT calculations of the oxidized and reduced macrocycle. The new near-IR bands that appear upon both oxidation (λ_max 1250 nm) and reduction (λ_max 1780 nm) serve as additional supporting evidence for this conclusion