Second sphere control of spin state: Differential tuning of axial ligand bonds in ferric porphyrin complexes by hydrogen bonding

Mittra, Kaustuv; Sengupta, Kushal; Singha, Asmita; Bandyopadhyay, Sabyasachi; Chatterjee, Sudipta; Rana, Atanu; Samanta, Subhra; Dey, Abhishek

doi:10.1016/j.jinorgbio.2015.11.013

Cited by 21 publications

(28 citation statements)

References 81 publications

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“…These marker bands originate from the symmetric normal modes of the porphyrin macrocycle and are excited by a laser having a wavelength corresponding to π➔π* electronic transitions of the heme complexes [42,43]. These vibrations are extremely sensitive to the oxidation and spin state of the central metal ion and thus, report the electronic structure of the metal center with high fidelity [43][44][45][46][47][48]. This is also the case for heme active sites, as indicated by ν 4 and ν 2 vibrations at 1375 ± 1, 1586 ± 2 cm -1 , typical of S = 1/2 Fe III heme proteins [49,50].…”

Section: Fe III -Omentioning

confidence: 99%

Synthetic heme dioxygen adducts: electronic structure and reactivity

Singha

Mittra

Dey

2022

Trends in Chemistry

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A lot of research is currently dedicated to the understanding of reactivity of iron-oxy adducts with both heme and non-heme ligands. This perspective attempts to discuss the effect of distal H-bonding and axial ligand on the electronic structure of FeO 2 adducts of synthetic Fe-porphyrin complexes. Further, the reactivity of FeO 2 adducts, including electrophilic addition, hydrogen atom transfer (HAT), proton coupled electron transfer (PCET), and the role of axial ligand and H-bonding on these are discussed. Electronic structure of FeO 2Electron paramagnetic resonance (EPR) measurements on most known FeO 2 species, natural and synthetic, have shown that these have S = 0, diamagnetic, ground state (GS). Consequently, three different electronic structure descriptions for FeO 2 species have been proposed, the net spin being zero in all of them.

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Section: Fe III -Omentioning

confidence: 99%

Synthetic heme dioxygen adducts: electronic structure and reactivity

Singha

Mittra

Dey

2022

Trends in Chemistry

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“…These, and similar molecules such as phthalocyanine, are polyaromatic complexes that can accommodate a range of atoms at their centers to induce changes in magnetic and optical properties [1][2][3][4]. As a result of their versatility, these complexes have found a range of exciting applications in spintronics [5][6][7][8][9][10][11][12][13][14], optoelectronics [15,16], solar cells [17][18][19][20][21][22], and as building blocks of magnetic materials [23][24][25][26][27][28][29] or highly tunable qubits for quantum computing applications [30]. These complexes display important correlation physics, such as spin and orbital variants of the Kondo effect in phthalocyanine (FePc) molecules deposited on the (111) surface of noble metals [31][32][33][34][35][36][37][38].…”

Section: Introductionmentioning

confidence: 99%

Many-Body Effects in FeN4 Center Embedded in Graphene

et al. 2020

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We introduce a computational approach to study porphyrin-like transition metal complexes, bridging density functional theory and exact many-body techniques, such as the density matrix renormalization group (DMRG). We first derive a multi-orbital Anderson impurity Hamiltonian starting from first principles considerations that qualitatively reproduce generalized gradient approximation (GGA)+U results when ignoring inter-orbital Coulomb repulsion U ′ and Hund exchange J. An exact canonical transformation is used to reduce the dimensionality of the problem and make it amenable to DMRG calculations, including all many-body terms (both intra- and inter-orbital), which are treated in a numerically exact way. We apply this technique to FeN 4 centers in graphene and show that the inclusion of these terms has dramatic effects: as the iron orbitals become single occupied due to the Coulomb repulsion, the inter-orbital interaction further reduces the occupation, yielding a non-monotonic behavior of the magnetic moment as a function of the interactions, with maximum polarization only in a small window at intermediate values of the parameters. Furthermore, U ′ changes the relative position of the peaks in the density of states, particularly on the iron d z 2 orbital, which is expected to affect the binding of ligands greatly.

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“…49–51,55,56,93–98 Notable examples include those by the laboratories of de Visser and Rath, along with Dey, who reported on the reversible SCO in synthetic iron(III) complexes in the presence of inter- and intramolecular H-bonding, respectively. 94,95 In synthetic heme systems, the conversion from HS to LS iron(III) is most often associated with a strong σ -donor ligand (e.g. imidazole) binding axially to the iron, which raises the Fe d z 2 orbital energy.…”

Section: Introductionmentioning

confidence: 99%

Spin Interconversion of Heme-Peroxo-Copper Complexes Facilitated by Intramolecular Hydrogen-Bonding Interactions

et al. 2019

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Synthetic peroxo-bridged high-spin (HS) heme-(μ-η2:η1-O22−)-Cu(L) complexes incorporating (as part of the copper ligand) intramolecular hydrogen-bond (H-bond) capabilities and/or steric effects are herein demonstrated to affect the complex’s electronic and geometric structure, notably impacting the spin state. An H-bonding interaction with the peroxo core favors a low-spin (LS) heme-(μ-η1:η1-O22−)-Cu(L) structure, resulting in a reversible temperature-dependent interconversion of spin state (5 coordinate HS to 6 coordinate LS). The LS state dominates at low temperatures, even in the absence of a strong trans-axial heme ligand. Lewis base addition inhibits the H-bond facilitated spin interconversion by competition for the H-bond donor, illustrating the precise H-bonding interaction required to induce spin-crossover (SCO). Resonance Raman spectroscopy (rR) shows that the H-bonding pendant interacts with the bridging peroxide ligand to stabilize the LS but not the HS state. The H-bond (to the Cu-bound O atom) acts to weaken the O–O bond and strengthen the Fe–O bond, exhibiting ν(M–O) and ν(O–O) values comparable to analogous known LS complexes with a strong donating trans-axial ligand, 1,5-dicyclohexylimidazole, (DCHIm)heme-(μ-η1:η1-O22−)-Cu(L). Variable-temperature (−90 to −130 °C) UV–vis and 2H NMR spectroscopies confirm the SCO process and implicate the involvement of solvent binding. Examining a case of solvent binding without SCO, thermodynamic parameters were obtained from a van’t Hoff analysis, accounting for its contribution in SCO. Taken together, these data provide evidence for the H-bond group facilitating a core geometry change and allowing solvent to bind, stabilizing a LS state. The rR data, complemented by DFT analysis, reveal a stronger H-bonding interaction with the peroxo core in the LS compared to the HS complexes, which enthalpically favors the LS state. These insights enhance our fundamental understanding of secondary coordination sphere influences in metalloenzymes.

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Second sphere control of spin state: Differential tuning of axial ligand bonds in ferric porphyrin complexes by hydrogen bonding

Cited by 21 publications

References 81 publications

Synthetic heme dioxygen adducts: electronic structure and reactivity

Synthetic heme dioxygen adducts: electronic structure and reactivity

Many-Body Effects in FeN4 Center Embedded in Graphene

Spin Interconversion of Heme-Peroxo-Copper Complexes Facilitated by Intramolecular Hydrogen-Bonding Interactions

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