Intermediate-spin (S = 3/2) porphyrinatoiron(III) complexes

Dolphin, David; Sams, J. R.; Tsin, Tsang Bik

doi:10.1021/ic50169a043

Cited by 117 publications

(64 citation statements)

References 4 publications

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“…The same electronic configuration has been obtained by Hoshino et al for the ruffled six‐coordinate ferric 5,10,15,20‐tetraisopropylporphyrin with dioxane as axial ligands. The energy of the 3d x2‐y2 orbital is consistent with the criteria pointed out by Dolphin et al for obtaining an intermediate quartet spin state, that is, it must lie well above the other d orbitals and be unoccupied.…”

Section: Resultssupporting

confidence: 88%

Electronic properties of the low-lying spin states of dimethylnitrosamine coordinated to Fe(III) heme models: An ab initio study

Leitão

Ventura

Santana

et al. 2013

Int. J. Quantum Chem.

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The unusual O-coordination mode of nitrosamines to Fe(III) heme models has been observed in the bis(dimethylnitrosamine)(meso-tetraphenylporphyrinate)iron(III) cation. For the first time, this latter as well as the simpler bis(dimethylnitrosamine)(porphinate)iron(III) heme model cations have been studied through ab initio methods. The sextet, quartet, and doublet spin states of both cations have been studied through singlepoint calculations based on the experimental (X-ray) geometry. Their energies, charges, and spin densities have been analyzed. The obtained results (at the UHF/cc-pVDZ and ROHF/cc-pVDZ levels) indicate that the peripheral benzene rings are of secondary importance for the coordination of dimethylnitrosamine to the Fe(III) porphyrin core. The obtained energy ordering is sextet < quartet < doublet, at all computational levels. The UHF, ROHF, and UMP2 results indicate an excess of alpha spin density around the Fe atom, a low covalency for the FeAO bond and a substantial charge transfer to the Fe atom. Our best estimates [obtained at ROMP2 level with the mixed cc-pVDZ/cc-pVTZ-DK(Fe) basis set] for the energy differences (in eV) between the three spin states considered are 0.929 for the sextet-quartet gap and 0.812 for the quartetdoublet gap, which indicate that the spin crossover (at room temperature) is very unlikely. These results represent the substantial decrease in the uncorrelated values. The implications of spin contaminations at the UHF and UMP2 levels for subsequent geometry optimizations to be performed in the smaller cation have also been discussed.

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Section: Resultssupporting

confidence: 88%

Electronic properties of the low-lying spin states of dimethylnitrosamine coordinated to Fe(III) heme models: An ab initio study

Leitão

Ventura

Santana

et al. 2013

Int. J. Quantum Chem.

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“…4 The resulting microcrystalline material was dried at 130°C under a vacuum of 90 mTorr for 18 h. MnO 2 was provided by Chemetals, Inc. ͑chemically prepared ␥-MnO 2 ). Kynar vinylidene fluoride resin ͑Kynar Flex 2801͒ was purchased from Elf Atochem North America, Inc. Poly͑vinylidene fluoride͒ ͑PVDF͒ binder and acetylene black were purchased from Aldrich.…”

Section: Experimentalõcomputational Methodsmentioning

confidence: 99%

Composite Cathode with Li[sub 2]Pc

Scanlon

Lucente

Feld

et al. 2004

J. Electrochem. Soc.

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Computational chemistry calculations performed with Gaussian 98 were used to develop an experimental method that facilitates ionic connection between the solid-state electrolyte dilithium phthalocyanine (Li 2 Pc) and manganese dioxide (MnO 2 ). The planar configuration of the phthalocyanine ring and the fact that the lithium ions are very close to the ring may sterically hinder effective ionic coupling between Li 2 Pc and any potential cathode. This same argument has been used for understanding the insertion and removal of magnesium from water solutions of deuteroporphyrins. Calculated results show that lithium ions are drawn closer to the phthalocyanine ring upon formation of (Li 2 Pc) 2 via molecular self-assembly when compared to the single-molecule Li 2 Pc. However, extension of lithium ions above the planar phthalocyanine ring in (Li 2 Pc) 2 can be enhanced through formation of a complex at the axial position above lithium. Calculations show that corannulene at the axial position above lithium forms an asymmetric structure with (Li 2 Pc) 2 and extends lithium further above the ring. To test the theoretical results, an electrically conducting carbon with a curved lattice was used in the fabrication of an all solid-state electrochemical cell with a lithium metal foil anode, Li 2 Pc electrolyte, and a MnO 2 cathode. Slow-scan-rate cyclic voltammograms of a Li x MnO 2 cathode demonstrate the charging and discharging of cells.During the last several years, we have been trying to develop a solid-state electrolyte that is a single-ion conductor for lithium ions where the transference number for lithium is equal to unity. We have referred to this solid-state electrolyte as a lithium-ion conducting channel. 1 The purpose of the channel is to provide a continuous negative electrostatic potential field for the lithium ion throughout the solid-state electrolyte. If there is a discontinuity of the negative electrostatic potential field within the channel, it is then reasoned that lithium-ion conduction would be terminated. The possibility exists for forming a continuous negative electrostatic potential field for lithium-ion conduction through molecular self-assembly of dilithium phthalocyanine (Li 2 Pc). Ab initio calculations discussed in this paper show that there are attractive forces between molecules of Li 2 Pc that favor formation of an assembled structure. Electrostatic potential calculations for a section of the assembled self-assembled structure suggest that one could have a continuous negative electrostatic potential field between individual molecules of Li 2 Pc throughout the molecular system for lithium-ion transport. Although these theoretical results were encouraging for using Li 2 Pc as a solid-state electrolyte, attempts at preparing functioning full electrochemical cells were not successful. In this regard, a potential problem area was the lack of electrical connection between the solid-state electrolyte and the solid-state cathode. Specifically, a lack of lithium-ion transfer between the electrolyte and...

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“…(S = 3/2) ground state for iron(III) porphyrins have taken advantage of the weak nucleophilicity of certain anions, such as perchlorate, tetrafluoridoborate or halogenated closo-boranates, in combination with weak-field ligands (typically ethers or water), and could approach almost pure intermediate spin states in heme analogues by synthetically emphasizing the tetragonality of the ligand field. [5] A second and very successful approach towards i.s. Fe III porphyrins was developed from the finding that nonplanar distortion modes of the tetrapyrrole macrocycle induce changes in the orbital ordering of a bound metal ion.…”

Section: Introductionmentioning

confidence: 99%

Iron 10‐Thiacorroles: Bioinspired Iron(III) Complexes with an Intermediate Spin (S=3/2) Ground State

Sakow

Baabe

Böker

et al. 2014

Chemistry A European J

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A first systematic study upon the preparation and exploration of a series of iron 10-thiacorroles with simple halogenido (F, Cl, Br, I), pseudo-halogenido (N3 , I3 ) and solvent-derived axial ligands (DMSO, pyridine) is reported. The compounds were prepared from the free-base octaethyl-10-thiacorrole by iron insertion and subsequent ligand-exchange reactions. The small N4 cavity of the ring-contracted porphyrinoid results in an intermediate spin (i.s., S=3/2) state as the ground state for the iron(III) ion. In most of the investigated cases, the i.s. state is found unperturbed and independent of temperature, as determined by a combination of X-ray crystallography and magnetometry with (1) H NMR-, EPR-, and Mössbauer spectroscopy. Two exceptions were found. The fluorido iron(III) complex is inhomogenous in the solid and contains a thermal i.s. (S=3/2)→high spin (h.s., S=5/2) crossover fraction. On the other side, the cationic bis(pyridine) complex resides in the expected low spin (l.s., S=1/2) state. Chemically, the iron 10-thiacorroles differ from the iron porphyrins mainly by weaker axial ligand binding and by a cathodic shift of the redox potentials. These features make the 10-thiacorroles interesting ligands for future research on biomimetic catalysts and model systems for unusual heme protein active sites.

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Intermediate-spin (S = 3/2) porphyrinatoiron(III) complexes

Cited by 117 publications

References 4 publications

Electronic properties of the low-lying spin states of dimethylnitrosamine coordinated to Fe(III) heme models: An ab initio study

Electronic properties of the low-lying spin states of dimethylnitrosamine coordinated to Fe(III) heme models: An ab initio study

Composite Cathode with Li[sub 2]Pc

Iron 10‐Thiacorroles: Bioinspired Iron(III) Complexes with an Intermediate Spin (S=3/2) Ground State

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