Binuclear complexes with single M-F-M bridge (M: Fe, Mn, and Cu): A critical analysis of the impact of fluoride for isoelectronic hydroxide substitution

Sarkar, Sabyasachi; Khan, Firoz Shah Tuglak; Guchhait, Tapas; Rath, Sankar Prasad

doi:10.1016/j.ccr.2022.215003

“…Evidence in favor of the first possibility comes from comparison of the spectra in Figures 4a and 4c: the differences between the two kinds of ortho ‐F and meta ‐F atoms in ( 1 ‐Ga) 2 are about 2 times larger than in the product obtained from combination of ( 1 ‐Fe) 2 with NO. This finding suggests that NO coordination to ( 1 ‐Fe) 2 triggers dissociation to mononuclear units via detachment of the imidazole that holds them together, consistent with the very strong trans effect of nitric oxide [36,37] . Examination of the same solution by 1 H NMR provided even stronger evidence for the formation of 1 ‐Fe(NO).…”

Section: Methodsmentioning

confidence: 58%

“…This finding suggests that NO coordination to (1-Fe) 2 triggers dissociation to mononuclear units via detachment of the imidazole that holds them together, consistent with the very strong trans effect of nitric oxide. [36,37] Examination of the same solution by 1 H NMR provided even stronger evidence for the formation of 1-Fe(NO). Unlike (1-Ga) 2 but much like its free base 1-H 3 , 17 all the β-pyrrole CÀ H and imidazole NÀ H resonances appeared in the 'normal' aromatic region.…”

mentioning

confidence: 92%

Reversible Reactions of Nitric Oxide with a Binuclear Iron(III) Nitrophorin Mimic

Sharma,

Saini,

Fridman

et al. 2023

Chemistry A European J

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Construction of functional synthetic systems that can reversibly bind and transport the most biologically important gaseous molecules, oxygen and nitric oxide (NO), remains a contemporary challenge. Myoglobin and nitrophorin perform these respective tasks employing a protein‐embedded heme center where one axial iron site is occupied by a histidine residue and the other is available for small molecule ligation, structural features that are extremely difficult to mimic in protein‐free environments. Indeed, the hitherto reported designs rely on sophisticated multistep syntheses for limiting access to one of the two axial coordination sites in small molecules. We have shown previously that binuclear Ga(III) and Al(III) corroles have available axial sites, and now report a redox‐active binuclear Fe(III) corrole, (1‐Fe)2, in which each (corrolato)Fe(III) center is 5‐coordinate, with one axial site occupied by an imidazole from the other corrole. The binuclear structure is further stabilized by attractive forces between the corrole π systems. Reaction of NO with (1‐Fe)2 affords mononuclear iron nitrosyls, and of functional relevance, the reaction is reversible: nitric oxide is released upon purging the nitrosyls with inert gases, thereby restoring (1‐Fe)2 in solutions or films.

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Unusual Stabilisation of Remarkably Bent Tetra‐Cationic Tetra‐radical Intermolecular Fe(III) μ‐Oxo Tetranuclear Complexes

Sarkar,

Tiwari,

Samanta

et al. 2024

Angewandte Chemie

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A hitherto unknown series of air stable, π‐conjugated, remarkably bent tetra‐cation tetra‐radical intermolecular Fe(III) µ‐oxo tetranuclear complex, isolated from the dication diradical diiron(III) porphyrin dimers, has been synthesised and spectroscopically characterised along with single crystal X‐ray structure determination of two such molecules. These species facilitate long‐range charge/radical delocalisation through the bridge across the entire tetranuclear unit manifesting an unusually intense NIR band. Assorted spin states of Fe(III) centres are stabilised within these unique tetranuclear frameworks: terminal six‐coordinate iron centres stabilise the admixed intermediate spin states while the central five‐coordinate iron centres stabilise the high‐spin states. Variable temperature magnetic susceptibility measurements indicated strong antiferromagnetic coupling for the Fe(III)‐O‐Fe(III) unit while the exchange interactions between the Fe centres and the porphyrin π‐cation radicals are weaker as supported both by magnetic data and DFT calculations. The nature of orbital overlap between the SOMOs of Fe(III) and π* orbital of the porphyrin was found to rationalise the observed exchange coupling, establishing such a complex magnetic exchange in this tetranuclear model with a significant bioinorganic relevance.

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Unusual Stabilisation of Remarkably Bent Tetra‐Cationic Tetra‐radical Intermolecular Fe(III) μ‐Oxo Tetranuclear Complexes

Sarkar,

Tiwari,

Samanta

et al. 2024

Angew Chem Int Ed

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0

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A hitherto unknown series of air stable, π‐conjugated, remarkably bent tetra‐cation tetra‐radical intermolecular Fe(III) µ‐oxo tetranuclear complex, isolated from the dication diradical diiron(III) porphyrin dimers, has been synthesised and spectroscopically characterised along with single crystal X‐ray structure determination of two such molecules. These species facilitate long‐range charge/radical delocalisation through the bridge across the entire tetranuclear unit manifesting an unusually intense NIR band. Assorted spin states of Fe(III) centres are stabilised within these unique tetranuclear frameworks: terminal six‐coordinate iron centres stabilise the admixed intermediate spin states while the central five‐coordinate iron centres stabilise the high‐spin states. Variable temperature magnetic susceptibility measurements indicated strong antiferromagnetic coupling for the Fe(III)‐O‐Fe(III) unit while the exchange interactions between the Fe centres and the porphyrin π‐cation radicals are weaker as supported both by magnetic data and DFT calculations. The nature of orbital overlap between the SOMOs of Fe(III) and π* orbital of the porphyrin was found to rationalise the observed exchange coupling, establishing such a complex magnetic exchange in this tetranuclear model with a significant bioinorganic relevance.

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Binuclear complexes with single M-F-M bridge (M: Fe, Mn, and Cu): A critical analysis of the impact of fluoride for isoelectronic hydroxide substitution

Cited by 5 publications

References 199 publications

Reversible Reactions of Nitric Oxide with a Binuclear Iron(III) Nitrophorin Mimic

Reversible Reactions of Nitric Oxide with a Binuclear Iron(III) Nitrophorin Mimic

Unusual Stabilisation of Remarkably Bent Tetra‐Cationic Tetra‐radical Intermolecular Fe(III) μ‐Oxo Tetranuclear Complexes

Unusual Stabilisation of Remarkably Bent Tetra‐Cationic Tetra‐radical Intermolecular Fe(III) μ‐Oxo Tetranuclear Complexes

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