Single-molecule junctions of multinuclear organometallic wires: long-range carrier transport brought about by metal–metal interaction

Tanaka, Yuya; Kato, Yoshitaka; Sugimoto, Kaho; Kawano, Reo; Tada, Tomofumi; Fujii, Shintaro; Kiguchi, Manabu; Akita, Munetaka

doi:10.1039/d0sc06613c

Cited by 27 publications

(30 citation statements)

References 46 publications

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“…Broadly speaking, this work demonstrates the ease and practicality of introducing asymmetry across a redox-center and how this can be used to subtly alter said center’s electronic structure. Asymmetric molecules have previously shown promise in the field of molecular electronics in devising new systems for diodes, rectifiers, and in the tuning of optical band gaps. − The stepwise nature of our synthesis provides a routine method of incorporating an organometallic redox-active fragment into these designs and also provides an opportunity to study how their properties can be changed by externally controlling the ferrocene redox processes through the use of electrochemical gating. − In addition, this fine control of electronic structure provides a further parameter for the predictable tuning of FMO energies, which has large implications in both electronic and thermal conductivity as both are highly dependent on the alignment of the energy levels of electrodes and analytes. − We are currently undertaking further work to examine how these molecules can be assembled onto a surface and how they differ in terms of their conductivity when studied as either single molecules or as parallel arrays of molecules, such as those seen in a self-assembled monolayer.…”

Section: Discussionmentioning

confidence: 99%

Synthesis, Electrochemistry, and Optical Properties of Highly Conjugated Alkynyl-Ferrocenes and -Biferrocenes

et al. 2021

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Sonogashira reactions are utilized herein to react iodoferrocenes and -biferrocenes with terminal alkyne ligands, functionalized with both pyridine and thioanisole groups. High-yielding reactions generate both monoalkynyl and dialkynyl derivatives, the ratio of which can be altered through changes in the reaction stoichiometry. This methodology allowed us to synthesize a large family of derivatives, comprising four symmetrical derivatives (3xx, where x represents a phenylsubstituted terminal alkyne) and six less-studied asymmetrical derivatives (3xy, where x and y represent two different phenyl-substituted terminal alkynes), as well as a number of their biferrocenyl analogues (6x, 7xx, and 7xy), including the first known examples of asymmetrically disubstituted biferrocenes. We examined the electrochemical behavior of all the systems in solution through the use of cyclic voltammetry and demonstrate that these highly conjugated alkynyl ligands exert delicate redox control over the central ferrocene motif. We also note that these substituents display some control over the mixed-valence character present in biferrocene monocations, with thioanisole substituents imparting almost an order of magnitude higher K c than their pyridyl analogues, and asymmetric systems displaying rare characteristic properties of mixed-valence isomers. The electronic structure of these systems was further elucidated through a combination of UV/vis spectroscopy and density functional theory calculations. Our methodology provides a facile and adaptable route toward the isolation of a number of novel ferrocene and biferrocene derivatives. From our perspective, the asymmetric nature of these systems, along with the delicate and predictable redox control that these ligands exert on the central ferrocene unit(s), could lead to applications in molecular electronics, where these properties have previously shown promise in the fabrication of diodes and rectifiers, as well as in the synthesis of donor-π-acceptor systems.

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Section: Discussionmentioning

confidence: 99%

Synthesis, Electrochemistry, and Optical Properties of Highly Conjugated Alkynyl-Ferrocenes and -Biferrocenes

et al. 2021

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“…Herein, we report the synthesis and charge-delocalization properties of the dinuclear metal acetylide-type complexes 1-6 bearing the various (p-diethynylacene)diyl linkers (Figure 2) and the electron-rich Ru(dppe) 2 fragments. [29][30][31][32][33][34][35][36] The diethynylacene linkers studied here involve diethynyl-benzene (1), -naphthalene (2), -anthracene (3, 4), -tetracene (5) and -pentacene derivatives (6). The systematic study revealed that the location of the radical centers in the MV species was dependent on the acene moieties, varying from the conventional metal-delocalized and ligand-delocalized states to the non-classical ligand-localized states (Figure 1b).…”

Section: Introductionmentioning

confidence: 99%

Acene Size‐Dependent Transition of The Radical Centers From the Metal to The Acene Parts In Monocationic Dinuclear (Diethynylacene)diyl Complexes

Tanaka

Kawano

Akita

2022

Chemistry A European J

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Controlling radical localization/delocalization is important for functional materials. The present paper describes synthesis and results of electrochemical, spectroscopic, and theoretical studies of diruthenium (pdiethynylacene)diyl complexes, Me 3 Si-(C�C) 2 -Ru(dppe) 2 -C�CÀ Ar-C�CÀ Ru(dppe) 2 -(C�C) 2 -SiMe 3 (1-6) (dppe: 1,2bis(diphenylphosphino)ethane), and their monocationic radical species ([1] + -[6] + ). The HOMO-LUMO energy gaps can be finely tuned by the acene rings in the bridging ligands installed, as indicated by the absorption maxima of the electronic spectra of 1-6 ranging from the UV region even to the NIR region. The cationic species [1] + -[6] + show two characteristic NIR bands, which are ascribed to the charge resonance (CR) and π-π* transition bands, as revealed by spectroelectrochemistry. Expansion of the acene rings in [1] + -[6] + causes (1) blue shifts of the CR bands and red shifts of the π-π* transition bands and (2) charge localization on the acene parts as evidenced by the ESR, DFT and TD-DFT analyses. Notably, the monocationic complexes of the larger acene derivatives are characterized as the non-classical acene-localized radicals.

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“…Metal alkynyl complexes have been an attractive target for both synthetic and material chemists since the pioneering work of Nast and subsequent development in polymerization by Hagihara . Exploration of novel alkynyl complexes based on transition metals has remained topical as evidenced by many comprehensive reviews that have appeared during the ensuing decades. − Both the extended conjugation and structural rigidity of metal-oligoynes render them appealing candidates for opto-electronic materials, − molecular wires, − and active species for molecular devices. − It is noteworthy that many of the efforts mentioned above have been based on 4 d and 5 d metals such as Ru, Re, Ir, and Pt, which are rare and precious metals. To transform these interesting properties and functions into technological applications, surrogates based on earth abundant elements are desired.…”

Section: Introductionmentioning

confidence: 99%

A Series of Mono- and Bis-Alkynyl Co(III) Complexes Supported by a Tetra-imine Macrocyclic Ligand (TIM)

et al. 2021

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Reported herein is the synthesis and characterization of a series of monoand bis-alkynyl Co III (TIM) complexes, where TIM is 2,3,9,10-tetramethyl-1,4,8,11tetraazacyclotetradeca-1,3,8,10-tetraene. The trans-[Co(TIM)(C 2 Ar)Cl] + type complexes (Ar = phenyl (Ph, 1a), naphthalene (Np, 1b), and -C 6 F 5 (1c)) were prepared by the addition of HC 2 Ar to trans-[Co(TIM)Cl 2 ]PF 6 in the presence of Et 3 N. Treatment of the mono-alkynyl complexes with AgOTf in MeCN resulted in the trans-[Co(TIM)(C 2 Ar)-(NCMe)](OTf) 2 complexes (Ar = Ph (2a), Np (2b), and -C 6 F 5 (2c)). Complexes 2a and 2b react with the respective HC 2 Ar ligand in the presence of Et 3 N to afford the symmetrical bis-alkynyl complexes trans-[Co(TIM)(C 2 Ar) 2 ] + (Ar = Ph (3a) and Np (3b)). trans-[Co(TIM)(C 2 C 6 F 5 ) 2 ] + (3c) was obtained directly from the prolonged reaction of trans-[Co(TIM)Cl 2 ]PF 6 with HC 2 C 6 F 5 . Furthermore, the addition of HC 2 Ph to 2c in the presence of a weak base yielded the unsymmetrical bis-alkynyl complex trans-[Co(TIM)(C 2 C 6 F 5 )(C 2 Ph)]OTf (4). Molecular structures of complexes 1a/b, 2a/b, [3a]PF 6 , 3b, and 4 were established through single crystal X-ray diffraction. The absorption spectra for 1−4 display d−d bands between 380 and 470 nm. Complexes 1b−3b exhibited Np-based fluorescence. Electrochemical studies revealed that all complexes display an irreversible reduction characteristic of the Co III center, as well as up to two irreversible reduction(s) localized on the TIM macrocycle.

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Single-molecule junctions of multinuclear organometallic wires: long-range carrier transport brought about by metal–metal interaction

Abstract: Here, we report multinuclear organometallic molecular wires having the (2,5-diethynylthiophene)diyl-Ru(dppe)2 repeating units. Despite the molecular dimension of 2 – 4 nm the multinuclear wires show high conductance (up to 10–2...

Cited by 27 publications

References 46 publications

Synthesis, Electrochemistry, and Optical Properties of Highly Conjugated Alkynyl-Ferrocenes and -Biferrocenes

Synthesis, Electrochemistry, and Optical Properties of Highly Conjugated Alkynyl-Ferrocenes and -Biferrocenes

Acene Size‐Dependent Transition of The Radical Centers From the Metal to The Acene Parts In Monocationic Dinuclear (Diethynylacene)diyl Complexes

A Series of Mono- and Bis-Alkynyl Co(III) Complexes Supported by a Tetra-imine Macrocyclic Ligand (TIM)

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