Hexaaryl-: Carbo -benzenes revisited: A novel synthetic route, crystallographic data, and prospects of electrochemical behavior

Article abstract of DOI:10.1039/c7nj00028f

An improved 12-step synthetic route and full characterization of hexaphenyl-carbo-benzene (4, 8%) and the p-bis-3,5-di-tert-butylphenyl homologue (11, 4%), are described. The carbo-benzene reference 4 is now accurately described in the crystal state by X-

Full text of DOI:10.1039/c7nj00028f

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Chem., 2017, DOI: 10.1039/C7NJ00028F.
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ISSN 1144-0546
PAPER
Jason B. Benedict et al.
The role of atropisomers on the photo-reactivity and fatigue of
diarylethene-based metal–organic frameworks
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New Journal of Chemistry
ARTICLE
Hexaaryl-carbo-benzenes revisited: novel synthetic route,
crystallographic data, and prospects of electrochemical behavior
Received 00th January 20xx,
Accepted 00th January 20xx
Chongwei Zhu,a,b Carine Duhayon,a,b Daniel Romero-Borja, c José-Luis Maldonado,c Gabriel Ramos-
Ortíz,c Alix Saquet, a,b Valerie Maravala,b* and Remi Chauvina,b
*
DOI: 10.1039/x0xx00000x
An improved 12-step synthetic route and full characterization of hexaphenyl-carbo-benzene (4, 8 %) and the p-bis-3,5-di-
tert-butylphenyl homologue (11, 4 %), are described. The carbo-benzene reference 4 is now accurately described in the
crystal state by X-ray diffraction analysis in the chiral space group P212121, and in comparison to the less symmetric
derivative 11 giving a centro-symmetric packing. According to cyclic voltammetry, both hexaaryl-carbo-benzenes 4 and 11
can behave as both reversible potent electron acceptors and standard electron donors, with respective potentials of –0.73
± 1 V and +1.17 ± 2 V/SCE, respectively. Due to an extremely low solubility, solid films of 11 fabricated by the "wet
method", with the initial view to studying charge transport properties, were found to display high roughness.
www.rsc.org/
obtained through [14+4] macro-cyclization processes, in nine
steps with 11 % overall yield, and eight steps with 12 % overall
yield, respectively.8
1 Introduction
By January 1995, the title term "carbo-benzene" was proposed
for
, as a putative example of Hückel-aromatic carbo-mer,1
A much shorter alternative route would be based on a [8+10]
macro-cyclization process and a key [6]pericyclynedione 10 9
which more recently proved efficient for the synthesis of
centro-symmetric tetraphenyl-carbo-benzene
targets.10
Application of this method to the preparation of the carbo-
benzene paradigm is hereafter described, along with the
synthesis of the a priori more liphophilic p-bis-(di-3,5-tert-
butylphenyl) derivative 11
1
,
namely a structure devised by D6h symmetry-preserving C2-
expansion of the benzene molecule (Figure 1).2 In spite of an
attempt at synthesis via a hexaoxy-[6]pericyclynediol 2 (itself
targeted by a [9+9] macro-cyclization route from the triynal
4
3
),3 the "bare" carbo-benzene
1 could not be obtained and
remains hitherto experimentally unknown.4 Exactly at the
.
same time, Ueda, Kuwatani et al. communicated the synthesis
of 3,6,9,12,15,18-hexaphenyldodecadehydro[18]annulene
4
OH
H
and a few congeners,5 standing as the first examples of carbo-
H
H
OH
H
H
OH
H
OH
OH
benzene derivatives, in tri- or hexa-substituted versions
[9+9]
H
H
H
+
H
H
O
O
(Scheme 1). The highly chromophoric compound
4
and its
HO
H
H
H
[6]pericyclynetriol precursor
5
were described in more details
H
OH
by the same authors in 1998.6 The employed route was based
H
H
OH
H
H
OH
1
2
OH
H
on a [11+7] macro-cyclization step, where a bis-terminal
3
H
Ph
tetrayne
as a dielectrophile. The original synthetic route thus consisted
in 15 steps, with a 1 % overall yield, and a 59 % yield for the
reductive aromatization step.5,6 In 2007, the same
hexaphenyl-carbo-benzene was reported to be also
accessible by reductive aromatization of a [6]pericyclynediol
and [6]pericyclynetetraol in 12 and 22 yield,
respectively.7 The precursors
and were themselves
6 reacts as a dinucleophile with a skipped bis-ynal 7
Ph Ph
Ph
Ph
THPO
Ph
OMe
HO
Ph
OMe
SnCl2
HCl
[11+7]
OH
6
H
5
Ph
Ph
MeO
Et2O
59 %
O
MeO
Ph
Ph
OMe
+
→
4
H
H
4
O
OH Ph
5
Ph
Ph
4
OMe
SnCl2
HCl
8
H
Ph
7
Et2O
Et2O
22 %
SnCl2
HCl
a
9,
%
12 %
Ph Ph
Ph Ph
8
9
HO
OH
OMe
HO
Ph
MeO
Ph
OH
Ph
OMe
Ph
MeO
Ph
Ph
OMe
OH
OMe Ph
OH Ph
9
8
Scheme 1. Strategies envisaged for the preparation of the unsubstituted carbo-benzene
1 (top); known syntheses of hexaphenyl-carbo-benzene 4 (bottom).
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In the 1998 pioneer report,6 X -ray diffraction (XRD) analysis of butyl groups on two phenyl substituents of
4
thus appears to
a single crystal of 4 allowed confirmation of the quasi-D6h have a limited effect on the solubility of such rigid carbon-rich
symmetric structure and provided information on bond compounds. Indeed, the solubility of 11 was determined to be
distances and bond angles. Nevertheless, the quality of the ca 0.46 ± 0.03 mg/mL, namely less than twice the solubility of
crystallographic structure was likely not sufficient for
4 of ca 0.29 ± 0.03 mg/mL, in spite of the presence of four tert-
deposition at the CCDC, where no corresponding cif file is butyl groups on two of the aromatic substituents of 11. For
currently available. The challenge of gaining accurate comparison, direct anchoring of aliphatic chains at two
crystallographic data to make a cif file of
CCDC is particularly addressed below.
4
available at the vertices the C18 macrocycle was recently reported to be much
more efficient with the view to increasing solubility of carbo-
benzenes.13
2 Results and discussion
Ph Ph
The carbo-benzene targets
4 and 11 were thus envisaged by
Ph Ph
Ph Ph
MeO
OMe
H
MeO
OMe
MeO
OMe
reductive aromatization of the [6]pericyclynediols 12 and 13.
The latter were targeted from the known [6]pericyclynedione
10, obtainable by oxidation of the corresponding secondary
[6]pericyclynediol 14 (Scheme 2).9 An optimal procedure for
the synthesis of 14 is based on a [8+10] macro-cyclization step
involving the C8 triyne 15 and the C10 dialdehyde 16. As
compared to the previously used [11+7] and [14+4] strategies
(see Introduction), an advantage of the [8+10] strategy is its
late divergence character: the sensitive dialdehyde 16 is
indeed readily obtained from the triyne 15 just before the
macro-cyclization step, which gives the [6]pericyclynediol 14 in
ca 40 % yield (see SI for a detailed comparison of the original
15
MnO2
2 EtMgBr
H
O
HO
OH
O
O
+
O
0 °C
THF
40 %
DCM
72 %
H
H
Ph
OMe
Ph
OMe
OMe Ph
OMe Ph
Ph
OMe
14
OMe Ph
10
16
Ph Ph
Ph
Ph
1) SnCl2
HCl.Et2O
DCM
MeO
HO
Ar
OMe
Ar
ArMgBr
10
Ar
Ar
THF
0 °C
OH
2) NaOH 1 M
Ph
OMe
OMe Ph
, Ar = Ph, 82 %
13, -3,5-tBu2-C6H3, 64 %
Ph
Ph
12
4, Ar = Ph, 65 %
t
11
, Ar = -3,5- Bu2-C6H3, 65 %
and
[6]pericyclynedione 10 is then obtained by oxidation of 14 with
MnO2. From 10, the targets and 11 were prepared in two
improved
synthesis
strategies).9
The
key
Scheme 2. Synthesis of carbo-benzene targets through a [8+10] macro-cyclization
route.
4
steps following a procedure previously experienced for the
synthesis of other carbo-benzenes.10 Addition of two
equivalents of either PhLi or PhMgBr to the diketone 10 was
thus attempted. Treatment of 10 with PhLi was found to
induce an opening of the C18 ring, allowing access to the
diadduct 12 in trace amount only. In contrast, the use of
PhMgBr allowed isolation of 12 with a remarkably high 82%
yield (Scheme 2). The Grignard reagent was thus also used for
anchoring two 3,5-di-tert-butylphenyl groups to 10, providing
the [6]pericyclynediol 13 with 64 % yield.
In spite of this, accurate spectroscopic data were obtained for
and 11 (1H NMR, 13C NMR, UV-vis), thus confirming the data
4
1
In particular, H NMR
ranges of Ueda, Kuwatani et al. for 4 5,6
.
spectra of
4 and 11 reveal the characteristic deshielding of the
ortho-1H nuclei of the aryl substituents resulting from the
magnetic anisotropy induced by the strong diatropic C18 ring
current (Figure 1).1,5-7,10
Using a classical procedure,10 reductive aromatization of 12
and 13 in dichloromethane (DCM) solution with 10 equivalents
of SnCl2 and 20 equivalents of HCl•Et2O, followed by
neutralization with 1 M aqueous NaOH, gave the targets
4 and
11 with the same 65 % yield. This procedure differs from the
original one by the nature of the solvent and the hydrolysis
conditions.6 The results confirm recent observations that the
use of DCM as solvent instead of diethyl ether, along with
milder hydrolytic conditions (1 M instead of 10 M NaOH),
provides higher yields in carbo-benzenes, essentially by
enhancement of the solubility of both the reagents and
products.10 In comparison with the original method,5,6 not only
Figure 1. Aromatic region of the 1H NMR spectra of
CDCl3 solutions (400 MHz, 12 h acquisition time).
4 and 11 in highly diluted
the yield in
4 of the last reductive elimination step has been
The UV-vis absorption spectrum of
4 in chloroform solution
improved from 59 to 65 %, but also the total number of steps
has been reduced from 15 to 12, while the global yield has
been increased from about 1 % to 8 % (see SI for comparative
synthesis schemes).
confirms the λmax value of 472 nm previously reported (Figure
2).6 The carbo-benzene 11 exhibits an identical spectral profile
with the same λmax value. The molar extinction coefficient of 4
was however measured to be lower than the value initially
reported (234 000 vs 363 000 L.mol-1.cm-1).6 The absorption
The hexa-aryl-carbo-benzenes
4 and 11 have been isolated as
poorly soluble dark red solids. The introduction of two tert-
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spectra of
4
and 11 are classical for carbo-benzenes, and their
max = 472 nm is a
common maximum absorption wavelength λ
median value of all the reported values, varying from 424 nm
for the octupolar triphenyl-carbo-benzene,5,6 to 521 nm for the
quadrupolar
benzene.10b
para-N,N-dimethylanilinyl-tetraphenyl-carbo-
Figure 3. Molecular views of the X-ray crystal structures of the carbo-
benzenes 4 (top) and 11 (bottom). Numbering of non-equivalent C atoms
are indicative of the crystal symmetry. For clarity, hydrogen atoms and
solvent molecules are omitted.
14
Table 1. Selected crystallographic data for 4 and 11.
4
11
Empirical
formula
Formula mass
Crystal system
Space group
T [K]
C54H30,CHCl3
C70H62,
2(CHCl3)
1142.02
Triclinic
P -1
Figure 2. Normalized absorption spectra of 4 and 11 in chloroform solution.
798.21
Orthorhombic
P212121
100
The structures of
4 and 11 were confirmed by XRD analysis of
single crystals deposited from chloroform solutions (Figure 3,
Table 1).14 Contrary to the pioneer crystallographic data,6 the
120
a [Å]
12.4948(5)
16.0972(6)
20.2765(9)
90
10.1720(5)
11.8006(8)
12.8576(7)
90.105(5)
101.559(5)
94.484(5)
1507.20(8)
1.258
quality of the present crystals of 4 proved sufficient for refined
resolution, having allowed deposition at the CCDC.14 The same
b [Å]
c [Å]
allotropic variety, involving one CHCl3 molecule per molecule
α [°]
β [°]
90
of
symmetric molecule
space group P212121. Crystallization of a highly symmetrical
achiral molecule such as in a chiral space group is not
4, was obtained. Noteworthy, the highly planar- and centro-
γ [°]
90
4
thus crystallizes in the Sohncke chiral
V [Å3]
4078.24(18)
1.300
Dc
4
Z
4
1
common, but examples have been previously reported for
other rigid compounds.15
µ [mm-1]
Refl. measured
Refl.
0.263
0.327
97066
23700
9935/0.048
6699/0.045
unique/Rint
Refl. with I >
3σ(I)
7863
4214
Nb parameters
560
379
0.045
0.0516
/
R
0.0351
0.0369
0.05(5)
Rw
Flack
parameter
Nb Friedel-
pairs
4448
/
ꢀρmax
/
ꢀρmin
0.66/-0.58
0.50/-0.33
[e.Å-3]
Geometrical features of the macrocycle of
4 are typical of
generic carbo-benzenes, with average sp2C-spC and spC-spC
bond lengths of 1.39 and 1.22 Å respectively. The average
angle at the sp2 vertices of the macrocycle is of 118.9°. The C18
ring is slightly distorted: the maximum deviation from planarity
mounts to 0.11 Å, while the globally hexagonal shape is not
regular, the diameters (between facing sp2 vertices) varying
from 7.79 Å to 8.17 Å. Torsion angles between the phenyl
mean planes and the macrocycle mean plane vary from 2.9° to
29.8°. In the crystal of 11, the molecules pack in a parallel
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Table 2. CV and SWV data for the carbo-benzenes 4 and 11 in chloroform solutions.
fashion, the distance between the mean planes of two
successive carbo-benzene macrocycles being of 3.62 Å, i.e.
Product
Reductions
Oxidations
much larger than in the recently reported first examples of
stacked carbo-benzenes.13a No
π
-stacking is indeed here
-
a
c
red d
a
c
ox d
E1/2
RIP
EP
E1/2
RIP
EP
(ꢀEP)b
- 0.72e
(0.44)
(ꢀEP)b
π
observed between two C18 rings, or between a C18 ring and a
4
0.58
1.01
1.14f
C6 ring of the aryl substituents. Instead of a chlorine atom of
- 1.15f
- 1.30
the chloroform molecule co-crystallized with 4, (see above),
one of the methyl groups of a tert-butyl substituent of 11
points towards the center of the C18 ring of the nearest
molecule: the closest H atom the methyl group reside 1.43 Å
away from the centroid and 1.38 Å from the mean plane of the
11
- 0.74e
(0.59)
1.19e
0.68
(0.53)
1.70
Half-wave potential E1/2 = (EP + EPox)/2, in V/SCE. Separation between the
a
red
b
two peak potentials: ꢀEP = ǀEPred - EPoxǀ, in V. c Peak current ratio RIP = ǀIPox/IPredǀ.
d
e
EP values measured from CV in V/SCE. Reversibility observed at high scan rate
only.f The compound underwent polymerization and deposited on the electrode.
While the first reduction processes were found to occur
reversibly at similar potentials (- 0.72 V for 4, – 0.74 V for 11),
the second reduction happens to be irreversible for both
compounds (Table 2). These values are consistent with
previous values reported for other para-diaryl-tetraphenyl-
carbo-benzenes, the first reduction occurring between –0.75
and –0.85 V depending on the nature of the aryl groups.10a,10b
This process is however made easier upon substitution of the
C18 ring by acetylenic substituents: the lowest reduction
potential (in absolute value) of – 0.60 V observed to date for a
carbo-benzene was indeed measured for
a
para-bis-
fluorenylethynyl-substituted representative.10f In oxidation
neighboring C18 ring (Figure 4).
regime, the first potentials of the two carbo-benzenes have
comparable values (1.14 V for
4 and 1.19 V for 11), but the
process is reversible for 11 only: the oxidation product of
4
indeed undergoes polymerization, leading to a deposit on the
electrode. A second non-reversible oxidation process was also
observed for 11
.
Carbo-benzenes generally undergo
irreversible oxidation, most of them giving a polymeric film on
the electrode after the first oxidation process, the latter
occurring at potentials between +0.51 and +0.90 V for donor-
substituted hexaaryl-carbo-benzenes,10a,10b and reaching +1.17
V for a fluorenylethynyl-substituted derivative exhibiting a
more extended -conjugation.10f
Figure 4. Views of the crystalline molecular packing of
4 (top) and 11 (bottom)
evidencing both the absence of π-stacking between the C18 rings, and interactions with
solvent molecules (for 4) and between two carbo-benzene molecules (for 11).
The electrochemical behavior of
studied (Table 2). Cyclic (CV) and square-wave (SWV)
voltammograms were recorded for and 11 in chloroform
4 and 11 has also been
4
solutions (see S.I.). More conventional DCM solutions could
indeed not be used because of an extremely low solubility in
this solvent. For a reference diethyl-carbo-benzene exhibiting
sufficient solubility in either solvents, this solvent change was
recently shown to make redox processes less reversible, but
keep almost unchanged the redox potential values, thus
allowing comparison between data obtained from either DCM
or chloroform solutions.13b
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data. The expected enhancement of solubility upon
substitution of by four tert-butyl groups was found limited,
4
preventing the use of thin films of 11 for charge transport in
organic photovoltaics. Nevertheless, the much higher solubility
of recently described p-dialkyl-tetraphenyl-carbo-benzenes13
allows consideration of their possible use for such applications.
Results of the envisaged studies will be communicated in due
course.
4 Experimental
4.1 General remarks
THF, diethyl ether (Et2O), pentane and dichloromethane (DCM)
were dried with a PureSolv-MD-5 Innovative Technology
system for the purification of solvents. All other reagents were
used as commercially available. In particular, solutions of PhLi
were 1.9 M in dibutyl ether, solutions of PhMgBr were 3 M in
diethyl ether, solutions of HCl were 2 M in diethyl ether. All
reactions were carried out under argon atmosphere using
Schlenk and vacuum line techniques. Column chromatography
was carried out on silica gel (60 Å, C.C 70-200 μm). Silica gel
thin layer chromatography plates (60F254, 0.25 mm) were
revealed under UV-light and/or by treatment with an ethanolic
solution of phosphomolybdic acid (20%). The following
analytical instruments were used, 1H and 13C NMR: Avance 400
and Avance 400 HD spectrometers; mass spectroscopy:
Quadrupolar Nermag R10-10H spectrometer; UV-Visible:
Perkin-Elmer UV-Vis Win-Lab Lambda 950; NMR chemical
shifts are given in ppm with positive values to high frequency
relative to the tetramethylsilane reference. Coupling constants
J are in Hertz. UV-Visible extinction molar coefficient ε is in
L.mol-1.cm-1 and wavelengths λ in nm.
Figure 5. Morphology of spin-casted films of 11 (blended with PC71BM: 1:1, w/w ratio)
on a glass substrate: microscopic optical image taken by a digital camera installed on
the AFM instrument used (top), and AFM image showing the film roughness (rms) ~ 355
nm (bottom). An additional AFM image is available in the S.I.
The low reduction potential of
4 and 11 (ca – 0.73 V) suggests
their possible use as electron acceptors, alternatives to C60
(and PCBM) for photovoltaics (the first reduction potential of
C60 is -0.55 V in chloroform).16 The accessible and possibly
reversible character of the first oxidation of 11 (at 1.19 V)
might also be compatible with a use as an organic electron
donor. However, the very low solubility of these hexa-aryl-
carbo-benzenes, even that of the slightly more soluble
derivative 11, did not allow preparing highly regular thin solid
films by the "wet method", thus preventing measurement of
their efficiency for charge transport.17 Indeed, while
microscopic optical images clearly show the non-uniformity of
the films, AFM images allowed the measurement of their high
roughness, mounting to ca 355 nm (Figure 5). This entails a
poor optical quality of the films, as evidenced by their UV-vis
absorption spectra exhibiting large light scattering competing
with absorption (see S.I.).
4.2 Experimental procedures and characterization
4.2.1
Hexaphenylcyclooctadeca-1,2,3,7,8,9,13,14,15-nonaen-
5,11,17-triyne (4). A solution of [6]pericyclynediol 12 (77 mg, 0.087
mmol) in DCM (50 mL) was treated with SnCl2 (165 mg, 0.87 mmol)
and HCl (0.87 ml, 1.74 mmol, 2 M in Et2O) at -78 °C. The mixture
was stirred at -78 °C for 10 min, then at room temperature for 25
min. After addition of aqueous 1 M NaOH (1.74 mL) and filtration
through celite®, the organic layer was washed with brine three
times, dried over MgSO4, and concentrated under reduced
pressure. The residue was purified by washings with Et2O (3x5 mL)
and pentane (3x5 mL) to give 4 as a dark violet solid with 65% yield
(38 mg, 0.057 mmol). 1H NMR (400 MHz, CDCl3) δ 9.48 (d, J = 7.3 Hz,
12H, o-C6H5), 8.01 (t, J = 7.7 Hz, 12H, m-C6H5), 7.74 (t, J = 7.4 Hz, 6H,
p-C6H5). 13C{1H} NMR (101 MHz, CDCl3) δ 140.25 (i-C6H5), 130.56 (o-
C6H5), 129.92 (m-C6H5 ), 129.44 (p-C6H5), 118.46 (=C=C=, -C≡C-),
104.53 (=CPh-). HRMS (MALDI-TOF/DCTB): m/z: [M+Na]+ calculated
for C54H30Na: 701.2245, found: 701.2225. UV-vis (CHCl3): λmax = 472
nm (ε = 234000 L·mol-1·cm-1). Melting-decomposition temperature:
221 °C.
3 Conclusions
Hexaphenyl-carbo-benzene
4 is a fully symmetrical paradigm
and model of the carbo-benzene family: 20 years after its first
description, its synthetic accessibility has been significantly
improved through the implementation of a [8+10] macro-
cyclization strategy, and its characterization has been
completed by accurate crystallographic and electrochemical
4.2.2
1,10-bis(3,5-di-tert-butylphenyl)-4,7,13,16-
tetraphenylcyclooctadeca-1,2,3,7,8,9,13,14,15-nonaen-5,11,17-
triyne (11). A solution of [6]pericyclynediol 13 (130 mg, 0.123
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mmol) in DCM (100 mL) was treated with SnCl2 (233 mg, 1.23 C6H5), 123.34, 123.25 (p-C6H3), 120.24 – 120.10 (o-C6H3), 87.24 –
mmol) and HCl (1.3 mL, 2.453 mmol, 2 M in Et2O) at -78 °C. The 86.94, 84.63 – 84.37, 82.65 – 82.54 (-C≡C-), 72.02 71.81
–
mixture was stirred at -78 °C for 20 min, then at room temperature (>C(OH)Ph), 65.77 – 65.70 (>C(OCH3)Ph), 53.37 – 53.19 (-OCH3),
for 15 min. After addition of 1 M aqueous NaOH (2.6 mL) and 34.96, 34.93 (-C(CH3)3), 31.20 – 31.10 (-C(CH3)3). HRMS (MALDI-
filtration through celite®, the organic layer was washed with brine TOF/DCTB): m/z: [M+Na]+ calculated for C74H76O6Na: 1083.5540,
three times, dried over MgSO4 and concentrated under reduced found: 1083.5476.
pressure. The residue was purified by washings with Et2O (3x5 mL)
4.3 Crystal structure determination
and pentane (3x5 mL) to give 11 as a dark red solid with 65% yield
(47 mg, 0.052 mmol). 1H NMR (400 MHz, CDCl3) δ 9.59 – 9.55 (m, Intensity data were collected at low temperature on an Apex2
8H, o-C6H5), 9.45 (d, J = 1.7 Hz, 4H, o-C6H3), 7.96 (dd, J = 8.1, 7.2 Hz, Bruker diffractometer equipped with
a 30W air-cooled
8H, m-C6H5), 7.83 (t, J = 1.7 Hz, 2H, p-C6H3), 7.72 (t, J = 7.3 Hz, 4H, p- microfocus source or on an Oxford-Diffraction Gemini (λMo
=
C6H5), 1.78 (s, 36H, -C(CH3)3). 13C{1H} NMR (101 MHz, CDCl3) δ 0.71073 Å). The structures were solved using SUPERFLIP, and
152.55 (m-C6H3), 140.39 (i-C6H5), 130.50 (o-C6H5), 129.85 (m-C6H5 ), refined by means of least-squares procedures on F using the
129.34 (p-C6H5), 127.05 (i-C6H3), 125.02 (o-C6H3), 124.22 (p-C6H3), programs of the PC version of CRYSTALS.11 Atomic scattering
118.17 (=C=C=, -C≡C-), 105.63 (=CPh-), 35.55 (-C(CH3)3), 31.88 (- factors were taken from the International Tables for X-Ray
C(CH3)3). HRMS (MALDI-TOF/DCTB): m/z: [M]+• calculated for C70H62 Crystallography.12 For
4, the asymmetric unit consists in a
902.4852, found: 902.4787. UV-vis (CHCl3): λmax = 472 nm (ε = whole carbo-benzene molecule. For 11, it contains half a
248000 L·mol-1·cm-1). Melting-decomposition temperature: 230 °C. molecule. Both asymmetric units contain a disordered CHCl3
solvent molecule. All non-hydrogen atoms were refined
4.2.3
4,7,13,16-tetramethoxy-1,4,7,10,13,16-
anisotropically. Hydrogen atoms were refined using a riding
model. Absorption corrections were introduced using the
program MULTISCAN.
hexaphenylcyclooctadeca-2,5,8,11,14,17-hexayne-1,10-diol (12). A
solution of [6]pericyclynedione 10 (86 mg, 0.126 mmol) in THF (20
mL) was treated with PhMgBr (0.1 mL, 0.291 mmol) at 0 oC. The
reaction mixture was stirred for 1 h at this temperature and 0.5 h at 4.4 Voltammetric measurements.
room temperature. After addition of a saturated aqueous solution
Voltammetric measurements were carried out with
a
potentiostat Autolab PGSTAT100 controled by GPES 4.09
software. Experiments were performed at room temperature
in a home-made airtight three-electrode cell connected to a
vacuum/agon line. The reference electrode consisted of a
saturated calomel electrode (SCE) separated from the solution
by a bridge compartment. The counter electrode was a
platinum wire of ca 1 cm2 apparent surface. The working
of NH4Cl, the aqueous layer was separated and extracted with Et2O.
The combined organic layers were dried over MgSO4 and
concentrated under reduced pressure. The residue was purified by
chromatography on silica gel (pentane : ethyl acetate 4 : 1) to give
12 as a yellow oil with 82 % yield (87 mg, 0.104 mmol). 1H NMR
(400 MHz, CDCl3) δ 7.89 – 7.62 (m, 12H, o-C6H5), 7.49 – 7.27 (m,
18H, m-, p-C6H5), 3.71 – 3.35 (m, 12H, -OCH3), 3.35 – 3.05 (m, 2H, -
OH). 13C{1H} NMR (101 MHz, CDCl3) δ 140.90 – 140.69 (i-C6H5-
C(OH)<), 139.49 – 139.24 (i-C6H5-C(OCH3)<), 129.13 – 128.92 (p-
C6H5), 128.73 – 128.49 (m-C6H5), 126.56 – 126.40 (o-C6H5-C(OCH3)<),
125.78 – 125.74 (o-C6H5-C(OH)<), 87.22 – 86.63, 84.65 – 84.37,
82.96 – 82.57 (-C≡C-), 72.02 – 71.91 (>C(OH)Ph), 65.10, 65.07
(>C(OCH3)Ph), 53.48, 53.45 (-OCH3). HRMS (MALDI-TOF/DCTB): m/z:
[M]+• calculated for C58H44O6 836.3138, found: 836.3015.
electrode was
a Pt microdisk (0.5 mm diameter). The
supporting electrolyte [n-Bu4N][PF6] was used as received
(Fluka, 99 % electrochemical grade) and simply degassed
under argon. The chloroform solutions used in the
electrochemical study was 10-3 M in carbo-benzene and 0.1 M
in supporting electrolyte. Before each measurement, the
solutions are degassed by bubbling argon, and the working
electrode was polished with a polishing machine (Presi P230).
Typical instrumental parameters for recording square-wave
voltammograms were: SW frequency f = 20 Hz, SW amplitude
4.2.4
1,10-bis(3,5-di-tert-butylphenyl)-4,7,13,16-tetramethoxy-
4,7,13,16-tetraphenylcyclooctadeca-2,5,8,11,14,17-hexayne-1,10-
diol (13). A solution of [6]pericyclynedione 10 (165 mg, 0.243
mmol) in THF (20 mL) was treated with 3,5-di-tertbutyl-C6H3MgBr
Esw = 20 mV, scan increment dE = 5 mV.
o
(0.625 mmol in 1 mL THF) at 0 C. The reaction mixture was stirred
4.5 Solid film fabrication and AFM measurements.
for 1.5 h at this temperature and 0.5 h at room temperature. After
addition of a saturated aqueous solution of NH4Cl, the aqueous
layer was separated and extracted with Et2O. The organic layers
were combined, dried over MgSO4 and concentrated under reduced
pressure. The residue was purified by chromatography on silica gel
(pentane : ethyl acetate 4 : 1) to give 13 as a yellow oil with 64 %
yield (165 mg, 0.156 mmol). 1H NMR (400 MHz, CD2Cl2) δ 7.93 –
7.54 (m, 12H, o-C6H5), 7.54 – 7.24 (m, 14H, m, p-C6H5, p-C6H3), 3.70
– 3.40 (m, 12H, -OCH3), 3.36 – 3.17 (m, 2H, -OH), 1.41 – 1.22 (m,
36H, -C(CH3)3). 13C{1H} NMR (101 MHz, CD2Cl2) δ 151.41 – 151.34
(m-C6H3), 139.88 – 139.68 (i-C6H5), 139.62 – 139.52 (i-C6H3) 129.08 –
128.94 (p-C6H5), 128.56 – 128.46 (m-C6H5), 126.45 – 126.26 (o-
Glass substrates were cleaned with ethanol in an ultrasonic
bath and were rubbed with alcohol-wetted cotton. Substrates
were then dried with clean and dry air and kept at 85 °C over
15 min. Before deposition of the compound layers by spin-cast
(blend of 11:PCBM) from a chlorobenzene solution (at 30
mg/mL), substrates were treated with UV oxygen plasma for 5
min. The solution was stirred for 4 h and deposited by spin-
coating at 1500 rpm for 30 s in a N2 glovebox. Morphology,
roughness and thickness were analyzed by means of atomic
force microscopy (AFM) with a microscope easyscan2 from
Nanosurf, with a maximum square scanning area of 110 μm,
operating in contact mode under ambient conditions (see S.I.).
6 | New J. Chem. 2017., 2017, 00, 1-3
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ARTICLE
2703-2706; (f) I. Baglai, M. de Anda-Villa, R. M. Barba-Barba,
C. Poidevin, G. Ramos-Ortíz, V. Maraval, C. Lepetit, N. Saffon-
Merceron, J.-L. Maldonado and R. Chauvin, Chem. Eur. J.,
2015, 21, 14186-14195; (g) I. Baglai, V. Maraval, Z. Voitenko,
Y. Volovenko and R.Chauvin, French-Ukrainian J. Chem.,
5 Acknowledgements
C. Z. thanks the China Scholarship Council for his PhD
scholarship. The Toulouse IDEX Emergence program 2014 is
acknowledged for funding (Carbo-device project). R. C. Thanks
the Centre National de la Recherche Scientifique (CNRS) for
half a teaching sabbatical in 2015-2016. The authors thank the
French-Mexican International Associated Laboratory (LIA)
“Molecular Chemistry with Applications in Materials and
Catalysis” funded by the CNRS and the CONACyT.
2013, 1, 48-53; (h) K. Cocq, N. Saffon-Merceron, A. Poater, V.
Maraval and R. Chauvin, Synlett, 2016, 27, 2105−2112.
11 P. W. Betteridge, J. R. Carruthers, R. I. Cooper, K. Prout and
D. J. Watkin, J. Appl. Cryst. 2003, 36, 1487.
12 International Tables for X-ray Crystallography, vol. IV, Kynoch
Press, Birmingham, England, 1974
.
13 (a) C. Zhu, A. Rives, C. Duhayon, V. Maraval and R. Chauvin,
J. Org. Chem., 2017, 82, 925-935; (b) C. Zhu, C. Duhayon, A.
Saquet, V. Maraval and R. Chauvin, Can. J. Chem. in press,
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6 Notes and references
14 CCDC 1503931
(
4
)
and 1518487
(
11
)
contain the
1
2
3
4
(a) R. Chauvin, Tetrahedron Lett., 1995, 36, 397-400; (b) V.
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In simple words, a carbo-mer is a molecular structure
derived from a parent Lewis covalent structure by systematic
insertion of one dicarbon unit in each original covalent bond
of given type (e.g. any bond, or C–C bond only).
supplementary crystallographic data for this paper. The data
can be obtained free of charge from the Cambridge
Crystallographic
http://www.ccdc.cam.ac.uk/getstructures.
Data
Centre
via
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