Donors and acceptors based on triangular dehydrobenzo[12]annulenes: Formation of a triple-layered rosette structure by a charge-transfer complex

Article abstract of DOI:10.1021/ja804604y

We present here the results of studies of the synthesis and properties of donors and acceptors based on triangular dehydrobenzo[12]annulene ([12]DBA) system as a π core. These studies were aimed at controlling the supramolecular crystal structure. Toward

Full text of DOI:10.1021/ja804604y

Published on Web 09/25/2008
Donors and Acceptors Based on Triangular
Dehydrobenzo[12]annulenes: Formation of a Triple-Layered
Rosette Structure by a Charge-Transfer Complex
Kazukuni Tahara,† Takumi Fujita,† Motohiro Sonoda,†,§ Motoo Shiro,‡ and
Yoshito Tobe*,†
DiVision of Frontier Materials Science, Graduate School of Engineering Science, Osaka
UniVersity, Toyonaka, Osaka 560-8531, Japan, and Rigaku Corporation, 3-9-12 Matsubaracho,
Akishima, Tokyo 196-8666, Japan
Received June 17, 2008; E-mail: tobe@chem.es.osaka-u.ac.jp
Abstract: We present here the results of studies of the synthesis and properties of donors and acceptors
based on triangular dehydrobenzo[12]annulene ([12]DBA) system as a π core. These studies were aimed
at controlling the supramolecular crystal structure. Toward this end, the tricyano[12]DBA 2 and
dodecafluoro[12]DBA (3) were synthesized as acceptors (A) and the tris(dialkylamino)[12]DBAs 4a-d as
donors (D), and their electronic properties were determined by electronic absorption spectroscopy and
electrochemical measurements. The main focus, though, was the formation of supramolecular structures
in crystals. These compounds form distinct packing patterns as a result of the different intermolecular
interactions. Tricyano[12]DBA 2 forms a two-dimensional (2D) sheet structure via hydrogen-bonding
interactions, whereas a tilted-stack structure was found for 3 because of the lack of significant intermolecular
interactions. Tris(dibutylamino)[12]DBA 4b exhibits a ladder-type 2D structure, probably because of van
der Waals interactions between the butyl groups. The most significant finding is that charge-transfer
interactions between donor 4a and acceptor 3 combined with their triangular molecular shapes and lateral
CH· · ·F hydrogen bonding result in the formation of a 2D rosette structure consisting of two different trimeric
(DAD- and ADA-type) sandwich structures with 1:2 and 2:1 A/D ratios, respectively.
Introduction
approach, numerous superstructures with unique topologies have
been constructed.1-6
Engineering the self-assembly of π-conjugated molecules into
well-defined nanometer-scale structures by controlling inter-
molecular noncovalent interactions1 has led to major advances
in the production of novel materials, such as porous crystals
for gas storage,2 liquid-crystalline materials,3 and gel or sol
materials.4 The first step in achieving a highly ordered nano-
structure is to investigate the correlation of the molecular
features, such as directional intermolecular interactions origi-
nating from the functionality and electronic properties as well
as the intrinsic molecular shape, with the resulting topology of
the self-assembled architectures. Through the use of this
Despite their ability to exhibit unique assemblies such as
hexagonal close packing, molecules with threefold symmetry
have not been fully investigated because of the limited number
of known compounds having π cores. Triphenylene derivatives
with tuned intermolecular forces and electronic properties show
various intriguing properties, such as formation of one-
dimensional (1D) columnar assembly,3,7 hole-transport proper-
ties in the column,8 and formation of charge-transfer complexes
with a triplet ground state.9 Formal expansion of the triphenylene
(5) (a) Schmidt, G. M. J. Pure Appl. Chem. 1971, 27, 647–678. (b) Crystal
Engineering: The Design of Organic Solids; Desiraju, G. R., Ed.;
Elsevier: Amsterdam, 1989. (c) Desiraju, G. R. Angew. Chem., Int.
Ed. Engl. 1995, 34, 2311–2327. (d) Blagden, N.; Davey, R. J. Cryst.
Growth Des. 2003, 3, 873–885.
† Osaka University.
‡ Rigaku Corporation.
§ Present address: Department of Applied Chemistry, Graduate School
of Engineering, Osaka Prefecture University, Japan.
(6) (a) Barth, J. V. Annu. ReV. Phys. Chem. 2007, 58, 375–407 (b)
Furukawa, S.; De Feyter, S. Top. Curr. Chem., DOI 10.1007/
128_2008_6.
(7) (a) Malthete, J.; Destrade, C.; Tinh, N. H.; Jacques, J. Mol. Cryst.
Liq. Cryst. Lett. 1981, 64, 233–238. (b) Destrade, C.; Nguyen, H. T.;
Gasparoux, H.; Malthete, J.; Levelut, A. M. Mol. Cryst. Liq. Cryst.
1981, 71, 111–114.
(1) (a) Hoeben, F. J. M.; Jonkheijm, P.; Meijer, E. W.; Schenning,
A. P. H. J. Chem. ReV. 2005, 105, 1491–1546. (b) Grimsdale, A. C.;
Mu¨llen, K. Angew. Chem., Int. Ed. 2005, 44, 5592–5629.
(2) (a) Eddaoudi, M.; Kim, J.; Rosi, N.; Vodak, D.; Wachter, J.; O’Keeffe,
M.; Yagi, O. M. Science 2002, 295, 469–472. (b) Zhao, X.; Xiao, B.;
Fletcher, A. J.; Thomas, K. M.; Bradshaw, D.; Rosseinsky, M. J.
Science 2008, 306, 1012–1015. (c) Matsuda, R.; Kitaura, R.; Kitagawa,
S.; Kubota, Y.; Belosludov, R. V.; Kobayashi, T. C.; Sakamoto, H.;
Chiba, T.; Takata, M.; Kawazoe, Y.; Mita, Y. Nature 2005, 436, 238–
241.
(8) (a) Adam, D.; Schuhmacher, P.; Simmerer, J.; Ha¨ussling, L.; Paulus,
W.; Siemensmeyer, K.; Etzbach, K.-H.; Ringsdorf, H.; Haarer, D. AdV.
Mater. 1995, 7, 276–280. (b) Adam, D.; Schuhmacher, P.; Simmerer,
J.; Ha¨ussling, L.; Siemensmeyer, K.; Etzbachi, K. H.; Ringsdorf, H.;
Haarer, D. Nature 1994, 371, 141–143.
(3) Laschat, S.; Baro, A.; Steinke, N.; Giesselmann, F.; Ha¨gele, C.; Scalia,
G.; Judele, R.; Kapatsina, E.; Sauer, S.; Schreivogel, A.; Tosoni, M.
Angew. Chem., Int. Ed. 2007, 46, 4832–4887.
(9) (a) Breslow, R.; Jaun, B.; Kluttz, R. Q.; Xia, C.-Z. Tetrahedron 1982,
38, 863–867. (b) LePage, T. J.; Breslow, R. J. Am. Chem. Soc. 1987,
109, 6412–6421.
(4) Terech, P.; Weiss, R. G. Chem. ReV. 1997, 97, 3133–3160.
9
10.1021/ja804604y CCC: $40.75
2008 American Chemical Society
J. AM. CHEM. SOC. 2008, 130, 14339–14345 14339

A R T I C L E S
Tahara et al.
Figure 1. Chemical structures of the parent molecule [12]DBA (1) and [12]DBAs functionalized with electron-withdrawing groups (the tricyano[12]DBA
2 and dodecafluoro[12]DBA 3) and with electron-donating groups (the tris(dialkylamino)[12]DBAs 4a-d and hexamethoxy[12]DBA 5).
conjugation with the trigonal shape by benzoannulation leads
to a nanographene system,10 but insertion of triple bonds leads
to dehydrobenzo[12]annulene ([12]DBA)11 and dehydrobenzo-
[18]annulene ([18]DBA),12 which consist of weakly antiaromatic
12-membered and aromatic 18-membered rings, respectively,
that are stabilized by the three fused aromatic rings.13 Contrary
to the triphenylene and [18]DBA14,15 systems, little has been
done with respect to systematic electronic modulation of the
[12]DBA π system,11d though [12]DBAs have currently become
subjects of interest in supramolecular chemistry involving
formation of liquid crystals,17 vesicles,18 and two-dimensional
(2D) molecular networks at solid-liquid interfaces.19 There-
fore, there is plenty of room to create novel materials util-
izing the assembly of appropriately functionalized triangular
[12]DBAs.
Whitesides and co-workers20 proposed the rosette structure
consisting of cyanuric acid and melamine and performed
pioneering work on the formation of supramolecular complexes
between derivatives of these compounds. Later on, Rao and co-
workers confirmed the formation of the 2D rosette structure in
a crystal prepared by a hydrothermal synthesis.21 Since then,
rosette units have been employed for the construction of many
supramolecular assemblies, such as a tubular assembly22 and a
monolayer on a surface.23
Motivated by the possible formation of supramolecular
assemblies that reflect the unique C3-symmetric structure of the
[12]DBA core, we planned to prepare electronically tuned
[12]DBAs. Toward this end, we designed [12]DBAs substituted
with electron-donating groups (such as the tris(dialkyl-
amino)[12]DBAs 4a-d) or electron-withdrawing groups (such
as tricyano[12]DBA 2 and dodecafluoro[12]DBA 3) (Figure 1).
We expected that the supramolecular structures would be
affected by not only charge transfer but also specific intermo-
lecular interactions between the functional groups. Analysis of
the superstructures in crystals of 2, 3, and 4b revealed that they
form distinct packing structures: a perfect 2D sheet structure
for 2, a tilted-stack structure for 3, and a ladder-type 2D structure
for 4b, depending on the features of the functionalities.
Moreover, we found that a 1:1 charge-transfer complex between
3 and 4a formed a 2D triple-layered rosette structure consisting
of two different trimeric molecular sandwiches containing 3 and
4a in 2:1 and 1:2 ratios. The two trimers together with two
One of the intriguing molecular assemblies based on a C3-
symmetric trigonal molecular unit is a bimolecular rosette.
(10) (a) Feng, X.; Wu, J.; Ai, M.; Pisula, W.; Zhi, L.; Rabe, J. P.; Mu¨llen,
K. Angew. Chem., Int. Ed. 2007, 46, 3033–3036. (b) Fujioka, Y. Bull.
Chem. Soc. Jpn. 1985, 58, 481–489.
(11) (a) Campbell, I. D.; Eglinton, G.; Henderson, W.; Raphael, R. A. Chem.
Commun. 1996, 87–89. (b) Staab, H. A.; Graf, F. Tetrahedron Lett.
1966, 7, 751–757. (c) Huynh, C.; Linstrumelle, G. Tetrahedron 1988,
44, 6337–6344. (d) Iyoda, M.; Vorasingha, A.; Kuwatani, Y.; Yoshida,
M. Tetrahedron Lett. 1998, 39, 4701–4704. (e) Iyoda, M.; Sirinintasak,
S.; Nishiyama, Y.; Vorasingha, A.; Sultana, F.; Nakao, K.; Kuwatani,
Y.; Matsuyama, H.; Yoshida, M.; Miyake, Y. Synthesis 2004, 1527–
1531. (f) Kehoe, J. M.; Kiley, J. H.; English, J. J.; Johnson, C. A.;
Peterson, R. C.; Haley, M. M. Org. Lett. 2000, 2, 969–972.
(12) (a) Behr, O. M.; Eglinton, G.; Galbraith, A. R.; Raphael, R. A. J. Chem.
Soc. 1960, 3614–3625. (b) Haley, M. M.; Brand, S. C.; Pak, J. J.
Angew. Chem., Int. Ed. Engl. 1997, 36, 836–838. (c) Wan, W. B.;
Brand, S. C.; Pak, J. J.; Haley, M. M. Chem.sEur. J. 2000, 6, 2044–
2052.
(16) (a) Kinder, J. D.; Tessier, C. A.; Youngs, W. J. Synlett 1993, 149–
ˇ
150. (b) Miljanic´, O. S.; Vollhardt, K. P. C.; Whitener, G. D. Synlett
2003, 29–34. (c) Li, Y.; Zhang, J.; Wang, W.; Miao, Q.; She, X.;
Pan, X. J. Org. Chem. 2005, 70, 3285–3287. (d) Zhang, W.; Brombosz,
S. M.; Mendoza, J. L.; Moore, J. S. J. Org. Chem. 2005, 70, 10198–
10201.
(13) For recent reviews on dehydrobenzoannulenes, see: (a) Youngs, W. J.;
Tessier, C. A.; Bradshaw, J. D. Chem. ReV. 1999, 99, 3153–3180. (b)
Spitler, E. L.; Johnson, C. A.; Haley, M. M. Chem. ReV. 2006, 106,
5344–5386. (c) Tobe, Y.; Sonoda, M. In Modern Cyclophane
Chemistry; Gleiter, R., Hopf, H., Eds.; Wiley-VCH: Weinheim,
Germany, 2004; pp 1-40. (d) Jones, C. S.; O’Connor, M. J.; Haley,
M. M. In Acetylene Chemistry: Chemistry, Biology and Material
Science; Diederich, F., Stang, P. J., Tykwinski, R. R., Eds.; Wiley-
VCH: Weinheim, Germany, 2005; pp 303-385.
(14) (a) Zhou, Q.; Carroll, P. J.; Swager, T. M. J. Org. Chem. 1994, 59,
1294–1301. (b) Nishinaga, T.; Nodera, N.; Miyata, Y.; Komatsu, K.
J. Org. Chem. 2002, 67, 6091–6096. (c) Nishinaga, T.; Miyata, Y.;
Nodera, N.; Komatsu, K. Tetrahedron 2004, 60, 3375–3382. (d) Pak,
J. J.; Weakley, T. J. R.; Haley, M. M. J. Am. Chem. Soc. 1999, 121,
8182–8192. (e) Sarkar, A.; Pak, J. J.; Rayfield, G. W.; Haley, M. M.
J. Mater. Chem. 2001, 11, 2943–2945. (f) Tahara, K.; Johnson, C. A.;
Fujita, T.; Sonoda, M.; De Schryver, F. C.; De Feyter, S.; Haley,
M. M.; Tobe, Y. Langmuir 2007, 23, 10190–10197. (g) Zhou, X.;
Ren, A.-M.; Feng, J.-K.; Liu, X.-J. Can. J. Chem. 2004, 82, 1172–
1178.
(17) Seo, S. H.; Jones, T. V.; Seyler, H.; Peters, J. O.; Kim, T. H.; Chang,
J. Y.; Tew, G. N. J. Am. Chem. Soc. 2006, 128, 9264–9265.
(18) Seo, S. H.; Chang, J. Y.; Tew, G. N. Angew. Chem., Int. Ed. 2006,
45, 7526–7530.
(19) (a) Furukawa, S.; Uji-i, H.; Tahara, K.; Ichikawa, T.; Sonoda, M.; De
Schryver, F. C.; Tobe, Y.; De Feyter, S. J. Am. Chem. Soc. 2006,
128, 3502–3503. (b) Tahara, K.; Furukawa, S.; Uji-i, H.; Uchino, T.;
Ichikawa, T.; Zhang, J.; Sonoda, M.; De Schryver, F. C.; De Feyter,
S.; Tobe, Y. J. Am. Chem. Soc. 2006, 128, 16613–16625. (c) Lei, S.;
Tahara, K.; De Schryver, F. C.; Van der Auweraer, M.; Tobe, Y.; De
Feyter, S. Angew. Chem., Int. Ed. 2008, 47, 2964–2968. (d) Furukawa,
S.; Tahara, K.; De Schryver, F. C.; Van der Auweraer, M.; Tobe, Y.;
De Feyter, S. Angew. Chem., Int. Ed. 2007, 46, 2831–2834. (e) Lei,
S.; Tahara, K.; Feng, X.; Furukawa, S.; De Schryver, F. C.; Mu¨llen,
K.; Tobe, Y.; De Feyter, S. J. Am. Chem. Soc. 2008, 130, 7119–7129.
(f) Tahara, K.; Lei, S.; Mo¨ssinger, D.; Kozuma, H.; Inukai, K.; Van
der Auweraer, M.; De Schryver, F. C.; Ho¨ger, S.; Tobe, Y.; De Feyter,
S. Chem. Commun. 2008, 3897–3899.
(15) For similar electronic modulation in dehydrobenzo[14]annulene
π-systems, see: (a) Marsden, J. A.; Miller, J. J.; Haley, M. M. Angew.
Chem., Int. Ed. 2004, 43, 1694–1697. (b) Marsden, J. A.; Miller, J. J.;
Shirtcliff, L. D.; Haley, M. M. J. Am. Chem. Soc. 2005, 127, 2464–
2476. (c) Spitler, E. L.; Monson, J. M.; Haley, M. M. J. Org. Chem.
2008, 73, 2211–2223.
(20) (a) Seto, C. T.; Whitesides, G. M. J. Am. Chem. Soc. 1991, 113, 712–
713. (b) Seto, C. T.; Whitesides, G. M. J. Am. Chem. Soc. 1993, 115,
905–916. (c) Whitesides, G. M.; Simanek, E. E.; Mathias, J. P.; Seto,
C. T.; Chin, D.; Mammen, M.; Gordon, D. M. Acc. Chem. Res. 1995,
28, 37–44. (d) Whitesides, G. M.; Mathias, J. P.; Seto, C. T. Science
1991, 254, 1312–1319.
9
14340 J. AM. CHEM. SOC. VOL. 130, NO. 43, 2008

Formation of a Triple-Layered Rosette Structure
A R T I C L E S
Figure 2. HOMO-1, HOMO, LUMO, and LUMO+1 energy levels (eV) and the HOMO-LUMO gaps (eV) obtained from DFT calculations on the [12]DBAs
1-3, 4a, 5, A, and B at B3LYP/6-31G* level of theory.
chloroform molecules constitute the repeating units, and they
align alternatingly in forming the triple-layered rosette structure.
To the best of our knowledge, this is the first example of the
formation of a 2D bimolecular rosette by triangular-shaped
molecules.
of 1, again as expected. Notably, introducing three amino
groups (as in 4a) enhances the electron-donating ability better
than introducing six methoxy groups (as in 5).
For comparison, the energy levels of the triphenylene
derivatives having the same functional groups were computed.
All of the triphenylene compounds possess lower HOMO and
higher LUMO energies (e.g., -5.82 and -0.93 eV for parent
triphenylene, -7.05 and -2.52 eV for the tricyanotriphenylene,
and -4.76 and -0.42 eV for the tris(dimethylamino)triph-
enylene; see Figure S1 in the Supporting Information) than the
corresponding [12]DBA derivatives as a result of the reduced
π conjugation.
Though the theoretical study predicted that the model
compounds A and B would be the most efficient acceptor and
donor, respectively, in view of obstacles that we met in the
synthesis of 2 (i.e., low solubility in common organic solvents)
and in our attempts to prepare a suitable precursor of B (i.e.,
via halogenation of N,N-dimethyltetrahydroquinoxaline by an
electrophilic substitution reaction), we decided to focus on 2
and 3 as acceptors and 4a-d as donors.
The [12]DBAs 2, 3, and 4a-d were synthesized by the
cyclotrimerization reactions of the corresponding o-ethynyliodo-
benzene derivatives under two different conditions, the
Sonogashira-Hagihara-type reaction for 2 and 3 and the
Stephens-Castro-type reaction for 4a-d, in view of the
threefold-symmetric nature of the target molecules and mini-
mization of the number of synthetic steps. Absorption and
fluorescence spectra of 2, 3, 4a, and 5 are qualitatively in accord
with the theoretical predictions for their MO levels. Details of
the syntheses of 2, 3, and 4a-d and electronic absorption and
emission spectra of 1-3, 4a-d, and 5 are provided in the
Supporting Information.
Results and Discussion
1. Molecular Design and Syntheses. To predict the effect
of the functional groups on the π-electron systems of the
[12]DBAs, density functional theory (DFT) calculations at
theB3LYP/6-31G*levelfor1,2,3,4a,5,thehexacyano[12]DBA
A, and the tris(N,N-dimethyltetrahydropyrazino)[12]DBA B
were performed, and the energy levels of their frontier
molecular orbitals (MOs) were computed. The HOMO-1,
HOMO, LUMO, and LUMO+1 levels are summarized in
Figure 2. Molecules A, 2, and 3 are acceptors; their HOMO
and LUMO levels, respectively, are located at -7.07 and
-4.19 eV for A, -6.29 and -3.20 eV for 2, and -6.20 and
-2.97 eV for 3. Not surprisingly, both levels of each acceptor
are lower than the corresponding levels of the parent 1 (-5.28
and -2.00 eV) as a result of the electron-accepting ability
of the substituents. In addition, as far as the MO levels are
concerned, it appears that cyano groups enhance the electron-
acceptability of the [12]DBA system more efficiently than
fluoro groups. On the other hand, the HOMO and LUMO
levels, respectively, of the donors 4a, B, and 5 (-4.35 and
-1.27 eV for 4a, and -3.73 and -0.98 eV for B, and -4.47
and -1.56 eV for 5) are higher than the corresponding levels
(21) Ranganathan, A.; Pedireddi, V. R.; Rao, C. N. R. J. Am. Chem. Soc.
1999, 121, 1752–1753.
(22) Yagai, S.; Nakajima, T.; Kishikawa, K.; Kohmoto, S.; Karatsu, T.;
Kitamura, A. J. Am. Chem. Soc. 2005, 127, 11134–11139.
(23) Scho¨nherr, H.; Paraschiv, V.; Zapotoczny, S.; Crego-Calama, M.;
Timmerman, P.; Frank, C. W.; Vancso, G. J.; Reinhoudt, D. N. Proc.
Natl. Acad. Sci. U.S.A. 2002, 99, 5024–5027.
2. Electrochemical Measurements. Electrochemical measure-
ment is a powerful tool for investigating the electronic properties
9
J. AM. CHEM. SOC. VOL. 130, NO. 43, 2008 14341

A R T I C L E S
Tahara et al.
Table 1. Results of Cyclic Voltammetry Measurements on
electron-donating ability comparable to those of triary-
lamine31 and tetrathiafulvalene.32
[12]DBAsa
compound
solvent
E
1/2(red) (V)b
Epa(ox 1) (V)b
Epa(ox 2) (V)b
3. Crystal Structure Analyses. a. Packing Diagrams for
[12]DBAs. In general, crystal structures of planar aromatic
molecules (without functional groups) are classified into four
different types, as proposed by Desiraju and Gavezzotti:33
herringbone, sandwich herringbone, ꢀ, and γ. Crystal structures
are determined by (1) the balance between maximizing the
dispersion forces and minimizing repulsive forces and (2)
various intermolecular directional forces, such as hydrogen-
bonding interactions. Previously, two types of crystal structures
were reported for the [12]DBA derivatives. The parent 1 was
reported to show a herringbone structure, reflecting weak
intermolecular π-π interactions.34 Recently, Hisaki, Miyata,
and co-workers35 reported the perfect face-to-face 1D columnar
structure of a tricarboxy-substituted [12]DBA, which was
maintained by hydrogen-bonding interactions between the
carboxy groups and the dimethyl sulfoxide solvent molecules.
In order to clarify the effect of substituents on the packing
structure, single-crystal X-ray structural analyses of 2, 3, and
4b were undertaken. These molecules adopt characteristic
packing diagrams, including a perfect 2D sheet structure,
depending on the nature of the functional groups on the π
system.
b. Packing Diagram for Tricyano[12]DBA 2. Cyano substitu-
tion on an aromatic ring has been used for the construction of
superstructures by CN · · · H hydrogen-bonding interactions.36
Not surprisingly, the molecules of compound 2 pack to form
2D sheets via hydrogen-bonding interactions between the
nitrogen atoms of the cyano groups on one molecule and
hydrogen atoms attached to the benzene rings of adjacent
molecules (Figure 3a,b). The N · · ·H distances range from 2.47
to 2.85 Å, corresponding to the typical CN · · ·H hydrogen-
bonding distance.36 Though there are no significant directional
intersheet interactions (Figure 3c), the average distance between
adjacent 2D sheets is 3.2 Å, which is shorter than the typical
π-π interaction distance.
1
2
3
4a
5
CH2Cl2
C2H2Cl4
C2H2Cl4
CH2Cl2
CH2Cl2
-2.21
-1.70
-1.70
se
sd
sd
sd
sd
sd
sd
0.30c
0.56
0.61c
1.00c
se
a Conditions: 0.55-1.0 mM solution with 0.10 M (n-Bu4N)(ClO4) as
the supporting electrolyte. b All of the potentials are given vs the
ferrocene/ferrocenium redox couple as an internal standard. c Irreversible
anodic peak. d Oxidation peaks were not observed e Reduction peaks
were not observed.
of π-conjugated molecules. The parent 1 showed two reversible
one-electron reduction waves in THF.24 Moreover, chemically
generated dianionic species were transformed into bisfulvalene
dianions.25 To evaluate the electronic properties of the new
acceptors 2 and 3 and donors 4a and 5, cyclic voltammetry
measurements were carried out (Table 1).
Parent 1 in CH2Cl2 displayed only one reversible one-electron
reduction wave, at E1/2 ) -2.21 V under our experimental
conditions. On the other hand, 2 in 1,1,2,2-tetrachloroethane
showed a reversible one-electron reduction wave at E1/2 ) -1.70
V. The use of 1,1,2,2-tetrachloroethane instead of CH2Cl2 was
necessary because of the low solubility of 2. In 1,1,2,2-
tetrachloroethane, 3 also accepts an electron at the same potential
(E1/2 ) -1.70 V). No indications of further reduction or
oxidation were observed for either acceptor. The difference in
E1/2 values demonstrates the higher electron-accepting abilities
of 2 and 3 compared to 1, in qualitative agreement with the
LUMO levels estimated from the theoretical study (-2.00 eV
for 1, -2.97 eV for 3, and -3.20 eV for 2).26
In the case of 4a in CH2Cl2, an irreversible oxidation process
at Epa ) 0.30 V that was subsequently subjected to further
oxidations was observed. On the other hand, 5 in CH2Cl2 showed
a reversible one-electron oxidation wave at Epa ) 0.56 V and
an irreversible wave corresponding to further oxidation. Com-
parison of the first oxidation potentials of the [12]DBAs with
electron-donating groups indicates that the electron-donating
ability of 4a is stronger than that of 5, in agreement with the
order of the theoretically calculated HOMO levels (-4.47 eV
for 5 and -4.35 eV for 4a).
c. Packing Diagram for Dodecafluoro[12]DBA 3. The analy-
sis of 3 showed a columnar packing structure in which each
molecule is tilted with respect to the main axis of the column
(Figure 4a,b). According to the Desiraju-Gavezzotti scheme,
this structure is classified as a ꢀ structure. In the molecular
column, one of the tetrafluorobenzene rings of 3 is aligned
face-to-face with the center of an adjacent [12]annulene ring,
while the other two tetrafluorobenzene rings do not overlap
with their top and bottom neighbors (Figure 4c). The observed
positional relationships of the adjacent molecules can be
ascribed to intermolecular electrostatic interactions.14b In fact,
natural-population analysis based on B3LYP/6-31G* calcula-
tions gave high partial positive charges (0.32 to 0.40) for
carbon atoms attached to the electronegative fluorine atoms
The potentials of the donor- and acceptor-substituted
[12]DBAs were also compared with those of common organic
donors and acceptors. Apparently, the electron-accepting
abilities of 2 and 3 are lower than those of fullerene C60,27
perylene diimide,28 perfluoropentacene,29 and tetracyano-
quinodimethane (TCNQ),30 whereas 4a exhibits a high
(24) Ferrara, J. D.; Tanaka, A. A.; Fierro, C.; Tessier-Youngs, C. A.;
Youngs, W. J. Organometallics 1989, 8, 2089–2098.
(25) Malaba, D.; Djebli, A.; Chen, L.; Zarate, E. A.; Tessier, C. A.; Youngs,
W. J. Organometallics 1993, 12, 1266–1276.
(31) Steckhan, E. Top. Curr. Chem. 1987, 142, 1–69.
(32) Morita, Y.; Miyazaki, E.; Fukui, K.; Maki, S.; Nakasuji, K. Bull. Chem.
Soc. Jpn. 2005, 78, 2014–2018.
(26) Though both 2 and 3 were reduced at the same potential (-1.70 V)
in the electrochemical measurements, the LUMO of 2 is lower in
energy than that of 3. One of the plausible reasons for this discrepancy
is the difference in the stabilities of their anionic species in solution.
(27) Keshavarz-K, M.; Knight, B.; Srdanov, G.; Wudl, F. J. Am. Chem.
Soc. 1995, 117, 11371–11372.
(33) Desiraju, G. R.; Gavezzotti, A. J. Chem. Soc., Chem. Commun. 1989,
621–623.
(34) Irngartinger, H.; Leiserowitz, L.; Schmidt, G. M. J. Chem. Ber. 1970,
103, 1119–1131.
(35) Hisaki, I.; Sakamoto, Y.; Shigemitsu, H.; Tohnai, N.; Miyata, M.; Seki,
S.; Saeki, A.; Tagawa, S. Chem.sEur. J. 2008, 14, 4178–4187.
(36) Yokoyama, T.; Yokoyama, S.; Kamikado, T.; Okuno, Y.; Mashiko,
S. Nature 2001, 413, 619–621.
(28) Pasaogullari, N.; Icil, H.; Demuth, M. Dyes Pigm. 2006, 69, 118–
127.
(29) Sakamoto, Y.; Suzuki, T.; Kobayashi, M.; Gao, Y.; Fukai, Y.; Inoue,
Y.; Sato, F.; Tokito, S. J. Am. Chem. Soc. 2004, 126, 8138–8140.
(30) Gross-Lannert, R.; Kaim, W.; Olbrich-Deussner, B. Inorg. Chem. 1990,
29, 5046–5053.
(37) (a) Meyer, E. A.; Castellano, R. K.; Diederich, F. Angew. Chem., Int.
Ed. 2003, 42, 1210–1250. (b) Hunter, C. A.; Lawson, K. R.; Perkins,
J.; Urch, C. J. J. Chem. Soc., Perkin Trans. 2 2001, 651–669.
9
14342 J. AM. CHEM. SOC. VOL. 130, NO. 43, 2008

Formation of a Triple-Layered Rosette Structure
A R T I C L E S
interactions between a donor and an acceptor.37 Unusual
properties of perfluoroaromatic compounds were discovered
five decades ago in a study of the formation of a crystal from
a mixture of perfluorobenzene and benzene.38 The formation
of an alternating, perfectly face-to-face packing structure has
been ascribed to favorable quadrupole-quadrupole interac-
tions and reduction of unfavorable electrostatic repulsions.39
This type of interaction has been successfully used for the
construction of not only superstructures in crystals but also
supramolecules.40 The other important interaction is the
charge-transfer interaction. The simplest charge-transfer
complex was discovered four decades ago in a study of a
mixture of perfluorobenzene and N,N-dimethylaniline;41 this
complex adopts a slightly displaced parallel-packing mode
in crystals.42 In both cases, the donor and acceptor molecules
favor the formation of 1D columnar structures with alternat-
ing alignment. On the basis of these precedents, we examined
the formation of cocrystals between dodecafluoro[12]DBA
3 and parent [12]DBA 1 and of charge-transfer complexes
between the donor 4a and the acceptors 2 and 3.43 However,
in a systematic investigation of the mixtures, we obtained
cocrystals only for 4a and 3; slow evaporation of the solvent
from a mixture of 3 and 4a in CHCl3 formed red-colored
crystals suitable for X-ray analysis. Nevertheless, single-
crystal X-ray structural analysis turned out to be challenging
because of the exotic packing diagram. However, in the unit
cell, there are two different trimers: trimer A consists of one
molecule of 3 and two molecules of 4a (acceptor/donor ratio
of 1:2), and trimer B contains two molecules of 3 and one
molecule of 4a (acceptor/donor ratio of 2:1) (Figure 6a). The
unit cell also contains two chloroform molecules (Figure 6b)
and overall is very large (V ) 6721 Å3).
Figure 3. Single-crystal X-ray analysis of 2. (a) ORTEP diagram (50%
probability level). (b) Packing structure. The red lines connecting nitrogen
atoms (blue) and hydrogen atoms (white) highlight the CN · · ·H hydrogen-
bonding interactions. (c) Positional relationship between the molecular
sheets. Molecules forming the upper layer are drawn darker than those in
the lower layer.
Each [12]DBA adopts displaced parallel packing, with one
C-C bond of one benzene ring located above the center of
Figure 4. Single-crystal X-ray analysis of 3. (a) ORTEP diagram (50%
probability level). (b) Packing structure. (c) Positional relationship between
adjacent molecules in a molecular column. The upper molecules are drawn
darker than the lower molecules.
(38) Patrick, C. R.; Prosser, G. S. Nature 1960, 187, 1021.
(39) Williams, J. H.; Cockcroft, J. K.; Fitch, A. N. Angew. Chem., Int. Ed.
Engl. 1992, 31, 1655–1657.
(40) (a) Coates, G. W.; Dunn, A. R.; Henling, L. M.; Ziller, J. W.;
Lobkovsky, E. B.; Grubbs, R. H. J. Am. Chem. Soc. 1998, 120, 3641–
3649. (b) Weck, M.; Dunn, A. R.; Matsumoto, K.; Coates, G. W.;
Lobkovsky, E. B.; Grubbs, R. H. Angew. Chem., Int. Ed. 1999, 38,
2741–2745. (c) Ponzini, F.; Zagha, R.; Hardcastle, K.; Siegel, J. S.
Angew. Chem., Int. Ed. 2000, 39, 2323–2325. (d) Shu, L.; Mayor, M.
Chem. Commun. 2006, 4134–4136.
but negative or very weakly positive charges (-0.14 to 0.03)
for carbons in the [12]annulene ring. Consequently, we
assume that electrostatic repulsions between tetrafluoroben-
zene rings and attractive forces between tetrafluorobenzene
and [12]annulene rings led to the formation of the tilted-
stack structure.
(41) Beaumont, T. G.; Davis, K. M. C. Nature 1968, 218, 865.
(42) Dahl, T. Acta Crystallogr. 1977, B33, 3021–3024.
(43) We also attempted the preparation of charge-transfer complexes of
donor 4a with common acceptors such as TCNQ. However, treatment
of 4a with TCNQ afforded the covalently bonded products 6a and 6b
via [2 + 2] cycloaddition followed by electrocyclic ring opening.
Similar reactions were employed by Diederich and co-workers44 to
prepare compounds containing charge-transfer chromophores.
d. Packing Diagram for Tris(dibutylamino)[12]DBA 4b. The
analysis of 4b revealed a 2D sheet structure consisting of 1D
tapes (Figure 5a,b) in which the [12]DBA units roughly align
within the plane. The butyl groups occupy the spaces between
the π cores both within a plane and between planes, indicating
that van der Waals interactions play a major role in this packing
diagram. In regard to intersheet interactions, two of the benzene
rings of each 4b molecule show short distances (3.47 to 3.80
Å) with respect to rings of neighboring molecules (one above
and one below), as shown in Figure 5c.
4. Formation of Charge-Transfer Complexes between
[12]DBAs. In general, for small π systems without π-π
interactions significant enough to form a stacked structure,
two interactions can be used to achieve a face-to-face packing
pattern: quadrupole-quadrupole interactions between a per-
fluorobenzene ring and a benzene ring and charge-transfer
,
(44) Kivala, M.; Boudon, C.; Gisselbrecht, J.-P.; Seiler, P.; Gross, M.;
Diederich, F. Chem. Commun. 2007, 4731–4733.
(45) Gung, B. W.; Amicangelo, J. C. J. Org. Chem. 2006, 71, 9261–9270.
(46) Rowland, R. S.; Taylor, R. J. Phys. Chem. 1996, 100, 7384–7391.
9
J. AM. CHEM. SOC. VOL. 130, NO. 43, 2008 14343

A R T I C L E S
Tahara et al.
Figure 5. Single-crystal X-ray analysis of 4b. (a) ORTEP diagram (50% probability level). (b) Packing structure. (c) Positional relationships of the adjacent
molecules between molecular sheets. The upper molecules are drawn darker than the lower molecules. The red squares highlight the position of short
interring distances.
Figure 6. Single-crystal X-ray analysis of the charge-transfer complex 4a·3. (a) ORTEP diagrams (50% probability level) of layered trimers A and B. (b)
Unit cell structure. The pink-colored atoms are chlorine atoms of chloroform. (c) Columnar structure in the unit cell b direction, consisting of four units of
trimer B. (d) Structure in the unit cell b direction, consisting of two units of trimer A and four molecules of chloroform. (e) Positional relationship between
adjacent molecules of 3 in the b direction. The upper molecule is drawn darker than the lower one. (f) Triple-layered rosette structure in the crystal. The
color gradation shades the upper molecules darker than the lower molecules. (g, h) Partial structures within the molecular sheet. The red lines highlight
places where short CH · · ·F contacts were observed.
the adjacent ring, instead of a perfect sandwich configuration.
This geometry is similar to that observed for the charge-
transfer complex of perfluorobenzene and N,N-dimethyl-
aniline.42 In addition, a theoretical study has indicated that
the stable form of that charge-transfer complex is a slightly
displaced parallel-packing mode.45 Thus, the observed struc-
ture in trimers A and B can be regarded as arising from the
typical packing pattern for the charge-transfer complex of
9
14344 J. AM. CHEM. SOC. VOL. 130, NO. 43, 2008

Formation of a Triple-Layered Rosette Structure
A R T I C L E S
perfluorobenzene and dimethylaniline. However, the cocrystal
of 3 and 4a consists of 1:2 and 2:1 rather than 1:1 complexes,
even though the net ratio of 3 to 4a is 1:1. The formation of
the sandwich trimers may be ascribed to their height, which
provides sufficient space to accommodate the two chloroform
molecules occupying the void formed as a result of the
difference in the bulkiness of the substituents of 3 and 4a
(Figure 6b). As a result, one of the trimers, B, forms a
columnar assembly along the unit cell b direction (Figure
6c). At the contact between the trimer units, the orientation
of the adjacent 3 molecules is antiparallel in order to avoid
the electrostatic repulsion between fluorinated rings and to
maximize close-packing (Figure 6e). On the other hand,
trimer A does not form a 1D column in the b direction; two
chloroform molecules occupy the space between the trimers
(Figure 6d). The absence of columnar assembly can be
ascribed to the unfavorable interactions between the donor
4a molecules that would arise at the contacts between trimer
A units.
More significantly, all of the trimers align in the ac plane to
form a 2D rosette pattern (Figure 6f). The formation of this
particular packing structure is attributed not only to the triangular
shapes of 3 and 4a, which are favorable for packing them into
a 2D hexagonal pattern, but also to the side-by-side intermo-
lecular interactions between adjacent triangular cores. Indeed,
relatively short interatomic distances are found between the
fluorine atoms of 3 and the hydrogen atoms of 4a; the average
CH· · ·F distances are 2.49, 2.82, and 2.73 Å, respectively, for
contacts (i), (ii), and (iii) shown in Figure 6g,h. In particular,
the average distance for (i) is shorter than the sum of the van
der Waals radii of the two nuclei (2.56 Å),46indicating the
existence of a favorable CH · · ·F interaction.47Therefore, the 2D
rosette structure consisting of the two types of trimers is formed
by (1) intermolecular charge-transfer interactions between the
donor 4a and the acceptor 3 along the b direction and (2) the
favorable packing geometry due to the triangular shapes together
with lateral CH · · ·F hydrogen bonding. To our knowledge, this
unique structural feature has not been reported previously.
surements. The crystal structures of 2, 3, and 4b were
determined by single-crystal X-ray analyses, which revealed
the formation of distinct packing patterns, such as the perfect
2D sheet structure of 2 arising from intraplane CN · · · H
interactions. In addition, in crystals of the charge-transfer
complex 3 · 4a, the combination of charge-transfer interac-
tions, the characteristic triangular molecular shapes, and
intermolecular CH · · · F interactions results in the formation
of a 2D bimolecular rosette structure using two different
molecular trimers as building blocks. The present study
provides some new insights regarding methods for controlling
the spatial arrangement of π-conjugated molecules, which
is crucial for optoelectronic applications.
Acknowledgment. This work was supported by a Grant-in-
Aid for Scientific Research from the Ministry of Education,
Culture, Sports, Science, and Technology of Japan. The authors
thank Prof. M. Miyata and Dr. I. Hisaki (both of Osaka
University) and Dr. Y. Matsuo (ERATO, Nakamura Functional
Carbon Cluster Project) for their help with single-crystal X-ray
analysis.
Note Added after ASAP Publication. After this paper was
published ASAP September 25, 2008, production errors in the next-
to-last sentence of the second paragraph, including reference
numbering, were corrected. The corrected version was published
October 1, 2008.
Supporting Information Available: Synthetic procedures and
experimental and computational procedures; characterization
data for [12]DBA derivatives 2, 3, and 4a-d; calculated
HOMO/LUMO levels of triphenylene derivatives; crystal-
lographic data for 2, 3, 4b, and the charge-transfer complex
4a·3 (CIF); cyclic voltammograms and electronic absorption
and emission spectra of 1, 2, 3, 4a, and 5; NMR spectra of all
of the new compounds; and optimized structures of the model
compounds. This material is available free of charge via the
Internet at http://pubs.acs.org.
JA804604Y
Summary
In summary, donors and acceptors based on [12]DBA,
namely, the donors tricyano[12]DBA 2 and perfluoro[12]DBA
3 and the tris(dialkylamino)[12]DBA acceptors 4a-d, were
synthesized and their electronic properties characterized by
electronic absorption and emission spectra and redox mea-
(47) (a) Dahl, T. Acta Crystallogr. 1990, B46, 283–288. (b) Collings, J. C.;
Roscoe, K. P.; Thomas, R. L.; Batsanov, A. S.; Stimson, L. M.;
Howard, J. A. K.; Marder, T. B. New J. Chem. 2001, 25, 1410–1417.
(c) Batsanov, A. S.; Collings, J. C.; Howard, J. A. K.; Marder, T. B.
Acta Crystallogr. 2001, E57, o950–o952.
9
J. AM. CHEM. SOC. VOL. 130, NO. 43, 2008 14345