Synthesis and Optical Characterization of Hybrid Organic−InorganicHeterofluorene PolymersValentin H. K. Fell,† Annabel Mikosch,† Ann-Kathrin Steppert,† Wojciech Ogieglo,† Erdem Senol,§

Damien Canneson,‡ Manfred Bayer,‡ Franziska Schoenebeck,§ Alex Greilich,‡

and Alexander J. C. Kuehne*,†

†DWI − Leibniz Institute for Interactive Materials, RWTH Aachen University, Forckenbeckstraße 50, 52076 Aachen, Germany‡Experimentelle Physik 2, Technische Universitat Dortmund, 44221 Dortmund, Germany§Institute of Organic Chemistry, RWTH Aachen University, Landoltweg 1, 52074 Aachen, Germany

*S Supporting Information

ABSTRACT: We synthesize heterofluorene monomers with Si, Ge, N,As, Se, and Te occupying the 9-position of the fluorene motif, which arethen polymerized by Suzuki coupling. The optical properties of theobtained polymers are investigated in their solid state. We compare andelucidate effects in the materials absorption, emission, quantum yield (Φ),and fluorescence lifetime. Moreover, we determine the refractive indices nand absorption coefficient k by variable angle spectroscopic ellipsometry(VASE). We show that in addition to already known C, Si, and Ncontaining polyfluorenes also Ge and As containing polymers exhibitamplified spontaneous emission.

Polyfluorene homo- and copolymers are a powerful class ofpolymers for optoelectronic applications such as lasers,1

solar cells,2,3 transistors,4 and OLEDs.5 Polyfluorenes exhibitgood quantum yield,6 large optical gain,7 and high charge-carrier mobility.8 The polymer solubility is mediated throughalkylation of the C9 position, where incomplete alkylationpromotes oxidation,10 leading to a shift in fluorescence to thegreen spectrum8 and a decrease in quantum yield.11 To preventoxidation and improve the solid state quantum yield, the 9-position can be replaced with silicon. Such polysilafluorenes arethermally stable and resistant toward oxidation.9,12 Otherfluorene polymers where the carbon atom in the 9-position hasbeen replaced for nitrogen,13 germanium,14,15 phosphorus,16

oxygen,17 and sulfur18 have been reported. Nitrogen containingpolycarbazoles are well-known hole-transport (p-type) materi-als.19,20 Polycarbazoles are applied in solar cells,21 PLEDs,22

and transistors.23 Because of the nitrogen lone pair at thefluorene 9-position, the carbazole moiety is fully aromatic.20

For metalloids, DFT studies predict an interaction between theσ* antibonding orbital of the metalloid to carbon bond and theπ* antibonding orbital of the butadiene fragment.24,25 Thisinteraction extends the π-conjugation26 and improves theelectron affinity and conductivity of the heterofluorenepolymer.12 The higher the atomic number of the atom at theC9 position, the less effective is this σ*−π* conjugation.24

There exist several examples of organic−inorganic semi-conductor hybrid materials, where Si27 and Ge28 nanoparticlesand GaAs,29 GaN,30,31 CdSe,32 and PbTe33 nanocrystals havebeen compounded in conjugated polymers for photonic andelectronic applications and devices.34 Interfaces between

inorganic and organic materials represent heterojunctions.Charge transport across the inorganic/organic interface isoften impeded by the topological, morphological, and energeticmismatch of the materials.34 Self-assembled monolayers can beapplied to minimize the morphological constraints at theinterface and direct crystal growth of the inorganiccomponent.35 To achieve a more gradual transition betweenthe interfaces of an organic and an inorganic semiconductor,conjugated polymers with incorporated heteroatoms could beapplied to reduce interfacial energy. The heteroatoms shouldrepresent elements and metalloids commonly applied in maingroup IV, III−V, and IV−VI inorganic semiconductor materials.Polysilafluorenes (PSiF) and polycarbazoles (PCz) arerelatively well studied and characterized; however, polygerma-fluorenes (PGeF) have been prepared but are hardlycharacterized.14,15 Whereas polyselenafluorene (PSeF) hasbeen theoretically described and characterized using DFTtheory,36 polyarsafluorenes (PAsF), polystannafluorenes(PSnF), and polytellurafluorene (PTeF) have never beensynthesized or investigated with computational chemistry.Here we synthesize a variety of heterofluorenes, which are

copolymerized with fluorene using Suzuki coupling. Wecharacterize the optical properties of the hybrid inorganic/organic polymers with respect to their absorption, spectralrefractive index, photoluminescence, quantum yield, andphotoluminescence lifetime. We also investigate their ability

Received: December 7, 2016Revised: February 26, 2017Published: March 9, 2017

Article

pubs.acs.org/Macromolecules

© 2017 American Chemical Society 2338 DOI: 10.1021/acs.macromol.6b02611Macromolecules 2017, 50, 2338−2343

to emit laser light. The materials have acceptable molecularweights, can be processed from solution, and are stable in air.

■ RESULTS AND DISCUSSION

We start by synthesizing the heterofluorene monomers. Mostof the heterofluorenes are accessible through lithiation of 4,4′-dibromo-2,2′-diiodobiphenyl (2) using n-butyllithium (seeFigure 1).11 2,7-Dibromo-9,9-diphenylsilafluorene (SiF), 2,7-dibromo-9,9-diphenylgermafluorene (GeF), and 2,7-dibromo-9,9-di-n-butylstannafluorene (SnF) are prepared by adding therespective organyl metalloid dichloride to 3 (see Figure 1).37

2,7-Dibromo-9-phenyl-9H-carbazole (Cz) is synthesized bystirring 4,4′-dibromo-2,2′-diamine (1) in hot phosphoric acidto induce ring closure,38 followed by Ullmann coupling withiodobenzene (see Figure 1).39,40

Since compound 2 is too reactive toward arsenic trichloride,it is first converted into a cadmium fluorene before addition ofAsCl3.

41 Phenyllithium is added to afford the 2,7-dibromo-9-phenylarsafluorene (AsF) (see Figure 1). The chalcogenfluorenes are prepared from disodium selenide and disodiumtelluride, which are derived by stirring elementary sodium withelementary selenide or telluride in dry THF (with a small

amount of naphthalene).42 After conversion of these slurrieswith copper(I) iodide in NMP, compound 2 is added and whileheating to 190 °C. 2,7-Dibromo-9,9-selenafluorene (SeF) and2,7-dibromo-9,9-tellurafluorene (TeF) are obtained respectively(see Figure 1).43,44 To obtain conjugated polymers from theseheterofluorene monomers, we apply Suzuki coupling with 9,9-dioctylfluorene-2,7-diboronic acid bis(1,3-propanediol) ester ascomonomer (see Figure 2). As a control polymer wepolymerize a carbon equivalent using 2,7-dibromospirofluorene(spiroF). The obtained polymers are purified by Soxhletextraction, followed by reprecipitation in methanol. Themolecular weight and conversion of the polymers aremonitored using size exclusion chromatography (SEC) and1H NMR (see Supporting Information). SnF cannot bepolymerized into a soluble polymer, probably because thestannyl moiety takes part in a competing Stille-type couplingreaction producing a cross-linked product, which is insoluble.45

All other polymers can be obtained as soluble powders withmedium to high molecular weights ranging between 4 and 16kDa. Only PTeF is obtained in lower molecular weight (seeTable 1).

Figure 1. Synthesis of heterofluorene monomers: (a) Cu, DMF, 125 °C, 3.5 h; (b) Sn, EtOH/HCl, 100 °C, 2.5 h; (c) HCl/MeCN/H2O, NaNO2,−10 °C, 1 h, then KI, −15 °C, then 80 °C, 67 h; (d) n-BuLi, THF, −78 °C, 2 h; (e) Ph2SiCl2, THF, −78 °C, then RT, overnight; (f) Ph2GeCl2,THF, −78 °C, then RT, overnight; (g) CdI2, Et2O, −78 °C, 1 h; (h) AsCl3, Et2O, −78 °C, 1 h, then reflux, 4 h; (i) PhLi, Et2O, −78 °C, 0.5 h, thenRT, overnight; (j) H3PO4, 180 °C, 46 h; (k) Cu, K2CO3, PhI, DMF, 140 °C, 8.5 h; (l) CuI, Na2Se, NMP, then addition of 2, 190 °C, 5.5 h; (m) CuI,Na2Te, NMP, then addition of 2, 190 °C, 17 h.

Figure 2. Synthesis of heterofluorene copolymers: Aliquat 336, 2 M aqueous K2CO3, Pd(PPh3)4, toluene, 100 °C, 2 days. Overview over thesynthesized polymers. PspiroF: X = C, R = spiro; PSiF: X = Si, R = diphenyl; PGeF: X = Ge, R = diphenyl; PCzF: X = N, R = Ph; PAsF: X = As, R =Ph; PSeF: X = Se, R = O; PTeF: X = Te, R = O.

Table 1. Molecular and Optical Properties of the Heterofluorene Monomers and Polymers

polymer θDFT (deg) λabsmax (nm) λem

max (nm) nmax Φ (%) Mw (Da) Đ S0−1 τ1 (ns) S0−1 τ2 (ns)

PspiroF 101.44 379 423 1.96 17.18 ± 0.07 1.5 × 104 3.2 0.79 1.69PSiF 91.48 367 417 1.97 18.74 ± 0.08 6.4 × 103 2.7 0.77 1.83PGeF 89.02 383 429 2.30 21.98 ± 0.05 5.6 × 104 2.8 0.65 1.61PCzF 108.46 402 450 2.05 7.13 ± 0.08 3.8 × 103 4.1 0.86 1.75PAsF 85.54 387 458 2.21 10.89 ± 0.04 1.6 × 104 3.4 0.78 4.79PSeF 87.03 381 424 2.22 11.37 ± 0.04 6.3 × 103 1.7 0.80 1.62PTeF 81.83 376 1.5 × 103 1.5

Macromolecules Article

DOI: 10.1021/acs.macromol.6b02611Macromolecules 2017, 50, 2338−2343

2339

To characterize the new heterofluorene monomers, weperform DFT studies46 to examine the ground state geometries(see Figure S1 and the applied computational methods in theSupporting Information). With increasing atomic number thecarbon−heteroatom−carbon bond angles θDFT decrease. This isdue to the increased atomic radius and the resulting separationfrom the pentacycle leading to a more acute angle (see FigureS1 and Table 1). To investigate the spectral influence of theheteroatoms, we perform absorption and fluorescence spec-troscopy on thin films spin-coated from toluene on quartz. Themain group IV polymers (PspiroF, PSiF, PGeF) exhibit verysimilar absorption spectra and vibronically resolved fluores-cence spectra (see Figure 3). The fluorescence quantum yield(Φ) increases with rising atomic number of the heteroatom inthe 9-position of the fluorene moiety (see Table 1). This couldoriginate from different polymer packing in the solid state. Thelarger heteroatom radius may leads to an increasedintermolecular distance similar to what has been observed in(benzofurano)tetrels.47 Smaller intermolecular distances entailincreased nonradiative decay.47 PCzF and PAsF do not showvibronic structure in their photoluminescence spectra, and theabsorption and emission of the main group V polymers are red-shifted in comparison to the main group IV polymers (seeFigure 3).48 We hypothesize that these properties originatefrom the heteroatom featuring a lone pair. To test thishypothesis, we perform DFT calculations to investigate theHOMO and LUMO frontier molecular orbitals of hetero-fluorene trimers (fluorene−heterofluorene−fluorene). We findthat the HOMOs are delocalized over the trimer, whereas theLUMOs are primarily localized at the heterofluorene moiety(see Figure S2). In case of the group V heterofluorene trimers,the LUMOs comprise the heteroatoms, which thereforecontribute to π-conjugation. The bathochromic shift inabsorption of PCzF is larger than for PAcF, suggesting aweaker interaction of the more diffuse 4p lone pair orbital ofarsenic with the π-electron system than the 2p lone pair orbitalof nitrogen. This assumption is substantiated by the DFTresults (see Figure S2). The Stokes shift of PAsF is greater thanfor PCzF, which results in reduced self-absorption leading to anincreased Φ.49 In general, the Φ of the main group V polymersis lower than for main group IV polymers. Because of the lack

of an interacting lone pair, the absorptions of the main groupVI heterofluorene polymers (PSeF and PTeF) resemble that ofthe group IV polyheterofluorenes. Whereas PSeF also shows asimilar fluorescence profile as the group IV polyhetero-fluorenes, PTeF does not exhibit fluorescence (see Figure 3).This result is somewhat surprising; however, it is in agreementwith previously reported undetectably low photoluminescencein polytellurophenes.50−52 One can speculate that telluriumincorporated in an organic backbone quenches the fluores-cence.To investigate whether the heteroatoms have an impact on

the fluorescence lifetime, we probe fluorescence lifetime on thinfilms of our material. The 0 → 0 transition usually hasconsiderable overlap with the absorption profile in fluorenederived polymers, which is why we examine the 0 → 1transition instead. The fluorescence lifetime in our hetero-fluorene polymers is governed by biexponential decay with timeconstants τ1 and τ2 (see Figure S3 in the SupportingInformation). For the τ1 decay time in the singlet state thetrend is analogous to the Φ. In group IV the decay times τ1 arebelow 1 ns and decrease with increasing atomic number. This isalso valid for group V heterofluorenes. No trend is observablefor the τ2 decay times, which describes the leveling of thefluorescence decay.To determine the influence of the heteroatom in the organic

polymer on its refractive index n, we perform variable anglespectroscopic ellipsometry (VASE) of the different hetero-fluorene polymers on a silicon wafer. VASE measurementsreveal that the maximum refractive index of the polymers isaround two or higher. For the main group IV and V polymers,the refractive index increases with the main atomic number ofthe heteroatom, as can be seen in Table 1. The determinedabsorption coefficients k exhibit the same maxima as the UV−vis absorption spectra of the thin films (see Figure 3). Theagreement between the VASE and UV−vis absorptionmeasurements reflects the good quality of the polymer filmsin terms of homogeneity, roughness, and depolarization effectsas well as consistency of the optical model applied to fit theVASE data (see Figure 3). Altogether PGeF and PAsF exhibitthe highest refractive indices at their respective maximumfluorescence wavelength, the highest quantum yields and lowest

Figure 3. Absorption (open circles), emission (full circles), refractive index, and absorption coefficient of the synthesized polymers PSpiroF (black),PSiF (dark blue), PGeF (blue), PCzF (green), PAsF (orange), PSeF (red), and PTeF (dark red). The absorption and emission of the main group Vare red-shifted in comparison to the main group IV polymers. The emission behavior of the main group VI polymers is similar to the main group IVpolymers.

Macromolecules Article

DOI: 10.1021/acs.macromol.6b02611Macromolecules 2017, 50, 2338−2343

2340

fluorescence lifetimes decay rates in their respective maingroups (see Table 1). When pumped with nanosecond laserpulses, films of PGeF and PAsF exhibit amplified spontaneousemission (ASE), where the fluorescence spectrum of theconjugated polymer films collapses into narrow line emission(see Figure 4). The threshold for this behavior is as low as 20 J/

cm2. As such, PGeF and PAsF represent potentially powerfulnew gain materials for organic−inorganic hybrid photonics andlaser devices.

■ CONCLUSION

We investigate a series of polyheterofluorene-9,9-dioctylfluor-ene copolymers for their optical properties. While amplifiedspontaneous and laser emission have previously been observedin polyfluorenes,53 polycarbazoles,54 and polysilafluorenes,55 wehave identified two new heterofluorene polymers, namely PGeFand PAsF, with superior optical properties and show that theyexhibit ASE. In the future, these polymers could presentimportant materials for interfacing inorganic semiconductorssuch as elemental Ge and III−V arsenides (GaAs, AlAs, InAs,etc.) with organic materials. This will pave the way for hybridoptoelectronic devices with improved properties, merging thebest qualities of both the inorganic and the organic worlds.

■ ASSOCIATED CONTENT

*S Supporting InformationThe Supporting Information is available free of charge on theACS Publications website at DOI: 10.1021/acs.macro-mol.6b02611.

Experimental details and fluorescence lifetime plots(PDF)

■ AUTHOR INFORMATION

Corresponding Author*E-mail: kuehne@dwi.rwth-aachen.de (A.J.C.K.).

ORCIDFranziska Schoenebeck: 0000-0003-0047-0929Alexander J. C. Kuehne: 0000-0003-0142-8001NotesThe authors declare no competing financial interest.

■ ACKNOWLEDGMENTSThis work was performed in part at the Center for ChemicalPolymer Technology CPT, which was supported by the EU andthe federal state of North Rhine-Westphalia (Grant EFRE 3000 883 02).

■ REFERENCES(1) Tsiminis, G.; Ruseckas, A.; Samuel, I. D. W.; Turnbull, G. A. ATwo-Photon Pumped Polyfluorene Laser. Appl. Phys. Lett. 2009, 94(25), 253304.(2) Kim, Y.; Cook, S.; Choulis, S. A.; Nelson, J.; Durrant, J. R.;Bradley, D. D. C. Organic Photovoltaic Devices Based on Blends ofRegioregular Poly(3-Hexylthiophene) and Poly(9,9-Dioctylfluorene-Co -Benzothiadiazole). Chem. Mater. 2004, 16 (23), 4812−4818.(3) Wang, X.; Perzon, E.; Delgado, J. L.; de la Cruz, P.; Zhang, F.;Langa, F.; Andersson, M.; Inganas, O. Infrared Photocurrent SpectralResponse from Plastic Solar Cell with Low-Band-Gap Polyfluoreneand Fullerene Derivative. Appl. Phys. Lett. 2004, 85 (21), 5081.(4) Zaumseil, J.; Donley, C. L.; Kim, J.-S.; Friend, R. H.; Sirringhaus,H. Efficient Top-Gate, Ambipolar, Light-Emitting Field-EffectTransistors Based on a Green-Light-Emitting Polyfluorene. Adv.Mater. 2006, 18 (20), 2708−2712.(5) Geng, Y.; Chen, A. C. A.; Ou, J. J.; Chen, S. H.; Klubek, K.;Vaeth, K. M.; Tang, C. W. Monodisperse Glassy-Nematic ConjugatedOligomers with Chemically Tunable Polarized Light Emission. Chem.Mater. 2003, 15 (23), 4352−4360.(6) Prieto, I.; Teetsov, J.; Fox, M. A.; Vanden Bout, D. A.; Bard, A. J.A Study of Excimer Emission in Solutions of Poly (9,9-Dioctyl-fluorene) Using Electrogenerated Chemiluminescence. J. Phys. Chem.A 2001, 105, 520−523.(7) Xia, R.; Heliotis, G.; Bradley, D. D. C. Fluorene-Based PolymerGain Media for Solid-State Laser Emission across the Full VisibleSpectrum. Appl. Phys. Lett. 2003, 82 (21), 3599.(8) Zhao, Q.; Liu, S.-J.; Huang, W. Polyfluorene-Based Blue-EmittingMaterials. Macromol. Chem. Phys. 2009, 210 (19), 1580−1590.(9) Chan, K. L.; McKiernan, M. J.; Towns, C. R.; Holmes, A. B.Poly(2,7-Dibenzosilole): A Blue Light Emitting Polymer. J. Am. Chem.Soc. 2005, 127 (21), 7662−7663.(10) List, E. J. W.; Guentner, R.; Scanducci de Freitas, P.; Scherf, U.The Effect of Keto Defect Sites on the Emission Properties ofPolyfluorene-Type Materials. Adv. Mater. 2002, 14 (5), 374−378.(11) Keyworth, C. W.; Chan, K. L.; Labram, J. G.; Anthopoulos, T.D.; Watkins, S. E.; McKiernan, M.; White, A. J. P.; Holmes, A. B.;Williams, C. K. The Tuning of the Energy Levels of DibenzosiloleCopolymers and Applications in Organic Electronics. J. Mater. Chem.2011, 21, 11800−11814.(12) McDowell, J. J.; Schick, I.; Price, A.; Faulkner, D.; Ozin, G. PureBlue Emitting poly(3,6-Dimethoxy-9,9-Dialkylsilafluorenes) Preparedvia Nickel-Catalyzed Cross-Coupling of Diarylmagnesate Monomers.Macromolecules 2013, 46 (17), 6794−6805.(13) Levesque, I.; Bertrand, P.; Blouin, N.; Leclerc, M.; Zecchin, S.;Zotti, G.; Ratcliffe, C. I.; Klug, D. D.; Gao, X.; Gao, F.; et al. Synthesisand Thermoelectric Properties of Polycarbazole, Polyindolocarbazole,and Polydiindolocarbazole Derivatives. Chem. Mater. 2007, 19, 2128−2138.(14) Allard, N.; Aïch, R. B.; Gendron, D.; Boudreault, P.-L. T.;Tessier, C.; Alem, S.; Tse, S.-C.; Tao, Y.; Leclerc, M. Germafluorenes:New Heterocycles for Plastic Electronics.Macromolecules 2010, 43 (5),2328−2333.(15) Chen, R.; Zhu, R.; Zheng, C.; Liu, S.; Fan, Q.; Huang, W.Germafluorene Conjugated Copolymersynthesis and Applicationsin Blue-Light-Emitting Diodes and Host Materials. Sci. China, Ser. B:Chem. 2009, 52 (2), 212−218.(16) Chen, R.-F.; Zhu, R.; Fan, Q.-L.; Huang, W. Synthesis,Structure, and Optoelectronic Properties of Phosphafluorene Copoly-mers. Org. Lett. 2008, 10 (13), 2913−2916.(17) Simonet, J.; Rault-Berthelot, J.; Granger, M. M.; Le Deit, H.Cathodic Cleavage of Organic Compounds on Electrodes Coated with

Figure 4. ASE of PGeF (blue) and PAsF (orange). For PGeF, the laseremission arises from the 0−1 vibronic transition.

Macromolecules Article

DOI: 10.1021/acs.macromol.6b02611Macromolecules 2017, 50, 2338−2343

2341

Polymeric Materials. Catalytic Efficiency of Solid Cathodes Modifiedby Polyfluorenes or Polydibenzofuran. J. Electroanal. Chem. 1994, 372(1−2), 185−193.(18) Jin, E.; Du, C.; Wang, M.; Li, W.; Li, C.; Wei, H.; Bo, Z.Dibenzothiophene-Based Planar Conjugated Polymers for HighEfficiency Polymer Solar Cells. Macromolecules 2012, 45, 7843−7854.(19) Li, Y.; Ding, J.; Day, M.; Tao, Y.; Lu, J.; D’iorio, M. Synthesisand Properties of Random and Alternating Fluorene/CarbazoleCopolymers for Use in Blue Light-Emitting Devices. Chem. Mater.2004, 16 (11), 2165−2173.(20) Blouin, N.; Michaud, A.; Leclerc, M. A Low-Bandgap Poly(2,7-Carbazole) Derivative for Use in High-Performance Solar Cells. Adv.Mater. 2007, 19 (17), 2295−2300.(21) Chu, T.-Y.; Alem, S.; Tsang, S.-W.; Tse, S.-C.; Wakim, S.; Lu, J.;Dennler, G.; Waller, D.; Gaudiana, R.; Tao, Y. Morphology Control inPolycarbazole Based Bulk Heterojunction Solar Cells and Its Impacton Device Performance. Appl. Phys. Lett. 2011, 98 (25), 253301.(22) Baba, A.; Onishi, K.; Knoll, W.; Advincula, R. C. InvestigatingWork Function Tunable Hole-Injection/Transport Layers of Electro-deposited Polycarbazole Network Thin Films. J. Phys. Chem. B 2004,108 (49), 18949−18955.(23) Rani, V.; Santhanam, K. S. V. Polycarbazole-Based Electro-chemical Transistor. J. Solid State Electrochem. 1998, 2 (2), 99−101.(24) Yamaguchi, S.; Itami, Y.; Tamao, K. Group 14 Metalloles withThienyl Groups on 2, 5-Positions: Effects of Group 14 Elements onTheir π -Electronic Structures †. Organometallics 1998, 17, 4910−4916.(25) Palilis, L. C.; Makinen, a. J.; Uchida, M.; Kafafi, Z. H. HighlyEfficient Molecular Organic Light-Emitting Diodes Based on ExciplexEmission. Appl. Phys. Lett. 2003, 82 (14), 2209.(26) Lu, G.; Usta, H.; Risko, C.; Wang, L.; Facchetti, A.; Ratner, M.A.; Marks, T. J. Synthesis, Characterization, and Transistor Responseof Semiconducting Silole Polymers with Substantial Hole Mobility andAir Stability. Experiment and Theory. J. Am. Chem. Soc. 2008, 130(24), 7670−7685.(27) Dietmueller, R.; Stegner, A. R.; Lechner, R.; Niesar, S.; Pereira,R. N.; Brandt, M. S.; Ebbers, A.; Trocha, M.; Wiggers, H.; Stutzmann,M. Light-Induced Charge Transfer in Hybrid Composites of OrganicSemiconductors and Silicon Nanocrystals. Appl. Phys. Lett. 2009, 94(11), 113301.(28) Gao, X.; Luo, W.; Zhong, C.; Wexler, D.; Chou, S.-L.; Liu, H.-K.; Shi, Z.; Chen, G.; Ozawa, K.; Wang, J.-Z. Novel Germanium/polypyrrole Composite for High Power Lithium-Ion Batteries. Sci. Rep.2014, 4, 6095.(29) Ren, S.; Zhao, N.; Crawford, S. C.; Tambe, M.; Bulovic, V.;Gradecak, S. Heterojunction Photovoltaics Using GaAs Nanowires andConjugated Polymers. Nano Lett. 2011, 11 (2), 408−413.(30) Sardar, K.; Dan, M.; Schwenzer, B.; Rao, C. N. R. A SimpleSingle-Source Precursor Route to the Nanostructures of AlN, GaNand InN. J. Mater. Chem. 2005, 15 (22), 2175.(31) Zhang, C.; Heeger, A. J. Gallium Nitride/conjugated PolymerHybrid Light Emitting Diodes: Performance and Lifetime. J. Appl.Phys. 1998, 84 (3), 1579.(32) Huynh, W. U.; Dittmer, J. J.; Alivisatos, A. P. Hybrid Nanorod-Polymer Solar Cells. Science 2002, 295 (5564), 2425−2427.(33) Xu, H.; Pang, X.; He, Y.; He, M.; Jung, J.; Xia, H.; Lin, Z. AnUnconventional Route to Monodisperse and Intimately ContactedSemiconducting Organic-Inorganic Nanocomposites. Angew. Chem.,Int. Ed. 2015, 54 (15), 4636−4640.(34) Reiss, P.; Couderc, E.; De Girolamo, J.; Pron, A. ConjugatedPolymers/Semiconductor Nanocrystals Hybrid Materials-Preparation,Electrical Transport Properties and Applications. Nanoscale 2011, 3,446−489.(35) Singh, A.; Lee, I. S.; Kim, K.; Myerson, A. S. Crystal Growth onSelf-Assembled Monolayers. CrystEngComm 2011, 13 (1), 24−32.(36) Chen, R.-F.; Zheng, C.; Fan, Q.-L.; Huang, W. Structural,Electronic, and Optical Properties of 9-Heterofluorenes: A QuantumChemical Study. J. Comput. Chem. 2007, 28 (13), 2091−2101.

(37) Imai, K.; Kihara, Y.; Kimoto, A.; Abe, J.; Tamai, Y.; Nemoto, N.Synthesis and Characterization of Poly(tetramethylsilarylenesiloxane)Derivatives Bearing Diphenylfluorene or DiphenyldibenzosiloleMoieties. Polym. J. 2011, 43, 58−65.(38) Patrick, D. A.; Boykin, D. W.; Wilson, W. D.; Tanious, F. A.;Spychala, J.; Bender, B. C.; Hall, J. E.; Dykstra, C. C.; Ohemeng, K. A.;Tidwell, R. R. Anti-Pneumocystis Carinii Pneumonia Activity ofDicationic Carbazoles. Eur. J. Med. Chem. 1997, 32, 781−793.(39) Kim, S. H.; Cho, I.; Sim, M. K.; Park, S.; Park, S. Y. HighlyEfficient Deep-Blue Emitting Organic Light Emitting Diode Based onthe Multifunctional Fluorescent Molecule Comprising CovalentlyBonded Carbazole and Anthracene Moieties. J. Mater. Chem. 2011, 21(25), 9139−9148.(40) Jiang, W.; Duan, L.; Qiao, J.; Dong, G.; Zhang, D.; Wang, L.;Qiu, Y. High-Triplet-Energy Tri-Carbazole Derivatives as HostMaterials for Efficient Solution-Processed Blue PhosphorescentDevices. J. Mater. Chem. 2011, 21 (13), 4918−4926.(41) Hellwinkel, D.; Kilthau, D. Elektrophile Und NucleophileSubstitutionsreaktionen an Verbindugnen Des PentakoordiniertenArsens. Chem. Ber. 1968, 101, 121−137.(42) Kasemann, R.; Lichenheim, C.; Naumann, D.; Nowicki, G. EinNeuer Syntheseweg Fur Perfluororganoselen- Und -Tellur-Verbindun-gen. Z. Anorg. Allg. Chem. 1995, 621, 213−217.(43) Suzuki, H.; Nakamura, T.; Sakaguchi, T.; Ohta, K. A ConvenientSynthesis of Functionalized Dibenzotellurophenes and RelatedCompounds via the Intramolecular Telluro Coupling Reaction. ThePositive Effect of Heavy Chalcogen Atoms on the MolecularHyperpolarizability of a Captodative Conjugation System. J. Org.Chem. 1995, 60 (16), 5274−5278.(44) Suzuki, H.; Nakamura, T. A Convenient One-Pot Preparation ofBis(nitroary1) Tellurides Using a Tellurium-Copper Couple as theTelluration Reagent. Chem. Ber. 1994, 127, 783−785.(45) Gu, C.; Zhu, D.; Qiu, M.; Han, L.; Wen, S.; Li, Y.; Yang, R.Design, Synthesis and Optical Properties of Small Molecules Based ondithieno[3,2-b:2′,3′-D]stannole and Stannafluorene. New J. Chem.2016, 40 (9), 7787−7794.(46) Calculations were done with Gaussian 09, Revision A.02: Frisch,M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb, M. A.;Cheeseman, J. R.; Scalmani, G.; Barone, V.; Petersson, G. A.;Nakatsuji, H.; Li, X.; Caricato, M.; Marenich, A.; Bloino, J.; Janesko, B.G.; Gomperts, R.; Mennucci, B.; Hratchian, H. P.; Ortiz, J. V.;Izmaylov, A. F.; Sonnenberg, J. L.; Williams-Young, D.; Ding, F.;Lipparini, F.; Egidi, F.; Goings, J.; Peng, B.; Petrone, A.; Henderson,T.; Ranasinghe, D.; Zakrzewski, V. G.; Gao, J.; Rega, N.; Zheng, G.;Liang, W.; Hada, M.; Ehara, M.; Toyota, K.; Fukuda, R.; Hasegawa, J.;Ishida, M.; Nakajima, T.; Honda, Y.; Kitao, O.; Nakai, H.; Vreven, T.;Throssell, K.; Montgomery, J. A., Jr.; Peralta, J. E.; Ogliaro, F.;Bearpark, M.; Heyd, J. J.; Brothers, E.; Kudin, K. N.; Staroverov, V. N.;Keith, T.; Kobayashi, R.; Normand, J.; Raghavachari, K.; Rendell, A.;Burant, J. C.; Iyengar, S. S.; Tomasi, J.; Cossi, M.; Millam, J. M.; Klene,M.; Adamo, C.; Cammi, R.; Ochterski, J. W.; Martin, R. L.;Morokuma, K.; Farkas, O.; Foresman, J. B.; Fox, D. J. Gaussian,Inc.: Wallingford, CT, 2016.(47) Zhang, F.-B.; Adachi, Y.; Ooyama, Y.; Ohshita, J. Synthesis andProperties of Benzofuran-Fused Silole and Germole Derivatives:Reversible Dimerization and Crystal Structures of Monomers andDimers. Organometallics 2016, 35 (14), 2327−2332.(48) Takagi, K.; Takao, H.; Nakagawa, T. Synthesis and Character-ization of Nitrogen-Linked Carbazole-Containing Fluorescent Poly-mers. J. Polym. Sci., Part A: Polym. Chem. 2010, 48 (17), 3729−3735.(49) Araneda, J. F.; Piers, W. E.; Heyne, B.; Parvez, M.; McDonald,R. High Stokes Shift Anilido-Pyridine Boron Difluoride Dyes. Angew.Chem., Int. Ed. 2011, 50 (51), 12214−12217.(50) Lapkowski, M.; Motyka, R.; Suwin ski, J.; Data, P. Photo-luminescent Polytellurophene Derivatives of Conjugated Polymers as aNew Perspective for Molecular Electronics. Macromol. Chem. Phys.2012, 213 (1), 29−35.

Macromolecules Article

DOI: 10.1021/acs.macromol.6b02611Macromolecules 2017, 50, 2338−2343

2342

(51) Jahnke, A. A.; Howe, G. W.; Seferos, D. S. Polytelluropheneswith Properties Controlled by Tellurium-Coordination. Angew. Chem.,Int. Ed. 2010, 49 (52), 10140−10144.(52) Jahnke, A. A.; Seferos, D. S. Polytellurophenes. Macromol. RapidCommun. 2011, 32 (13), 943−951.(53) Heliotis, G.; Bradley, D. D. C.; Turnbull, G. A.; Samuel, I. D. W.Light Amplification and Gain in Polyfluorene Waveguides. Appl. Phys.Lett. 2002, 81 (3), 415.(54) Li, X.; Li, M.; Gao, N.; Li, F.; Zhang, M.; Baumgarten, M. ANew Blue-Emitting Conjugated Polycarbazoles: Low Threshold ofAmplified Spontaneous Emission and Charge-Transporting Properties.Synth. Met. 2013, 176, 51−54.(55) McDowell, J. J.; Maier-Flaig, F.; Wolf, T. J. A.; Unterreiner, A.N.; Lemmer, U.; Ozin, G. Synthesis and Application of Photolitho-graphically Patternable Deep Blue Emitting poly(3,6-Dimethoxy-9,9-Dialkylsilafluorene)s. ACS Appl. Mater. Interfaces 2014, 6 (1), 83−93.

Macromolecules Article

DOI: 10.1021/acs.macromol.6b02611Macromolecules 2017, 50, 2338−2343

2343