Charge-transfer or excimeric state? Exploring the nature of the excited state in cofacially arrayed polyfluorene derivatives

Abzhanova, Ainur; Ivanov, Maxim V.; Wang, Denan; Navale, Tushar S.; Abdelwahed, Sameh H.; Lindeman, Sergey V.; Rathore, Rajendra; Reid, Scott A.

doi:10.1016/j.jphotochem.2019.01.030

Cited by 2 publications

(1 citation statement)

References 22 publications

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“…The striking constancy in the position of the excimer emission band for F2-F6 suggests that the exciton must reside over only two fluorene moieties [41,42]. The energetic penalty for excimer formation, which requires an ideal sandwich-like arrangement of a pair of interacting units [43], must be easily overcome by the energetic gain due to the excimeric stabilization in F2.…”

Section: Electronic and Emission Spectroscopy Of Polyfluorenesmentioning

confidence: 99%

Design and Synthesis of Cofacially-Arrayed Polyfluorene Wires for Electron and Energy Transfer Studies

Rathore

Abdelwahed

2023

Molecules

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A study of cofacially arrayed π-systems is of particular importance for the design of functional materials for efficient long-range intra-chain charge transfer through the bulk semiconducting materials in the layers of photovoltaic devices. The effect of π-stacking between a pair of aromatic rings has been mainly studied in the form of cyclophanes, where aromatic rings are forced into a sandwich-like geometry, which extensively deforms the aromatic rings from planarity. The synthetic difficulties associated with the preparation of cyclophane-like structures has prevented the synthesis of many examples of their multi-layered analogues. Moreover, the few available multi-layered cyclophanes are not readily amenable to the structural modification required for the construction of D–spacer–A triads needed to explore mechanisms of electron and energy transfer. In this review, we recount how a detailed experimental and computational analysis of 1,3-diarylalkanes led to the design of a new class of cofacially arrayed polyfluorenes that retain their π-stacked structure. Thus, efficient synthetic strategies have been established for the ready preparation of monodisperse polyfluorenes with up to six π-stacked fluorenes, which afford ready access to D–spacer–A triads by linking donor and acceptor groups to the polyfluorene spacers via single methylenes. Detailed 1H NMR spectroscopy, X-ray crystallography, electrochemistry, and He(I) photoelectron spectroscopy of F2–F6 have confirmed the rigid cofacial stacking of multiple fluorenes in F2–F6, despite the presence of rotatable C–C bonds. These polyfluorenes (F2–F6) form stable cation radicals in which a single hole is delocalized amongst the stacked fluorenes, as judged by the presence of intense charge-resonance transition in their optical spectra. Interestingly, these studies also discern that delocalization of a single cationic charge could occur over multiple fluorene rings in F2–F6, while the exciton is likely localized only onto two fluorenes in F2–F6. Facile synthesis of the D–spacer–A triads allowed us to demonstrate that efficient triplet energy transfer can occur through π-stacked polyfluorenes; the mechanism of energy transfer crosses over from tunneling to hopping with increasing number of fluorenes in the polyfluorene spacer. We suggest that the development of rigidly held π-stacked polyfluorenes, described herein, with well-defined redox and optoelectronic properties provides an ideal scaffold for the study of electron and energy transfer in D-spacer-A triads, where the Fn spacers serve as models for cofacially stacked π-systems.

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Section: Electronic and Emission Spectroscopy Of Polyfluorenesmentioning

confidence: 99%

Design and Synthesis of Cofacially-Arrayed Polyfluorene Wires for Electron and Energy Transfer Studies

Rathore

Abdelwahed

2023

Molecules

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Exploring copper as a catalyst for cost effective synthesis of polyfluorenes: an alternative to platinum and palladium

et al. 2020

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In the present study, we report the synthesis of a series of anthracene based polyfluorenes containing alkyl substituted 9,10-diphenylanthracene and hydrazone substituted fluorene moieties. The polymers were synthesized via copper catalysed Ullmann coupling, which comparatively is inexpensive as compared to palladium and platinum used in Suzuki coupling. The synthesized polymers were characterized by various spectroscopic techniques. All the polymers exhibited blue emission having band gap in the range of 2.7-2.83 eV. The polymers showed good thermal stability with decomposition temperature over 330 °C and glass transition temperature in the range of 125-140 °C. All the polymers were soluble in common organic solvents with weight average molecular weight in the range of 21,000-25,000. The electrochemical study reveals that the HOMO energy levels of the polymers were in the range of − 5.16 to − 5.26 eV which had elevated compared with that of polyfluorene (5.7 eV). It matched the work function of ITO and ITO/PEDOT: PSS (4.7 and 5.0 eV respectively). These results indicated that the synthesized polymers could be promising materials for applications in light emitting diode.

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Charge-transfer or excimeric state? Exploring the nature of the excited state in cofacially arrayed polyfluorene derivatives

Cited by 2 publications

References 22 publications

Design and Synthesis of Cofacially-Arrayed Polyfluorene Wires for Electron and Energy Transfer Studies

Design and Synthesis of Cofacially-Arrayed Polyfluorene Wires for Electron and Energy Transfer Studies

Exploring copper as a catalyst for cost effective synthesis of polyfluorenes: an alternative to platinum and palladium

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