PolymerChemistry

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Max-Planck-Institute for Polymer Researc

Germany. E-mail: muellen@mpip-mainz.

Fax: +49-6131-379-350; Tel: +49-6131-379-1

† Electronic supplementary informationdetailed synthetic procedures, characterias additional photophysical and computFor ESI and crystallographic data in CI10.1039/c3py00166k

Cite this: Polym. Chem., 2013, 4, 2963

Received 31st January 2013Accepted 24th March 2013

DOI: 10.1039/c3py00166k

www.rsc.org/polymers

This journal is ª The Royal Society of

p-Congested poly(paraphenylene) from2,20,6,60-tetraphenyl-1,10-biphenyl units:synthesis and structural characterization†

Florian Schlutter, Tomohiko Nishiuchi,* Volker Enkelmann and Klaus Mullen*

The synthesis of poly(paraphenylene)s (PPPs) bearing sterically

p-congested 2,20,6,60-tetraphenyl-1,10-biphenyl (1) units has been

achieved for the first time. By enhancing the synthesis of 1, followed

by its polymerization, we were able to compare the photophysical

properties of the oligomeric and polymeric fractions with non-

crowded PPPs. This revealed significant p-orbital interactions along

the paraphenylene backbone of the p-congested systems together

with through-space conjugation among the p-orbitals of the stacked

peripheral phenyl rings, resulting in an increased effective conjuga-

tion length and a remarkable bathochromic shift in absorption.

In the last few decades tremendous progress has been made inthe synthesis of phenylene-based nanostructures, e.g., oligo-and poly(paraphenylene)s (OPPs and PPPs).1–13 These materialshave been of particular interest as blue-emitting materials foruse in light-emitting diodes (LEDs), due to their intrinsicallyhigh bandgaps (Eg) but they usually suffer from insolu-bility.10,14–16 Substitution with long alkyl or alkoxy groups caninduce solubility, but was accompanied by reduced p-con-jugative interactions along the paraphenylene core and a cor-responding hypsochromic shi of the emission bands into theUV region.13,17 The synthesis of phenylene-based nanostructuresis driven by an interest in the relationship between stericcongestion, reactivity, and the resulting properties. Withrespect to this, several extremely p-congested oligophenylenespossessing highly unusual geometries were synthesized inrecent years.18–26 One of these examples is 2,20,6,60-tetraphenyl-1,10-biphenyl units (1, Scheme 1), in which the biphenyl core isshielded by four surrounding benzene rings, which leads to

h, Ackermannweg 10, D-55128 Mainz,

mpg.de; nishiuch@mpip-mainz.mpg.de;

51

(ESI) available: Materials, methods,zation data for all compounds as wellational studies. CCDC 918310–918313.F or other electronic format see DOI:

Chemistry 2013

signicant torsion between the mean planes of the central bond(�65�) while the peripheral phenyls are stacked in a face-to-faceorientation.20 Furthermore it can be considered as a substruc-ture of the hypothetical carbon allotrope “cubic graphite”.27 Thesolid state properties of this structural motif were extensivelystudied, however, the inuence of the mutual twist and the p-stacked peripheral phenyls on the electronic properties in fore.g. p-extended systems has not been investigated so far.18–20

Thus, we aimed for a synthetic pathway to introduce theintriguing structural features of 1 into the main chain of OPPsand PPPs, to study the thereby affected photophysicalproperties.

The synthesis of highly p-congested 2,20,6,60-tetraphenyl-1,10-biphenyl units (1, Scheme 1) was reported for the rst timeby Ozasa et al. in 1983, and 15 years later, the crystal structurewas determined by Pascal Jr.18–20 Further investigations wereimpeded due to the low yields of their synthetic protocols(below 5% overall yield), thus, we aimed for a new, more effi-cient synthetic approach towards sterically p-congested 1,which should simultaneously give access to the 4,40-positionsfor further extension, e.g., polymerization. From a retro-synthetic point of view, 1 is accessible via two concepts: (A)dimerization along the sterically unfavourable 20-position of thecentral benzene ring of ameta-terphenyl derivative 3 referring tothe work of Ozasa and Pascal Jr (Scheme 1 le, dashed arrow)and (B) reduction of the steric demand of one reaction partnerby attaching the peripheral phenyl rings to tetrahalogenatedbiphenyl 4 (Scheme 1 right, solid arrow).

Initially we focussed on the dimerization of 20-iodo-1,10:30,10 0-terphenyl (2) by utilizing Yamamoto conditions (Scheme 1, leside, top).28,29 2 was synthesized in a two-step manner and sub-jected to Ni0-mediated Yamamoto coupling. Although acompound with the same stoichiometric composition as 1 wasisolated, NMR spectroscopy and single crystal X-ray diffraction(see the ESI for details†) revealed the formation of an isomericspecies (II). In order to understand the mechanism of the rear-rangement reaction, the procedure was repeated with 2b, bearinga methyl-blocked 50-position. In this situation the formation of

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Scheme 1 Synthetic approaches towards 2,20 ,6,60-tetraphenyl-1,10-biphenyl derivatives (1). (a) Ni(COD)2, COD, 2,20-bipyridine, COD ¼ 1,5-cyclooctadiene. (b)Pd(PPh3)4, K2CO3.

Fig. 1 Solid state structure of 1a from different views: (a) top view. (b) Viewalong the 4,40-postions (hydrogens omitted for clarity in both views).37 (c)Numbering and characteristic metrics of 1a.

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neither 1 nor II was observed, suggesting migration of the activeNi0 complex to the less hindered p-face of 2a. This was accom-panied by a C–C bond formation at the 40-position of 2a, which issterically shielded in the case of a methyl substituted 50-position(2b) resulting in dehalogenation (see the ESI for details†). Theobserved “ring walk” of the Ni0 species is in agreement withtheoretical studies of Nakamura and coworkers on low valent Nimediated cross-coupling reactions.30

In addition, Suzuki–Miyaura cross-coupling was tested forthe synthesis of 1, since several procedures for the formation ofsterically hindered biaryls are available and halogen selectivityis enabled (Scheme 1, le side, bottom).31–36 By introducing apinacolato boronic ester to the gulf region, 3 was obtained inalmost quantitative yields and subsequently subjected toSuzuki–Miyaura cross-coupling with 2 applying various reactionconditions (see the ESI for details†). Again NMR spectroscopyand single crystal X-ray analysis conrmed the formation ofcompound III as an isomer of 1. This behaviour could beexplained by C–H activation of the 2/20-positions of terphenyls 2and 3 by the Pd0-complex during the catalytic cycle (see the ESIfor details†). This migration results in a decreased stericdemand of the C–C bond formation and a more favourableconformation.

Since both dimerization procedures along the 20-positionresulted in undesired migration or rearrangement, thesynthetic strategy towards 2,20,6,60-tetraphenyl-1,10-biphenylunits (1) was changed to concept (B) (Scheme 1, right side). Withrespect to this a simple two-step synthesis, comprising diazo-tation of 2,6-dibromo-4-methylaniline followed by an oxidativedimerization using CuCl2, led to precursor biphenyl 4 in goodyields. Subsequent Suzuki–Miyaura coupling under optimizedconditions with phenyl boronic acid lead nally to 1 in a 47%yield (see the ESI for details†). NMR spectroscopy and singlecrystal X-ray analysis revealed the absence of any isomericspecies and showed a 66� mutual distortion of the biphenylsubunits (Fig. 1).37 Moreover an ordinary central bond length(r1 ¼ 1.49(1) A) is revealed despite the high degree of strain. Theperipheral phenyls show a p-stacking distance of 3.16(9) A and3.30(5) A, respectively.

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The overall yield of this reaction sequence (22% over threesteps) was thus improved by one order of magnitude comparedwith the procedure developed by Ozasa et al. (�2% over foursteps).18,19

In order to extend the conjugation of highly p-congested 1,we aimed for a polymerizable precursor. For this purpose thereaction sequence was repeated, resulting in 1b bearing Cl in 4-and 40-positions and solubilizing tert-butyl groups at theperipheral phenyls. In order to overcome the drawbacks of ABtype polymerizations, e.g., highly accurate stoichiometries, weutilized Ni0-mediated Yamamoto coupling for the polymeriza-tion of 1b (Scheme 2).28,29 Due to the lower reactivity of thedichloro-functionalities, microwave assisted polymerizationconditions with extended reaction times were applied resultingnally in a polymerization yield of 79%. Preparative size-exclu-sion chromatography (SEC) allowed for the separation of theobtained polymer into the monodisperse dimer 6 and trimer 7,as well as seven polydisperse fractions (8–14). The structures ofdimer 6, trimer 7, separated oligomers 8–13 and polymer 14 (Mn

¼ 10 400 g mol�1, PDI ¼ 1.19) were conrmed by NMR spec-troscopy, MALDI-TOFMS and SEC (see the ESI for details†). Dueto the decreased ionization tendency under the applied MALDI-TOF conditions, no end group analysis was possible for 10–14.Comparing the 1H NMR spectra of dimer 6 and trimer 7with thepolymeric fraction revealed, however, a similar appearance of arelatively sharp singlet (7.14 ppm) was observed for the isolated

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Scheme 2 Synthesis of oligomers 6–13 and polymer 14. (a) Ni(COD)2, COD, 2,20-bipyridine, COD ¼ 1,5-cyclooctadiene.

Fig. 3 HOMO orbitals of 6th (a), and p-quaterphenyl (b). Left: molecular struc-tures, right: HOMO orbitals (isocounter value: 0.026 [a.u.] for both molecularorbitals). (c) HOMO orbital of 1th. Arrows indicate a through-space conjugationamong peripheral phenyl rings (isocounter value: 0.010 [a.u.]).

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polymer, suggesting Cl termination for 8–14 related to 6 and 7(see the ESI for details†).

The specic UV-vis absorption spectra of 6–14 are shown inScheme 2 and Fig. 2a, respectively. All the compounds exhibittypical transitions in the range of 360–310 nm and below 300nm. From time-dependent DFT calculations (TD-DFT, B3LYP/6-31G*) on a simplied derivative 1th, these two absorptions areassigned as HOMO � 1 to LUMO + 1 and HOMO–LUMO tran-sitions (see the ESI for details†).38 In addition, these compoundsexhibited deep blue emissions between 360 and 450 nm(Fig. 2b). By extending the p-conjugation towards dimer 6 andtrimer 7, bathochromic shis of the absorption and emissionmaxima by about 10 nm and 30 nm were observed. Thistendency is also followed by TD-DFT calculations. The observedred-shis indicate that effective p-conjugation along the para-position of the sterically p-crowded subunits exists despite thelarge torsional angle in the central biphenyl units. In fact,theoretical calculations revealed that HOMO and LUMOorbitals of 1th, dimer 6th and trimer 7th are delocalized over theentire molecule. In particular, the peripheral phenyl ringsincrease the densities of p-electrons along the paraphenylenebackbone in 6 and 7. Comparing the HOMO orbital of 6th withthat of p-quaterphenyl possessing identical twists in the core, asignicant p-orbital interaction in the p-congested biphenylunits can be observed for 6th, whereas no such interaction isobserved in p-quaterphenyl at the same isocounter value (Fig. 3,arrow). Similar p-orbital interactions also exist in trimer 7th (seethe ESI†). Furthermore, the through-space conjugation amongthe p-orbitals of the peripheral phenyl rings, related to stacked[2.2]paracyclophanes, is also conrmed (Fig. 3c) and can beconsidered as a nature of the present p-congested systems.39

Both aspects contribute to the observed bathochromic shis in

Fig. 2 (a) Normalized UV-vis absorption spectra of 6–13. (b) Emission spectra of 6energy (En) of 6–14 with the inverse number of the repeating units and the linear

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absorption by 10 nm for dimer 6 and trimer 7, compared withthe analogous p-quaterphenyl and p-sexiphenyl. This trend wasalso revealed by comparing the UV-vis absorption maximumof p-congested PPP 14 (Mn ¼ 10 400 g mol�1, n z 15, lmax ¼371 nm) with a non-crowded n-hexyl substituted PPPs

–14 (for all spectra: 10�6 M in CH2Cl2). (c) Correlation of the optical absorptionequation.

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(Mn ¼ 7600 g mol�1, n z 31, lmax z 300 nm) synthesized byRehahn and Wegner.6 Although 14 consists of almost the samenumber of benzene units along the paraphenylene main chain(PPP : DPn z 31), the longest wavelength absorption is bath-ochromically shied by 71 nm. Taking this into account, thep-orbital interaction along the paraphenylene backbone andthe through-space conjugation are expected to compensate forthe unfavourable torsions along the main chain.

The convergence of optical and electronic parameters suchas absorption and photoluminescence maxima or redoxpotentials with increasing chain length of the p-conjugatedsystem are dened by the value of the effective conjugationlength.12,40,41 This value describes the size of the p-system,which is necessary to reach size-independent photophysicalproperties.41 It is well established that the absorption maxima(lmax) and the associated effective conjugation length of p-conjugated polymers with sufficiently high molecular weightscan be estimated from the empirical relationship between thenumber of repeating units with lmax of the p-conjugated olig-omers (En ¼ EN + E/n with En ¼ h/lmax).39,41–44 By applying thisrelationship to the present p-congested poly(paraphenylenes),we plotted the UV-vis absorption maxima (E in eV) of oligomers6–13 against the inverse number of repeating units obtaining alinear correlation (Fig. 2c). The corresponding extrapolationresults in a maximum absorption of 377 nm (E ¼ 3.29 eV) for apolymer with an innite number of p-congested units (n ¼ N).In addition the obtained absorption maxima of 6–13 wereplotted against the number of repeating units (see the ESI fordetails†) approaching a limit of convergence.42 By exponentiallytting this correlation, an absorption limit of 371 nm for thepresented p-congested systems is obtained, which is in goodagreement with the previous correlation. Since the extrapola-tion of the linear correlation for 1/n / 0 does not take intoaccount that the curve is bent for very high values of n, the slightdifferences in both values can be explained.42

With respect to this analysis, polymer 14 closely approachesthe maximum conjugation length (lmax ¼ 371 nm, E ¼3.34 eV). In other words, polymer chains with more than 16 p-congested repeating units have little to no additional effect onthe absorption energies. By comparing these data with clas-sical OPP without solubilizing alkyl-chains (linear correlation:lmax ¼ 366 nm, E ¼ 3.38 eV for n ¼N, exponential correlation:lmax ¼ 330 nm for n ¼ N, see the ESI for details†), the longestwavelength absorption could be shied by ca. 10–40 nm tohigher wavelengths through the incorporation of 2,20,6,60-tet-raphenyl-1,10-biphenyl units. These experimental resultsclearly show that planarization of the aromatic p-system is notthe only factor for enhancing the p-conjugation along theoligomeric or polymeric chain. By attaching additional phenylmoieties the effective conjugation length is increased, and agradual convergence of the photophysical properties withincreasing size of the p-system is achieved.

Conclusions

In summary we successfully improved the synthesis of stericallyp-congested 2,20,6,60-tetraphenyl-1,10-biphenyls 1a and 1b with

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the help of an efficient three-step protocol. In a crucial step, theperipheral phenyl rings were attached through a four-foldSuzuki–Miyaura coupling since the direct dimerization usingpreorganized m-terphenyl derivatives 2 and 3 resulted in rear-rangement or migration processes. With the help of polymeri-zation at the 4,40-positions, the conjugation of stericallyp-congested 1b was extended. Preparative SEC allowed for theseparation of the polymer into oligomeric fractions, which wasanalysed by UV-vis absorption and emission spectroscopy.By comparing the results with classical OPPs and PPPs,pronounced bathochromic shis in absorption were observedfor the p-congested systems. These ndings were attributed to asignicant p-orbital interaction along the paraphenylenebackbone of the p-congested systems, together with a through-space conjugation among the p-orbitals of the peripheralphenyl rings, which is absent in non-crowded PPPs. In additionthe inuence of the sterically p-congested subunits on theeffective conjugation length was investigated, revealing a UV-visabsorption maximum of 371 nm, which is achieved with ca. 16repeating units. In continuation of these encouraging ndings,synthetic pathways will be pursued in our group for extendingthe density of benzene rings in 1 towards additional “cubicgraphite” substructures, as well as for attaching donor andacceptor moieties to 1 to study the inuence on the electronicproperties with respect to potential optoelectronic applications.

Acknowledgements

This work was supported by the Transregio SFB TR49 (Frank-furt, Mainz, Kaiserslautern). We are grateful to Dr. MasashiHasegawa (Kitasato University, Japan) for the help with the TD-DFT calculations.

Notes and references

1 C. S. Marvel and G. E. Hartzell, J. Am. Chem. Soc., 1959, 81,448–452.

2 M. Akiyama, Y. Iwakura, S. Shiraish and Y. Imai, J. Polym.Sci., Part B: Polym. Lett., 1966, 4, 305–308.

3 P. Kovacic, V. Marchion, F. W. Koch and J. Oziomek, J. Org.Chem., 1966, 31, 2467–2470.

4 M. Rehahn, A. D. Schluter, G. Wegner and W. J. Feast,Polymer, 1989, 30, 1060–1062.

5 M. Rehahn, A. D. Schluter, G. Wegner and W. J. Feast,Polymer, 1989, 30, 1054–1059.

6 M. Rehahn, A. D. Schluter and G. Wegner, Makromol. Chem.,1990, 191, 1991–2003.

7 U. Scherf and K. Mullen, Makromol. Chem. Rapid Commun.,1991, 12, 489–497.

8 U. Scherf and K. Mullen, Synthesis, 1992, 23–38.9 M. B. Goldnger and T. M. Swager, J. Am. Chem. Soc., 1994,116, 7895–7896.

10 A. C. Grimsdale and K. Mullen, Adv. Polym. Sci., 2006, 199, 1–82.

11 C. Li, M. Y. Liu, N. G. Pschirer, M. Baumgarten andK. Mullen, Chem. Rev., 2010, 110, 6817–6855.

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12 M. D. Watson, A. Fechtenkotter and K. Mullen, Chem. Rev.,2001, 101, 1267–1300.

13 A. D. Schluter and G. Wegner, Acta Polym., 1993, 44, 59–69.14 A. Kra, A. C. Grimsdale and A. B. Holmes, Angew. Chem.,

Int. Ed., 1998, 37, 402–428.15 U. Mitschke and P. Bauerle, J. Mater. Chem., 2000, 10, 1471–

1507.16 A. C. Grimsdale and K. Mullen, Adv. Polym. Sci., 2008, 212,

1–48.17 K. C. Park, L. R. Dodd, K. Levon and T. K. Kwei,

Macromolecules, 1996, 29, 7149–7154.18 S. Ozasa, Y. Fujioka, J. Kikutake and E. Ibuki, Chem. Pharm.

Bull., 1983, 31, 1572–1581.19 Y. Fujioka, S. Ozasa, K. Sato and E. Ibuki, Chem. Pharm. Bull.,

1985, 33, 22–29.20 L. Tong, H. Lau, D. M. Ho and R. A. Pascal, J. Am. Chem. Soc.,

1998, 120, 6000–6006.21 R. A. Pascal, N. Hayashi and D. M. Ho, Tetrahedron, 2001, 57,

3549–3555.22 X. F. Shen, D. M. Ho and R. A. Pascal, Org. Lett., 2003, 5, 369–

371.23 J. Lu, D. M. Ho, N. J. Vogelaar, C. M. Kraml and R. A. Pascal,

J. Am. Chem. Soc., 2004, 126, 11168–11169.24 X. F. Shen, D. M. Ho and R. A. Pascal, J. Am. Chem. Soc., 2004,

126, 5798–5805.25 D. Wasserfallen, G. Mattersteig, V. Enkelmann and

K. Mullen, Tetrahedron, 2006, 62, 5417–5420.26 C. L. Hilton, J. M. Crowfoot, P. Rempala and B. T. King, J. Am.

Chem. Soc., 2008, 130, 13392–13399.27 J. Gibson, M. Holohan and H. L. Riley, J. Chem. Soc., 1946,

456–461.28 T. Yamamoto, Prog. Polym. Sci., 1992, 17, 1153–1205.29 T. Yamamoto, Bull. Chem. Soc. Jpn., 1999, 72, 621–638.30 N. Yoshikai, H. Matsuda and E. Nakamura, J. Am. Chem. Soc.,

2008, 130, 15258–15259.

This journal is ª The Royal Society of Chemistry 2013

31 J. J. Yin, M. P. Rainka, X. X. Zhang and S. L. Buchwald, J. Am.Chem. Soc., 2002, 124, 1162–1163.

32 S. D. Walker, T. E. Barder, J. R. Martinelli and S. L. Buchwald,Angew. Chem., Int. Ed., 2004, 43, 1871–1876.

33 T. E. Barder, S. D. Walker, J. R. Martinelli and S. L. Buchwald,J. Am. Chem. Soc., 2005, 127, 4685–4696.

34 K. L. Billingsley, T. E. Barder and S. L. Buchwald, Angew.Chem., Int. Ed., 2007, 46, 5359–5363.

35 A. Suzuki, Angew. Chem., Int. Ed., 2011, 50, 6722–6737.

36 X. Y. Yang, X. Dou and K. Mullen, Chem.–Asian J., 2008, 3,759–766.

37 Crystal data for 1a (CCDC 918312†): Single crystals of 1awereobtained by slow evaporation of a dichloromethane/methanol solution. These have been treated as a diffusecontribution to the overall scattering without specic atompositions by SQUEEZE/PLATON (A. L. Spek, J. Appl.Crystallogr., 2003, 36, 7). C38H30, M ¼ 486.66, monoclinic,C2/c, a ¼ 7.3789(2), b ¼ 22.1571(8), c ¼ 16.3043(5) A, b ¼102.0571(18)�. R ¼ 0.0423, Rw ¼ 0.0502.

38 M. J. Frisch, et al., in Gaussian 03, Revision C.02, Gaussian,Inc., Wallingford CT, 2004, (see the ESI† for a full citation).

39 Y. Morisaki, S. Ueno, A. Saeki, A. Asano, S. Seki and Y. Chujo,Chem.–Eur. J., 2012, 18, 4216–4224.

40 H.-H. Horhold, M. Helbig, D. Raabe, J. Opfermann,U. Scherf, R. Stockmann and D. Weiß, Z. Chem., 1987, 27,126–137.

41 J. Grimme, M. Kreyenschmidt, F. Uckert, K. Mullen andU. Scherf, Adv. Mater., 1995, 7, 292–295.

42 U. Stalmach, H. Kolshorn, I. Brehm and H. Meier, LiebigsAnn., 1996, 1449–1456.

43 H. Meier, U. Stalmach and H. Kolshorn, Acta Polym., 1997,48, 379–384.

44 T. Gibtner, F. Hampel, J. P. Gisselbrecht and A. Hirsch,Chem.–Eur. J., 2002, 8, 408–432.

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