Coulombic-enhanced hetero radical pairing interactions

Zheng, Xujun; Zhang, Yang; Cao, Ning; Li, Xin; Zhang, Shuo‐Qing; Du, Renfeng; Wang, Haiying; Ye, Zhenni; Wang, Yan; Cao, Fahe; Li, Haoran; Hong, Xin; Sue, Andrew C.‐H.; Yang, Chuluo; Liu, Wei-Guang

doi:10.1038/s41467-018-04335-0

Cited by 30 publications

(16 citation statements)

References 33 publications

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“…Scheme ). Spin pairing, which apparently occurs at certain oxidation levels, may be achieved either directly along oligomer chains ( vide infra ), or via π-stacking interactions, which are known to induce spin pairing in polymers and some small molecules . Considerable ESR activity was however observed at negative potentials (between −0.73 and −1.5 V), suggesting that neither of the two above mechanisms of spin pairing is efficient for radical anion and diradical dianion segments of the polymer.…”

Section: Resultsmentioning

confidence: 99%

Electrochemical Polymerization of Pyrrole–Perimidine Hybrids: Low-Band-Gap Materials with High n-Doping Activity

et al. 2020

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Conductive π-conjugated polymers were electrochemically generated from a variety of donor–acceptor pyrroles containing fused perimidine subunits. Alternating oxidative and reductive polarization of these precursors induces multidirectional coupling involving both perimidine and acenaphtho[1,2-c]pyrrole moieties, producing cross-linked polymeric structures. Chemical oxidation experiments and computational analyses of spin densities in the charged pyrrole intermediates indicate that the formation of inter-perimidine linkages occurs prior to pyrrole–pyrrole couplings. In the resulting polymers, a very stable dication state is achievable with the positive charge located on the bis-perimidine linker. These polymers do not show any stable neutral state and can be easily reduced. Cationic and anionic states of these electrogenerated films were investigated in the solid state by UV–vis–NIR and EPR spectroelectrochemistry, assisted by DFT calculations.

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Section: Resultsmentioning

confidence: 99%

Electrochemical Polymerization of Pyrrole–Perimidine Hybrids: Low-Band-Gap Materials with High n-Doping Activity

et al. 2020

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“…Subsequently, we measured the temperature dependent NMR experiments to further confirm. As shown in Figure S5, in the temperature range of 25–50 °C, the NMR signals of TPE-3-stack showed no obvious change in deuterated chloroform, suggesting the compact and rigid nature of the supramolecular self-assembled compound. , Thus, the intramolecular steric effect is expected to block the nonradiative decay channels by restricting the rotational and vibrational motions of the molecule, which may lead to a high emission efficiency.…”

Section: Resultsmentioning

confidence: 99%

Self-Assembly of a Highly Emissive Pure Organic Imine-Based Stack for Electroluminescence and Cell Imaging

et al. 2019

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We demonstrated that a purely organic stack, namely, TPE-3-stack, can be assembled in high yield by using dynamic imine chemistry. TPE-3-stack emits strong fluorescence not only in the solid state (ϕ PL = 83%) but also in dilute solutions (e.g., ϕ PL = 82% in DMSO), which is significantly distinct from the case of the aggregation-caused quenching (ACQ) and aggregation-induced emission (AIE) chromophores. In addition, it shows high spectral, thermal, and chemical stabilities as well as excellent solubility in common solvents. Therefore, this stack is feasible for fabricating a solution-processed electroluminescent device, which displays brightness over 1000 cd m −2 and a current efficiency up to 2.3 cd A −1 . TPE-3-stack is also demonstrated as a promising fluorescent visualizer for lysosome imaging. Such characteristics of the stack compound were attributed to the efficient suppression of intramolecular rotation and vibration by locking its structure into the rigid framework by means of a self-assembly strategy.

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“…Electronic structure, doping processes, electronic conductivity, and air stability of electron-acceptor-conjugated materials and polymers in particular are crucial for the further development of efficient electronic devices such as organic photovoltaics, light-emitting diodes, or thermoelectric generators. − These properties heavily depend, among other parameters, on their frontier orbital energy levels. − n -Doping is necessary to increase charge-carrier densities and thus electrical conductivity of electron-acceptor polymers. , Unlike inorganic semiconductors, doping of organic semiconductors refers to a redox process, in which electron acceptor and donor materials are chemically reduced and oxidized, respectively, on a substochiometric level . The material’s electron affinity must be more negative than the ionization potential of the dopant used to obtain a reasonable n -doping efficacy. , It is generally assumed that air stability of the resulting radical anions requires a lowest unoccupied molecular orbital (LUMO) more negative than −4.0 eV. − A class of air-stable materials with excellent electron-transport properties is built from substituted benzodifurandione-phenylenevinylene derivatives. , Also, naphthalene diimide (NDI)-based materials are popular candidates for n -type semiconductors and were used in several forms, ranging from small molecules, − supramolecular assemblies, , and side-chain polymers to conjugated main chain copolymers. , PNDIT2, also referred to as N2200, is a conjugated donor–acceptor copolymer composed of alternating units of NDI and bithiophene (T2), which has been n -doped with dihydro-1H-benzimidazole-2-yl (N-DBI) derivatives, amines, , anions, as well as metallocenes. , The doping efficacy of PNDIT2 with benzimidazoles, however, is limited by their miscibility . This is an often seen limitation especially for semicrystalline copolymers, as for the doping of organic semiconductors a significant amount of dopant is needed (typically 5–30 wt %) .…”

Section: Introductionmentioning

confidence: 99%

“…24,25 PNDIT2, also referred to as N2200, is a conjugated donor−acceptor copolymer composed of alternating units of NDI and bithiophene (T2), which has been ndoped with dihydro-1H-benzimidazole-2-yl (N-DBI) derivatives, 26 amines, 27,28 anions, 29 as well as metallocenes. 30,31 The doping efficacy of PNDIT2 with benzimidazoles, however, is limited by their miscibility. 32 This is an often seen limitation especially for semicrystalline copolymers, as for the doping of organic semiconductors a significant amount of dopant is needed (typically 5−30 wt %).…”

Section: ■ Introductionmentioning

confidence: 99%

Radical Anion Yield, Stability, and Electrical Conductivity of Naphthalene Diimide Copolymers n-Doped with Tertiary Amines

Schmidt

Hönig

Shin

et al. 2020

ACS Appl. Polym. Mater.

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Doped organic semiconductors are required for applications such as organic solar cells, organic light-emitting diodes and thermoelectric generators. To further establish structure-property relationships and improve the efficiency of these devices, electron acceptor conjugated polymers and suitable doping schemes are required. A key criterion is a sufficiently low lowest unoccupied molecular orbital (LUMO), which enables air-stability of excess electrons. In this work, a series of naphthalene diimide (NDI) copolymers with varying highest occupied molecular orbital (HOMO) and LUMO energy levels are made and used to investigate photochemically and thermally induced electron transfer from a small molecule NDI carrying dimethylaminopropyl (DMAP) side chains. Density functional theory calculations, UV-vis and electron spin resonance (ESR) spectroscopies indicate that the LUMO energy level of the NDI copolymer governs thermal electron transfer from the HOMO of the DMAP side chain and dictates air stability of the corresponding radical anions. Conversely, photoinduced electron transfer from DMAP to the NDI copolymer is governed by the position of the HOMO energy levels. While dicyano-substituted NDI copolymers with very low LUMO levels display the highest radical anion yield and excellent air stability, their conductivity is limited by electron mobility, which in turn is strongly influenced by backbone torsion and localized radical anions. These results establish fundamental structure-function relationships and shine light on the use of simple and cost-economic, covalently bound tertiary amines as potential n-dopants for electron acceptor copolymers.

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Coulombic-enhanced hetero radical pairing interactions

Cited by 30 publications

References 33 publications

Electrochemical Polymerization of Pyrrole–Perimidine Hybrids: Low-Band-Gap Materials with High n-Doping Activity

Electrochemical Polymerization of Pyrrole–Perimidine Hybrids: Low-Band-Gap Materials with High n-Doping Activity

Self-Assembly of a Highly Emissive Pure Organic Imine-Based Stack for Electroluminescence and Cell Imaging

Radical Anion Yield, Stability, and Electrical Conductivity of Naphthalene Diimide Copolymers n-Doped with Tertiary Amines

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