Sil, Debangsu ; Bhowmik, Susovan ; Khan, Firoz Shah Tuglak ; Rath, Sankar Prasad (2016) 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 Inorganic Chemistry, 55 (7). pp. 3239-3251. ISSN 0020-1669
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Official URL: http://doi.org/10.1021/acs.inorgchem.5b02226
Related URL: http://dx.doi.org/10.1021/acs.inorgchem.5b02226
Abstract
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 meso resonances, unlike the case for the diiron(III) analogues, where the meso 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 (J) values ranging from −29.5 to −38.6 cm–1. Fairly good correlations are observed for J 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.
Item Type: | Article |
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Source: | Copyright of this article belongs to American Chemical Society. |
ID Code: | 120855 |
Deposited On: | 06 Jul 2021 07:31 |
Last Modified: | 06 Jul 2021 07:31 |
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