Synthesis and Characterization of Fluorinated Heterofluorene-Containing Donor−Acceptor Systems

Abstract

A series of oligothiophene-perfluoro-9-heterofluorene donor-acceptor (DA) compounds was synthesized via a combination of nucleophilic aromatic substitution (S(N)Ar(F)) and palladium coupling reactions. These compounds are of interest as possible building blocks for materials with useful electron transport properties, since they possess relatively low LUMO energy levels of -3.3 to -3.6 eV (as determined by differential pulse voltammetry). The HOMO-LUMO energy gaps, as determined by UV-vis spectroscopy, range between 2.4 and 2.5 eV, and photoluminescence emission spectra reveal lambda(ems) values in the range of 480-600 nm (corresponding to yellow-orange emission). Dilute solution-state photoluminescence quantum yields were significantly lower than those of the pure acceptor heterofluorenes (0.02-0.38 for the DA compounds vs approximately 1 for the pure acceptors), and notable solvatochromism in the fluorescence suggests emission from a charge-separated state. Theoretical calculations show that HOMO-level electron density is more localized on the thiophene fragment, while the LUMO level electron density is mostly associated with the electron-deficient portion of the molecule. Photovoltaic (PV) devices based on DA/poly-3-hexylthiophene (P3HT) blends exhibit improved performance over P3HT-only devices, suggesting the ability of these DA compounds to transport electrons in the solid state.

Molecular Wires with Controllable π‐Delocalization Incorporating Redox‐Triggered π‐Conjugated Switching Units

“…We continued our synthesis by taking advantage of the S N Ar‐reactivity of perfluorobiphenyls that proceeds selectively at the 4,4′‐positions, which is desirable for extending the π‐conjugation along the long‐axis of the biphenyl skeleton. As shown in Scheme , the reaction of 2 with ethynyltriisopropylsilane (1.2 equiv.)…”

Synthesis, Crystal Structure, Photophysical and Electrochemical Properties of rac‐6,13‐Dihydro‐6,13‐methanopentacene

“…The naphthalene ring is essentially planar, with a maximum deviation of 0.026(2) Å for atom C(3) in 1, 0.052(2) Å for atom C(10) in 2, and 0.039(2) Å for atom C(5) in 3, respectively. The bond distance of C(11)-C(12) in 1 (1.519(2) Å) is 120.9(2) 121.16 C(2)-C(1)-C (22) 133.44 (19) 132.54 C(10)-C(1)-C (22) 105.63 (18) 106.31 C(10)-C(11)-C (12) 107.39 (15) 105.89 C(10)-C(11)-C (23) 98.45 (16) 99.06 C(11)-C(23)-C (22) 94.24 (16) 94.16 Torsion angles (°) C(2)-C(1)-C(10)-C (11) 177.52 (18) 179.79 C(1)-C(10)-C(11)-C (12) 66.8 (2) 67.20 C(21)-C(22)-C(23)-C (11) 53.58 (19) 53.92 C(10)-C(1)-C(21)-C(12) 0.5(1) 0.4…”

Luminescent 2,7-disubstituted germafluorenes

“…[32] Tilley and coworkers reported the synthesis of a series of fluorinated heterofluorenes including germafluorene systems that exhibited high electron affinities and showed great potential as electron transporting materials. [33][34][35] A series of spirocyclic germafluorene-germoles that exhibited good photo-and thermal stability and with tunable luminescence were reported recently by Rivard and coworkers. [36] Many of the germafluorenes reported to date have been prepared by a lithium-halogen exchange reaction between a dihalobiphenyl precursor and nBuLi, followed by reaction with an appropriate dichlorogermane.…”

“…[36] Many of the germafluorenes reported to date have been prepared by a lithium-halogen exchange reaction between a dihalobiphenyl precursor and nBuLi, followed by reaction with an appropriate dichlorogermane. [31,[34][35][36][37] Recent reports have shown that transition-metal catalyzed routes can be used for the formation of germafluorene and silafluorene derivatives. [29,[38][39][40] An inexpensive, simplified, and higher yielding route to the tetra-halogenated precursor, 4,4ʹ-dibromo-2,2ʹ-diiodo-5,5ʹ-dimethoxy-1,1ʹ-biphenyl was reported by Huang et.…”