ProDOT-Assisted Isomerically Pure Indophenines | The Journal of

Subscriber access provided by Nottingham Trent University

Note

ProDOT-Assisted Isomerically Pure Indophenines Ted M. Pappenfus, Andrew J Helmin, Wyatt D Wilcox, Sarah M Severson, and Daron E. Janzen J. Org. Chem., Just Accepted Manuscript • DOI: 10.1021/acs.joc.9b01525 • Publication Date (Web): 12 Aug 2019 Downloaded from pubs.acs.org on August 13, 2019

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 17 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

The Journal of Organic Chemistry

ProDOT-Assisted Isomerically Pure Indophenines Ted M. Pappenfus,†,* Andrew J. Helmin,† Wyatt D. Wilcox,† Sarah M. Severson,† Daron E. Janzen‡ †Division

of Science and Mathematics, University of Minnesota, Morris, Minnesota 56267, United States ‡Department

of Chemistry and Biochemistry, St. Catherine University, St. Paul, Minnesota 55105, United States *Corresponding

author. Email: [email protected] (FAX: 320-589-6371; Phone: 320-

589-6340) Abstract R2 R2 R1 N

O

R1 O

Br + S O

O R2 R2

O

N Open air Room temperature Transition-metal free Direct Catalytic Selective

O

O

S S

Br

Br

O

O

N O

R1

R2 R2 Low band gap materials Amphoteric redox behavior High thermal stability Conformationally "locked" structures Favorable solid-state packing

Reactions between 3,4-propylenedioxythiophenes (ProDOTs) and N-alkyl isatins under ambient conditions result in isomerically pure indophenine materials as confirmed by TLC and 1H NMR analysis. The resulting low band gap materials exhibit favorable inter- and intramolecular interactions, high thermal stabilities, low electronic transitions and amphoteric redox behavior.

1 ACS Paragon Plus Environment

The Journal of Organic Chemistry 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 2 of 17

In the late 1800’s, the intensely colored blue dye indophenine was discovered serendipitously by Adolph von Baeyer.1 After some incorrect initial reports, the currently accepted molecular structure of indophenine was determined in 1924 by Heller.2 Although the indophenine dye can be easily prepared, very few studies were reported in the 20th Century due to its poor solubility properties. An advancement came in the early 1990’s when Cava and coworkers reported a soluble form of the dye that could be better analyzed and characterized.3 This work paved the way for a number of recent studies which showcase indophenines as an emerging class of high performing semiconducting materials for use in thin-film transistors and organic photovoltaic devices.4-9 As an example, a recently reported indophenine-based copolymer exhibits ambipolar charge transport with carrier mobilities >0.5 cm2 V-1 s-1 for both holes and electrons in thin-film transistors.9 O S N H

S

S O

O

N H

N H

Isomer A

S

N H

S

Isomer C

Isomer B O N

S O

N H

S

H N

S S

S O

Isomer D

N H

O

O H N

S

H N

H S

O

O

Isomer E

N O

H

N O

H

Isomer F

Figure 1. Six possible stereoisomers of indophenine. A major obstacle in realizing the full potential of indophenine-based materials originates from the E/Z isomerism present in the structure which results in up to six geometric isomers (Figure 1) that are immensely challenging to separate.3-5 Two approaches to address this issue have been reported. The first approach involves the oxidation of indophenine to form the bissulfone IDTO (Figure 2) as a single pure isomer.5 The second involves the use of thieno[3,42 ACS Paragon Plus Environment

Page 3 of 17 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


b]thiophene within the indophenine structure which yields DTIP (Figure 2) as a single isomer.8 A downside to each of these approaches, however, is that pure isomers for each are obtained only after three steps and with low overall yield (33% for IDTO and 17% for DTIP). In addition, air and moisture sensitive reactions are required for the preparation of DTIP. Br O

R N

O O S S O O

R S

O N R

R N

O

S O

S Br

IDTO

R = alkyl

N R

S

DTIP

R

Figure 2. Previously reported isomerically pure indophenines. Based on the synthetic challenges outlined above, we hypothesized a more direct approach to isomerically pure materials would be to carefully select the thiophene building block to simplify the synthetic chemistry and to control the conformation of the resulting indophenine using nonbonding interactions. The use of noncovalent intramolecular interactions within conjugated materials has been shown to be an effective way to produce highly planar molecules for high-performing organic materials.10-12 Toward this end, we targeted alkylated forms of 3,4propylenedioxythiophene (ProDOT) as starting materials for isomerically pure indophenines. ProDOT has found widespread application in conjugated materials and is an attractive building block since sulfur-oxygen interactions between adjacent rings in ProDOTs allow for enhanced planarization and conjugation.13 Not only could ProDOT serve as a “conformational lock” in these materials, but the ability to put alkyl groups at the 2-position of the propylene bridge could help solubility and processability of the resulting materials.



Page 4 of 17

The “locked” transoid orientation14 of adjacent ProDOT units in conjugated systems is a desirable feature in the context of indophenine chemistry as three of the six possible isomers (A, B and C) in Figure 1 are potentially eliminated. As quantum mechanical methods have been shown to be useful for exploring “locking” schemes in conjugated materials,11 we calculated the energetics of the remaining three isomers (D, E and F) in Figure 1. DFT calculations (Table S1) reveal isomer F is most stable when ProDOTs are incorporated into the indophenine core with isomers D and E less stable by 7.6 and 3.8 kcal/mol respectively. These results strongly suggest a single isomer would likely dominate in synthesis of ProDOT-based indophenines. R1 N

R2 R2

O R1 O

O

N

O

O

S

Br

S

O

+

H2SO4

S

toluene rt, air O

R2 R2

Br

Br

O

O

N O

R1

R2 R2 1 R1 = 2-ethylhexyl, R2 = 2-ethylhexyloxy (44%) 2 R1 = n-butyl, R2 = n-butyl (43%) 3 R1 = 2-ethylhexyl, R2 = n-butyl (36%)

Scheme 1. Synthesis of ProDOT indophenines Scheme 1 outlines the syntheses of quinoidal indophenines from reactions between Nalkyl isatins and ProDOTs in toluene with catalytic sulfuric acid. Brominated isatins were used to maximize the utility of the resulting molecules for further derivatization/polymerization. Alkyl substitution patterns for the indophenines include ethyl-hexyl/ethyl-hexyloxy 1, butyl 2 and a mixed derivative 3 with butyl groups on the ProDOT core and ethyl-hexyl chains on the peripheral isatin. At the completion of each reaction, TLC displayed a single spot which could suggest the presence of a single isomer. After purification, 1H NMR experiments displayed well4 ACS Paragon Plus Environment

Page 5 of 17 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


defined spectra that are also consistent with a single isomer (Figures S1-S3, Supporting Information). The average yield for the three ProDOT indophenines was 41% which is good in comparison to the reaction methods mentioned previously for isomerically pure indophenines which require multiple steps. Single crystal X-ray structure analysis of 3 was performed and revealed the expected Z,E,Z isomer (Figure 3) as predicted using DFT calculations (vide supra). The crystal structure also verifies the quinoidal nature of the indophenine core (Figure S6, Supporting Information), with alternating shorter and longer carbon-carbon bond lengths in the -system across the molecule consistent with the Lewis structure in Scheme 1. Despite the fact that indophenines were discovered 140 years ago, to our knowledge, this is only the second reported crystal structure of an indophenine-based material and the first structure with an unoxidized core. The first indophenine-based structure was reported by Deng et al. for the bis-sulfone IDTO molecule which adopts the E,E,E conformation (Figure 2).5

Figure 3. Thermal ellipsoid plot of 3 (30% probability ellipsoids; hydrogens omitted for clarity). 5 ACS Paragon Plus Environment


Page 6 of 17

Despite significant alkyl substituents, molecules of 3 form infinite slipped -stacks in a layered arrangement with a single interplanar -stacking distance of 3.57 Å (Figure S8, Supporting Information). The slip angle of the -stack is 35°, corresponding to a 6.22 Å lateral parallel slippage between nearest neighboring planes. Aliphatic regions dominate regions in the ab plane between -stacks. The indophenine backbone is also remarkably planar with the isatin group plane twisted only 6.6° relative to the bithiophene core. The bonding geometry of the isatin nitrogen suggests sp2 hybridization consistent with inclusion in the -system. Short intramolecular sulfur…oxygen contacts involve both thiophene sulfur…isatin oxygen (S1…O3, 2.670(4) Å) as well as a thiophene sulfur…ProDOT oxygen (S1…O2, 2.788(4) Å) (Figure S9, Supporting Information). As each of these contacts is significantly shorter than the van der Waals radii sum of S and O (3.25 Å), these close contacts are believed to promote conformational locking.10-12 Table 1. Optical, Electrochemical and Thermal Properties of ProDOT Indophenines

molecule 1 2 3

Absmax, nma,b 648 647 650

, cm-1 88,000 95,000 91,000

M-1

EHOMO, eVc –5.34 –5.32 –5.30

ELUMO, eVc –3.88 –3.88 –3.86

EgCV, eVd 1.46 1.44 1.44

Egopt, eVe 1.39 1.39 1.39

Td (°C)f 269 347 352

a Measured in CH Cl . b Lowest energy absorption peak. c Calculated using the first oxidation/reduction potentials 2 2 relative to ferrocene and the following equations from ref. 25: EHOMO = – e[5.1 + Eox]; ELUMO = – e[5.1 + Ered]. d EHOMO – ELUMO. e Obtained from thin-film spectra. f Temperature at which 5% weight loss occurs via TGA.

Electronic, redox and thermal data of the indophenine molecules is summarized in Table 1. Consistent with previously reported thiophene-based indophenines,4-5 low energy -* electronic transitions are observed in solution and in thin-films (Figures S10-S11, Supporting Information). Shoulders present in solution UV-Vis spectra are assigned to vibronic structure which is typically observed in quinoidal oligomers.15-17 Values for these ProDOT indophenines 6 ACS Paragon Plus Environment

Page 7 of 17 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


are slightly red-shifted in comparison to thiophene-based indophenines which have solution max values near 640 nm.4 This may be due, in part, to greater planarity of quinoidal core for the ProDOT-based molecules.

1.0

0.5

0.0

-0.5

-1.0

-1.5

Potential (V) vs Ag/AgCl

Figure 4. Cyclic voltammogram of 2 in 0.1 M TBAPF6/CH2Cl2 ( = 100 mV/s).

Redox properties of molecules 1-3 are nearly identical and Figure 4 shows a representative cyclic voltammogram for 2 in dichloromethane. The most relevant feature of these materials is the existence of amphoteric redox behavior which display both quasi-reversible oxidation and reduction processes of one and two electrons respectively. Redox potentials from the CV experiments were used to estimate HOMO/LUMO levels as outlined in Table 1. Average HOMO (–5.32 eV) and LUMO (–3.87 eV) levels are very similar to those of the indophenine molecule with thiophene in place of ProDOT which displays HOMO and LUMO values of –5.41 eV and –3.86 eV respectively.5 The destabilization of the HOMO in ProDOT



Page 8 of 17

indophenines vs thiophene indophenines can be attributed to the electron-donating ability of the alkoxy groups in ProDOT. The thermal stability of molecules 1-3 was evaluated by thermogravimetric analysis (Figure S12, Supporting Information) and the results are outlined in Table 1. The decomposition temperatures at 5% weight loss for 1, 2, and 3 are 269, 347, and 352 oC, respectively. The lower decomposition temperature of 1 is attributed to the alkoxy-substitution at the 2-position of the propylene bridge in this particular ProDOT. Interestingly, the previously reported thiophenebased indophenine4 displays a decomposition temperature of 270 oC which is considerably lower than those values for molecules 2 and 3. The higher stability of 2 and 3 can be attributed to strong inter- and intramolecular interactions as shown in the X-ray structure of 3 (vide supra). Furthermore, differential scanning calorimetry (DSC) experiments showed no melting transitions before decomposition for all three compounds. In conclusion, substituted isatins and ProDOTs were reacted under mild conditions to form isomerically pure indophenines. X-ray crystallography provides unambiguous determination of the conformation and packing present for the ProDOT indophenine in the solid state which reveals favorable inter- and intramolecular interactions. All three ProDOT indophenines exhibit low energy electronic transitions and amphoteric redox behavior. These features suggest ProDOT indophenines are promising building blocks for use in organic electronic materials. Experimental Section Materials and Methods. All syntheses were performed in air under ambient conditions. 3,3-Bis[[(2-ethylhexyl)oxy]methyl]-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxepin (SunaTech) was purchased and used as received. 3,3-Dibutyl-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxepin was


Page 9 of 17 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


prepared as previously reported.18 Alkylated isatins were prepared from 6-bromoisatin and alkyl halides using a previously reported procedure for related molecules.19 NMR spectra were recorded on 300 MHz or 400 MHz instruments. X-ray crystallographic data were obtained on a bench-top single-crystal diffractometer using methods described previously.20 Infrared absorption spectra were recorded on a Bruker Tensor 27 FTIR using a single reflection ATR accessory with a germanium crystal. Thermogravimetric analysis (TGA) experiments were performed on a TA Instruments Q50 analyzer under a nitrogen atmosphere and the samples were heated at a rate of 10 °C / min. The differential scanning calorimetry (DSC) experiments were performed on a TA Instruments Q100 instrument calibrated with indium. The DSC curves were recorded on the second run at a scanning rate of 10 °C / min for heating and cooling under a nitrogen atmosphere. UV-vis spectra were recorded on Ocean Optics fiber optic spectrometers. Solution spectra were obtained in a 1 mm quartz cell. Thin films for absorption measurements were obtained by drop-casting chloroform solutions onto glass. DFT calculations were performed with the Gaussian 09 program.21 Geometries and orbital energies were calculated by means of the hybrid density functional B3LYP22,23 with the 6-31G(d,p) basis set. The input files were generated with GaussView. N-alkyl groups on each indophenine were replaced by n-propyl groups to save computational time similar to the approach for other conjugated systems.24 (3Z)-2H-Indol-2-one, 6-bromo-3-[(8E)-8-[(8Z)-8-[6-bromo-1,2-dihydro-1-(2-ethylhexyl)2-oxo-3H-indol-3-ylidene]-6(8H)-3,3-bis[[(2-ethylhexyl)oxy]methyl]-3,4-dihydro-2H-thieno[3, 4-b][1,4]dioxepinyl]-6(8H)-3,3-bis[[(2-ethylhexyl)oxy]methyl]-3,4-dihydro-2H-thieno[3,4-b][1, 4]dioxepinyl]-1,3-dihydro-1-(2-ethylhexyl) (1). Concentrated sulfuric acid (50 L) was added dropwise to a stirred solution of 6-bromo-1-(2-ethylhexyl)-isatin (0.203 g, 0.600 mmol) and 3,3bis[[(2-ethylhexyl)oxy]methyl]-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxepin (0.396 g, 0.900



Page 10 of 17

mmol) in toluene (6 mL). The reaction mixture immediately changed color to blue-green and then quickly to blue. After stirring the reaction mixture at room temperature for 2.5 h, water (6 mL) was added and the crude product was extracted with CH2Cl2. The organic extractions were combined, dried with MgSO4, filtered, and concentrated via rotary evaporation. The resulting solid was purified via silica gel column chromatography using 1:1 CH2Cl2:hexanes followed by 3:1 CH2Cl2:hexanes. The resulting solid was suspended in acetone and washed with additional acetone (3x) to afford 0.203 g (44%) of 1 as a dark blue solid. 1H NMR (300 MHz, CD2Cl2) δ 7.87 (d, 2H, J = 7.8 Hz), 7.01 (d, 2H, J = 7.8 Hz), 6.83 (s, 2H), 4.41 (s, 4H), 4.32 (s, 4H), 3.703.55 (m, 12H), 3.45-3.30 (m, 8H), 1.80 (m, 2H), 1.60-1.20 (m, 52H), 0.95-0.83 (m, 36H). IR (ATR, Ge crystal, ν/cm-1): 2959 (w), 2928 (w), 2873 (w), 2860 (w), 1658 (w), 1593 (m), 1562 (m), 1507 (vs), 1471 (m), 1359 (m), 1306 (m), 1189 (s), 1119 (s), 1055 (s), 867 (m) 854 (m), 835 (w), 810 (m), 725 (w), 676 (w), 642 (w). Anal. Calcd for C82H124Br2N2O10S2: C, 64.72; H, 8.21; N, 1.84. Found: C, 64.90; H, 8.36; N, 1.92. Solutions of sufficient concentration needed for 13C NMR could not be prepared, thus a 13C NMR spectrum was not obtained. (3Z)-2H-Indol-2-one, 6-bromo-3-[(8E)-8-[(8Z)-8-[6-bromo-1,2-dihydro-1-(butyl)-2-oxo3H-indol-3-ylidene]- 6(8H)-3,3-dibutyl-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxepinyl]-6(8H)-3, 3-dibutyl-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxepinyl]-1,3-dihydro-1-(butyl) (2). Concentrated sulfuric acid (50 L) was added dropwise to a stirred solution of 6-bromo-1-butyl-isatin (0.169 g, 0.600 mmol) and 3,3-dibutyl-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxepin (0.242 g, 0.900 mmol) in toluene (6 mL). The reaction mixture immediately changed color to blue-green and then quickly to blue. After stirring the reaction mixture at room temperature for 2.5 h, water (5 mL) was added and the crude product was extracted with CH2Cl2. The organic extractions were combined, dried with MgSO4, filtered, and concentrated via rotary evaporation. The crude solid


Page 11 of 17 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


was dissolved in chloroform, adsorbed on silica gel, and purified by column chromatography using 1:1 CH2Cl2:hexanes followed by 100% CH2Cl2. To remove trace amounts of ProDOT starting material, the solid was stirred in ethanol at 50 oC for 30 minutes, filtered and washed sequentially with ethanol, hexanes, and acetone to afford 0.139 g (43%) of 2 as a dark blue solid. 1H

NMR (400 MHz, CD2Cl2) δ 7.83 (d, 2H, J = 8.0 Hz), 6.98 (d, 2H, J = 8.8 Hz), 6.82 (s, 2H),

4.28 (s, 4H), 4.15 (s, 4H), 3.69 (t, 4H), 1.64-1.51 (m, 12H), 1.42-1.28 (m, 20H), 0.97-0.92 (m, 18H). IR (ATR, Ge crystal, ν/cm-1): 2957 (w), 2931 (w), 2861 (w), 1657 (w), 1593 (m), 1563 (m), 1507 (vs), 1471 (m), 1362 (s), 1341 (m), 1326 (m), 1299 (m), 1245 (m), 1198 (s), 1148 (m), 1118 (m), 1044 (m), 856 (s), 834 (w), 808 (m), 730 (w), 669 (w), 625 (m). Anal. Calcd for C54H68Br2N2O6S2: C, 60.90; H, 6.44; N, 2.63. Found: C, 61.01; H, 6.48; N, 2.69. Solutions of sufficient concentration needed for 13C NMR could not be prepared, thus a 13C NMR spectrum was not obtained. (3Z)-2H-Indol-2-one, 6-bromo-3-[(8E)-8-[(8Z)-8-[6-bromo-1,2-dihydro-1-(2-ethylhexyl)2-oxo-3H-indol-3-ylidene]- 6(8H)-3,3-dibutyl-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxepinyl]6(8H)-3,3-dibutyl-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxepinyl]-1,3-dihydro-1-(2-ethylhexyl) (3). Concentrated sulfuric acid (100 L) was added dropwise to a stirred solution of 6-bromo-1(2-ethylhexyl)-isatin (0.406 g, 1.20 mmol) and 3,3-dibutyl-3,4-dihydro-2H-thieno[3,4-b][1,4] dioxepin (0.483 g, 1.80 mmol) in toluene (12 mL). The reaction mixture immediately changed color to blue-green and then quickly to blue. After stirring the reaction mixture at room temperature for 2.5 h, water (12 mL) was added and the crude product was extracted with CH2Cl2. The organic extractions were combined, dried with MgSO4, filtered, and concentrated via rotary evaporation. The crude solid was dissolved in chloroform, adsorbed on silica gel, and purified column chromatography using 1:2 CH2Cl2:hexanes followed by 100% chloroform. The



Page 12 of 17

resulting solid was suspended in hexanes and washed with additional hexanes and then acetone to afford 0.252 g (36%) of 3 as a dark blue solid. 1H NMR (300 MHz, CD2Cl2) δ 7.85 (d, 2H, J = 8.4 Hz), 7.00 (dd, 2H, J = 8.6, 2.0 Hz), 6.79 (d, 2H, J = 1.8 Hz ), 4.30 (s, 4H), 4.17 (s, 4H), 3.59 (m, 4H), 1.78 (m, 2H), 1.68-1.22 (m, 40H), 1.03-0.83 (m, 24H). IR (ATR, Ge crystal, ν/cm1):

2957 (w), 2929 (w), 2860 (vw), 1656 (w), 1592 (m), 1563 (m), 1508 (vs), 1469 (m), 1359 (s),

1323 (m), 1249 (w), 1191 (s), 1148 (m) 1120 (s), 1044 (s), 985 (w), 857 (s), 835 (w), 807 (m), 730 (w), 680 (w), 641 (w). Anal. Calcd for C62H84Br2N2O6S2: C, 63.25; H, 7.19; N, 2.38. Found: C, 63.27; H, 7.12; N, 2.43. Solutions of sufficient concentration needed for 13C NMR could not be prepared, thus a 13C NMR spectrum was not obtained. Electrochemical Measurements. Room temperature electrochemical measurements were performed with a potentiostat and cell stand in a three-electrode configuration with a glassy carbon working electrode (A = 0.07 cm2), a platinum counter electrode, and a standard Ag|AgCl|KCl (1.0 M) reference electrode. A single compartment, low volume cell was used for all measurements. Tetrabutylammonium hexafluorophosphate electrolyte solution was added to the cell (5 mL, 0.1 M/CH2Cl2) and background cyclic voltammograms of the electrolyte solution were recorded prior to the addition of the sample. Suitable amounts of sample were added to create 0.5-0.75 mM solutions. The E0' values for the ferrocenium/ferrocene couple for concentrations similar to those used in this study were 0.47 V for dichloromethane solutions at a glassy carbon electrode. X-ray Crystallographic Data for molecule (3). C62H84Br2N2O6S2, F.W. = 1177.28, triclinic, space group P-1 (No. 2), a = 6.2227(12) Å, b = 13.638(3) Å, c = 17.947(4) Å;  = 78.429(6)°,  = 89.290(6)°,  = 88.540(6)°; V = 1491.6(5)Å3, Z = 1, Z’= 0.5, d = 1.311 g/cm3, T = 173 K, 14270 reflections collected, 6087 unique (Rint = 0.089), F(000) = 620.00, (MoK) =


Page 13 of 17 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


1.483 cm-1, GOF = 1.028, R1 (I>2.00(I)) 0.0759, wR2 (All reflections) = 0.1860. Additional data collection and refinement details can be found in the supporting information. Acknowledgements. T.M.P. acknowledges the following: (i) University of Minnesota, Morris (UMM) Faculty Research Enhancement Funds supported by the University of Minnesota Office of the Vice President for Research and the UMM Division of Science and Mathematics for financial assistance, and (ii) a Grant-in-Aid of Research, Artistry and Scholarship from the Office of the Dean of the Graduate School; (iii) the Howard Hughes Medical Institute (HHMI) Pathways to Science Program for financial assistance; and (iv) Dr. Bryan Nell for assistance with the NMR experiments. T.M.P. and D.E.J. acknowledge the National Science Foundation Major Research Instrumentation Award #1125975 for funding the acquisition of the X-ray diffractometer used for data collection in this investigation. Supporting Information. Computational results for ProDOT indophenine isomers; X-ray crystallographic file (CIF) for molecule 3 and crystallographic images; 1H spectra of all new compounds; UV-vis-NIR absorption spectra; TGA traces; and cyclic voltammograms for 1 and 3. This material is available free of charge via the Internet at http://pubs.acs.org. References 1. Baeyer, A. “Untersuchungen über die Gruppe des Indigblaus,” Ber. Dtsch. Chem. Ges. 1879, 12, 1309–1319. 2. Heller, G. “Zur Konstitution des Indophenins,” Angew. Chem. 1924, 37, 1017–1032. 3. Tormos, G. V.; Belmore, K. A.; Cava, M. P. “The Indophenine Reaction Revisited. Properties of a Soluble Dialkyl Derivative,” J. Am. Chem. Soc. 1993, 115, 11512–11515.



Page 14 of 17

4. Hwang, H.; Khim, D.; Yun, J.-M.; Jung, E.; Jang, S.-Y.; Jang, Y. H.; Noh, Y.-Y.; Kim, D.-Y. “Quinoidal Molecules as a New Class of Ambipolar Semiconductor Originating from Amphoteric Redox Behavior,” Adv. Funct. Mater. 2015, 25, 1146–1156. 5. Deng, Y.; Sun, B.; He, Yl.; Quinn, J.; Guo, C.; Li, Y. “Thiophene-S,S-dioxidized Indophenine: A Quinoid-Type Building Block with High Electron Affinity for Constructing nType Polymer Semiconductors with Narrow Band Gaps,” Angew. Chem. Int. Ed. 2016, 55, 3459–3462. 6. Deng, Y.; Quinn, J.; Sun, B.; He, Y.; Ellard, J.; Li, Y. “Thiophene-S,S-dioxidized Indophenine (IDTO) Based Donor–acceptor Polymers for n-Channel Organic Thin Film Transistors,” RSC Adv. 2016, 6, 34849–34854. 7. Deng, Y.; Sun, B.; Quinn, J.; He, Y.; Ellard, J.; Guo, C.; Li, Y. “Thiophene-S,S-dioxidized Indophenines as High Performance n-Type Organic Semiconductors for Thin Film Transistors,” RSC Adv. 2016, 6, 45410–45418. 8. Ren, L.; Fan, H.; Huang, D.; Yuan, D.; Di, C.; Zhu, X. “Dithienoindophenines: p-Type Semiconductors Designed by Quinoid Stabilization for Solar-Cell Applications,” Chem. Eur. J. 2016, 22, 17136–17140. 9. Hwang, H.; Kim, Y.; Kang, M.; Lee, M.-H.; Heo, Y.-J.; Kim, D.-Y. “A Conjugated Polymer with High Planarity and Extended π-Electron Delocalization via a Quinoid Structure Prepared by Short Synthetic Steps,” Polym. Chem. 2017, 8, 361–365. 10. Huang, H.; Yang, L.; Facchetti, A.; Marks, T. J. “Organic and Polymeric Semiconductors Enhanced by Noncovalent Conformational Locks,” Chem. Rev. 2017, 117, 10291–10318.


Page 15 of 17 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


11. Jackson, N. E.; Savoie, B. M.; Kohlstedt, K. L.; Olvera de la Cruz, M.; Schatz, G. C.; Chen, L. X.; Ratner, M. A. “Controlling Conformations of Conjugated Polymers and Small Molecules: The Role of Nonbonding Interactions,” J. Am. Chem. Soc. 2013, 135, 10475– 10483. 12. Aldrich, T. J.; Matta, M.; Zhu, W.; Swick, S. M.; Stern, C. L.; Schatz, G. C.; Facchetti, A.; Melkonyan, F. S.; Marks, T. J. “Fluorination Effects on Indacenodithienothiophene Acceptor Packing and Electronic Structure, End-Group Redistribution, and Solar Cell Photovoltaic Response,” J. Am. Chem. Soc. 2019, 141, 3274–3287. 13. Teran, N. B.; Reynolds, J. R. “Discrete Donor−Acceptor Conjugated Systems in Neutral and Oxidized States: Implications toward Molecular Design for High Contrast Electrochromics,” Chem. Mater. 2017, 29, 1290-1301. 14. Lin, C.; Endo, T.; Takase, M.; Iyoda, M.; Nishinaga, T. “Structural, Optical, and Electronic Properties of a Series of 3,4-Propylenedioxythiophene Oligomers in Neutral and Various Oxidation States,” J. Am. Chem. Soc. 2011, 133, 11339–11350. 15. Pappenfus, T. M.; Raff, J. D.; Hukkanen, E. J.; Burney, J. R.; Casado, J.; Drew, S. M.; Miller, L. L.; Mann, K. R. “Dinitro and Quinodimethane Derivatives of Terthiophene That Can Be Both Oxidized and Reduced. Crystal Structures, Spectra, and a Method for Analyzing Quinoid Contributions to Structure,” J. Org. Chem. 2002, 67, 6015–6024. 16. Casado, J.; Pappenfus, T. M.; Mann, K. R.; Milián, B.; Ortí, E.; Viruela, P. M.; Ruiz Delgado, M. C.; Hernández, V.; López Navarrete, J. T. “UV–Vis, IR, Raman and Theoretical Characterization of a Novel Quinoid Oligothiophene Molecular Material,” J. Mol. Struct. 2003, 651-653, 665–673.



Page 16 of 17

17. Casado, J.; Pappenfus, T. M.; Mann, K. R.; Ortí, E.; Viruela, P. M.; Milián, B.; Hernández, V.; López Navarrete, J. T. “Spectroscopic and Theoretical Study of the Molecular and Electronic Structures of a Terthiophene-Based Quinodimethane,” ChemPhysChem 2004, 5, 529–539. 18. Welsh, D. M.; Kloeppner, L. J.; Madrigal, L.; Pinto, M. R.; Thompson, B. C.; Schanze, K. S.; Abboud, K. A.; Powell, D.; Reynolds, J. R. “Regiosymmetric Dibutyl-Substituted Poly(3,4propylenedioxythiophene)s as Highly Electron-Rich Electroactive and Luminescent Polymers,” Macromolecules 2002, 35, 6517–6525. 19. Black, H. T.; Pelse, I.; Wolfe, R. M. W.; Reynolds, J. R. “Halochromism and Protonationinduced Assembly of a Benzo[g]indolo[2,3-b]quinoxaline Derivative,” Chem. Commun. 2016, 52, 12877–12880. 20. Christensen, E. M.; Oh, S.; Oliver, D.; Janzen, D. E.; Drew, S. M. “Solution and Solid-State Structure of cis-Dichloro-(N,N′-dimethylethylenediamine)platinum(II),” J. Chem. Crystallogr. 2014, 44, 236–242. 21. Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb, M. A.; Cheeseman, J. R.; Scalmani, G.; Barone, V.; Mennucci, B.; Petersson, G. A.; Nakatsuji, H.; Caricato, M.; Li, X.; Hratchian, H. P.; Izmaylov, A. F.; Bloino, J.; Zheng, G.; Sonnenberg, J. L.; Hada, M.; Ehara, M.; Toyota, K.; Fukuda, R.; Hasegawa, J.; Ishida, M.; Nakajima, T.; Honda, Y.; Kitao, O.; Nakai, H.; Vreven, T.; Montgomery, J. A., Jr.; Peralta, J. E.; Ogliaro, F.; Bearpark, M.; Heyd, J. J.; Brothers, E.; Kudin, K. N.; Staroverov, V. N.; Kobayashi, R.; Normand, J.; Raghavachari, K.; Rendell, A.; Burant, J. C.; Iyengar, S. S.; Tomasi, J.; Cossi, M.; Rega, N.; Millam, J. M.; Klene, M.; Knox, J. E.; Cross, J. B.; Bakken, V.; Adamo, C.; Jaramillo, J.; Gomperts, R.; Stratmann, R. E.; Yazyev, O.; Austin, A. J.; Cammi, R.; Pomelli, C.; Ochterski, 16 ACS Paragon Plus Environment

Page 17 of 17 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


J. W.; Martin, R. L.; Morokuma, K.; Zakrzewski, V. G.; Voth, G. A.; Salvador, P.; Dannenberg, J. J.; Dapprich, S.; Daniels, A. D.; Farkas, O.; Foresman, J. B.; Ortiz, J. V.; Cioslowski, J.; Fox, D. J.Gaussian 09, Revision A.02.; Gaussian, Inc., Wallingford, CT, 2009. 22. Becke, A. D. “Density‐functional Thermochemistry. III. The Role of Exact Exchange,” J. Chem. Phys. 1993, 98, 5648–5652. 23. Lee, C. T.; Yang, W. T.; Parr, R. G. “Development of the Colle-Salvetti correlation-energy formula into a functional of the electron density,” Phys. Rev. B 1988, 37, 785–789. 24. Pappenfus, T. M.; Schmidt, J. A.; Koehn, R. E.; Alia, J. D. “PBC-DFT Applied to Donor−Acceptor Copolymers in Organic Solar Cells: Comparisons Between Theoretical Methods and Experimental Data,” Macromolecules 2011, 44, 2354–2357. 25. Goswami, S.; Hernandez, J. L.; Gish, M. K.; Wang, J.; Kim, B.; Laudari, A. P.; Guha, S.; Papanikolas, J. M.; Reynolds, J. R.; Schanze, K. S. “Cyclometalated Platinum-Containing Diketopyrrolopyrrole Complexes and Polymers: Photophysics and Photovoltaic Applications,” Chem. Mater. 2017, 29, 8449–8461.


ProDOT-Assisted Isomerically Pure Indophenines | The Journal of

Recommend Documents