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Pandit YA, Usman M, Sarkar A, Shah SJ, Rath SP. Control of spin coupling through a redox-active bridge in a dinickel(II) porphyrin dimer: step-wise oxidations enable isolations of a chlorin-porphyrin heterodimer and a dication diradical with a singlet ground state. Dalton Trans 2023; 52:877-891. [PMID: 36464989 DOI: 10.1039/d2dt03283j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
A dinickel(II)porphyrin dimer has been used here in which the redox-active pyrrole-moiety, similar to the tryptophan residue in diheme enzymes such as MauG and bCcP, has been placed between two Ni(II)porphyrin centers connected via a flexible, but unconjugated methylene bridge. This arrangement provides a large physical separation between the two metal centers and thus displays almost no communication between them through the bridge. Upon treatment with DDQ as an oxidant, the dinickel(II) porphyrin dimer slowly gets converted into an indolizinium-fused chlorin-porphyrin heterodimer. However, oxidations of the dinickel(II) porphyrin dimer up to two oxidizing equivalents using oxidants such as AgSbF6 and FeCl3 resulted in the formation of a dication diradical complex. Interestingly, in order to stabilize such a highly oxidized dication diradical, two non-conjugated methylene spacers undergo facile 2e-/-2H+ oxidation to make the bridge fully π-conjugated for promoting through-bond communication. Through the oxidized and conjugated bridge, two porphyrin π-cation radicals display considerable communications leading to an efficient intramolecular spin coupling to form a singlet state. Interestingly, the redox-active nature of the bridge controls the electronic communication just by simple oxidation or reduction, and thereby, acts as a molecular switch for efficient magnetic relay.
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Affiliation(s)
- Younis Ahmad Pandit
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur-208016, India.
| | - Mohammad Usman
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur-208016, India.
| | - Anindya Sarkar
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur-208016, India.
| | - Syed Jehanger Shah
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur-208016, India.
| | - Sankar Prasad Rath
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur-208016, India.
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Sil D, Khan FST, Rath SP. Effect of intermacrocyclic interactions: Modulation of metal spin-state in oxo/hydroxo/fluoro-bridged diiron(III)/dimanganese(III) porphyrin dimers. ADVANCES IN INORGANIC CHEMISTRY 2023. [DOI: 10.1016/bs.adioch.2022.08.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
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Mizrahi A, Bhowmik S, Manna AK, Sinha W, Kumar A, Saphier M, Mahammed A, Patra M, Fridman N, Zilbermann I, Kronik L, Gross Z. Electronic Coupling and Electrocatalysis in Redox Active Fused Iron Corroles. Inorg Chem 2022; 61:20725-20733. [PMID: 36512733 PMCID: PMC9799712 DOI: 10.1021/acs.inorgchem.2c01389] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Conjugated arrays composed of corrole macrocycles are increasingly more common, but their chemistry still lags behind that of their porphyrin counterparts. Here, we report on the insertion of iron(III) into a β,β-fused corrole dimer and on the electronic effects that this redox active metal center has on the already rich coordination chemistry of [H3tpfc] COT, where COT = cyclo-octatetraene and tpfc = tris(pentafluorophenyl)corrole. Synthetic manipulations were performed for the isolation and full characterization of both the 5-coordinate [FeIIItpfc(py)]2COT and 6-coordinate [FeIIItpfc(py)2]2COT, with one and two axial pyridine ligands per metal, respectively. X-Ray crystallography reveals a dome-shaped structure for [FeIIItpfc(py)]2COT and a perfectly planar geometry which (surprisingly at first) is also characterized by shorter Fe-N (corrole) and Fe-N (pyridine) distances. Computational investigations clarify that the structural phenomena are due to a change in the iron(III) spin state from intermediate (S = 3/2) to low (S = 1/2), and that both the 5- and 6-coordinated complexes are enthalpically favored. Yet, in contrast to iron(III) porphyrins, the formation enthalpy for the coordination of the first pyridine to Fe(III) corrole is more negative than that of the second pyridine coordination. Possible interactions between the two corrole subunits and the chelated iron ions were examined by UV-Vis spectroscopy, electrochemical techniques, and density functional theory (DFT). The large differences in the electronic spectra of the dimer relative to the monomer are concluded to be due to a reduced electronic gap, owing to the extensive electron delocalization through the fusing bridge. A cathodic sweep for the dimer discloses two redox processes, separated by 230 mV. The DFT self-consistent charge density for the neutral and cationic states (1- and 2-electron oxidized) reveals that the holes are localized on the macrocycle. A different picture emerges from the reduction process, where both the electrochemistry and the calculated charge density point toward two consecutive electron transfers with similar energetics, indicative of very weak electron communication between the two redox active iron(III) sites. The binuclear complex was determined to be a much better catalyst for the electrochemical hydrogen evolution reaction (HER) than the analogous mononuclear corrole.
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Affiliation(s)
- Amir Mizrahi
- Chemistry
Department, Nuclear Research Centre Negev, Beer-Sheva84190, Israel,Schulich
Faculty of Chemistry, Technion Institute
of Technology, Haifa3200003, Israel
| | - Susovan Bhowmik
- Schulich
Faculty of Chemistry, Technion Institute
of Technology, Haifa3200003, Israel,Bankura
Sammilani College (W.B), Bankura722102, India
| | - Arun K. Manna
- Department
of Molecular Chemistry and Materials Science, Weizmann Institute of Science, Rehovot76100, Israel
| | - Woormileela Sinha
- Schulich
Faculty of Chemistry, Technion Institute
of Technology, Haifa3200003, Israel,Department
of Chemistry, BITS PilaniK K Birla Goa Campus, NH17B, Zuarinagar, Goa403726, India
| | - Amit Kumar
- Schulich
Faculty of Chemistry, Technion Institute
of Technology, Haifa3200003, Israel
| | - Magal Saphier
- Chemistry
Department, Nuclear Research Centre Negev, Beer-Sheva84190, Israel
| | - Atif Mahammed
- Schulich
Faculty of Chemistry, Technion Institute
of Technology, Haifa3200003, Israel
| | | | - Natalia Fridman
- Schulich
Faculty of Chemistry, Technion Institute
of Technology, Haifa3200003, Israel
| | - Israel Zilbermann
- Chemistry
Department, Nuclear Research Centre Negev, Beer-Sheva84190, Israel,Chemistry
Department, Ben-Gurion University of the
Negev, Beer-Sheva84105, Israel,
| | - Leeor Kronik
- Department
of Molecular Chemistry and Materials Science, Weizmann Institute of Science, Rehovot76100, Israel,
| | - Zeev Gross
- Schulich
Faculty of Chemistry, Technion Institute
of Technology, Haifa3200003, Israel,
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Sarkar S, Sarkar P, Samanta D, Pati SK, Rath SP. Cooperativity in Diiron(III)porphyrin Dication Diradical-Catalyzed Oxa-Diels–Alder Reactions: Spectroscopic and Mechanistic Insights. ACS Catal 2022. [DOI: 10.1021/acscatal.2c02479] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Sabyasachi Sarkar
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur 208016, India
| | - Pallavi Sarkar
- Theoretical Sciences Unit, School of Advanced Materials (SAMat), Jawaharlal Nehru Center for Advanced Scientific Research, Bangalore 560064, India
| | - Deepannita Samanta
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur 208016, India
| | - Swapan K Pati
- Theoretical Sciences Unit, School of Advanced Materials (SAMat), Jawaharlal Nehru Center for Advanced Scientific Research, Bangalore 560064, India
| | - Sankar Prasad Rath
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur 208016, India
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