Identifying the missing link in catalyst transfer polymerization

He, Weiying; Patrick, Brian O.; Kennepohl, Pierre

doi:10.1038/s41467-018-06324-9

Cited by 32 publications

(34 citation statements)

References 43 publications

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“…However, as we have discussed above, the Pnn2 phase is a low-symmetry subgroup of Pnna that results from a Bi-O octahedral breathing distortion. Our calculations show that the energy difference between these two phases is ∼ 5 meV per atom in accord with earlier estimates [40]. Since the electrical polarization is relatively large in Pnn2 Ag 2 BiO 3 (8.87 µC cm −2 ), the polar distortion can be suppressed by a relatively small external electric field applied in a direction opposite to that of the polarization axis [40].…”

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confidence: 90%

“…Ferroelectricity is an intriguing phenomenon that is driven by the formation of electric dipoles, which arise when the centers of positive and negative charges are separated under a polar distortion. Application of an external electric field in the direction opposite to that of the spontaneous polarization can be used to attenuate the distortion [38][39][40]. Ag 2 BiO 3 has been shown to exist in three distinct crystal structures of nonpolar (Pnna) and polar (Pnn2 and Pn) space groups.…”

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“…Ag 2 BiO 3 has been shown to exist in three distinct crystal structures of nonpolar (Pnna) and polar (Pnn2 and Pn) space groups. The nonpolar and polar structures are paraelectric semimetal and ferroelectric semiconductor, respectively, where the polar structure contains a centrosymmetric BiO 6 octahedral breathing distortion [40][41][42] This distortion has been attributed to the coexistence of two valence states, Bi 3+ and Bi 5+ , due to charge disproportionation of the formal Bi valence state, which induces a sizable ferroelectric polarization. An external electric field can then nullify charge disproportionation and transition the system into the metallic nonpolar Pnna structure.…”

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Topological Hourglass Dirac Semimetal in the Nonpolar Phase of Ag2BiO3

Singh

Ghosh

et al. 2018

Phys. Rev. Lett.

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Materials with tunable charge and lattice degrees of freedom provide excellent platforms for investigating multiple phases that can be controlled via external stimuli. We show how the charge-ordered ferroelectric oxide Ag2BiO3, which has been realized experimentally, presents a unique exemplar of a metal-insulator transition under an external electric field. Our first-principles calculations combined with a symmetry analysis, reveal the presence of a nearly ideal hourglass-Dirac-semimetal state in the nonpolar structure of Ag2BiO3. The low-energy band structure consists of two hourglass-like nodal lines located on two mutually orthogonal glide-mirror planes in the absence of spin-orbit coupling (SOC) effects. These lines cross at a common point and form an interlinked chain-like structure, which extends beyond the first Brillouin zone. Inclusion of the SOC opens a small gap in the nodal lines and results in two symmetry-enforced hourglass-like Dirac points on theC2y screw rotation axis. Our results indicate that Ag2BiO3 will provide an ideal platform for exploring ferroelectric-semiconductor to Dirac-semimetal transition by the application of an external electric field.

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Topological Hourglass Dirac Semimetal in the Nonpolar Phase of Ag2BiO3

Singh

Ghosh

et al. 2018

Phys. Rev. Lett.

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“…This ligand‐induced (push–pull) π‐backbonding is responsible for the large observed rotational barrier about the π‐ligand even with relatively poor π‐acidic ligands such as ethylene. This unique electronic structure can play an important role in the reactivity of such species . The situation is more complex in situations with highly electron‐poor π‐systems, in which metal‐centred backbonding increases and leads to Ni I character becoming significantly more important.…”

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The Importance of Ligand‐Induced Backdonation in the Stabilization of Square Planar d¹⁰ Nickel π‐Complexes

Desnoyer

Behyan

et al. 2019

Chemistry A European J

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The electronic nature of Ni π‐complexes is underexplored even though these complexes have been widely postulated as intermediates in organometallic chemistry. Herein, the geometric and electronic structure of a series of nickel π‐complexes, Ni(dtbpe)(X) (dtbpe=1,2‐bis(di‐tert‐butyl)phosphinoethane; X=alkene or carbonyl containing π‐ligands), is probed using a combination of 31P NMR, Ni K‐edge XAS, Ni Kβ XES, and DFT calculations. These complexes are best described as square planar d10 complexes with π‐backbonding acting as the dominant contributor to M−L bonding to the π‐ligand. The degree of backbonding correlates with 2JPP from NMR and the energy of the Ni 1s→4pz pre‐edge in the Ni K‐edge XAS data, and is determined by the energy of the π*ip ligand acceptor orbital. Thus, unactivated olefinic ligands tend to be poor π‐acids whereas ketones, aldehydes, and esters allow for greater backbonding. However, backbonding is still significant even in cases in which metal contributions are minor. In such cases, backbonding is dominated by charge donation from the diphosphine, which allows for strong backdonation, although the metal centre retains a formal d10 electronic configuration. This ligand‐induced backbonding can be formally described as a 3‐centre‐4‐electron (3c‐4e) interaction, in which the nickel centre mediates charge transfer from the phosphine σ‐donors to the π*ip ligand acceptor orbital. The implications of this bonding motif are described with respect to both structure and reactivity.

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“…Due to this complexation, the zerovalent center reacts next with the halide endgroup of the same polymer chain, and chain-growth, pseudoliving polymerization ensues (Bryan & McNeil, 2013). The existence of this CT effect has been borne out by a number of theoretical studies (He, Patrick & Kennepohl, 2018), as well as exploits in which CTP is used to prepare block copolymers and end-functionalized polymers (Zhang, Ohta & Yokozawa, 2018;Yokozawa & Yokoyama, 2009;Aplan & Gomez, 2017). Many of the most common applications of CPs involve their deposition in the form of thin films, including uses in photovoltaics, electrochromics, and sensors.…”

Section: Introductionmentioning

confidence: 99%

Cross-coupling polymerization at iodophenyl thin films prepared by spontaneous grafting of a diazonium salt

Marshall

Rodrı́guez

2020

PeerJ Materials Science

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Cross-coupling at aryl halide thin films has been well-established as a technique for the surface-initiated Kumada catalyst transfer polymerization (SI-KCTP), used to produce covalently bound conjugated polymer thin films. In this work, we report that the spontaneous grafting of 4-iodobenzenediazonium tetrafluoroborate on gold substrates creates a durable iodoarene layer which is effective as a substrate for cross-coupling reactions including SI-KCTP. Using cyclic voltammetry of a surface-coupled ferrocene terminating agent, we have measured initiator surface coverage produced by oxidative addition of Pd(t-Bu3P)2 and estimated the rate constant of the termination reaction in the SI-KCTP system with 2-chloromagnesio-5-bromothiophene and Pd(t-Bu3P)2. We used this system to prepare uniform polythiophene thin films averaging 90 nm in thickness.

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Identifying the missing link in catalyst transfer polymerization

Cited by 32 publications

References 43 publications

Topological Hourglass Dirac Semimetal in the Nonpolar Phase of Ag2BiO3

Topological Hourglass Dirac Semimetal in the Nonpolar Phase of Ag2BiO3

The Importance of Ligand‐Induced Backdonation in the Stabilization of Square Planar d¹⁰ Nickel π‐Complexes

Cross-coupling polymerization at iodophenyl thin films prepared by spontaneous grafting of a diazonium salt

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Identifying the missing link in catalyst transfer polymerization

Cited by 32 publications

References 43 publications

Topological Hourglass Dirac Semimetal in the Nonpolar Phase of Ag2BiO3

Topological Hourglass Dirac Semimetal in the Nonpolar Phase of Ag2BiO3

The Importance of Ligand‐Induced Backdonation in the Stabilization of Square Planar d10 Nickel π‐Complexes

Cross-coupling polymerization at iodophenyl thin films prepared by spontaneous grafting of a diazonium salt

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The Importance of Ligand‐Induced Backdonation in the Stabilization of Square Planar d¹⁰ Nickel π‐Complexes