The Mechanisms of Rectification in Au|Molecule|Au Devices Based on Langmuir–Blodgett Monolayers of Iron(III) and Copper(II) Surfactants

Wickramasinghe, Lanka D.; Mazumder, Shivnath; Gonawala, Sunalee; Perera, Meeghage Madusanka; Baydoun, Habib; Thapa, Bishnu; Li, Li; Xie, Lingxiao; Mao, Guangzhao; Zhou, Zhixian; Schlegel, H. Bernhard; Verani, Cláudio N.

doi:10.1002/anie.201408649

Cited by 24 publications

(66 citation statements)

References 54 publications

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“…We recently reported [9] that the relevant SOMO in the complex [Fe III (L 1 )Cl] (1)i sd escribed as al inear combination of Scheme1.The five-coordinate iron(III)complexes 1-4.…”

Section: Dedicatedtoprof Robertm Etzger On the Occasion Of His 75th mentioning

confidence: 99%

“…We recently reported [9] that the relevant SOMO in the complex [Fe III (L 1 )Cl] (1)i sd escribed as al inear combination of 3d xz + 3d yz molecular orbitals with predominantm etal character.T his is the lowest lying SOMO in af ive-coordinate HS iron(III) ion with an idealized square pyramidal C 4v configuration e(d xz 1 + d yz 1 ) b 2 (d xy 1 ) a 1 (d z 2 1 ) b 1 (d x 2 Ày 2 1 ). Asymmetric rectification is attributed to the 1e À reduction of this SOMO followed by rapid ET to the Au electrode without participation of the HOMO.T he 3d xz + 3d yz MOs are only 1eVa bove the Fermi levels of the electrodes and are therefore energetically compatible.…”

Section: Dedicatedtoprof Robertm Etzger On the Occasion Of His 75th mentioning

confidence: 99%

“…Asymmetric rectification is attributed to the 1e À reduction of this SOMO followed by rapid ET to the Au electrode without participation of the HOMO.T he 3d xz + 3d yz MOs are only 1eVa bove the Fermi levels of the electrodes and are therefore energetically compatible. [9] The HOMO is centered on the phenylenediamine moiety and is 1.4 eV below the Fermi levels, and is thust oo low in energy to take part in currentr ectification. Complex [Fe III (L 3 )] (3)w ith at ris(phenolate) ligand scaffold is expected to have ad ifferent elelctronic structure with aH OMO based on the phenolate moiety,r ather than on the phenylenediamine.…”

Section: Dedicatedtoprof Robertm Etzger On the Occasion Of His 75th mentioning

confidence: 99%

“…[3][4][5][6][7] Aiming to improve effective design, the understanding of complex rectifiers requires propere lucidation of metal/ligand electronic contributions on current rectification mechanisms. Our group has been at the forefront of complex rectifiers [8,9] and has evaluatedt he redox and electronic behavior of five-coordinate species [Fe III (L 1 )Cl] (1)a nd [Fe III (L 3 )] (3)w ith phenolate-richt etradentate and pentadentate ligands( Scheme 1). These ligandsb ind strongly to an iron(III) cation to form low-symmetry,h igh-spin metallosurfactants that show excellent molecular rectification properties when Langmuir-Blodgett( LB) monolayers of these complexes are embeddedb etween two gold electrodesi na n Au j LB j Au device.…”

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confidence: 99%

“…[1,[10][11][12] The use of physisorbed LB films minimizes or eliminates the Schottkyp athway. [13] In the asymmetric mechanism, the lowest unoccupied molecular orbital (LUMO) of the molecule is energeticallyc loser to the Fermi levels of the Au electrodes andt he highest occupied HOMO is much lower in energy, thus being unable to contribute to electron transfer.W eh ave recently proposed [9] the involvement of singly occupied MOs,r ather than unoccupied MOs, in complex rectifierss ot hat the Fermi/SOMO gap governs asymmetricr ectification.I nc ontrast,t he unimolecular pathway primarily observedf or organic systems [10][11][12][14][15][16] involves both the HOMO and LUMO (or SOMO in complexes) in ET as the HOMO of the donori se nergetically comparablet ot he Fermi level of one electrode, while the LUMO/SOMOo ft he acceptor moiety is comparable to the second electrode.T herefore, we can anticipate that the closer the energy of the singly occupiedS OMO of an Fe III complex to the Fermi levelso ft he Au electrodes, the more favored is the asymmetric pathway.O nt he other hand, havingb oth the SOMO and HOMO closer to the Fermi levels of the electrodes should lead to au nimolecular mechanism in which both SOMO and HOMO contributet ot he rectification process.Herein, we investigate the effects of electronic structure in modulating the SOMO-Fermi-HOMOe nergy gap in four highspin iron(III) complexes (Scheme 1), thus aiming to demonstrate viabilityo fu nimolecular rectification and expanding the current definitions of molecular rectifiers.We recently reported [9] that the relevant SOMO in the complex [Fe III (L 1 )Cl] (1)i sd escribed as al inear combination of Scheme1.The five-coordinate iron(III)complexes 1-4.[a] L.…”

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confidence: 99%

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

Wickramasinghe

Mazumder

Kpogo

et al. 2016

Chemistry A European J

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Amphiphilic five-coordinate iron(III) complexes with {N2 O2 Cl} and {N2 O3 } coordination spheres are studied to elucidate the roles of electronic structure on the mechanisms for current rectification. The presence of an apical chlorido or phenolato ligand plays a crucial role, and the [Fe(III) {N2 O2 Cl}] species supports an asymmetric mechanism while its [Fe(III) {N2 O3 }] counterpart seems to allow for unimolecular mechanism. The effects of electron-donating and electron-withdrawing substituents in the ligand frameworks are also considered.

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“…We recently reported [9] that the relevant SOMO in the complex [Fe III (L 1 )Cl] (1)i sd escribed as al inear combination of Scheme1.The five-coordinate iron(III)complexes 1-4.…”

Section: Dedicatedtoprof Robertm Etzger On the Occasion Of His 75th mentioning

confidence: 99%

Section: Dedicatedtoprof Robertm Etzger On the Occasion Of His 75th mentioning

confidence: 99%

Section: Dedicatedtoprof Robertm Etzger On the Occasion Of His 75th mentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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

Wickramasinghe

Mazumder

Kpogo

et al. 2016

Chemistry A European J

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A Molecular Approach for Mitigation of Aluminum Pitting based on Films of Zinc(II) and Gallium(III) Metallosurfactants

Weeraratne

Hewa-Rahinduwage

Gonawala

et al. 2019

Chemistry A European J

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The use of metallosurfactants to prevent pitting corrosion of aluminum surfacesi sd iscussed based on the behavior of the metallosurfactants [Zn II (L N2O2 )H 2 O] (1)a nd [Ga III (L N2O3 )] (2). These speciesw ere deposited as multilayer Langmuir-Blodgett films and characterized by IR reflection absorption spectroscopy and UV/Vis spectroscopy.S canning electron microscopy images, potentiodynamic polarization experiments,a nd electrochemical impedance spectroscopy were used to assessc orrosion mitigation. Both metallosurfactants demonstrate superior anticorrosiona ctivity due to the presence of redox-inactive3 d 10 metal ions that enhancet he structuralr esistance of the ordered molecular films and limit chloride mobility and electron transfer.Aluminumi salight, malleable, moldable, and nonmagnetic metal that resists atmosphericc orrosion,a nd displays electrical and thermalc onductivity. These attributes enable wideu se in automotive, aerospace, and naval industries. Although the metal is the third most abundant element in the crust (80 700 ppm), isolation from bauxite has ah igh environmental cost and generates an estimated1 3tons of CO 2 per ton of Al, [1] along with at oxic solid waste known as red mud. As such, conservation efforts are necessarya tall levelsa nd include recycling and corrosion mitigation.Unlike iron, in which adventitious oxygen and water leads to the formation of Fe(OH) 3 and Fe 2 O 3 , [2][3][4][5][6] the mechanismso fA l corrosion are more complex and less understood. Nonetheless, the action of pitting corrosionl eads to perniciouss tructural failures in car frames, airplane fuselages, and ship hulls, and demands immediate attention. With an electronic configuration given by [Ne] 3s 2 3p 1 ,t he metal has as tandard potential of À1.7 V SHE associated with the loss of the 3s 2 and3 p 1 electrons during the processg iven by Al (s) ÐAl 3 + + 3e À .P itting is initiated in neutral media by the presence of chloride [7] and other anions [8] that physisorb at the positively charged surface of the Al 2 O 3 passivation layer. [2,9] The Cl À anions penetrate through nanometer-sized cracks or migrate via oxygen vacancies [10][11][12] reaching the Al 2 O 3 j Al 0 interface, quickly converting Al 0 into AlCl 3 ,a nd then the anionic tetrahedral [13] complex [Al III Cl 4 ] À .T his soluble anion reacts with water forming aluminum hydroxide,g iven by [Al III Cl 4 ] À + 3H 2 O![Al III (OH) 3 ] + 3H + + 4Cl À .T he propagationp hase yields localized blisters of acidic pH that eventually erupt and exposet he corrosion pit. [14] The corrosion rate decreases over time, but perforation may occur, and chromium-based coatings have been commonly used. [15,16] However, concerns with the environmental impact of hexavalent chromium generated by these coatings imposes teep restrictionst ot heir use. [16] In searching for potential alternatives, we hypothesize that the presence of an ordered Langmuir-Blodgett (LB) multilayer of molecularm etallosurfactants would act as ah ydrophobic barriert hat decreases access of w...

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Programmed Heterostructures for Enhanced Electrical Conductivity

Singh,

Malik,

Sethi

et al. 2024

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Interfacial electron transport in multicomponent systems plays a crucial role in controlling electrical conductivity. Organic–inorganic heterostructures electronic devices where all the entities are covalently bonded to each other can reduce interfacial electrical resistance, thus suitable for low‐power consumption electronic operations. Programmed heterostructures of covalently bonded interfaces between ITO‐ethynylbenzene (EB) and EB‐zinc ferrite (ZF) nanoparticles, a programmed structure showing 67 978‐fold enhancement of electrical current as compared to pristine NPs‐based two terminal devices are created. An electrochemical approach is adopted to prepare nearly π‐conjugated EB oligomer films of thickness ≈26 nm on ITO‐electrode on which ZF NPs are chemically attached. A “flip‐chip” method is employed to combine two EB‐ZnFe2O4 NPs‐ITO to probe electrical conductivity and charge conduction mechanism. The EB‐ZnFe2O4 NPs exhibit strong electronic coupling at ITO‐EB and EB‐NPs with an energy barrier of 0.13 eV between the ITO Fermi level and the LUMO of EB‐ZF NPs for efficient charge transport. Both the DC and AC‐based electrical measurements manifest a low resistance at ITO‐EB and EB‐ZF NPs, revealing enhanced electrical current at ± 1.5 V. The programmed heterostructure devices can meet a strategy to create well‐controlled molecular layers for electronic applications toward miniaturized components that shorten charge carrier distance, and interfacial resistance.

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The Mechanisms of Rectification in Au|Molecule|Au Devices Based on Langmuir–Blodgett Monolayers of Iron(III) and Copper(II) Surfactants

Abstract: Langmuir-Blodgett films of metallosurfactants were used in Au|molecule|Au devices to investigate the mechanisms of current rectification.

Cited by 24 publications

References 54 publications

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

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

A Molecular Approach for Mitigation of Aluminum Pitting based on Films of Zinc(II) and Gallium(III) Metallosurfactants

Programmed Heterostructures for Enhanced Electrical Conductivity

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