CC BY-NC-ND 4.0 · Organic Materials 2021; 03(02): 337-345
DOI: 10.1055/s-0041-1730899
Emerging Stars in Organic and Polymer Materials
Short Communication

Carbonyl-to-Alkyne Electron Donation Effects in up to 10-nm-Long, Unimolecular Oligo(p-phenylene ethynylenes)

a  University of Vermont, Departments of Chemistry and Materials Science, 82 University Place, Burlington, VT 05405, United States
,
Olav Vestrheim#
a  University of Vermont, Departments of Chemistry and Materials Science, 82 University Place, Burlington, VT 05405, United States
,
Mona Sharafi
a  University of Vermont, Departments of Chemistry and Materials Science, 82 University Place, Burlington, VT 05405, United States
,
a  University of Vermont, Departments of Chemistry and Materials Science, 82 University Place, Burlington, VT 05405, United States
,
a  University of Vermont, Departments of Chemistry and Materials Science, 82 University Place, Burlington, VT 05405, United States
› Author Affiliations
Funding Information This work was supported by the Army Research Office (Grant 71015-CH-YIP awarded to S.T.S.). J.L. was partially supported by an NSF CAREER award (Grant CHE-1945394). The UVM Mass Spectrometry facilities were supported by National Institutes of Health (Grants S10-OD018126 and P30-GM118228). Part of the computational facilities was also supported by an NSF CAREER award (Grant CHE-1848444 awarded to STS).


Abstract

We synthesized some of the longest unimolecular oligo(p-phenylene ethynylenes) (OPEs), which are fully substituted with electron-withdrawing ester groups. An iterative convergent/divergent (a.k.a. iterative exponential growth – IEG) strategy based on Sonogashira couplings was utilized to access these sequence-defined macromolecules with up to 16 repeating units and 32 ester substituents. The carbonyl groups of the ester substituents interact with the triple bonds of the OPEs, leading to (i) unusual, angled triple bonds with increased rotational barrier, (ii) enhanced conformational disorder, and (iii) associated broadening of the UV/Vis absorption spectrum. Our results demonstrate that fully air-stable, unimolecular OPEs with ester groups can readily be accessed with IEG chemistry, providing new macromolecular backbones with unique geometrical, conformational, and photophysical properties.

Supporting Information

Supporting Information for this article is available online at https://doi.org/10.1055/s-0041-1730899.


# These authors have contributed equally to this work.


Supporting Information



Publication History

Received: 24 January 2021

Accepted: 30 April 2021

Publication Date:
18 June 2021 (online)

© 2021. The Author(s). This is an open access article published by Thieme under the terms of the Creative Commons Attribution-NonDerivative-NonCommercial License, permitting copying and reproduction so long as the original work is given appropriate credit. Contents may not be used for commercial purposes, or adapted, remixed, transformed or built upon. (https://creativecommons.org/licenses/by-nc-nd/4.0/)

Georg Thieme Verlag KG
Rüdigerstraße 14, 70469 Stuttgart, Germany

 
  • References and Notes

  • 1 New address: Sinu C. Rajappan, School of Polymer Science and Engineering, University of Southern Mississippi, 118 College Drive, Hattiesburg, MS 39406, USA
    • 2a Palmans A, Montali A, Weder C, Smith P. Proc. MRS 1999; 560: 265
    • 2b Sen CP, Valiyaveettil S. J. Polym. Sci., Part A: Polym. Chem. 2016; 54: 3652
    • 2c Liang J, Wu P, Tan C, Jiang Y. RSC Adv. 2018; 8: 9218
    • 2d Braeken Y, Cheruku S, Seneca S, Smisdom N, Berden L, Kruyfhooft L, Penxten H, Lutsen L, Fron E, Vanderzande D, Ameloot M, Maes W, Ethirajan A. ACS Biomater. Sci. Eng. 2019; 5: 1967
    • 2e Hleli E, Mbarek M, Gouid Z, Ulbricsht C, Romdhane S, Ben Said R, Guesmi M, Egbe DA. M, Bouchriha H. J. Phys. Chem. Solids 2020; 136: 109157
    • 2f Jagadesan P, Yu Z, Barboza-Ramos I, Lara HH, Vazquez-Munoz R, Lopez-Ribot JL, Schanze KS. Chem. Mater. 2020; 32: 6186
    • 2g Nie J, Wang Z, Huang X, Lu G, Feng C. Macromolecules 2020; 53: 6299
    • 2h Wang Q, Zhong Y, Miller DP, Lu X, Tang Q, Lu Z.-L, Zurek E, Liu R, Gong B. J. Am. Chem. Soc. 2020; 142: 2915
    • 2i Zhang Y, Zhan H, Chen J, Sun L, Fan L.-J. J. Polym. Sci. 2020; 58: 2088
    • 3a Remmers M, Schulze M, Wegner G. Macromol. Rapid Commun. 1996; 17: 239
    • 3b Levitsky IA, Kim J, Swager TM. J. Am. Chem. Soc. 1999; 121: 1466
    • 3c Brizius G, Pschirer NG, Steffen W, Stitzer K, zur Loye H.-C, Bunz UH. F. J. Am. Chem. Soc. 2000; 122: 12435
    • 3d Kim J, McQuade DT, McHugh SK, Swager TM. Angew. Chem. Int. Ed. 2000; 39: 3868
    • 3e McQuade DT, Hegedus AH, Swager TM. J. Am. Chem. Soc. 2000; 122: 12389
    • 3f McQuade DT, Kim J, Swager TM. J. Am. Chem. Soc. 2000; 122: 5885
    • 3g Kim J, Swager TM. Nature 2001; 411: 1030
    • 3h Schmitz C, Posch P, Thelakkat M, Schmidt H.-W, Montali A, Feldman K, Smith P, Weder C. Adv. Funct. Mater. 2001; 11: 41
    • 3i Nesterov EE, Zhu Z, Swager TM. J. Am. Chem. Soc. 2005; 127: 10083
    • 3j Moon JH, McDaniel W, MacLean P, Hancock LF. Angew. Chem. Int. Ed. 2007; 46: 8223
    • 3k Satrijo A, Swager TM. J. Am. Chem. Soc. 2007; 129: 16020
    • 3l Egbe DA. M, Tuerk S, Rathgeber S, Kuehnlenz F, Jadhav R, Wild A, Birckner E, Adam G, Pivrikas A, Cimrova V, Knor G, Sariciftci NS, Hoppe H. Macromolecules 2010; 43: 1261
    • 3m Jagadesan P, Valandro SR, Schanze KS. Mater. Chem. Front. 2020; 4: 3649
    • 3n Liu K, Shen Y, Li X, Zhang Y, Quan Y, Cheng Y. Chem. Commun. 2020; 56: 12829
    • 3o Luo SL, Lin C.-J, Ku KH, Yoshinaga K, Swager TM. ACS Nano 2020; 14: 7297
    • 4a Liu X, Weinert ZJ, Sharafi M, Liao C, Li J, Schneebeli ST. Angew. Chem. Int. Ed. 2015; 54: 12772
    • 4b Beaudoin D, Rominger F, Mastalerz M. Angew. Chem. Int. Ed. 2016; 55: 15599
    • 4c Beaudoin D, Rominger F, Mastalerz M. Angew. Chem. Int. Ed. 2016; 55: 15599
    • 4d Sharafi M, Weinert ZJ, Cohen IM, Liao C, Ivancic M, Li J, Schneebeli ST. Synlett 2016; 27: 2145
    • 4e Rommelmann P, Greschner W, Ihrig S, Neumann B, Stammler H.-G, Groeger H, Kuck D. Eur. J. Org. Chem. 2018; 2018: 3891
    • 4f Campbell JP, Rajappan SC, Jaynes TJ, Sharafi M, Ma Y.-T, Li J, Schneebeli ST. Angew. Chem. Int. Ed. 2019; 58: 1035
    • 4g Campbell JP, Sharafi M, Murphy KE, Bocanegra JL, Schneebeli ST. Supramol. Chem. 2019; 31: 565
    • 5a Nielsen MB, Diederich F. Chem. Rev. 2005; 105: 1837
    • 5b Baker MA, Tsai C.-H, Noonan KJ. T. Chem. Eur. J. 2018; 24: 13078
    • 6a Breen CA, Deng T, Breiner T, Thomas EL, Swager TM. J. Am. Chem. Soc. 2003; 125: 9942
    • 6b Smith RC, Tennyson AG, Lim MH, Lippard SJ. Org. Lett. 2005; 7: 3573
    • 6c Boden BN, Jardine KJ, Leung AC. W, MacLachlan MJ. Org. Lett. 2006; 8: 1855
    • 6d VanVeller B, Miki K, Swager TM. Org. Lett. 2010; 12: 1292
    • 7a Remmers M, Neher D, Gruener J, Friend RH, Gelinck GH, Warman JM, Quattrocchi C, dos Santos DA, Bredas J.-L. Macromolecules 1996; 29: 7432
    • 7b Montali A, Smith P, Weder C. Synth. Met. 1998; 97: 123
    • 7c Rozanski LJ, Bunz UH. F, Vanden Bout DA. Polym. Prepr. (Am. Chem. Soc., Div. Polym. Chem.) 2007; 48: 288
    • 7d Rozanski LJ, Vanden Bout DA, Bunz UH. F. In: Excimer Emission in Di-alkyl Poly(p-phenylene ethynylene) LEDs. American Chemical Society; Washington: 2007
    • 7e Burnworth M, Mendez JD, Schroeter M, Rowan SJ, Weder C. Macromolecules 2008; 41: 2157
    • 8a Zheng J, Swager TM. Chem. Commun. 2004; 2798
    • 8b Zhang L, Yin Q, Huang H, Wang B. J. Mater. Chem. B 2013; 1: 756
    • 8c Zhang L, Huang H, Xu N, Yin Q. J. Mater. Chem. B 2014; 2: 4935
    • 8d D'Olieslaeger L, Braeken Y, Cheruku S, Smits J, Ameloot M, Vanderzande D, Maes W, Ethirajan A. J. Colloid Interface Sci. 2017; 504: 527
    • 9a Grem G, Leditzky G, Ullrich B, Leising G. Adv. Mater. 1992; 4: 36
    • 9b Yamamoto T, Morita A, Miyazaki Y, Maruyama T, Wakayama H, Zhou ZH, Nakamura Y, Kanbara T, Sasaki S, Kubota K. Macromolecules 1992; 25: 1214
    • 9c Son S, Dodabalapur A, Lovinger AJ, Galvin ME. Science 1995; 269: 376
    • 9d Fou AC, Onitsuka O, Ferreira M, Rubner MF, Hsieh BR. J. Appl. Phys. 1996; 79: 7501
    • 9e Van Duren JK. J, Yang X, Loos J, Bulle-Lieuwma CW. T, Sieval AB, Hummelen JC, Janssen RA. J. Adv. Funct. Mater. 2004; 14: 425
    • 9f Weber J, Thomas A. J. Am. Chem. Soc. 2008; 130: 6334
    • 9g Garcia JM, Garcia FC, Serna F, de la Pena JL. Prog. Polym. Sci. 2010; 35: 623
    • 9h Lei T, Dou J.-H, Cao X.-Y, Wang J.-Y, Pei J. J. Am. Chem. Soc. 2013; 135: 12168
    • 9i Lei T, Xia X, Wang J.-Y, Liu C.-J, Pei J. J. Am. Chem. Soc. 2014; 136: 2135
    • 9j Sun H, Martinez D, Li Z, Schanze KS. ACS Appl. Mater. Interfaces 2020; 12: 53310
  • 10 Pawle RH, Agarwal A, Malveira S, Smith ZC, Thomas III SW. Macromolecules 2014; 47: 2250
    • 11a Gao H. Macromol. Rapid Commun. 2012; 33: 722
    • 11b Landry E, Ye Z. Macromol. Rapid Commun. 2013; 34: 1493
    • 11c Mullner M, Muller AH. E. Polymer 2016; 98: 389
    • 11d Wang Y, Wang L, Chen G, Gong S. Macromol. Biosci. 2017; 17: 1600292
    • 11e Golder MR, Jiang Y, Teichen PE, Nguyen HV. T, Wang W, Milos N, Freedman SA, Willard AP, Johnson JA. J. Am. Chem. Soc. 2018; 140: 1596
    • 12a Soos ZG, Mukhopadhyay D, Hennessy MH. Chem. Phys. 1996; 210: 249
    • 12b Harrison MG, Moller S, Weiser G, Urbasch G, Mahrt RF, Bassler H, Scherf U. Phys. Rev. B: Condens. Matter 1999; 60: 8650
    • 12c Muller JG, Lemmer U, Raschke G, Anni M, Scherf U, Lupton JM, Feldmann J. Phys. Rev. Lett. 2003; 91: 267403/1
    • 12d Yang X, Dykstra TE, Scholes GD. Phys. Rev. B: Condens. Matter 2005; 71: 045203/1
    • 12e Furmanchuk Ao, Leszczynski J, Tretiak S, Kilina SV. J. Phys. Chem. C 2012; 116: 6831
    • 13a Ickenroth D, Weissmann S, Rumpf N, Meier H. Eur. J. Org. Chem. 2002; 2808
    • 13b Chen J, Vachon J, Feringa BL. J. Org. Chem. 2018; 83: 6025
    • 13c Hergert M, Bender M, Seehafer K, Bunz UH. F. Chem. Eur. J. 2018; 24: 3132
    • 13d Schneider RV, Waibel KA, Arndt AP, Lang M, Seim R, Busko D, Braese S, Lemmer U, Meier MA. R. Sci. Rep. 2018; 8: 1
    • 13e Eder T, Vogelsang J, Bange S, Remmerssen K, Schmitz D, Jester S.-S, Keller TJ, Hoeger S, Lupton JM. Angew. Chem. Int. Ed. 2019; 58: 18898
    • 14a Barnes JC, Ehrlich DJ. C, Gao AX, Leibfarth FA, Jiang Y, Zhou E, Jamison TF, Johnson JA. Nat. Chem. 2015; 7: 810
    • 14b Leibfarth FA, Johnson JA, Jamison TF. Proc. Natl. Acad. Sci. U.S.A 2015; 112: 10617
  • 15 All DFT calculations were carried out with the Jaguar software package, with fully analytical integrals (Jaguar keyword: nops = 1) as well as with maximum sized DFT grids (Jaguar keywords: gdftgrad = −14, gdftmed = −14, and gdftfine = −14). Geometries were optimized with the B3LYP-MM dispersion-corrected functional (see: Ref. 16) with the LACVP* basis set (for which the parameters of the functional have been carefully optimized to also account for basis set superposition error; see: Ref. 16e), followed by single point energy calculations at the B3LYP-MM/cc-pVDZ + + level of theory. The vibrational frequencies for all minimized structures were then calculated at the B3LYP-MM/LACVP* level, and the corresponding zero-point energies were included in the calculation of the relative energies. Solvation energies were calculated via single-point calculations at the B3LYP-MM/LACVP* level, with the PBF CHCl3 solvent model implemented in the Jaguar software package. Torsional energy profiles were constructed by performing constrained structural optimizations with the dihedral angles ω (defined in Figure 2B) set to the specified values. Since the harmonic frequency approximation is only applicable to minimized structures (without constrained coordinates) zero-point energy corrections were not applied to the torsional energy profiles. Non-covalent interaction (NCI) plots as well as NCI interaction energies were obtained from the reduced density gradient at the B3LYP-MM/LACVP* level, following the methods of Johnson et al. (see: Ref. 17, Jaguar keyword: iplotnoncov = 1). Dipole moments were calculated at the B3LYP-MM/LACVP* level in vacuum
    • 16a Vosko SH, Wilk L, Nusair M. Can. J. Phys. 1980; 58: 1200
    • 16b Lee C, Yang W, Parr RG. Phys. Rev. B Condens. Matter 1988; 37: 785
    • 16c Becke AD. J. Chem. Phys. 1993; 98: 5648
    • 16d Stephens PJ, Devlin FJ, Chabalowski CF, Frisch MJ. J. Phys. Chem. 1994; 98: 11623
    • 16e Schneebeli ST, Bochevarov AD, Friesner RA. J. Chem. Theory Comput. 2011; 7: 658
  • 17 Johnson ER, Keinan S, Mori-Sánchez P, Contreras-García J, Cohen AJ, Yang W. J. Am. Chem. Soc. 2010; 132: 6498
    • 18a Jaguar, version 10.4. Schrodinger, Inc.; New York, NY: 2019
    • 18b Bochevarov AD, Harder E, Hughes TF, Greenwood JR, Braden DA, Philipp DM, Rinaldo D, Halls MD, Zhang J, Friesner RA. Int. J. Quantum Chem. 2013; 113: 2110
  • 19 Lingard H, Han JT, Thompson AL, Leung IK. H, Scott RT. W, Thompson S, Hamilton AD. Angew. Chem. Int. Ed. 2014; 53: 3650
  • 20 Zhang J, Moore JS, Xu Z, Aguirre RA. J. Am. Chem. Soc. 1992; 114: 2273
  • 21 Kim M, Boissonnault JA, Dau PV, Cohen SM. Angew. Chem. Int. Ed. 2011; 50: 12193
  • 22 General synthetic procedure for IEG growth deprotection: For TIPS deprotection, 4 M solutions of the TIPS-protected derivatives 36 (1.0 equiv) in anhydrous CH2Cl2 were prepared under an inert-gas atmosphere. Next, a 1 M solution of TBAF (1.5 equiv) in THF was added at room temperature and the reaction mixtures were stirred at room temperature for 1–2 h. Upon completion (monitored by TLC), the reaction mixtures were diluted with CH2Cl2 (25 mL) and then washed with water (3 × 20 mL) and brine (20 mL). Next, the organic layers were dried over anhydrous sodium sulfate, filtered, and the solvent was evaporated under reduced pressure. Any remaining catalyst was removed via a short flash column over silica gel (eluents: ethyl acetate/hexane mixtures). The TIPS-deprotected derivatives of the tetramer 5 and the octamer 6 were further purified with size-exclusion chromatography (stationary phase: Bio-Beads™ SX-1 Resin, eluent: CH2Cl2) before being carried forward to the Sonogashira coupling steps. Activation (via diazotization–iodination): Following a procedure adopted from Ref. 23, the aniline derivatives 36 (1.0 equiv) were dissolved in acetonitrile to form 0.1 M solutions. For compounds with low solubility in acetonitrile, toluene (10 vol%) was added as a co-solvent. Next, a 6 M aqueous HCl solution (10 vol% of the total reaction solvent) was added to the reaction mixtures and the reaction mixtures were cooled in an ice-bath. Diazotization was then initiated by adding an aqueous solution of NaNO2 (1.1 equiv) dropwise to the reaction mixtures at a reaction temperature of <5 °C. The reaction mixtures were then stirred at ∼0 °C for 15 minutes and subsequently added to ice-cold solutions of KI (3 equiv) in water. The resulting mixtures were again stirred at 0 °C for 1 h and then extracted with ethyl acetate. The combined organic layers were washed with water and with brine, dried over anhydrous sodium sulfate, filtered, and the solvent was evaporated under reduced pressure. Finally, the crude activated (iodinated) derivatives of 36 obtained in this manner were run through short silica gel columns (eluent: ethyl acetate/hexane solvent mixtures) and then directly carried forward to the Sonogashira coupling reactions. Sonogashira couplings: To oven-dried reaction flasks were added (i) the iodo-derivative (1.0 equiv), (ii) Pd(PPh3 4 (3 mol%), and (iii) CuI (6 mol%). The reaction flasks were then evacuated and backfilled with argon three times with standard Schlenk techniques. Next, the reaction flasks were charged with anhydrous DMF (12 mL) and triethylamine (2.0 equiv) followed by the TIPS-deprotected acetylene compounds (1.3 equiv). Finally, the reaction mixtures were stirred overnight at 70 °C. The progress of the reactions was monitored by TLC. Upon completion, the reaction mixtures were cooled to room temperature, filtered through Celite® 545, and washed with ethyl acetate. The filtrates were diluted with water and the products were extracted with ethyl acetate. The combined organic layers were washed with water and brine, dried over anhydrous magnesium sulfate, filtered, and the solvent was evaporated under reduced pressure. The crude Sonogashira-coupled materials 47 were purified by flash column chromatography (eluents: ethyl acetate in hexane mixtures) and, for the longer derivatives 57, subsequent size-exclusion chromatography (stationary phase: Bio-Beads™ SX-1 Resin, eluent: CH2Cl2)
  • 23 Droz AS, Neidlein U, Anderson S, Seiler P, Diederich F. Helv. Chim. Acta 2001; 84: 2243
    • 24a Schumm JS, Pearson DL, Tour JM. Angew. Chem. Int. Ed. Engl. 1994; 33: 1360
    • 24b Arias-Marin E, Arnault JC, Guillon D, Maillou T, Le Moigne J, Geffroy B, Nunzi JM. Langmuir 2000; 16: 4309
    • 24c Arias-Marin E, Le Moigne J, Maillou T, Guillon D, Moggio I, Geffroy B. Macromolecules 2003; 36: 3570
  • 25 Synthesis and characterization data of the dimer 4: Following the general reaction procedure for IEG growth (see: Ref. 22), the monomer 3 (2.0 mmol in 5 mL CH2Cl2) was deprotected with TBAF to afford 1.11 g (95% yield) of the TIPS-deprotected derivative of 3. At the same time, 3 (2.0 mmol) was activated following the general diazotization/iodination procedure to afford 1.06 g (57% yield) of the iodinated derivative of 3. The TIPS-deprotected (2.6 mmol) and iodinated (2.0 mmol) derivatives of 3 were then coupled together under Sonogashira coupling conditions to complete the IEG cycle, as detailed in the general IEG procedure. The crude product was purified by flash column chromatography (eluent: 0–20 vol% ethyl acetate in hexanes) to afford 1.72 g (88% yield) of the dimer 4. 1H NMR (500 MHz, CDCl3) δ 8.19 (s, 1 H), 8.11 (s, 1 H), 8.04 (s, 1 H), 7.22 (s, 1 H), 6.06 (s, 2 H), 4.29–4.20 (m, 8 H), 1.74 (dt, J = 12.0, 5.8 Hz, 2 H), 1.67 (td, J = 12.6, 6.3 Hz, 2 H), 1.55–1.28 (m, 28 H), 1.27–1.20 (m, 4 H), 1.16–1.14 (m, 21 H), 0.98–0.82 (m, 24 H). 13C (1H) NMR (125 MHz, CDCl3) δ 167.23, 165.90, 165.32, 165.22, 149.93, 137.99, 136.99, 136.85, 135.58, 135.15, 134.02, 123.84, 122.29, 118.67, 104.26, 99.30, 96.10, 89.23, 68.28, 68.19, 68.15, 67.49, 60.52, 38.95, 38.92, 38.87, 30.60, 30.48, 30.44, 29.12, 29.06, 29.05, 29.03, 24.06, 23.94, 23.90, 23.82, 23.08, 23.04, 18.79, 17.83, 14.18, 14.14, 12.42, 11.49, 11.14, 11.03. HRMS characterization for 4 was obtained after TIPS deprotection: HRMS (neg. ESI) calcd. for C52H74NO8 : m/z = 840.5420 [M – H]; found: 840.5421
  • 26 Synthesis and characterization data of the tetramer 5: Following the general reaction procedure for IEG growth (see: Ref. 22), the dimer 4 (1.0 mmol in 8 mL CH2Cl2) was deprotected with TBAF to afford 0.828 g (75% yield) of the TIPS-deprotected derivative of 4. At the same time, 4 (1.1 mmol) was activated following the general diazotization/iodination procedure to afford 1.038 g (62% yield) of the iodinated derivative of 4. The TIPS-deprotected (1.3 mmol) and iodinated (1.0 mmol) derivatives of 4 were then coupled together under Sonogashira coupling conditions to complete the IEG cycle, as detailed in the general IEG procedure. The crude product was purified by flash column chromatography (eluent: 0–20 vol% ethyl acetate in hexanes) to afford 0.910 g (82% yield) of the tetramer 5. 1H NMR (500 MHz, CDCl3) δ 8.28 (s, 1 H), 8.27 (s, 1 H), 8.24 (s, 1 H), 8.23 (s, 1 H), 8.21 (s, 1 H), 8.16 (s, 1 H), 8.12 (s, 1 H), 7.23 (s, 1 H), 6.07 (s, 2 H), 4.34–4.23 (m, 16 H), 1.79–1.67 (m, 8 H), 1.52–1.23 (m, 64 H), 1.16 (s, 21 H), 0.98–0.93 (m, 6 H), 0.91–0.84 (m, 42 H). 13C (1H) NMR (125 MHz, CDCl3) δ 167.09, 165.67, 165.01, 164.95, 164.91, 164.76, 149.82, 137.88, 136.87, 136.14, 136.01, 135.86, 135.61, 135.34, 134.54, 134.38, 134.07, 124.32, 123.24, 123.02, 122.57, 121.95, 118.55, 113.21, 109.86, 103.93, 100.16, 96.47, 95.07, 94.72, 94.47, 94.15, 89.19, 68.27, 68.25, 68.18, 68.06, 67.38, 38.82, 38.80, 38.78, 38.74, 30.47, 30.44, 30.32, 29.00, 28.95, 28.92, 23.94, 23.84, 23.78, 23.73, 22.95, 22.92, 18.66, 14.06, 14.03, 11.35, 11.00, 10.91. ∼46 13C (1H) NMR resonances coincide with other signals. HRMS (pos. ESI) calcd. for C113H168NO16Si+: m/z = 1823.2127 [M + H]+; found: 1823.2124
  • 27 Synthesis and characterization data of the octamer 6: Following the general reaction procedure for IEG growth (see: Ref. 22), the tetramer 5 (0.50 mmol in 10 mL CH2Cl2) was deprotected with TBAF and the product was purified further via size exclusion chromatography (stationary phase: Bio-Beads™ SX-1 Resin, eluent: CH2Cl2) to afford 0.900 g (93% yield) of the TIPS-deprotected derivative of 5. At the same time, 5 (0.32 mmol) was activated following the general diazotization/iodination procedure to afford 0.413 g (67% yield) of the iodinated derivative of 5. The TIPS-deprotected (0.27 mmol) and iodinated (0.21 mmol) derivatives of 5 were then coupled together under Sonogashira coupling conditions to complete the IEG cycle, as detailed in the general IEG procedure. The crude product was purified by flash column chromatography (eluent: 0–20 vol% ethyl acetate in hexanes) to afford 0.200 g (27% yield) of the octamer 6. 1H NMR (500 MHz, CDCl3) δ 8.29 (dd, J = 5.0, 2.8 Hz, 10 H), 8.25 (s, 1 H), 8.23 (s, 1 H), 8.21 (s, 1 H), 8.16 (s, 1 H), 8.12 (s, 1 H), 7.24 (s, 1 H), 6.06 (s, 2 H), 4.34–4.22 (m, 32 H), 1.78–1.68 (m, 16 H), 1.52–1.22 (m, 128 H), 1.16 (s, 21 H), 0.98–0.93 (m, 9 H), 0.92–0.84 (m, 87 H). MS (MALDI, DCTB matrix) calcd. for C217H311NNaO32Si+: m/z = 3494.2401 [M + Na]+; found: 3494.3000
  • 28 Synthesis and characterization data of the hexadecamer 7: Following the general reaction procedure for IEG growth (see: Ref. 22), the tetramer 6 (0.017 mmol in 5 mL CH2Cl2) was deprotected with TBAF and the product was purified further via size exclusion chromatography (stationary phase: Bio-Beads™ SX-1 Resin, eluent: CH2Cl2) to afford 0.056 g (95% yield) of the TIPS-deprotected derivative of 6. At the same time, 6 (0.029 mmol) was activated following the general diazotization/iodination procedure to afford 0.073 g (53% yield) of the iodinated derivative of 6. The TIPS-deprotected (0.017 mmol) and iodinated (0.015 mmol) derivatives of 6 were then coupled together under Sonogashira coupling conditions to complete the IEG cycle, as detailed in the general IEG procedure. The crude product was purified by flash column chromatography (eluent: 0–20 vol% ethyl acetate in hexanes) and further via size exclusion chromatography (stationary phase: Bio-Beads™ SX-1 Resin, eluent: CH2Cl2) to afford 0.020 g (19% yield) of the hexadecamer 7. 1H DOSY NMR (500 MHz, CDCl3, polystyrene standard, see Figure S1 for the calibration curve): w = 6.9 kDa (expected: 6.8 kDa)
  • 29 See Supplementary Figures S12 and S13 for the 13C (1H) NMR spectra (125 MHz, CDCl3, 298 K) as well as for the 1H–13C HMBC NMR spectra (500 MHz, CDCl3, 298 K) of 6 and 7. With over 200 carbon atoms in 6 and over 400 carbon atoms in 7, a large percentage of carbon signals is coinciding and/or is showing relatively weak signal-to-noise ratios. Yet, there are no carbon signals observed in the 80–85 ppm regions, where one would expect to find 13C resonances for potential homocoupled diacetylene byproducts (see, e.g., Ref. 33 for the 13C (1H) NMR spectra of ester-containing diacetylene derivatives with similar structures). Taken together with the observed (see: Refs. 27 and 28) molecular weights – and the fact that the 1H NMR resonances corresponding to the TIPS protecting groups are clearly observed at ∼1.16 ppm with the proper integrations – this finding excludes the formation of homocoupled diacetylene derivatives as potential side-products
  • 30 Xue C, Luo F.-T. Tetrahedron 2004; 60: 6285
  • 31 Sharafi M, Campbell JP, Rajappan SC, Dudkina N, Gray DL, Woods TJ, Li J, Schneebeli ST. Angew. Chem. Int. Ed. 2017; 56: 7097
  • 32 Since a racemic mixture of 2-ethylhexyl bromide was used for the synthesis, the OPEs are present as a mixture of diastereoisomers, which could further contribute to the observed line-broadening of the UV/Vis spectra
  • 33 Vestergaard M, Jennum K, Sørensen JK, Kilså K, Nielsen MB. J. Org. Chem. 2008; 73: 3175