Electronic Modulation of the SOMO–HOMO Energy Gap in Iron(III) Complexes towards Unimolecular Current Rectification

Wickramasinghe, Lanka D.; Mazumder, Shivnath; Kpogo, Kenneth K.; Staples, Richard J.; Schlegel, H. Bernhard; Verani, Cláudio N.

doi:10.1002/chem.201602444

Cited by 15 publications

(6 citation statements)

References 45 publications

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“…This is summarized in Figure 9d−f. Both of these proposed electron transport pathways differ from that described for 3d 5 iron- based species 3 10 and other Fe III species with similar ligand environments 57,58 in which the metal-centered SOMO is a linear combination of d xz + d yz located ca. 1.0 eV above the Fermi level (Figure 7).…”

Section: Synthesis and Characterizationscontrasting

confidence: 61%

Influence of Electronic Configurations on the Modulation of Fermi/Orbital Junction Energies for Directional Electron Transport through 3d¹, 3d³, and 3d⁵ Metallosurfactants

et al. 2022

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Two new metallosurfactants containing the 3d 1 vanadyl(IV) and 3d 3 chromium(III) ions bound to the phenylenediamine-bridged phenolate-rich ligand L N 2 O 2 were designed, deposited as monolayer films on gold electrodes, and probed for directional electron transfer in Au|LB|Au junctions. Both [V�O IV L N 2 O 2 ] (1) and [Cr III (L N 2 O 2 )(MeOH)(H 2 O)]Cl (2) promote current rectification. Through a concerted experimental and computational effort, we compare the behavior of 1 and 2 with that of our previously studied 3d 5 [Fe III (L N 2 O 2 )Cl] (3). Based on the analysis of comprehensive electrochemical, spectroscopic, and microscopy results allied to DFT calculations, we propose distinct mechanisms by which electronic configurations influence the energy gap between the electrode Fermi levels and the different molecular orbitals responsible for electron transport. While the 3d 5 species 3 shows electron transport through the metal-based SOMO located above the Fermi levels of the electrode, the 3d 1 species 1 uses a metal-based SOMO below Fermi, and the 3d 3 species 2 takes advantage of a ligand-based HOMO, which becomes available when a bias is applied.

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Section: Synthesis and Characterizationscontrasting

confidence: 61%

Influence of Electronic Configurations on the Modulation of Fermi/Orbital Junction Energies for Directional Electron Transport through 3d¹, 3d³, and 3d⁵ Metallosurfactants

et al. 2022

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“…1,51 Complexes C1-C3 all display a distorted trigonal bipyramidal geometry, in contrast to the square pyramidal geometries often observed with Fe(III) salen complexes. [52][53][54][55] The flexible coordination modes available when using phenoxyimine ligands may present an advantage over the well-established salen analogues. These findings suggest that phenoxyimine ligand supported metal complexes have significant potential for a broad scope of CO 2 /epoxide coupling reactions.…”

Section: Papermentioning

confidence: 99%

Stable Fe(iii) phenoxyimines as selective and robust CO₂/epoxide coupling catalysts

et al. 2018

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Three phenoxyimine Fe(iii)Cl complexes bearing electronically diverse -Cl, -H or -Bu substituents in the ortho position were synthesised. X-ray crystallographic analysis of the complexes reveals mononuclear structures with pentacoordinate iron centres and trigonal bipyramidal geometries. All three complexes demonstrated excellent catalytic activities towards CO/epoxide coupling to selectively form cyclic carbonates, with catalyst activity correlating with the electron withdrawing nature of the ortho-substituent (Cl > H > Bu) and thus the Lewis acidity of the metal centre. The chloro-substituted complex displayed remarkable activity in the synthesis of propylene carbonate from propylene oxide and CO, reaching turnover frequencies (TOF) up to 760 h in the presence of TBABr co-catalyst at 120 °C and 20 bars of CO pressure. Importantly, the catalyst is also very robust, functioning with high substrate loading, under air or in the presence of water. The substrate scope was successfully extended to other terminal epoxides including epichlorohydrin (TOF = 900 h) and to the more challenging internal epoxide, cyclohexene oxide (TOF = 80 h). These are amongst the highest TOF values reported for an iron CO/epoxide coupling catalyst to date.

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“…These energies are given in eV and are similar to the respective LUMO and HOMO energies of the metallosurfactants. 90,91 However, because 3d metals display electronic configurations with unpaired electrons, reduction usually entails population of the lowest singly occupied MO, and the orbital in question is indeed a metal-based SOMO. On the other hand, the oxidation process is ligand based and therefore associated with an available HOMO.…”

Section: X-ray Photoelectron Spectroscopy (Xps)mentioning

confidence: 99%

Studies on Monolayer Formation and Electron Transport in Au|LB|Au Junctions Containing 3d⁴ Mn^III Metallosurfactants

et al. 2023

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Three new metallosurfactants containing 3d 4 manganese(III) ions, namely, [Mn III (L NO2-N2O2 )Cl(MeOH)] (1), [Mn III (L N2O2 )(H 2 O)(MeOH)]Cl (2), and [Mn III (L N2O3 )] (3), bound to three distinct phenylenediamine-bridged phenolate-rich ligands were designed, deposited as Langmuir−Blodgett monolayer films on gold electrodes, and probed for directional electron transfer in Au|LB|Au junctions. All three Mn III metallosurfactants promote current rectification, and we compare the behavior of these metallosurfactants with that of our previously studied 3d 1 V�O IV , 3d 3 Cr III , and 3d 5 Fe III species in similar environments through a rigorous effort. Based on the analysis of electrochemical, spectroscopic, microscopic, and DFT results, we propose distinct mechanisms by which electronic configurations and ligand frameworks influence and modulate the energy gap between the electrode Fermi levels and the molecular orbitals responsible for electron transport. Our previous work characterized distinct mechanisms, i.e., electron transport through below-Fermi for V IV Obased SOMOs and above-Fermi for Fe III -based SOMOs and ligand-based HOMOs for the Cr III species. These Mn III species show electron transport similar to Fe III ; however, low current capacities suggest that film quality is an important factor to be considered.

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Electronic Modulation of the SOMO–HOMO Energy Gap in Iron(III) Complexes towards Unimolecular Current Rectification

Cited by 15 publications

References 45 publications

Influence of Electronic Configurations on the Modulation of Fermi/Orbital Junction Energies for Directional Electron Transport through 3d¹, 3d³, and 3d⁵ Metallosurfactants

Influence of Electronic Configurations on the Modulation of Fermi/Orbital Junction Energies for Directional Electron Transport through 3d¹, 3d³, and 3d⁵ Metallosurfactants

Stable Fe(iii) phenoxyimines as selective and robust CO₂/epoxide coupling catalysts

Studies on Monolayer Formation and Electron Transport in Au|LB|Au Junctions Containing 3d⁴ Mn^III Metallosurfactants

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Electronic Modulation of the SOMO–HOMO Energy Gap in Iron(III) Complexes towards Unimolecular Current Rectification

Cited by 15 publications

References 45 publications

Influence of Electronic Configurations on the Modulation of Fermi/Orbital Junction Energies for Directional Electron Transport through 3d1, 3d3, and 3d5 Metallosurfactants

Influence of Electronic Configurations on the Modulation of Fermi/Orbital Junction Energies for Directional Electron Transport through 3d1, 3d3, and 3d5 Metallosurfactants

Stable Fe(iii) phenoxyimines as selective and robust CO2/epoxide coupling catalysts

Studies on Monolayer Formation and Electron Transport in Au|LB|Au Junctions Containing 3d4 MnIII Metallosurfactants

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Influence of Electronic Configurations on the Modulation of Fermi/Orbital Junction Energies for Directional Electron Transport through 3d¹, 3d³, and 3d⁵ Metallosurfactants

Influence of Electronic Configurations on the Modulation of Fermi/Orbital Junction Energies for Directional Electron Transport through 3d¹, 3d³, and 3d⁵ Metallosurfactants

Stable Fe(iii) phenoxyimines as selective and robust CO₂/epoxide coupling catalysts

Studies on Monolayer Formation and Electron Transport in Au|LB|Au Junctions Containing 3d⁴ Mn^III Metallosurfactants