10-Mesityl-1,8-diphenylanthracene Dimer. Synthesis, Structure, and

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10-Mesityl-1,8-diphenylanthracene Dimer. Synthesis, Structure, and Properties Atsumi Shirai, Hiroto Sano, Yuki Nakamura, Masataka Takashika, Hiroyuki Otani, Masashi Hasegawa, Shin-ichiro Kato, and Masahiko Iyoda J. Org. Chem., Just Accepted Manuscript • DOI: 10.1021/acs.joc.8b00200 • Publication Date (Web): 02 Mar 2018 Downloaded from http://pubs.acs.org on March 2, 2018

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The Journal of Organic Chemistry

10-Mesityl-1,8-diphenylanthracene Dimer. Synthesis, Structure, and Properties Atsumi Shirai,1 Hiroto Sano,1 Yuki Nakamura,1 Masataka Takashika,1 Hiroyuki Otani,*1 Masashi Hasegawa,2 Shin-ichiro Kato,3 and Masahiko Iyoda*4 1

Graduate School of Environment and Information Sciences, Yokohama National University, Hodogaya-ku, Yokohama, Kanagawa 240-8501, Japan 2School of Science, Kitasato University, Sagamihara, Kanagawa 252-0373, Japan 3Department of Materials Science, School of Engineering, The University of Shiga Prefecture, 2500 Hassaka-cho, Hikone, Shiga 522-8533, Japan 4 Department of Chemistry, Graduate School of Science and Engineering, Tokyo Metropolitan University, Hachioji, Tokyo 192-0397, Japan e-mail: [email protected], [email protected] Abstract: Macrocyclic 10-mesityl-1,8-diphenylanthracene dimer 4 was synthesized by using the electron-transfer oxidation of Lipshutz cuprate derived from 1,8-bis(4-bromophenyl)-10-mesitylanthracene 7 in moderate yield. This dimer 4 is a considerably fluorescent molecule (F 0.40) with high thermal-, photo-, and air-stability. The X-ray analysis of 4 revealed a unique structure with a small inner cavity which can incorporate a small molecule or atom. 1H NMR spectra in solution and emission spectra of 4 in the solid state showed that copper(I) ion was incorporated to form a 1:1 complex 4ꞏCuOTf, whereas silver(I) ion only weakly interacted with 4 under similar conditions.

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Introduction A variety of photonic materials have been recently reported along with important scientific discoveries of new nanostructures.1 One of the most important requirements for photonic materials is stability against light and atmospheric oxygen, although many functional -systems are light- and air-sensitive by nature. Cyclophanes and cyclic oligophenylenes have attracted considerable attention because of their thermal-, light- and air-stability, shape-persistent structures, intramolecular and intermolecular - interactions, molecular strain, and aromaticity, and as substrates for host-guest chemistry.2-7 Dibenzo[2,2]paracyclophane 1 was synthesized by Wong et al. in 1985,5a and its strained 1,4-phenylene units behaved as a -donor. Cyclic oligophenylene 2 having a [3,3]biphenylophane frame also showed bent 4,4’-biphenylylene chains with a fairly strong intramolecular - interaction and strong fluorescence in solution and the solid state.8 Since 2 possesses a strained, rigid -frame with a high thermal stability, we planned to synthesize the less strained analogue 3 and 4 with 4,4’-biphenylylene chains and splayed anthracene rings (Figure 1).

1

2

R

R

CH3 3: R = H

4: R =

CH3 CH3

Figure 1. Dibenzo[2,2]paracyclophane 1, cyclic oligophenylene 2 with [3,3]biphenylophane frame, and cyclic oligophenylenes 3 and 4 with [5,5]biphenylophane frame. Our preliminary experiments have shown that 3 was highly insoluble, and we only characterized 3 as its silver complex, although the silver complex also scarcely soluble and could be determined by MS and UV-vis spectra.9 Therefore, we introduced bulky mesityl group at 10-position of the anthracene unit, because mesityl group can be expected to increase the solubility of the cyclic oligophenylene frame by hindering the aggregation of the anthracene units in solution.10 For the synthesis of 2, we employed the Cu(NO3)2-mediated coupling of 1,8-bis(4-tributylstannylphenyl)naphthalene.8 For the synthesis of 4, however, we adopted electron-transfer oxidation of Lipshutz cuprates derived from 1,8-bis(4lithiophenyl)anthracene, because the electron-transfer oxidation of Lipshutz cuprates proceeds smoothly


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to produce the coupling products with less amounts of side products as compared to the Cu(NO3)2mediated coupling.11-13 Here we report that the electron-transfer oxidation of the above-mentioned Lipshutz cuprate in THF produced 4 in good yield, and the crystal structures of 4 revealed unique structures with a small inner cavity which incorporated a copper(I) ion. Results and Discussion Synthesis. The synthesis of 10-mesityl-1,8-diphenylanthracene dimer 4 was carried out as outlined in Scheme 1. Nickel-catalyzed cross-coupling of 1,8-dichloro-10-mesitylanthracene 510 with excess amounts of p-trimethylsilylphenylmagnesium bromide produced 6 in 72% yield. The treatment of 6 with 2.5 equiv of NBS in CH2Cl2-acetone afforded dibromide 7 in 79% yield. For the synthesis of 4, we first tried nickel-catalyzed homo-coupling of 7 using NiBr2(PPh3)2, Et4NI, and Zn in THF.14 However, this reaction mainly afforded oligomeric products without 4. After trying various copper-mediated coupling reactions of 7,11 electron-transfer oxidation of Lipshutz cuprate derived from 7 was found to produce 4 in moderate yield (Table 1). Although the reaction of Lipshutz cuprate derived from 7 with duroqinone in ether produced 4 in 5% yield together with 10-mesityl-1,8-diphenylantracene 8 (39%) (Entry 1), a similar reaction in THF proceeded smoothly to afford 4 in 50% yield (Entry 4). It is noteworthy that only a small amount of linear oligomer was formed as the by-product except for polymer. Therefore, 4

Table 1. Synthesis of macrocycle 4 using electron-transfer oxidation of Lipshutz cuprate derived from 7 in ether or THFa Entry

t-BuLi

CuCN

Duroquinone

Solv.

Yield

(equiv)

(equiv)

(equiv)

1

4

1.1

3

ether

5b

2

4

1

3

THF

29

3

4

1.2

3

THF

4

4

5.2

1.1

3

THF

50

(%)

a

The dibromide 7 was reacted with t-BuLi at ‒78 ºC, followed by treatment with CuCN at 0‒5 ºC to produce Lipshutz cuprate, which was oxidized with duroquinone at 5‒25 ºC. b 10-Mesityl-1,8-diphenylantracene 8 was formed as the major product (39%).



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was easily isolated from the reaction mixture. Slightly excess amount of CuCN (1.2 equiv) decreased the yield of 4 because of incomplete formation of Lipshutz cuprate (Entry 3). In order to compare optical properties of 4 with those of non-cyclic compound, 9 was prepared by the nickel-catalyzed cross-coupling

of

7

with

phenylmagnesium

bromide

to

produce 1,8-bis(4-biphenylyl)-10-

mesitylanthracene 9 in 64% yield (Scheme 1). 4 has a high thermal-, photo-, and air-stablility: 4 is stable at 300 ºC for 1 h in air without decomposition. Furthermore, photo-irradiation of 4 with a high-pressure mercury lamp in benzene at room temperature produced no dimer and/or oxidation products.

Scheme 1. Synthesis of 10-mesityl-1,8-diphenylanthracene dimer 4 and 1,8-bis(4-biphenylyl)-10mesitylanthracene 9.

Crystal Structure. Single crystals of 4ꞏ(THF)2 suitable for the measurement of X-ray analysis were obtained by recrystallization from benzene/CH2Cl2/THF, and the structure was unambiguously confirmed (R1 = 5.3%). As shown in Figure 2a, 4 has a crystallographic C2-symmetry with a 2-fold axis at the center of the macroring. The theoretically optimized structure of 4 at B3LYP/6-31G(d,p) level showed a twisted form (Figure 2c), and X-ray structure of 4 (R1 = 9.7%) obtained by recrystallization from CHCl3 exhibited a similar twisted structure (Figure S8-2). The incorporated two THF molecules locate up and down the molecular plane and may force 4 to hold a flat shape in the crystal. The


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deviation from the plane between the two anthracene rings is only 1.8°. The dihedral angles between the anthracene and biphenyl rings are relatively large, and the angles of 1 and 2 are 49° and 70°, respectively. Due to fairly long interatomic distances between the biphenylylene linkages, the intramolecular interaction between the biphenylylene units can be negligible. Interestingly, the interatomic distances between the biphenylylene linkages in the calculated and X-ray analysed 4 [calculated: C1‒C8 4.979 Å, C11‒C18’ 5.096 Å, and C14‒C15’ 5.352 Å; X-ray: C1‒C8 4.954 Å, C11‒C18’ 5.002 Å and C14‒C15’ 5.047 Å] are fairly shorter than those in the calculated carbon-carbon distances between the biphenylylene units in 3 [C1‒C8 4.999 Å, C11‒C18’ 5.139 Å, and C14‒C15’ 5.405 Å], probably because of the buttressing effect of mesityl group at the C10 position in 4 (C4‒C5 distance > C1‒C8 distance). This smaller inner cavity may allow 4 to incorporate a smaller molecule or ion as compared with 3. In the crystal packing shown in Figure 2b, THF molecules fill the interspace between the molecules to produce a columnar structure.

Figure 2 (a) ORTEP diagram of 4. Interatomic distances: C1‒C8 4.954 Å, C4‒C5 4.962 Å, C11‒C18’ 5.002 Å, C14‒C15’ 5.047 Å, and C9‒C9’ 10.217 Å. Dihedral angles: 1 49°, 2 70°, 3 20°, 4 90°. Thermal ellipsoids are 50% probability, and hydrogen atoms and THF molecules are omitted for clarity. (b) Crystal packing of 4ꞏ(THF)2. THF molecules are shown as space-filling model, whereas 4 are shown as wireframe model. (c) Calculated structure of 4 at B3LYP/6-31G(d,p) level.



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To compare the cyclic structure of 4 with the acyclic one, X-ray analysis of 10-mesityl-1,8diphenylanthracene 8 and 10-mesityl-1,8-bis(4-biphenylyl)anthracene 9 were carried out (Figure 3). Single crystals of 8ꞏacetone were obtained by recrystallization from acetone/hexane. As shown in Figure 3a, 8 has a crystallographic C2-symmetry with a 2-fold axis passing through C1, C8, C15, and C18. The crystal structure of 8 is roughly identical to that of 4, but the carbon-carbon distance between C12 and C12’ atoms is much shorter than the distance between C9 and C9’ atoms. Since the calculated interatomic distances between the phenyl groups are normal [C9‒C9’ (5.153 Å), and C12‒ C12’ (5.728 Å)] (Figure 3b), the short C9‒C9’ and C12‒C12’ distances may be due to the effect of crystal packing in 8. Concerning 9, single crystals were obtained from CHCl3-hexane. Two biphenylyl arms connecting to anthracene were disordered owing to their ring flipping even at low temperatures (Figure S8-4). As shown in Figure 3c, the biphenylyl arms slightly spread over, and their interatomic distances were found to be C1–C8 (4.991 Å), C11–C19 (5.151 Å), C14–C22 (5.569 Å), and C18–C26 (5.955 Å) (Figure 3c). As compared with the structure of 4 shown in Figure 2a, the C11– C19, C14–C22, and C18–C26 distances in 9 are much longer than the C11–C18’ and C14–C15’ distances in 4, while the C1–C8 distance in 9 is almost similar to the C1–C8 distance in 4.

Figure 3 (a) ORTEP diagram of 8. Interatomic distances: C3‒C3’ 4.953 Å, C9‒C9’ 4.948 Å, C12‒C12’ 4.822 Å. Thermal ellipsoids are 50% probability. Hydrogen atoms are omitted for clarity. (b) Calculated structure of 8 at B3LYP/6-31G(d,p) level. (c) ORTEP diagram of 9. Interatomic distances: C1‒C8 4.991 Å, C11–C19, 5.151 Å, C14–C22, 5.569 Å, C18–C26 5.955 Å. Thermal ellipsoids are 50% probability. Hydrogen atoms are omitted for clarity. (d) Calculated structure of 9 at B3LYP/6-31G(d,p) level.


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Optical properties and oxidation potentials. As shown in Figure 4a, dilute (1×10-6 M) and concentrated (1×10-3 M) solutions of 4 in CH2Cl2 exhibited almost superimposable spectra (1×10-6 M, abs 370sh, 388, and 409 nm), reflecting no self-assembly in solution. In a dilute solution (1×10-6 M) in CH2Cl2, 9 showed similar absorption maxima (1×10-6 M, abs 370, 388, and 409 nm), indicating similar effective conjugation length. On the other hand, the absorption maxima of 8 (1×10-6 M, abs 364, 384, and 405 nm) showed a small blue shift, reflecting its slightly smaller -conjugation. In the emission spectra (Figure 4b) in CH2Cl2, 4 and 9 exhibited similar emission in a 1×10-6 M solution (4: em 431 with a shoulder at 455 nm, F = 0.40; 9: em 431 with a shoulder at 452 nm, F = 0.33), whereas the emission maxima of 8 showed a small blue shift (em 424, 446 nm, F = 0.30). In the solid state, a film of 4 on a quartz plate has a similar absorption spectrum (abs 371, 388, and 409 nm, Figure S3‒2) to those in solution, whereas the emission spectrum of the film of 4 (em 448 nm with shoulders at em 487

Figure 4 Absorption and emission spectra of 4, 8, and 9 in CH2Cl2. (a) Absorption spectra of 4 (1×10-3 M solution, red line; 1×10-6 M solution, red dotted line), 8 (1×10-3 M solution, black line), and 9 (1×10-3 M solution, blue line). (b) Emission spectra of 4 (1×10-6 M solution, red line; film, grey line), 8 (1×10-6 M solution, black line), and 9 (1×10-6 M solution, blue line).



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and 535 nm, F = 0.04) exhibited a large Stokes shift (2070 cm-1), reflecting electronic interactions in the excited state (Figure S3-3). To determine the interaction between the two anthracene units, oxidation potential of 4 was measured by cyclic voltammetry (CV). As shown in Table 2, 4 shows a reversible one two-electron oxidation, and the oxidation potential of 4 is the same as that of 9. In the case of 8, the oxidation potential is slightly higher than those of 4 and 9, reflecting the lower HOMO level of 8. The calculated HOMO levels are in agreement with the CV data. Table 2. Oxidation potentialsa of macrocycle 4, 10-mesityl-1,8-diphenylantracene 8, and 1,8-bis(4biphenylyl)-10-mesitylanthracene 9 Compound

Eox1/2 (V)

HOMO (eV)b

HOMO (eV)c

4

0.711

‒5.51

‒5.02

8

0.731

‒5.53

‒5.10

0.711

‒5.51

9 a

-1

‒5.05 + b

Scan rate 0.1 V s in 1,2-dichlorobenzene; V vs Fc/Fc . HOMO energy value

of 4, 8, and 9 was deduced from the measured Eox1/2. cHOMO level of 4, 8, and 9 was estimated at the B3LYP/6-31G(d,p) level.

Complexation of 4 with copper(I) and silver(I) ions. Calculated interatomic distances (5.14‒5.40 Å) of 3 between biphenylylene units are enough to incorporate a silver ion in the cavity (Figure S9‒1). In contrast, the interatomic distances (5.00‒5.05 Å) of 4 between biphenylylene units in Figure 2a seem to be too short to incorporate a silver ion in the cavity. Interestingly, however, this shorter inner cavity of 4 is suitable for incorporating a Cu(I) ion. A number of arene-Ag(I) complexes were synthesized and their structures were determined by X-ray analysis.15 However, only a limited number of arene-Cu(I) complexes were isolated,16 and their properties were not yet fully characterized. Although 4, 8, and 9 produced no single crystals of their Cu(I) and Ag(I) complexes, we measured 1H NMR spectra of 4, 8, and 9 in the presence of Cu(I) and Ag(I) ions. 1H NMR spectra of 8 and 9 in the presence of Cu(I) and Ag(I) ions showed no spectral change. However, 1H NMR spectrum of a mixture of 4 and CuOTf in benzene-d6 at 25 °C exhibited small low field shifts of Ha, Hb, Hc,d, and mesityl methyl protons. As shown in Figure 5 and Figure S6, 1H NMR spectrum of 4 in the presence of 2 equiv of CuOTf showed low field shifts of Ha, Hb, and Hc,d and 2-mesityl H by 0.002, 0.001, 0.001, and 0.001 ppm, respectively. Furthermore, 1H NMR spectrum of 4 in the presence of 5 equiv of CuOTf exhibited lower field shifts of Ha, Hb, and 2-mesityl protons by 0.011, 0.006, and 0.003 ppm, respectively. Although the low field shifts of Ha, Hb, and Hc,d and 2-mesityl protons are small, other protons of 4 remain unchanged in the presence of CuOTf. Therefore, 4 forms its Cu(I) complex in benzene at room temperature. 8 ACS Paragon Plus Environment

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Figure 5 1H NMR spectra of 4 and 4‒CuOTf in benzene-d6 at 25 °C. (a) 4 (1.3 mM). (b) 4 (1.3 mM) and CuOTf (2.6 mM). (c) 4 (1.3 mM) and CuOTf (6.5 mM).

In order to determine the structures of copper and silver complexes of 4, 8, and 9, we attempted the preparation of single crystals. However, 4, 8, and 9 only formed crystalline powder with CuOTf and AgOTf. Therefore, we measured absorption and emission spectra of films of 1:1 mixtures of 4, 8, or 9 and CuOTf or AgOTf. The absorption and emission spectra of cast films of 4, a 1:1 mixture of 4 and CuOTf, and a 1:1 mixture of 4 and AgOTf reflect a binding behavior of 4 with Cu+ and Ag+ ion (Figure 6). The absorption maxima of a 1:1 mixture of 4 and CuOTf in the solid state slightly changed (abs 370, 389, and 412 nm), whereas the absorption maxima of a 1:1 mixture of 4 and AgOTf in the solid state remained almost unchanged (abs 371, 389, and 413 nm). On the other hand, the emission spectrum of a 1:1 mixture of 4 and CuOTf in the solid state revealed almost different peaks at longer wavelength region (em 475 and 500sh nm; F = 0.016), and the quantum yield showed 96% decrease. The emission spectrum of a 1:1 mixture of 4 and AgOTf in the solid state exhibited a small change, i.e., a peak at 458 nm with a shoulder at longer wavelength region (F = 0.024). MALDI-TOF-MS spectra of 4 and CuOTf or 4 and AgOTf clearly showed molecular ion peaks of [4ꞏCu]+ and [4ꞏAg]+ (Figures S5‒2 and S5‒3). Since Cu(I) ion coordinates two or three p-orbitals of aromatic systems, we assume that Cu(I) ion coordinates p-orbitals of two phenyl and one anthracene units. In the case of Ag(I) ion, the change in the absorption and emission spectra is small, but the film of a 1:1 mixture of 4 and AgOTf resulted in 94% decrease of the quantum yield. Therefore, Ag(I) ion may only locates near p-orbitals of phenyl and anthracene rings. In the case of 9, the absorption and emission spectra of 1:1 mixtures of 9 and CuOTf



or AgOTf in the solid state were exactly same as the spectra of 9 in the solid state, and hence, 9 formed

Intensity /a.u.

no complex with CuOTf and AgOTf in the solid state (Figures S7-5~S7-8).

Intensity / a.u.

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

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Figure 6 Absorption and emission spectra of films of 4 and equimolar amount’s mixtures of 4 and copper(I) or silver(I) triflate. The film of copper(I) complex was prepared by casting a solution of a mixture of 4 and CuOTf (1:1) in benzene, and the film of silver(I) complex was prepared by casting a solution of a mixture of 4 and AgOTf (1:1) in benzene. Based on the 1H NMR data (Figure 5) and absorption and emission spectra (Figure 6), we propose the formation of the complex 4ꞏCuOTf in both solution and the solid state, although the binding constant of 4ꞏCuOTf seems to be very small in solution. Furthermore, fairly low solubility of 4 and CuOTf in organic solvents makes it difficult to determine the binding constant of 4ꞏCuOTf. It is noteworthy that the 1H NMR spectra and absorption and emission spectra of a mixture of 4 and CuOTf exhibited obvious spectral change, and the spectra of a mixture of 8 or 9 with CuOTf remained unaltered. In the case of AgOTF complexes, a film of a mixture of 4 and CuOTf only exhibited a small change depending on the interaction of 4 with AgOTf. As shown in Figure 2a, 4 possesses a narrow cavity, and Cu(I) ion may be incorporated in the hollow created by the C11, C1, C4, C9, C5, C8, and C18’ carbons and 2-mesityl methyl group. The electron-rich anthracene, parallel-arranged biphenylylene


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carbons, and sticking mesityl methyl group on the anthracene moiety can operate favorably to capture Cu(I) ion.

Conclusions In the present study, we revealed that the electron-transfer oxidation of Lipshutz cuprate derived from 1,8-bis(4-bromophenyl)-10-mesitylanthracene 7 proceeded smoothly to produce macrocyclic 10mesityl-1,8-diphenylanthracene dimer 4 in satisfactory yield. The macrocyclic dimer 4 is very stable to light, atmospheric oxygen and prolonged heating. In the solid state, a film of 4 has a similar absorption spectrum to that in solution, whereas the emission spectrum of the film of 4 exhibited a large Stokes shift, reflecting electronic interactions of the nonplanar macrocycle 4 in the excited state. X-ray analysis of 4 exhibited a rigid, shape-persistent structure, and CuOTf can be incorporated in the hollow constructed by the electron-rich anthracene, parallel-arranged biphenylylene carbons, and mesityl methyl group in 4. The 1:1 complex of 4 with CuOTf exhibited a low field shift of the signals of the anthracene and biphenyl protons in 1H NMR spectra, and a redshift of emission spectrum in the film state. On the other hand, AgOTf very weakly interacted with 4 under similar conditions.

Experimental Section 1

General. NMR spectra were recorded on Bruker DRX-500 (500 MHz H NMR and 125 MHz

13

C

NMR) spectrometers using tetramethylsilane as the intimal standard. UV-vis spectra were recorded on Perkin Elmer Lambda 750. Fluorescence emissions were recorded on Perkin Elmer FL55 or JASCO FP8500. Absolute photoluminescence quantum yields were determined by a calibrated integrating sphere system on JASCO FP-8500. High-resolution mass spectra were measured on a Hitachi High Technologies Nano Frontier LD spectrometer by the ESI method (calibration standard: Hitachi High Technologies Standard Sample) or MALDI/TOF mass spectra were recorded on Bruker Daltonics Autoflex speed MALDI TOF/TOF mass spectrometer (matrix: dithranol). X-ray crystal structure analysis was measured with Bruker APEX-II CCD, Rigaku MicroMax-007HF, VariMax-Mo and Rapid II, or Rigaku Pilatus 200K. DFT calculations were performed at the B3LYP/6-31G(d, p) level. Elemental analyses were performed Elementar Vario EL Ⅲ. Thin layer chromatography (TLC) was performed with Merck 60 F254 silica gel plates. Column chromatography was performed with Kanto Kagaku Silica gel 60N (spherical neutral). Melting Points were determined with MEL-TEMP 1001D120VAC. The solvents used for synthesis were dried and purified by usual techniques prior to use.



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10-Mesityl-1,8-bis(4-trimethylsilylphenyl)anthracene (6). To a solution of 10-mesityl-1,8dichloroanthracene (5) (4.36 g, 12 mmol), nickel(Ⅱ) acetylacetonate (727 mg, 2.5 mmol), and triphenylphosphine (1.31 g, 5.0 mmol) in 29 mL of THF was dropwise added a solution of Grignard reagent prepared from 1-bromo-4-trimetylsilylbenzene (11.1 g, 48 mmol) and Mg (1.22 g, 50 mmol) in diethyl ether (22 mL) during 1 h under argon atmosphere. The resulting brown mixture was refluxed for 22 h. The reaction mixture was quenched with aqueous 3 M HCl. The organic layer was separated and the aqueous layer was extracted with dichloromethane. The combined organic layer was dried over MgSO4, and the solvent was evaporated in vacuo to give a crude product. The product was column chromatographed on silica gel using hexane / carbon disulfide (v/v 10/1) as eluent to afford 10-mesityl1,8-bis(4-trimethylsilylphenyl)anthracene (6) (5.10 g, 72% yield) as pale yellow solid, mp 274‒275 °C, 1

H NMR (500 MHz, CDCl3):  (ppm) 8.90 (s, 1H), 7.62‒7.58 (m, 8H), 7.50 (d, J= 7.6 Hz, 2H), 7.39‒

7.37 (m, 4H), 7.14 (s, 2H), 2.49 (s, 3H), 1.80 (s, 6H), 0.34 (s, 18H);

13

C NMR (125 MHz, CDCl3): 

(ppm) 141.3, 140.7, 139.0, 137.6, 137.1, 136.2, 135.2, 133.1, 129.9, 129.7, 129.5, 128.3, 126.6, 125.6, 125.4, 123.4, 21.3, 20.1, 0.9; MS (EI): m/z 592 (M+); HRMS (ESI-TOF) m/z: M+ Calcd for C41H44Si2: 592.2976; Found: 592.2990. 1,8-Bis(4-bromophenyl)-10-mesitylanthracene (7). To a stirred solution of 10-mesityl-1,8-bis(4trimethylsilylphenyl)anthracene (6) (1.76 g, 3.0 mmol) in acetone (10 mL) and dichloromethane (50 mL) was added N-bromosuccinimide (1.35 mg, 7.5 mmol) in one portion at room temperature, and the resulting mixture was stirred for 43 h. After removing the solvent in vacuo, the residue was column chromatographed on silica gel eluting hexane/benzene (v/v 10/1) to afford 10-mesityl-1,8-bis(4bromophenyl)anthracene (7) (1.41 g, 79% yield) as yellow solid, mp 233‒234 °C, 1H NMR (500 MHz, CDCl3):  (ppm) 8.43 (s, 1H), 7.58 (d, J = 8.2 Hz, 4H), 7.51 (dd, J = 6.0, 3.8 Hz, 2H), 7.40‒7.36 (m, 8H), 7.13 (s, 2H), 2.48 (s, 3H), 1.77 (s, 6H); 13C NMR (125 MHz, CDCl3): δ (ppm) 139.7, 139.7, 137.8, 137.5, 136.6, 134.9, 131.9, 131.5, 130.1, 130.0, 128.6, 126.2, 126.1, 125.7, 123.3, 121.8, 21.5, 20.3; MS (EI): m/z 604 (M+); Anal. Calcd for C35H26Br2: C, 69.32; H, 4.32. Found: C, 69.23; H, 4.32. Typical procedure for the synthesis of 10-Mesityl-1,8-diphenylanthracene dimer (4) using ET oxidation of Lipshuts cuprate. To a solution of 10-mesityl-1,8-bis(4-bromophenyl)anthracene (7) (606 mg, 1.0 mmol) in THF (56 mL) was added t-BuLi (3.1 mL, 5.2 mmol, 1.7 M in n-pentane) at ‒78 °C under argon atmosphere. The mixture was stirred at the same temperature for 3.5 h, and CuCN (101 mg, 1.1 mmol) was added. The reaction mixture was allowed to warm up to 0 °C with vigorous stirring. when all the CuCN was completely dissolved, 2,3,5,6-tetramethyl-1,4-benzoquinone (498 mg, 3.0 mmol) was added in one portion at 0 °C, and the mixture was stirred at room temperature for 5 h to complete the reaction. The reaction mixture was quenched with water. The organic layer was separated


Page 13 of 16 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


and the aqueous layer was extracted with chloroform. The combined organic layer was dried over MgSO4, and the solvent was evaporated in vacuo to give a crude product. The product was column chromatographed on silica gel using hexane/benzene (v/v 10/1) as eluent to afford 4 (221 mg, 50% yield) as pale yellow solid (mp >370 °C (dec)); 1H NMR (500 MHz, CDCl3):  (ppm) 8.60 (s, 2H), 7.78 (d, J = 8.2 Hz, 8H), 7.62 (d, J = 8.2 Hz, 8H), 7.54 (d, J = 8.8 Hz, 4H), 7.50 (d, J = 6.5 Hz, 4H), 7.43 (dd, J = 8.8, 6.5 Hz, 4H), 7.16 (s, 4H), 2.51 (s, 6H), 1.84 (s, 12H); 13C NMR (125 MHz, CDCl3):  (ppm) 140.7, 139.7, 139.2, 137.7, 137.2, 135.9, 134.9, 130.6, 130.3, 129.9, 128.3, 126.3, 125.6, 125.4, 125.3, 124.2, 21.3, 20.2; MS (MALDI-TOF): m/z 892.402 (M+); HRMS (MALDI-TOF) m/z: M+ Calcd for C70H52 892.4069; Found: 892.4053. When the ET oxidation of Lipshutz cuprate derived from 7 was carried out in diethyl ether, 10mesityl-1,8-diphenylanthracene (8) was obtained in 39% yield together with 4 (5%). 8, pale yellow solid (mp 162‒163 °C); 1H NMR (500 MHz, CDCl3): δ (ppm) 8.66 (s, 1H), 7.55 (d, J = 7.6 Hz, 4H), 7.52 (dd, J = 7.4, 2.4, 2H), 7.44‒7.35 (m, 10H), 7.13 (s, 2H), 2.49 (s, 3H), 1.80 (s, 6H); 13C NMR (125 MHz, CDCl3): δ (ppm) 140.9, 140.7, 137.6, 137.1, 136.0, 135.1, 130.1, 129.9, 129.8, 128.3, 128.0, 127.1, 126.0, 125.5, 125.3, 123.8, 21.3, 20.1; MS (EI): m/z 448 (M+); HRMS (ESI-TOF) m/z: [M+H]+ Calcd for C35H29: 449.2264; Found: 449.2276. 1,8-Bis(4-biphenylyl)-10-mesitylanthracene (9). To a mixture of 7 (182 mg, 0.3 mmol) and [1,3bis(diphenylphosphino)propane]nickel(II) chloride (8.5 mg, 0.015 mmol) in diethyl ether (7.5 mL) was added dropwise a solution of PhMgBr (1.5 mL, 1.5 mmol) during 5 min under nitrogen atmosphere. The resulting reddishbrown mixture was refluxed for 19 h. The reaction mixture was quenched with aqueous 3 M HCl. The organic layer was separated and the aqueous layer was extracted with dichloromethane. The combined organic layer was dried over MgSO4, and the solvent was evaporated in vacuo to give a crude product. The product was column chromatographed on silica gel using hexane/benzene (v/v 10/1) as the eluent. The product was recrystallized from dichloromethane/hexane (v/v 1/1) to provide 10mesityl-1,8-bis(4-biphenylyl)anthracene (9) (115 mg, 64% yield) as pale yellow solid, mp 226.5‒228 °C, 1

H NMR (500 MHz, CDCl3):  (ppm) 8.78 (s, 1H), 7.65 (d, J= 8.2 Hz, 4H), 7.63 (d, J= 8.2 Hz, 4H),

7.54-7.51 (m, 6H), 7.48 (dd, J= 6.6, 1.5 Hz, 2H), 7.42 (dd, J= 8.6, 6.6 Hz, 2H), 7.38-7.33 (m, 6H), 7.15 (s, 2H), 2.50 (s, 3H), 1.82 (s, 6H); 13C NMR (125 MHz, CDCl3):  (ppm) 140.9, 140.8, 140.1, 139.6, 137.7, 137.2, 136.0, 135.0, 130.6, 130.0, 129.9, 128.8, 128.3, 127.2, 127.1, 126.9, 125.7, 125.6, 125.4, 123.9, 21.3, 20.2; MS (MALDI-TOF): m/z 600.936 (M+); HRMS (MALDI-TOF) m/z: M+ Calcd for C47H36: 600.2817; Found: 600.2816.



Page 14 of 16

Computational methods. DFT calculations were carried out with the Gaussian 09 program.17 All geometry optimizations were carried out at the B3LYP/6-31G(d,p) basis set unless otherwise noted. X-ray crystallographic data for 4ꞏ(THF)2. Molecular formula: C70H52‧2C4H8O, monoclinic, space group C2 (No. 5), a = 16.5890(10) Å, b = 9.0335(4) Å, c = 20.6981(10) Å,  = 94.977(7)°, V = 3090.0(3) Å3, T = 200 K, Z = 2, R1 (wR2) = 0.0530 (0.1491) for 501 parameters and 6267 unique reflections. GOF = 1.024. CCDC 1537880. X-ray crystallographic data for 4. Molecular formula: C70H52, triclinic, space group P-1 (No. 2), a = 10.338(4) Å, b = 11.016(6) Å, c = 22.351(9) Å,  = 88.20(4)°,  = 77.272(17)°,  = 86.40(3)°, V = 2477.6(19) Å3, T = 123 K, Z = 2, R1 (wR2) = 0.0970 (0.1640) for 608 parameters and 8720 unique reflections. GOF = 1.014. CCDC 1539203. ORTEP diagram: Figure S8-2. X-ray crystallographic data for 8ꞏacetone. Molecular formula: C35H28‧C3H6O, monoclinic, space group C2/c (No. 15), a = 10.0828 (4) Å, b = 31.5519 (11) Å, c = 9.4547 (5) Å,  = 110.0379 (13)°, V = 2825.8(2) Å3, T = 200 K, Z = 4, R1 (wR2) = 0.0756 (0.2341) for 199 parameters and 3245 unique reflections. GOF = 1.099. CCDC 1537881. X-ray crystallographic data for 9. The mesityl groups form some void space within the crystal lattice. These voids are occupied by disordered CHCl3 molecules. The SQUEEZE function equipped in the PLATON program was employed to remove their contribution in voids. Two biphenyl moieties are treated as a disorder. The occupation factors were determined to be 0.46 and 0.54, respectively. All the non-hydrogen atoms were refined with anisotropic displacement parameters. Molecular formula: C47H36, triclinic, P–1 (No. 2), a = 8.427(2) Å, b = 11.446(3) Å, c = 19.827(5) Å, = 105.602(4) °,  = 98.716(4) °, = 94.253(4) °, V= 1807.4(8) Å3, Z = 2, R1 (wR2) = 0.0785 (0.2076) for 552 parameters and 2606 (I > 2) unique reflections. GOF = 0.862. Acknowledgements. This work was supported by a Grant-in-Aid for Scientific Research from the Ministry of Education, Culture, Sports, Science and Technology, Japan and partly performed under the Cooperative Research Program of “Network Joint Research Center for Materials and Devices” (M.I.). We would like to thank Dr. Tomohiko Nishiuchi (Osaka University) for the X-ray crystallographic data analysis and helpful discussions.

Supporting Information Available. 1H and 13C NMR spectra of all new compounds; X-ray data of 4, 8, and 9; absorption and emission data of 4, 8, and 9. This material is available free of charge via the Internet at http://pubs.acs.org. 14 ACS Paragon Plus Environment

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10-Mesityl-1,8-diphenylanthracene Dimer. Synthesis, Structure, and

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