Elsevier Editorial System(tm) for Chinese

Chemical Letters

Manuscript Draft

Manuscript Number: CCLET-D-19-00134R1

Title: A Ketone-Functionalized Aromatic Saddle as a Potential Building

Block for Negatively Curved Carbon Nanobelts

Article Type: SI: To Prof. Henry Wong

Keywords: polycyclic arene; synthesis; negatively curved carbon

allotropes; carbon nanobelts; Scholl reaction

Corresponding Author: Professor Qian Miao, ph.D

Corresponding Author's Institution: The Chinese University of Hong Kong

First Author: Kwan Yin Cheung, PhD

Order of Authors: Kwan Yin Cheung, PhD; Qian Miao, ph.D

Abstract: A novel ketone-functionalized aromatic saddle consisting of 72

sp2 carbon atoms is successfully synthesized and unambiguously identified

with X-ray crystallography. It can, in principle, be used as a building

block for synthesis of negatively curved carbon nanobelts and for a

bottom-up approach to negatively curved carbon allotropes.

Suggested Reviewers:

Opposed Reviewers:

Response to Reviewers: We thank the reviewer for recognizing the value of

this work and providing valuable comments for improvement. Please see the

revision and response after each comment below.

Comment 1: (CD3)2CO was used as solvent in the 13C NMR spectrum of

compound 5, but the text in the SI of the 13C NMR was mistakenly marked

as CDCl3.

Revision: Corrected accordingly.

Comment 2: All new compounds in this manuscript lacks IR

characterization.

Response: According to the guidelines of the American Chemical Society,

"all new compounds, evidence adequate to establish both identity and

degree of purity (homogeneity) should be provided". These evidences

typically include melting point, 1H NMR, 13C NMR and HRMS. We have

already provided these data, and provided single crystal structures for

compound 3 and 5. In fact, the structural information of large polycyclic

aromatics that can be provided from IR is quite limited. Therefore we

think IR is not necessary.

1

Prof. Qian Miao

The Chinese University of Hong Kong,

Department of Chemistry

Shatin, New Territories

Hong Kong SAR, China

Tel: 852-26098127

Fax: 852-26035057

email: miaoqian@cuhk.edu.hk

01/28/2019

Prof. Xuechen Li

Associate Editor, Chinese Chemical Letters

Dear Prof. Li,

Thank you again for inviting me to contribute to the Special Issue of Chinese Chemical

Letters dedicated to Prof. Henry N. C. Wong. In the attachment please find a manuscript entitled

"A Ketone-Functionalized Aromatic Saddle as a Potential Building Block for Negatively Curved

Carbon Nanobelts" for your consideration of publication on Chinese Chemical Letters as a

communication.

Negatively curved carbon allotropes are theoretical nanocarbon materials, which are

predicted to have interesting properties and potential applications on the basis of computational

studies, but are yet to be synthesized. A promising bottom-up approach to negatively curved

nanocarbon materials is synthesis of negatively curved nanographenes, which are saddle-shaped

polycyclic arenes containing seven or eight-membered rings. As inspired by this idea, a few

negatively curved nanographenes have been designed and synthesized by us and other research

groups since 2012. A further step toward negatively curved carbon allotropes is synthesis of

negatively curved carbon nanobelts or nanotubes. Herein, we report synthesis and crystal

structure of a novel ketone-functionalized aromatic saddle, which consists of 72 sp2 carbon

atoms. It is a potential building block for synthesis of negatively curved carbon nanobelts.

Therefore, this work, in my opinion, would be suitable for the readership of Chinese Chemical

Letters.

Sincerely yours,

Qian Miao

Cover Letter

1

Prof. Qian Miao

The Chinese University of Hong

Kong,

Department of Chemistry

Shatin, New Territories

Hong Kong SAR, China

Tel: 852-26098127

email: miaoqian@cuhk.edu.hk

03/21/2019

Editorial Office

Chinese Chemical Letters

Dear Editor:

Thank you for your e-mail on Mar. 18 regarding our manuscript CCLET-D-19-00134,

which is entitled " A Ketone-Functionalized Aromatic Saddle as a Potential Building Block

for Negatively Curved Carbon Nanobelts". The Supporting Information has been revised

following the reviewer's comment. In the attachment please find the revised files for your

further consideration to be published in Chinese Chemical Letters.

We thank the reviewer for recognizing the value of this work and providing valuable

comments for improvement. Please see the revision and response after each comment below.

Comment 1: (CD3)2CO was used as solvent in the 13

C NMR spectrum of compound 5, but the

text in the SI of the 13

C NMR was mistakenly marked as CDCl3.

Revision: Corrected accordingly.

Comment 2: All new compounds in this manuscript lacks IR characterization.

Response: According to the guidelines of the American Chemical Society, "all new

compounds, evidence adequate to establish both identity and degree of purity

(homogeneity) should be provided". These evidences typically include melting

point, 1H NMR,

13C NMR and HRMS. We have already provided these data, and

provided single crystal structures for compound 3 and 5. In fact, the structural

information of large polycyclic aromatics that can be provided from IR is quite

limited. Therefore we think IR is not necessary.

Thanks for further considering the revised manuscript for publication on Chinese

Chemical Letters.

Sincerely yours,

Qian Miao

*Detailed Response to Reviewers

Graphical Abstract

A ketone-functionalized aromatic saddle as a potential building block for negatively curved carbon

nanobelts

Kwan Yin Cheung, Qian Miao

Department of Chemistry, The Chinese University of Hong Kong, Hong Kong, China

Herein, we report the synthesis and crystal structure of a novel ketone-functionalized aromatic saddle,

which is a potential building block for synthesis of negatively curved carbon nanobelts.

Corresponding author.

E-mail address: miaoqian@cuhk.edu.hk

*Graphical Abstract (for review)

Graphical Abstract

A ketone-functionalized aromatic saddle as a potential building block for negatively curved carbon nanobelts

Kwan Yin Cheung, Qian Miao

Department of Chemistry, The Chinese University of Hong Kong, Hong Kong, China

Herein, we report the synthesis and crystal structure of a novel ketone-functionalized aromatic saddle, which is a potential

building block for synthesis of negatively curved carbon nanobelts.

———

Corresponding author.

E-mail address: miaoqian@cuhk.edu.hk

*Manuscript

Communication

A ketone-functionalized aromatic saddle as a potential building block for negatively

curved carbon nanobelts

Kwan Yin Cheung, Qian Miao

Department of Chemistry, The Chinese University of Hong Kong, Hong Kong, China

———

Corresponding author.

E-mail address: miaoqian@cuhk.edu.hk

Negatively curved carbon allotropes are theoretical structures

of sp2 carbon atoms, which present saddle-shaped surfaces as a

result of embedding seven- or eight-membered rings in a

graphitic network. Negatively curved periodical structures of

carbons are known as Mackay crystals or carbon schwarzites

because Mackay together with Terrones in 1991 first proposed

negatively curved carbon allotropes [1], whose topological

model was described by Schwarz, a German mathematician [2].

Although they are predicted to have interesting properties and

potential applications on the basis of computational studies [3-5],

negatively curved carbon allotropes are yet to be synthesized. A

promising bottom-up approach to negatively curved nanocarbon

materials is synthesis of negatively curved nanographenes, which

are saddle-shaped polycyclic arenes containing seven- or eight-

membered rings [6]. They are not only segments of negatively

curved carbon allotropes containing important structural

information, but also are envisioned as templates or monomer

units for synthesis of negatively curved carbon allotropes in a

controlled growth process or by polymerization, respectively

[7,8]. As inspired by this idea, a few negatively curved

nanographenes have been designed and synthesized by us [9,10]

and other research groups [11] since 2012. A further step toward

negatively curved carbon allotropes is synthesis of negatively

curved carbon nanobelts or nanotubes, which present key

segments of Mackay crystals. We envision that a negatively

curved carbon nanobelt can in principle be synthesized by

connecting properly functionalized aromatic saddles, whose

curved structure can facilitate formation of a macrocycle. For

example, as shown in Fig. 1a, nanobelt 1 can in principle be

synthesized by connecting two molecules of ketone-

functionalized aromatic saddle (2) through a McMurry reaction

and subsequent oxidative cyclodehydrogenation or photo-

chemical cyclization. Herein, we report synthesis and crystal

structure of 3 (Fig. 1b), which is an alkoxylated derivative of 2.

Fig. 1. (a) Retrosynthesis of negatively curved carbon nanobelt 1; (b)

structure of ketone-functionalized aromatic saddle 3.

ART ICLE INFO AB ST R ACT

Article history:

Received 28 January 2019

Received in revised form 21 March 2019

Accepted 1 April 2019

Available online

A novel ketone-functionalized aromatic saddle consisting of 72 sp2 carbon atoms is successfully

synthesized and unambiguously identified with X-ray crystallography. It can, in principle, be

used as a building block for synthesis of negatively curved carbon nanobelts and for a bottom-up

approach to negatively curved carbon allotropes.

Keywords:

Polycyclic arenes

Synthesis

Negatively curved carbon allotropes

Carbon nanobelts

Scholl reaction

Scheme 1. (a) Synthesis of 3 and (b) preparation of 5.

As shown in Scheme 1a, the synthesis of 3 started from the

Suzuki coupling of compound 4 and borinic acid 5, which gave

compound 6 in a good yield (80%). Compound 4 was reported

by us earlier [10], while borinic acid 5 is a new compound,

which was synthesized for the first time in this study. As shown

in Scheme 1b, halogen-lithium exchange of 8 [12] with n-

butyllithium followed by quenching with 1.3 equiv. of

triisopropyl borate yielded borinic acid 5 as the major product in

a yield of 84%. The structure of 5 was unambiguously identified

by X-ray crystallography (CCDC 1893914 contain the

supplementary crystallographic data of 5) as shown in Fig. 2a. It

is worth mentioning that the Suzuki coupling of diarylborinic

acid is rare in the literature [13], and using such a reaction to

form an extra ring [14] is even rarer. The two methylene bridges

in 6 were converted to carbonyl groups in 7 by successive

oxidation using potassium permanganate and pyridinium

chlorochromate. When potassium permanganate was used alone,

the corresponding diol was identified by 1H NMR but could not

be separated by column chromatography from the reaction

mixture in a pure form. Finally, the Scholl reaction of 7 with

DDQ and triflic acid gave compound 3 in excellent yield (92%).

However, our attempts to connect two molecules of 3 into a

macrocycle through McMurry coupling reaction or Barton-

Kellogg reaction were not successful.

Compound 3 is soluble in common organic solvents resulting

in red solutions and appears almost nonfluorescent. As shown in

Fig. S1 in Supporting information, the UV-vis absorption of 3

(5×10−6

mol/L in CH2Cl2) exhibits a broad and relatively weak

absorption band in the visible light region with λmax of 495 nm.

The cyclic voltammogram of 3 in CH2Cl2 (Fig. S2 in Supporting

information) exhibits one reversible oxidation wave with a half-

wave oxidation potential of 0.42 V vs. ferrocenium/ferrocene

(Fc+/Fc) and one reversible reduction wave with a half-wave

reduction potential of −1.68 V vs. Fc+/Fc. From the half-wave

oxidation and reduction potentials, the HOMO and LUMO

energy level of 3 are estimated as −5.52 eV and −3.42 eV,

respectively [15], which lead to a HOMO-LUMO gap of 2.1 eV.

It is in good agreement with the optical gap of 2.07 eV as

obtained from the absorption edge at around 600 nm.

Fig. 2. Structures of 5 and 3 in single crystals: (a) top view of 5; (b)

side view of 3; (c) front view of 3; (d) top view of 3. (Carbon,

oxygen and boron atoms are shown with ellipsoids set at 50%

probability, and octyl groups in 3 are removed for clarity.)

Crystals of 3 were characterized with X-ray crystallography

(CCDC 1893913 contain the supplementary crystallographic data

of 3). As shown in Figs. 2b and c, the polycyclic backbone of 3 is

curved like a saddle, which is 12.4 Å wide and 6.7 Å deep in the

upper part, and is 10.1 Å wide and 3.7 Å deep in the lower part.

As a result, 3 presents a deeper saddle shape than closely related

aromatic saddles reported by us earlier [10], and resembles half

of a negatively curved carbon nanobelt. Having a bond length of

1.46-1.48 Å, the C−C bonds shown in blue are significantly

longer than a typical C-C aromatic bond (1.38-1.40 Å) but

resemble C−C single bonds between sp2-sp

2 carbons, which have

a typical bond length of 1.45-1.48 Å depending on the degree of

conjugation [16]. This indicates that the π-bonds are not fully

delocalized in the polycyclic backbone. Instead, the π-bonds are

largely localized on the aromatic sextets following Clar’s rule.

[17].

In summary, a novel ketone-functionalized aromatic saddle

(3) was successfully synthesized and unambiguously identified

with X-ray crystallography. It can, in principle, be used as a

building block for synthesis of negatively curved carbon

nanobelts, although our preliminary attempts to connect two

molecules of 3 into a macrocycle through reactions of carbonyl

groups were not successful.

Acknowledgment

We thank Ms. Hoi Shan Chan (the Chinese University of

Hong Kong) for the single crystal crystallography. This work

was supported by the Research Grants Council of Hong Kong

(No. GRF 14300218). This work is dedicated to Prof. Henry N.

C. Wong.

References

[1] A.L. Mackay, H. Terrones, Nature 352 (1991) 762–762.

[2] R. Vajtai, Springer Handbook of Nanomaterials, Springer

Berlin Heidelberg, Berlin, Heidelberg, 2013, pp. 83-104.

[3] S. Park, K. Kittimanapun, J.S. Ahn, Y.K. Kwon, D. Tománek,

J. Phys. Condens. Matter. 22 (2010) 334220.

[4] N. Park, M. Yoon, S. Berber, et al., Phys. Rev. Lett. 91 (2003)

237204.

[5] D. Odkhuu, D.H. Jung, H. Lee, et al., Carbon 66 (2014) 39–47.

[6] S.H. Pun, Q. Miao, Acc. Chem. Res. 51 (2018) 1630–1642.

[7] Y. Segawa, H. Ito, K. Itami, Nat. Rev. Mater. 1 (2016) 15002.

[8] A. Narita, X.Y. Wang, X. Feng, K. Müllen, Chem. Soc. Rev.

44 (2015) 6616–6643.

[9] (a) J. Luo, X. Xu, R. Mao, Q. Miao, J. Am. Chem. Soc. 134

(2012) 13796–13803;

(b) X. Yang, Q. Miao, Synlett 27 (2016) 2091–2094;

(c) X. Gu, H. Li, B. Shan, Z. Liu, Q. Miao, Org. Lett. 19 (2017)

2246–2249;

(d) K.Y. Cheung, C.K. Chan, Z. Liu, Q. Miao, Angew. Chem.

Int. Ed. 56 (2017) 9003–9007;

(e) S.H. Pun, C.K. Chan, J. Luo, Z. Liu, Q. Miao, Angew.

Chem. Int. Ed. 57 (2018) 1581–1586.

[10] K.Y. Cheung, X. Xu, Q. Miao, J. Am. Chem. Soc. 137 (2015)

3910–3914.

[11] (a) K. Kawasumi, Q. Zhang, Y. Segawa, L.T. Scott, K. Itami,

Nat. Chem. 5 (2013) 739–744;

(b) C.N. Feng, M.Y. Kuo, Y.T. Wu, Angew. Chem. Int. Ed. 52

(2013) 7791–7794;

(c) Y. Sakamoto, T. Suzuki, J. Am. Chem. Soc. 135 (2013)

14074–14077;

(d) R.W. Miller, A.K. Duncan, S.T. Schneebeli, D.L. Gray,

A.C. Whalley, Chem. -Eur. J. 20 (2014) 3705–3711;

(e) R.W. Miller, S.E. Averill, S.J. Van Wyck, A.C. Whalley, J.

Org. Chem. 81 (2016) 12001–12005;

(f) I.R. Márquez, N. Fuentes, C.M. Cruz, et al., Chem. Sci. 8

(2017) 1068–1074.

[12] T.K. Wood, W.E. Piers, B.A. Keay, M. Parvez, Chem. -Eur. J.

16 (2010) 12199–12206.

[13] (a) D.D. Winkle, K.M. Schaab, Org. Process Res. Dev. 5 (2001)

450–451;

(b) X. Chen, H. Ke, Y. Chen, C. Guan, G. Zou, J. Org. Chem.

77 (2012) 7572–7578;

(c) H. Ke, X. Chen, G. Zou, J. Org. Chem. 79 (2014) 7132–

7140.

[14] E. Dimitrijević, M. Cusimano, M.S. Taylor, Org. Biomol.

Chem.. 12 (2014) 1391.

[15] C.M. Cardona, W. Li, A.E. Kaifer, D. Stockdale, G.C. Bazan,

Adv. Mater. 23 (2011) 2367–2371.

[16] E.V. Anslyn, D.A. Dougherty, Modern Physical Organic

Chemistry, University Science, Sausalito, CA, 2004, p. 22.

[17] E. Clar, The Aromatic Sextet, J. Wiley, London, New York,

1972.

1

Supplementary information

A ketone-functionalized aromatic saddle as a potential building block for negatively curved

carbon nanobelts

Kwan Yin Cheung, Qian Miao*

Department of Chemistry, the Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China

1. Synthesis

General: The reagents and starting materials employed were commercially available and used without any further

purification unless otherwise noted or made following reported methods as indicated. Anhydrous and O2-free

dichloromethane and THF were purified by an Advanced Technology Pure-Solv PS-MD-4 system. NMR spectra were

recorded on a Bruker AVANCE III 400MHz spectrometer (1H NMR: 400 MHz,

13C NMR: 100 MHz). Chemical shift values

(δ) are expressed in parts per million using residual solvent (1H NMR, δH = 7.26 for CDCl3;

13C NMR, δC = 77.16 for

CDCl3; 29.84 for (CD3)2CO) as internal standard. Mass spectra were recorded on Bruker SolariX 9.4T FTICR MS or Bruker

Autoflex speed MALDI-TOF. X-ray crystallography data were collected on a Bruker AXS Kappa ApexII Duo

Diffractometer. UV-vis absorption spectra were recorded on a Varian CARY 1E UV-vis spectrophotometer. Fluorescence

spectra were taken on a Hitachi F-4500 spectrofluorometer. Melting points, without correction, were measured using a

Nikon Polarized Light Microscope ECLIPSE 50i POL equipped with an INTEC HCS302 heating stage. Cyclic voltammetry

was performed on a PAR Potentiostat / Galvanostat Model 263A Electrochemical Station (Princeton Applied Research).

Dibenzo[b,e]borinin-5(10H)-ol (5)

To a solution of bis-(2-bromophenyl)-methane (8)1 (10.8 g, 33 mmol) in anhydrous Et2O (140 ml) cooled with a liquid

N2/ acetone bath under an atmosphere of N2 was added n-BuLi (45.5 ml, 1.6 M hexane solution, 73 mmol) over 5 minutes

by syringe. The reaction mixture was stirred for 30 minutes and the cooling bath was removed. After the reaction mixture

was stirred at room temperature for 1 hour, it was cooled again with a liquid N2/ acetone bath. Triisopropyl borate (10 ml, 43

mmol) was added to the reaction mixture by syringe over 3 minutes. The reaction mixture was allowed to slowly warm to

room temperature overnight and was quenched with saturated NH4Cl (aq). The aqueous layer was extracted with Et2O, the

combined organic layer was washed with brine, dried with anhydrous Na2SO4, and filtered through a pad of silica gel. The

silica gel pad was further washed with Et2O. The filtrate was concentrated under reduced pressure and precipitated by

adding hexane. Filtration gave Dibenzo[b,e]borinin-5(10H)-ol (5) (5.43 g, 84%) as white solid. mp: decompose at around

100-110°C. 1H NMR (CDCl3) δ (ppm): 7.96 (d,

3J = 7.2 Hz, 2H), 7.51 (dt,

3J = 7.2 Hz,

4J = 1.6 Hz, 2H), 7.46 (d,

3J = 7.6 Hz,

2H), 7.37 (dt, 3J = 7.6 Hz,

4J = 0.4 Hz, 2H), 5.86 (s, 1H), 4.39 (s, 2H).

13C NMR (acetone-d6) δ (ppm): 148.6, 132.5, 131.8,

129.0, 126.0, 37.5. 11

B NMR (CDCl3) δ (ppm): 40.2. HRMS (EI+): calcd. for C13H10BO ([M]

+): 193.0822, found: 193.0822.

Compound 6

To a mixture of 4 (1.41 g, 1.0 mmol), 5 (975 mg, 5.0 mmol), K2CO3 (1.67 g, 12 mmol) and Pd(PPh3)4 (232 mg, 0.2 mmol)

in a Schlenk flask under an atmosphere of N2 was added 40 ml of toluene and 10 ml of dioxane/water 3/2 (V/V) solution,

both of which were bubbled with nitrogen for 30 minutes beforehand. The Schlenk flask was then sealed and the reaction

1. T.K. Wood, W.E. Piers, B.A. Keay, M. Parvez, Chem. Eur. J. 16 (2010) 12199–12206.

Support Information

2

mixture was heated to 100oC for 42 hours, cooled to room temperature, and then treated with water. The resulting mixture

was extracted with CH2Cl2, and the organic layer was washed with brine, dried with anhydrous Na2SO4 and the solvent was

evaporated under reduced pressure. The crude mixture was purified by column chromatography on silica gel with

hexane/CH2Cl2 3/1 (V/V) as eluent. 6 (1.14 g, 80%) was obtained as yellow solid. mp: 298-301°C. 1H NMR (CDCl3) δ

(ppm): 9.11 (dd, 3J = 8 Hz,

4J = 1.2 Hz, 4H), 7.40 (t,

3J = 8 Hz, 4H), 7.13 (dd,

3J = 7.6 Hz,

4J = 1.2 Hz, 4H), 7.07 (d,

3J = 7.2

Hz, 4H), 7.06 (s, 4H), 6.77 (t, 3J = 7.6 Hz, 4H), 6.40 (t,

3J = 7.2 Hz, 4H), 6.08 (d,

3J = 7.2 Hz, 4H), 4.23-4.28 (m, 4H), 4.13

(d, 2J = 16.4 Hz, 2H), 4.02-4.07 (m, 4H), 3.69 (d,

2J = 16.8 Hz, 2H), 1.85-1.92 (m, 8H), 1.48-1.52 (m, 8H), 1.25-1.34 (m,

32H), 0.83 (t, 3J = 7.2 Hz, 12H).

13C NMR (CDCl3) δ (ppm): 156.2, 142.6, 139.0, 137.7, 136.7, 133.5, 130.9, 130.0, 129.1,

128.2, 127.4, 126.2, 125.9, 125.6, 125.3, 125.1, 124.9, 110.4, 100.4, 70.1, 37.3, 31.9, 29.6, 29.5, 29.3, 26.4, 22.8, 14.2 .

HRMS (MALDI-TOF): calcd. for C104H102O4 ([M]+): 1415.7806, found: 1415.7755.

Compound 7

To suspension of 6 (1.14 g, 0.81 mmol) in 400 ml acetone was added KMnO4 (6.36 g, 40 mmol) and the mixture was stirred

at room temperature for 1 day. The reaction mixture was then concentrated under reduced pressure and the solid residue was

washed with CH2Cl2 and filtered. The filtrate was concentrated under reduced pressure. 87 mg of pyridinium

chlorochromate and 80 ml CH2Cl2 was added to the residue and stirred at room temperature for 4 hours. The reaction

mixture was concentrated under reduced pressure and purified by column chromatography on silica gel with hexane/CH2Cl2

1/3 to 1/4 (V/V) as eluent. 7 (682 mg, 59%) was obtained as yellow solid. mp: 348-351°C. 1H NMR (CDCl3) δ (ppm): 9.20

(dd, 3J = 8 Hz,

4J = 0.8 Hz, 4H), 7.95 (dd,

3J = 8 Hz,

4J = 1.2 Hz, 4H), 7.44 (t,

3J = 8 Hz, 4H), 7.06-7.09 (m, 10H), 6.70 (dt,

3J = 8 Hz,

4J = 1.2 Hz, 4H), 6.22 (d,

3J = 8 Hz, 4H), 4.29-4.35 (m, 4H), 4.03-4.09 (m, 4H), 1.88-1.95 (m, 8H), 1.50-1.54 (m,

8H), 1.26-1.36 (m, 32H), 0.83 (t, 3J = 7.2 Hz, 12H).

13C NMR (CDCl3) δ (ppm): 186.2, 156.5, 144.5, 141.9, 138.7, 133.0,

130.8, 139.2, 130.2, 129.7, 129.1, 128.0, 127.4, 127.1, 126.1, 125.7, 125.2, 124.8, 124.6, 110.0, 100.2, 70.0, 31.9, 29.6, 29.4,

29.3, 26.4, 22.8, 14.2. HRMS (MALDI-TOF): calcd. for C104H98O6 ([M]+): 1443.7392, found: 1443.7370.

Compound 3

To a stirred solution of 7 (147 mg, 0.10 mmol) and DDQ (115 mg, 0.51 mmol) in 28 ml of anhydrous CH2Cl2 under an

atmosphere of N2 was added 0.7 ml of trifluoromethanesulfonic acid. The mixture was stirred for 1 hour at room

temperature, and then quenched with an aqueous solution of NaHCO3. The resulting mixture was extracted with CH2Cl2, and

the organic layer was washed with brine, dried with anhydrous Na2SO4, and concentrated under reduced pressure. The crude

product was purified by column chromatography on silica gel with CH2Cl2/Et2O 1/0 to 20/1 (V/V) as eluent. 3 (135 mg,

92%) was obtained as red solid. mp: decompose during heating to around 340-350°C. 1H NMR (CDCl3) δ (ppm): 8.98 (d,

3J

= 9.2 Hz, 4H), 8.54 (d, 3J = 7.6 Hz, 4H), 8.50 (d,

3J = 8.4 Hz, 4H), 8.32 (d,

3J = 9.2 Hz, 4H), 7.65 (t,

3J = 7.6 Hz, 4H), 6.82

(s, 2H), 4.14 (broad s, 8H), 1.86 (t, 3J = 7.2 Hz, 8H), 1.47 (t,

3J = 6.8 Hz, 8H), 1.21-1.31 (m, 32H), 0.80 (t,

3J = 6.8 Hz, 12H).

13C NMR (CDCl3) δ (ppm): 185.1, 155.0, 135.0, 132.0, 129.9, 129.4, 129.2, 129.1, 129.0, 128.5, 128.3, 128.0, 127.6, 127.3,

127.2, 125.7, 122.0, 120.3, 108.0, 98.8, 69.5, 31.8, 29.4, 29.3, 29.2, 26.2, 22.7, 14.2. HRMS (MALDI-TOF): calcd. for

C104H90O6 ([M]+): 1435.6766, found: 1435.6778.

2. X-ray crystallography

X-ray crystallography data were collected on a Bruker AXS Kappa ApexII Duo Diffractometer.

3

Table S1

Summary of Crystal Structures of 5 and 3.

5 3

Space Group P3121 P-1

Unit Cell Lengths (Å) a = 13.0362(6)

b = 13.0362(6)

c = 5.0703(3)

a = 15.3414(10)

b = 17.0870(12)

c = 17.3983(12)

Unit Cell Angles (°) α = 90

β = 90

γ = 120

α = 115.120(2)

β = 100.102(2)

γ = 98.707(2)

Cell Volume (Å3) 746.219 3932.75

R factor 0.0421 0.0978

3. Absorption spectrum

UV-vis spectra were recorded with a Varian CARY 5G UV-vis spectrophotometer.

Fig. S1. Absorption spectrum of 3 in CH2Cl2 (5 × 10−6 mol/L).

4. Cyclic Voltammetry

The cyclic voltammetry was performed in a solution of CH2Cl2 with 0.1M Bu4NPF6 as the supporting electrolyte. A

platinum bead was used as a working electrode, a platinum wire was used as an auxiliary electrode, and a silver wire was

used as a pseudo-reference. Ferrocene/ferrocenium was used as the internal standard. Potentials were referenced to

ferrocenium/ferrocene (FeCp2+/FeCp2

0).

Fig. S2. Cyclic voltammogram of 3

4

5. NMR Spectra

1H NMR spectrum of 5 in CDCl3

13C NMR spectrum of 5 in acetone-d6

5

11B NMR spectrum of 5 in CDCl3

1H NMR spectrum of 6

6

13C NMR spectrum of 6

1H NMR spectrum of 7

7

13C NMR spectrum of 7

1H NMR spectrum of 3

8

13C NMR spectrum of 3

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Crystallographic Data (.cif) - aromatic-saddle-3.cif

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Crystallographic Data (.cif) - borinic-acid-5.cif

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