Synthesis, stabilities, and redox behavior of mono-, di-, and tetracations composed of di(1-azulenyl)methylium units connected to a benzene ring by phenyl- and 2-thienylacetylene spacers. A concept of a cyanine-cyanine hybrid as a stabilized electrochromi

Article abstract of DOI:10.1021/jo0618324

This paper describes the preparation of two tetracations 4a⁴⁺ and 4b⁴⁺ composed of di(1-azulenyl)-methylium units based on a new structural principle of a cyanine-cyanine hybrid for the design of electrochromic materials with two col

Full text of DOI:10.1021/jo0618324

Synthesis, Stabilities, and Redox Behavior of Mono-, Di-, and
Tetracations Composed of Di(1-azulenyl)methylium Units Connected
to a Benzene Ring by Phenyl- and 2-Thienylacetylene Spacers.
A Concept of a Cyanine-Cyanine Hybrid as a Stabilized
Electrochromic System
Shunji Ito,*,† Koji Akimoto,† Jun Kawakami,† Akio Tajiri,† Taku Shoji,‡
Hiroyuki Satake,‡ and Noboru Morita‡
Department of Frontier Materials Chemistry, Faculty of Science and Technology, Hirosaki UniVersity,
Hirosaki 036-8561, Japan, and Department of Chemistry, Graduate School of Science, Tohoku UniVersity,
Sendai 980-8578, Japan
itsnj@cc.hirosaki-u.ac.jp
ReceiVed September 5, 2006
This paper describes the preparation of two tetracations 4a4+ and 4b4+ composed of di(1-azulenyl)-
methylium units based on a new structural principle of a cyanine-cyanine hybrid for the design of
electrochromic materials with two color changes. Di- and monocations 5a2+, 5b2+ and 6a+, 6b+ composed
of di(1-azulenyl)methylium units were also prepared for the purpose of comparison. The pKR+ values of
the tetracations are rather high despite their tetracationic structure, although the stability of these cations
decreases with the increase of the number of the existing cation units. The cyclic voltammetry (CV) of
these cations revealed the presumed multielectron redox properties. However, the tetracations did not
exhibit the idealized electrochemical behavior, in which subsequent two-electron reduction was presumed
as the cyanine-cyanine hybrid, probably due to the less effective electrochemical interaction among the
positive charges. The scope of the creation of the novel polyelectrochromic materials taking the new
structural principle is demonstrated by these examples.
Introduction
of novel polyelectrochromic materials, which respond to dif-
ferent potentials with a variety of colors.2 Recently, Hu¨nig et
al. proposed a concept of a violene-cyanine hybrid to produce
a stabilized organic electrochromic system.3 The hybrid is
constructed by the violene-type redox system containing delo-
Electrochromism is observed in reversible redox systems,
which exhibit significant color changes in different oxidation
states.1 Construction of organic molecules that contain multiple
redox-active chromophores is fairly important for the preparation
(3) (a) Hu¨nig, S.; Kemmer, M.; Wenner, H.; Perepichka, I. F.; Ba¨uerle,
P.; Emge, A.; Gescheid, G. Chem.sEur. J. 1999, 5, 1969-1973. (b) Hu¨nig,
S.; Kemmer, M.; Wenner, H.; Barbosa, F.; Gescheidt, G.; Perepichka,
I. F.; Ba¨uerle, P.; Emge, A.; Peters, K. Chem.sEur. J. 2000, 6, 2618-
2632. (c) Hu¨nig, S.; Perepichka, I. F.; Kemmer, M.; Wenner, H.; Ba¨uerle,
P.; Emge, A. Tetrahedron 2000, 56, 4203-4211. (d) Hu¨nig, S.; Langels,
A.; Schmittel, M.; Wenner, H.; Perepichka, I. F.; Peters, K. Eur. J. Org.
Chem. 2001, 1393-1399.
* To whom correspondence should be addressed. Telephone: +81-172-39-
3568. Fax: +81-172-39-3541.
† Hirosaki University.
‡ Tohoku University.
(1) Monk, P. M. S.; Mortimer, R. J.; Rosseinsky, D. R. Electro-
chromism: Fundamentals and Applications; VCH: Weinheim, Germany,
1995.
(2) Deuchert, K.; Hu¨nig, S. Angew. Chem., Int. Ed. Engl. 1978, 17, 875-
886.
(4) Ito, S.; Morita, N.; Kubo, T. J. Synth. Org. Chem. 2004, 62, 766-
777.
10.1021/jo0618324 CCC: $37.00 © 2007 American Chemical Society
Published on Web 12/09/2006
162
J. Org. Chem. 2007, 72, 162-172

Di(1-azulenyl)methylium Ion Based Tetracations
SCHEME 1. General Structure of the Violene-Cyanine
We selected di(1-azulenyl)(phenyl- and 2-thienyl)methylium
units (2+ and 3+) for the construction of the hybrid system as
polymethine end groups, due to their high stability and also the
existence of strong absorption in the visible region owing to
the contribution of their cyanine substructure. The 2-thienyl
derivative 3+ might further stabilize the presumed two-electron
reduction state by the contribution of the thienoquinoid sub-
structure instead of the quinoidal form of benzene rings.8,9 The
tert-butyl substituents were introduced into the azulene ring for
the improvement of thermodynamic stabilities and the revers-
ibility of both electrochemical reduction and oxidation upon CV.
As the central π-electron system, we chose a benzene ring with
acetylene spacers for decreasing steric hindrance between the
large cationic centers. Thus, tetracations 4a4+ and 4b4+ were
designed as the first examples of the cyanine-cyanine hybrid
with the general structure in Scheme 4. As illustrated in Scheme
5, tetracations 4a4+ and 4b4+ (Chart 2) exemplify the redox
system for the new hybrid system by the presumed two-electron
transfer.
Hybrid
calized closed-shell polymethine (e.g., cyanine) dyes as end
groups. The hybrid is expected to provide a color of a cyanine
dye by an overall two-electron transfer, as illustrated by the
general structure in Scheme 1. In contrast to the violene-type
redox system, both the colored and the discolored species for
the hybrid consist of closed-shell systems. Thus, the persistency
for the electrochromic system will be improved by the hybrid
system. However, the system will not exhibit multiple color
changes important for the construction of polyelectrochromic
materials.
Recently, we have proposed the general structure for the
construction of the system with multiple color changes, as shown
in Schemes 2-4.4 The system is consistent with the polymethine
dye containing the moieties of either one or two polymethine
dyes as end groups. In the case of the system illustrated in
Scheme 2, the two-step redox reaction is expected by the
captodative substituents effect,5 similar to those of violene-type
electrochromics. Di(1-azulenyl)(6-azulenyl)methylium hexafluo-
rophosphates, which were recently reported by us, would
exemplify such a system.4,6
In order to examine the effect of the hybrid structure on
tetracations 4a4+ and 4b4+, a series of di- and monocations 5a2+
,
5b2+ and 6a+, 6b+ were also synthesized. Dications 5a2+ and
5b2+ are typical examples for the violene-cyanine hybrid in
the point of the connection of two polymethine substructures
to the two terminals of the violene-like π-electron core (Chart
3). Monocations 6a+ and 6b+ can be considered as the parent
compounds of the multicharged methylium compounds (Chart
4).10
When both end groups are replaced by the polymethine dyes,
a defect of the conjugation will arise in the core cyanine unit
because the core subunit is constructed by an odd number of
polymethine chains (Scheme 3). The system should also
represent the redox properties with color changes. However,
such a defect should decrease the stability of the redox cycle.
We proposed the connection of two such units by a violene
chain to improve the redox stability (Scheme 4). For this reason,
the system in Scheme 4 should be called a violene-cyanine-
cyanine hybrid. However, we called such a system a cyanine-
cyanine hybrid since the colored cyanine system is converted
into another cyanine system by two-electron transfer. Both the
colored species in Scheme 4 should be represented by the
closed-shell systems, from which higher persistency is expected.
The scope of this new structural principle is demonstrated by
two examples with oxidation levels varying from +4 to 0.
Synthesis. The reaction of 2 molar amounts of 1,6-di-tert-
butylazulene (8)11 with 4-ethynylbenzaldehyde (7a)12 and
5-ethynylthiophene-2-carbaldehyde (7b),13 which were prepared
starting from 4-bromobenzaldehyde and 5-bromothiophene-2-
carbaldehyde, respectively, in acetic acid at room temperature
afforded bis(3,6-di-tert-butyl-1-azulenyl)(4-ethynylphenyl- and
5-ethynyl-2-thienyl)methanes (9a and 9b) in 82 and 79% yield,
respectively (Scheme 6).
Preparation of the corresponding tetrahydro derivatives 11a
and 11b for the precursors of tetracations was accomplished
by a simple one-pot reaction involving repeated Pd-catalyzed
alkynylation of 1,2,4,5-tetraiodobenzene (10)14 with 9a and 9b
(7) (a) Ito, S.; Morita, N.; Asao, T. Bull. Chem. Soc. Jpn. 1995, 68, 1409-
1436. (b) Ito, S.; Kikuchi, S.; Morita, N.; Asao, T. Bull. Chem. Soc. Jpn.
1999, 72, 839-849. (c) Ito, S.; Kikuchi, S.; Morita, N.; Asao, T. J. Org.
Chem. 1999, 64, 5815-5821. (d) Ito, S.; Morita, N.; Asao, T. Bull. Chem.
Soc. Jpn. 2000, 73, 1865-1874.
(8) Ito, S.; Kikuchi, S.; Okujima, T.; Morita, N.; Asao, T. J. Org. Chem.
2001, 66, 2470-2479.
(9) (a) Takahashi, K.; Nihira, T. Tetrahedron Lett. 1989, 30, 5903-5906.
(b) Takahashi, K.; Nihira, T.; Tomitani, K. J. Chem. Soc., Chem. Commun.
1993, 1617-1619.
(10) These results were presented, in part, at (a) 2005 International
Chemical Congress of Pacific Basin Societies, Honolulu, Hawaii, December
2005 (Ito, S.; Akimoto, K.; Morita, N. Program Number 1539) and (b) The
7th International Symposium on Functional π-Electron Systems, Osaka,
Japan, May 2006 (Ito, S.; Akimoto, K.; Morita, N. Book of Abstracts,
PS-A63).
Results and Discussion
Structural Principle. For the construction of the new hybrid
system illustrated in Scheme 4, it is very important to select
highly colored polymethine end groups with high stability.
Recently, we have reported the synthesis of tri(1-azulenyl)-
methylium hexafluorophosphates (1+‚PF6-) with high thermo-
dynamic stabilities by hydride abstraction of the corresponding
hydrocarbon derivatives (Chart 1).7 The high stability is
attributed to the large π-conjugate effect of 1-azulenyl groups
with cationic carbon (e.g., 1′).
(11) Ito, S.; Morita, N.; Asao, T. Bull. Chem. Soc. Jpn. 1995, 68, 1409-
1436.
(12) (a) Austin, W. B.; Bilow, N.; Kelleghan, W. J.; Lau, K. S. Y.
J. Org. Chem. 1981, 46, 2280-2286. (b) Thorand, S.; Krause, N. J. Org.
Chem. 1998, 63, 8551-8553. (c) Vicente, M. G. H.; Shetty, S. J.;
Wickramasinghe, A.; Smith, K. M. Tetrahedron Lett. 2000, 41, 7623-
7627.
(13) Wu, I.-Y.; Lin, J. T.; Luo, J.; Li, C.-S.; Tsai, C.; Wen, Y. S.; Hsu,
C.-C.; Yeh, F.-F.; Liou, S. Organometallics 1998, 17, 2188-2198.
(14) Mattern, D. L. J. Org. Chem. 1984, 49, 3051-3053.
(5) (a) Stella, L.; Janousek, Z.; Mere´nyi, R.; Viehe, H. G. Angew. Chem.,
Int. Ed. Engl. 1978, 17, 691-692. (b) Viehe, H. G.; Mere´nyi, R.; Stella,
L.; Janousek, Z. Angew. Chem., Int. Ed. Engl. 1979, 18, 917-932. (c) Viehe,
H. G.; Janousek, Z.; Mere´nyi, R. Acc. Chem. Res. 1985, 18, 148-154.
(6) Ito, S.; Kubo, T.; Morita, N.; Ikoma, T.; Tero-Kubota, S.; Tajiri, A.
J. Org. Chem. 2003, 68, 9753-9762.
J. Org. Chem, Vol. 72, No. 1, 2007 163

Ito et al.
SCHEME 2. General Structure of the Cyanine-Cyanine Hybrid with a Cyanine Unit at One Terminal
SCHEME 3. General Structure of the Cyanine-Cyanine Hybrid with a Cyanine Unit at Both Terminals
SCHEME 4. Improved Structure of the Cyanine-Cyanine Hybrid with a Cyanine Unit at Both Terminals
CHART 1
SCHEME 5
under Sonogashira-Hagihara conditions.15 The cross-coupling
reaction of 10 with 9a using Pd(PPh3)4 as a catalyst and
subsequent chromatographic purification of the reaction mixture
on silica gel afforded the desired 11a in 33% yield along with
trisadduct 12a in 9% yield (Chart 5). Likewise, the reaction of
10 with 9b afforded the desired 11b in 33% yield together with
trisadduct 12b in 21% yield (Chart 5).
The cross-coupling reaction of 1,4-diiodobenzene (13) with
9a and 9b in the presence of the Pd catalyst afforded bisadducts
14a (76%) and 14b (54%), respectively. Compounds 16a and
16b for the precursors of monocations were also obtained by
the similar Pd-catalyzed reaction of iodobenzene (15) with 9a
and 9b in 64 and 53% yield, respectively (Chart 6). Diacetylene
derivatives (17a and 17b) were isolated as byproducts in some
reactions because of the homocoupling of the starting acetylenes
9a and 9b under the Pd-catalyzed reaction conditions
(Chart 7).16
(15) Sonogashira, K. Cross-Coupling Reactions to sp Carbon Atoms. In
Metal-Catalyzed Cross-Coupling Reactions; Diederich, F., Stang, P. J., Eds.;
Wiley-VCH: Weinheim, Germany, 1998; Chapter 5, pp 203-229. (b)
Sonogashira, K. Coupling Reactons Between sp2 and sp Carbon Centers.
In ComprehensiVe Organic Synthesis; Trost, B. M., Fleming, I., Eds.;
Pergamon Press: Oxford, U.K., 1991; Vol. 3, Chapter 2.4, pp 521-549.
(c) Takahashi, S.; Kuroyama, Y.; Sonogashira, K.; Hagihara, N. Synthesis
1980, 627-630. (d) Sonogashira, K.; Tohda, Y.; Hagihara, N. Tetrahedron
Lett. 1975, 4467-4470.
(16) (a) Rossi, R.; Carpita, A.; Bigelli, C. Tetrahedron Lett. 1985, 26,
523-526. (b) Takahashi, A.; Endo, T.; Nozoe, S. Chem. Pharm. Bull. 1992,
40, 3181-3184. (c) Li, J.-H.; Liang, Y.; Xie, Y.-X. J. Org. Chem. 2005,
70, 4393-4396.
164 J. Org. Chem., Vol. 72, No. 1, 2007

Di(1-azulenyl)methylium Ion Based Tetracations
CHART 2
CHART 5
CHART 3
CHART 4
CHART 6
SCHEME 6. Preparation of Bis(3,6-di-tert-butyl-1-azulenyl)
(4-ethynylphenyl- and 5-ethynyl-2-thienyl)methanes (9a and
9b)
addition of a 60% aqueous HPF6 solution, yielded 4a4+ (80%)
as tetrakis(hexafluorophosphate). Likewise, the oxidation of 14a
and 16a with 2 and 1 molar amounts of DDQ, followed by the
addition of an HPF6 solution, afforded the corresponding bis-
and mono(hexafluorophosphate)s 5a2+‚2PF6- and 6a+‚PF6- in
78 and 87% yields, respectively. Similarly, the reaction of 11b,
14b, and 16b with DDQ afforded the corresponding tetra-, bis-,
and monocations 4b4+ (87%), 5b2+ (75%), and 6b+ (86%) as
tetrakis-, bis-, and mono(hexafluorophosphate)s, after the treat-
ment with an HPF6 solution.
The synthesis of tetra-, di-, and monocations 4a4+, 4b4+, 5a2+
,
5b2+, and 6a+, 6b+ was accomplished by the hydride abstraction
from the corresponding hydro derivatives 11a, 11b, 14a, 14b,
and 16a, 16b.7 The reaction of 11a with 4 molar amounts of
DDQ in dichloromethane at room temperature, followed by an
These new salts 4a4+, 4b4+‚4PF6-, 5a2+, 5b2+‚2PF6-, and
6a+, 6b+‚PF6- are stable, deep-colored crystals and are storable
in the crystalline state. Carbocations which have more than four
J. Org. Chem, Vol. 72, No. 1, 2007 165

Ito et al.
CHART 7
cationic centers are rare species, and isolable compounds are
very little. Tetrahedrally arrayed tetracation,17 which is stable
only at low temperature, was generated by Olah et al. The
preparation of trications utilizing 2-amino-5-thienyl-substituted
methylium units was reported by Hartmann et al.18 Recently,
Rathore et al.19 prepared isolable tetra- and hexatrityl cations
utilizing tetraphenylmethane and hexaphenylbenzene as plat-
forms. The tetracations 4a4+ and 4b4+ are two of a new
multicharged methylium compounds with considerably high
stability.
Spectroscopic Properties. Tetra-, di-, and monocations 4a4+
,
4b4+, 5a2+, 5b2+, and 6a+, 6b+ were fully characterized by the
FIGURE 1. UV-vis spectra of (a) 4a4+ (solid line), 5a2+ (broken
line), and 6a+ (dotted line); (b) 4b4+ (solid line), 5b2+ (broken line),
and 6b+ (dotted line) in acetonitrile.
spectral data as shown in the Experimental Section. Mass spectra
-
-
of monocation salts 6a+‚PF6 and 6b+‚PF6 ionized by ESI
showed the correct (M - PF6)+ ion peaks, which indicated the
cationic structures of these products. Dication salts 5a2+‚2PF6
-
TABLE 1. Longest Wavelength Absorption Maxima (nm) and
Their Coefficients of Cations 4a4+, 4b4+, 5a2+, 5b2+, and 6a+, 6b+ in
Acetonitrile
and 5b2+‚2PF6 showed the correct (M - PF6)+ and (M -
-
-
2PF6)2+ ion peaks. In the case of tetracation salts 4a4+‚4PF6
and 4b4+‚4PF6-, (M - 2PF6)2+ and (M - PF6)3+ ion peaks
were also obtained in addition to the presumed (M - 4PF6)4+
ion peaks. The characteristic bands of hexafluorophosphate were
observed at 841-843 (strong) and 558 (medium) cm-1 in their
IR spectra, which also supported the cationic structure of these
compounds.
sample
λ
max (log ꢀ)
sample
λ
max (log ꢀ)
ref
4a4+
4b4+
5a2+
5b2+
692 (5.17)
565 (5.07), 699 (5.15)
689 (4.90)
6a+
6b+
2+
687 (4.65)
544 (4.47), 698 (4.58)
681 (4.61)
7a
8
564 (4.85), 700 (4.86)
3+
687 (4.56)
UV-vis spectra of 4a4+, 4b4+, 5a2+, 5b2+, and 6a+, 6b+ in
acetonitrile are shown in Figure 1. As expected by their
polymethine substructures, these salts showed characteristic
charge-transfer absorption in the visible region. Their absorption
maxima (nm) and coefficients (log ꢀ) are summarized in Table
1. The UV-vis spectra of 4b4+, 5b2+, and 6b+ in the visible
region were characterized by two strong absorption bands,
although 4a4+, 5a2+, and 6a+ exhibited an absorption band in
+
TABLE 2. pKR Valuesa and Redox Potentialsb of Tetra-, Di-, and
Monocations 4a4+, 4b4+, 5a2+, 5b2+, and 6a+, 6b+
+ c
red
ox
sample
pKR
E1
E1
4a4+
4b4+
5a2+
5b2+
6a+
8.7 ( 0.1 (7%)
8.1 ( 0.1 (7%)
10.8 ( 0.1 (6%)
9.6 ( 0.1 (3%)
12.3 ( 0.1 (21%)
11.4 ( 0.1 (5%)
-0.68 (-0.65)
-0.61 (-0.58)
-0.70 (-0.68)
-0.63 (-0.62)
-0.70 (-0.68)
-0.65 (-0.63)
+0.93 (+0.91)
+0.95 (+0.93)
+0.93 (+0.92)
+0.96 (+0.94)
+0.93 (+0.91)
+0.96 (+0.94)
6b+
this region. The longest wavelength absorption of 4b4+, 5b2+
,
a The pKR+ values were determined spectrophotometrically in a buffered
solution prepared in 50% aqueous acetonitrile. b Redox potentials were
measured by CV and DPV [V vs Ag/AgNO3, 1 mM in benzonitrile
containing Et4NClO4 (0.1 M), Pt electrode (i.d.: 1.6 mm), scan rate ) 100
mV s-1, and Fc/Fc+ ) +0.15 V]. The peak potentials measured by DPV
are shown in parentheses. c Regenerated absorption maxima (%) of the
cations in the visible region by immediate acidification of the alkaline
solution with HCl are shown in parentheses.
and 6b+ showed a bathochromic shift of 7, 11, and 11 nm,
respectively, compared to those of 4a4+, 5a2+, and 6a+, similar
to the results of the carbocations between 2+ and 3+ stabilized
by 1-azulenyl groups. Dications 5a2+ and 5b2+ and tetracations
4a4+ and 4b4+ exhibited only a slight bathochromic shift
compared to those of monocations 6a+ and 6b+. The extinction
coefficients of the dications 5a2+ and 5b2+ and tetracations 4a4+
and 4b4+ are approximately 2- and 4-fold as large as those of
monocations 6a+ and 6b+, respectively.
di-, and monocations were determined spectrophotometrically
in a buffer solution prepared in 50% aqueous acetonitrile. The
KR+ scale is defined by the equilibrium constant for the reaction
of a carbocation with a water molecule (KR+ ) [ROH][H3O+]/
Thermodynamic Stability. As a measure of the thermody-
+
namic stability of the carbocations, the pKR values of tetra-,
+
+
[R+]). Therefore, the larger pKR index value (pKR ) -log
(17) (a) Head, N. J.; Prakash, G. K. S.; Bashir-Hashemi, A.; Olah,
G. A. J. Am. Chem. Soc. 1995, 117, 12005-12006. (b) Heagy, M. D.; Wang,
Q.; Olah, G. A.; Prakash, G. K. S. J. Org. Chem. 1995, 60, 7351-7354.
(18) Noack, A.; Schro¨der, A.; Hartmann, H.; Rohde, D.; Dunsch, L. Org.
Lett. 2003, 5, 2393-2396.
(19) Rathore, R.; Burns, C. L.; Guzei, I. A. J. Org. Chem. 2004, 69,
1524-1530.
KR+) indicates higher stability of the carbocation.
+
The values are summarized in Table 2. The pKR value of
6a+ is almost equal to that of 2+ (pKR ) 12.4).7a In contrast
+
to the stabilizing ability of the 2-thienyl substituent, monocation
6b+ is less stable than the corresponding benzylcation 6a+,
166 J. Org. Chem., Vol. 72, No. 1, 2007

Di(1-azulenyl)methylium Ion Based Tetracations
similar to the results of the cations between 2+ and 3+ (pKR
) 11.8)8 stabilized by 1-azulenyl groups.
+
In the case of the dications, the two cation units could be
neutralized by two steps because of the through-bond electro-
static repulsion of the two positively charged units. However,
the two cation units in the dications 5a2+ and 5b2+ were
neutralized simultaneously at pH 10.8 ( 0.1 and 9.6 ( 0.1,
respectively, although the titration curve for the neutralization
caused some fluctuation, probably due to the instability of the
neutralized species. The pH should correspond to the average
of the pKR2+ values and the pKR+ values of the dications 5a2+
and 5b2+. Thus, dications 5a2+ and 5b2+ exhibit still high
thermodynamic stability like those of the corresponding mono-
cations 6a+ and 6b+, although some destabilization is observed.
In the case of the tetracations 4a4+ and 4b4+, four cation units
were neutralized simultaneously at pH 8.7 ( 0.1 and 8.1 (
0.1, respectively. The pH should correspond to the average of
+
the values pKR4+, pKR3+, pKR2+, and pKR of the tetracations
4a4+ and 4b4+. Thus, tetracations 4a4+ and 4b4+ are even more
destabilized than monocations 6a+ and 6b+ by 3.6 and 3.3 pK
units and dications 5a2+ and 5b2+ by 1.5 and 1.8 pK units. The
destabilization in dications and tetracations could be explained
by the existence of some intramolecular interaction that arises
from the conjugation among the cation units through the central
benzene ring, although it might be attributable to the difference
of solvation to the sterically congested positive site in dications
and tetracations.
FIGURE 2. Cyclic voltammograms of (a) reduction and (b) oxidation
of tetracation 4a4+ (1 mM) in benzonitrile containing Et4NClO4 (0.1
M) as a supporting electrolyte; scan rate ) 100 mV s-1
.
The neutralization of these cations was not completely
reversible. This is attributable to the instability of the neutralized
products under the conditions of the pKR+ measurement. After
the measurement, acidification of the alkaline solutions of 4a4+
,
4b4+, 5a2+, 5b2+, and 6a+, 6b+ with HCl regenerated the
characteristic absorption in the visible region in 3-21%
(Table 2).
Redox Potentials. To clarify the electrochemical property,
the redox behavior of tetra-, di-, and monocations 4a4+, 4b4+
,
5a2+, 5b2+, and 6a+, 6b+ was examined by cyclic voltammetry
(CV) and differential pulse voltammetry (DPV). The first redox
potentials (in volts vs Ag/AgNO3) of 4a4+, 4b4+, 5a2+, 5b2+
,
and 6a+, 6b+ are summarized in Table 2. The redox potentials
observed at higher potentials are summarized in the Supporting
Information. The first oxidation and reduction waves of 4a4+
and 4b4+ are shown in Figures 2 and 3, and those of 5a2+, 5b2+
and 6a+, 6b+ are summarized in the Supporting Information.
As seen from Table 2, the electrochemical reduction of
monocation 6a+ showed a reversible wave at -0.70 V and an
irreversible wave at -1.54 V upon CV due to the formation of
a radical and an anionic species. The reduction potentials of
tetracation 4a4+ (E1 ) -0.68 V) and dication 5a2+ (E1
)
red
red
-0.70 V) are almost equal to those of monocation 6a+, in
contrast to the decreasing pKR values with increasing cation
FIGURE 3. Cyclic voltammograms of (a) reduction and (b) oxidation
of tetracation 4b4+ (1 mM) in benzonitrile containing Et4NClO4 (0.1
+
units. Apparently, the CV waves of tetracation 4a4+ and dication
5a2+ exhibit more current compared to the first reduction wave
of monocation 6a+ in the same concentration. Therefore, the
first reduction wave of tetracations 4a4+ and dication 5a2+ could
be concluded to four- and two-electron transfer in one step (at
a constant potential) to generate neutral species.
M) as a supporting electrolyte; scan rate ) 100 mV s-1
.
tetracations were reduced in one step upon CV and DPV; this
indicates that the presumed redox interaction among the cation
units should be rather small.
The electrochemical oxidation of monocation 6a+ showed a
reversible wave at +0.93 V upon CV, due to the oxidation of
an azulene ring to give a dication radical. These redox potentials
The first reduction potentials of 4b4+, 5b2+, and 6b+ are
slightly less negative compared to those of 4a4+, 5a2+, and 6a+;
this indicates the electrochemical destabilization of the methyl
cations by the 2-thienyl substituents as similar to the results on
ox
are almost equal to those of analogous benzyl cation 2+ (E1
) +0.87 V),7a comparable with the results of pKR values
+
+
the pKR measurements. Thus, all the cation units up to
(Table 2). The oxidation of tetracations 4a4+ and dication 5a2+
J. Org. Chem, Vol. 72, No. 1, 2007 167

Ito et al.
also exhibited a wave at +0.93 V upon CV. The wave should
be ascribed to the oxidation of four and two azulene rings to
generate octa- and tetracationic species, respectively, since the
wave is in similar potential ranges with those of monocation
6a+ and exhibits more current compared to the first oxidation
wave of monocation 6a+ in the same concentration. The first
oxidation potentials of 4b4+, 5b2+, and 6b+ are slightly more
positive compared to those of 4a4+, 5a2+, and 6a+, similar to
reduction. However, these cations represented multiple-electron
transfer as a function of the substituted di(1-azulenyl)methylium
units and also exhibited color change during the electrochemical
reduction, although the reversibility of the redox reaction upon
electrochromic measurements was rather low for all cases. The
electrochemical behavior was not ideal for the presumed
cyanine-cyanine hybrid, probably due to the less effective
electrochemical interaction among the positive charges. This
might be attributable to the disadvantage of conjugation of the
positively charged units by the central benzene ring, although
those of cations 2+ and 3+ (E1 ) +0.91 V)8 stabilized by
ox
1-azulenyl groups.
+
Electrochromic Analysis. Visible spectra of 4a4+, 4b4+
,
measurement of the pKR value of dications and tetracations
5a2+, 5b2+, and 6a+, 6b+ were monitored to clarify the
formation of a colored cyanine-type substructure under the
electrochemical reduction conditions, although the CV analysis
revealed the less effective electrochemical interaction among
all the cation units in the dications and tetracations. A constant-
exhibited the existence of some interaction among the cation
units. However, tetracations which we have prepared are highly
stable despite their tetracationic structure. Thus, the use of di-
(1-azulenyl)methylium units as stabilized redox-active polymeth-
ine units would be highly effective in the point of their high
stability and their strong absorption in the visible region with
their redox activity. Preparations of the polycationic species
using the di(1-azulenyl)methylium units with different π-electron
core systems are now in progress.
current reduction was applied to the solutions of 4a4+, 4b4+
,
5a2+, 5b2+, and 6a+, 6b+ with a platinum mesh for working
electrode and a wire counter electrode.
When the visible spectra of 4a4+ were measured in benzoni-
trile containing Et4NClO4 (0.1 M) as a supporting electrolyte
at room temperature under the electrochemical reduction condi-
tions, the strong absorption at 692 nm in the visible region of
4a4+ was gradually decreased (see Supporting Information). The
color of the solution of 4a4+ gradually changed from dark green
to yellow during the electrochemical reduction. However, the
reverse oxidation of the pale-colored solution did not regenerate
the spectrum of the tetracation 4a4+ (regeneration 35%)
completely, although good reversibility was observed upon CV.
Several acetylenes with pyridinyl end groups have been reported
to afford extremely sensitive reduction products.20 Therefore,
the instability of the reduced species might be attributable to
the facile polymerization of the neutral radical formed by the
electrochemical reduction with acetylene spacers.
Experimental Section
General. For general and electrochemical measurement details,
1
see Supporting Information. The peak assignment of H and 13C
NMR spectra reported was accomplished by decoupling, H-H
COSY, NOE, HMQC, and/or HMBC experiments.
Bis(3,6-di-tert-butyl-1-azulenyl)(4-ethynylphenyl)methane (9a).
A mixture of 1,6-di-tert-butylazulene (8) (1.37 g, 5.70 mmol) and
4-ethynylbenzaldehyde (7a) (371 mg, 2.85 mmol) in acetic acid
(34 mL) was stirred at room temperature for 24 h. The reaction
mixture was diluted with CH2Cl2. The organic layer was washed
with a 5% NaHCO3 solution and water, dried over MgSO4, and
concentrated under reduced pressure. The residue was purified by
column chromatography on silica gel with CH2Cl2 to afford 9a (1.39
g, 82%): blue crystals; mp 155.6-158.1 °C dec (CH2Cl2/methanol);
MS (ESI negative) m/z (relative intensity) 592 (M-, 100%), 591
(M- - H, 62); HRMS calcd for C45H52- 592.4075, found 592.4017;
IR (KBr disk) νmax 3320 (m, CtC-H), 3303 (w, CtC-H), 2965,
2109 (w, CtC), 1578, 1364, 1229, 835 cm-1; UV-vis (CH2Cl2)
The dark green color of the solution of 5a2+ and 6a+ also
changed to a yellow one under the reduction conditions. Absence
of the isosbestic point suggests the decomposition of the fully
reduced ones of 5a2+ and 6a+ under the electrochemical
conditions. The reverse oxidation of the yellow-colored solution
slightly regenerated the UV-vis spectra of the deep-colored
5a2+ (regeneration 13%) and 6a+ (regeneration 4%), respec-
tively. Therefore, the color change of the solution should
correspond to the formation of radical species in multiple-
electron transfer, as observed upon CV.
We also tried electrochemical reduction of 4b4+, 5b2+, and
6b+ under visible spectral monitoring. We anticipated that the
formation of the thienoquinoid forms during the redox reaction
might improve the reversibility. In these cases, however, we
could not also obtain any evidence of the formation of a colored
cyanine-type structure in the two-electron reduction of tetraca-
tion 4b4+. Low reversibility for all the reduction of 4b4+
(regeneration 30%), 5b2+ (regeneration 22%), and 6b+ (regen-
eration 10%) also suggests the formation of the neutral radical
species for the presumed reduction products under the conditions
of the visible spectral measurements.
λ
max, nm (log ꢀ) 245 (4.63), 285 (4.90), 302 (4.87), 341 sh (3.96),
345 sh (3.99), 356 (4.05), 374 (3.98), 560 sh (2.68), 609 (2.82),
1
664 sh (2.74), 744 sh (2.22); H NMR (400 MHz, CDCl3) δ )
8.55 (d, 2H, J ) 10.7 Hz, H4), 8.13 (d, 2H, J ) 10.6 Hz, H8), 7.35
(d, 2H, J ) 7.8 Hz, H3′,5′), 7.34 (s, 2H, H2), 7.17 (dd, 2H, J )
10.7, 1.9 Hz, H5), 7.07 (d, 2H, J ) 7.8 Hz, H2′,6′), 7.06 (dd, 2H, J
) 10.6, 1.9 Hz, H7), 6.62 (s, 1H, CH), 3.00 (s, 1H, Hâ), 1.49 (s,
18H, 3-t-Bu), 1.40 (s, 18H, 6-t-Bu); 13C NMR (100 MHz, CDCl3)
δ ) 160.5, 147.4, 137.7, 136.1, 134.7, 134.6, 134.2, 132.1, 132.0,
129.7, 128.8, 119.3, 119.1, 118.4, 84.1, 76.4, 42.0, 38.2, 33.2 (2C),
31.8. Anal. Calcd for C45H52: C, 91.16; H, 8.84. Found: C, 91.10;
H, 9.00.
Bis(3,6-di-tert-butyl-1-azulenyl)(5-ethynyl-2-thienyl)-
methane (9b). The same procedure as for the preparation of 9a
was adopted here. The reaction of 8 (1.84 g, 7.65 mmol) with
4-ethynylthiophene-2-carbaldehyde (7b) (520 mg, 3.82 mmol) in
acetic acid (46 mL) at room temperature for 24 h followed by
column chromatography on silica gel with hexane and toluene
afforded 9b (1.81 g, 79%): blue crystals; mp 143.5-146.2 °C dec
(methanol/water); MS (ESI negative) m/z (relative intensity) 597
(M- - H, 100%); HRMS calcd for C43H50S- - H 597.3560, found
597.3565; IR (KBr disk) νmax 3310 (w, CtC-H), 3279 (w, Ct
C-H), 2965, 2101 (w, CtC), 1578, 1364 cm-1; UV-vis (CH2-
Cl2) λmax, nm (log ꢀ) 245 (4.52), 287 (4.90), 301 sh (4.86), 340 sh
(4.03), 347 (4.05), 356 (4.07), 374 (3.99), 560 sh (2.67), 606 (2.78),
Conclusion
The first examples for the cyanine-cyanine hybrid prepared
by the general structure in Scheme 4 did not exhibit the
presumed multiple color change during the electrochemical
1
660 sh (2.69), 731 sh (2.20); H NMR (400 MHz, CDCl3) δ )
(20) Hu¨nig, S.; Berneth, H. Top. Curr. Chem. 1980, 92, 1-44.
168 J. Org. Chem., Vol. 72, No. 1, 2007
8.56 (d, 2H, J ) 10.6 Hz, H4), 8.22 (d, 2H, J ) 10.6 Hz, H8), 7.54

Di(1-azulenyl)methylium Ion Based Tetracations
(s, 2H, H2), 7.19 (dd, 2H, J ) 10.6, 1.8 Hz, H5), 7.12 (dd, 2H, J )
10.6, 1.8 Hz, H7), 7.06 (d, 1H, J ) 3.7 Hz, H4′), 6.77 (s, 1H, CH),
6.47 (d, 1H, J ) 3.7 Hz, H3′), 3.24 (s, 1H, Hâ), 1.51 (s, 18H, 3-t-
Bu), 1.41 (s, 18H, 6-t-Bu); 13C NMR (100 MHz, CDCl3) δ ) 160.6,
154.2, 137.8, 135.5, 134.7, 134.4, 134.3, 132.9, 131.8, 129.2, 125.0,
119.8, 119.6, 118.7, 80.5, 77.8, 38.2, 37.4, 33.2, 32.2, 31.8. Anal.
Calcd for C43H50S: C, 86.23; H, 8.41; S, 5.35. Found: C, 86.15;
H, 8.59; S, 5.30.
General Procedure for the Pd-Catalyzed Reaction of 9a and
9b with Aryl Iodides (10, 13, and 15). To a degassed solution of
9a and 9b, aryl iodides (10, 13, and 15), and CuI in triethylamine
and toluene was added tetrakis(triphenylphosphine)palladium(0).
The resulting mixture was stirred at room temperature for 24 h
under an Ar atmosphere. The reaction mixture was poured into a
5% NH4Cl solution and extracted with CH2Cl2. The organic layer
was washed with brine, dried over MgSO4, and concentrated under
reduced pressure. The products were isolated by column chroma-
tography on silica gel and/or gel permeation chromatography (GPC)
with CHCl3.
1,2,4,5-Tetrakis{4-[bis(3,6-di-tert-butyl-1-azulenyl)methyl]-
phenylethynyl}benzene (11a). The general procedure was followed
by using 9a (400 mg, 0.675 mmol), 1,2,4,5-tetraiodobenzene (10)
(98 mg, 0.17 mmol), CuI (14 mg, 0.073 mmol), tetrakis(triph-
enylphosphine)palladium(0) (40 mg, 0.035 mmol), triethylamine
(8 mL), and toluene (18 mL) at room temperature for 24 h.
Chromatographic purification on silica gel with 50% CH2Cl2/hexane
and GPC afforded 11a (136 mg, 33%), 1-iodo-2,4,5-tris{4-[bis-
(3,6-di-tert-butyl-1-azulenyl)methyl]phenylethynyl}benzene (12a)
(30 mg, 9%), and 4,4′-bis[bis(3,6-di-tert-butyl-1-azulenyl)methyl]-
diphenyldiacetylene (17a) (71 mg, 18%).
(C3′,5′), 126.0 (C2, C4, or C5), 125.5 (C2, C4, or C5), 119.9 (C1′ or
C4′), 119.8 (C1′ or C4′), 119.7 (C1′ or C4′), 119.3 (C7′′), 118.4 (C5′′),
99.3 (C1), 96.5 (Câ), 95.5 (Câ), 95.3 (Câ), 90.6 (CR), 86.5 (CR),
86.3 (CR), 42.1 (CH), 38.2 (s, 6′′-t-Bu), 33.2 (s, 3′′-t-Bu), 32.2 (q,
3′′-t-Bu), 31.8 (q, 6′′-t-Bu). Anal. Calcd for C141H155I‚1/2H2O: C,
85.29; H, 7.92. Found: C, 85.20; H, 8.10.
17a: blue crystals; mp 222.5-224.9 °C dec (methanol); MS (ESI
negative) m/z (relative intensity) 1182 (M- - H, 100%); HRMS
calcd for C90H102- - H 1181.7909, found 1181.7911; IR (KBr disk)
ν
max 2965, 2213 (w, CtC), 2145 (w, CtC), 1576, 833 cm-1; UV-
vis (CH2Cl2) λmax, nm (log ꢀ) 243 (4.80), 288 (5.08), 301 (5.08),
345 sh (4.55), 356 (4.51), 374 (4.37), 563 sh (2.99), 609 (3.12),
663 sh (3.03), 743 sh (2.47); H NMR (400 MHz, CDCl3) δ )
1
8.55 (d, 4H, J ) 10.7 Hz, H4′), 8.12 (d, 4H, J ) 10.6 Hz, H8′),
7.37 (d, 4H, J ) 8.2 Hz, H2,6), 7.33 (s, 4H, H2′), 7.17 (dd, 4H, J )
10.7, 1.8 Hz, H5′), 7.07 (d, 4H, J ) 8.2 Hz, H3,5), 7.07 (dd, 4H, J
) 10.6, 1.8 Hz, H7′), 6.61 (s, 2H, CH), 1.49 (s, 36H, 3′-t-Bu), 1.40
(s, 36H, 6′-t-Bu); 13C NMR (100 MHz, CDCl3) δ ) 160.5, 147.9,
137.8, 136.1, 134.7, 134.6, 134.2, 132.3, 132.1, 129.6, 128.9, 119.3,
118.9, 118.4, 81.8, 73.5, 42.1, 38.2, 33.2, 32.2, 31.8. Anal. Calcd
for C90H102‚2H2O: C, 88.62; H, 8.76. Found: C, 88.56; H, 8.84.
1,2,4,5-Tetrakis{5-[bis(3,6-di-tert-butyl-1-azulenyl)methyl]-2-
thienylethynyl}benzene (11b). The general procedure was followed
by using 9b (404 mg, 0.675 mmol), 10 (98 mg, 0.17 mmol), CuI
(13 mg, 0.068 mmol), tetrakis(triphenylphosphine)palladium(0) (39
mg, 0.034 mmol), triethylamine (4 mL), and toluene (8 mL) at room
temperature for 24 h. Chromatographic purification on silica gel
with 50% toluene/hexane and GPC afforded 11b (137 mg, 33%)
and 1-iodo-2,4,5-tris{5-[bis(3,6-di-tert-butyl-1-azulenyl)methyl]-2-
thienylethynyl}benzene (12b) (69 mg, 21%).
11a: blue crystals; mp 217.7-220.6 °C dec (toluene/hexane);
MS (MALDI TOF) m/z 2439.61 (M+), found 2439.44; IR (KBr
disk) νmax 2963, 2205 (w, CtC), 1576, 1364, 833 cm-1; UV-vis
(CH2Cl2) λmax, nm (log ꢀ) 241 (5.12), 284 (5.41), 288 sh (5.41),
300 (5.42), 323 (5.21), 346 sh (5.01), 356 (5.00), 373 (4.93), 397
sh (4.59), 563 sh (3.27), 609 (3.40), 663 sh (3.31), 746 sh (2.79);
1H NMR (400 MHz, CDCl3) δ ) 8.53 (d, 8H, J ) 10.7 Hz, H4′′),
8.12 (d, 8H, J ) 10.6 Hz, H5′′), 7.70 (s, 2H, H3,6), 7.41 (d, 8H, J
) 8.3 Hz, H2′,6′), 7.33 (s, 8H, H2′′), 7.15 (dd, 8H, J ) 10.7, 1.8 Hz,
H5′′), 7.08 (d, 8H, J ) 8.3 Hz, H3′,5′), 7.05 (dd, 8H, J ) 10.6, 1.8
Hz, H7′′), 6.60 (s, 4H, CH), 1.46 (s, 72H, 3′′-t-Bu), 1.39 (s, 72H,
6′′-t-Bu); 13C NMR (100 MHz, CDCl3) δ ) 160.4, 147.3, 137.7,
136.2, 135.2, 134.7, 134.5, 134.2, 132.1, 131.6, 129.8, 128.9, 125.0,
120.1, 119.3, 118.3, 95.7, 87.2, 42.1, 38.2, 33.2, 32.2, 31.8. Anal.
Calcd for C186H206‚H2O: C, 90.83; H, 8.52. Found: C, 90.74; H,
8.70.
11b: green crystals; mp 212.4-214.6 °C dec (hexane/ethanol);
MS (MALDI TOF) m/z 2463.44 (M+), found 2463.25; IR (KBr
disk) νmax 2965, 2197 (w, CtC), 1578, 1364, 833 cm-1; UV-vis
(CH2Cl2) λmax, nm (log ꢀ) 242 (5.10), 283 (5.42), 300 (5.39), 347
sh (5.07), 357 (5.13), 373 sh (5.01), 408 sh (4.77), 429 sh (4.65),
1
562 sh (3.40), 605 (3.50), 660 sh (3.42), 739 sh (2.96); H NMR
(400 MHz, CDCl3) δ ) 8.53 (d, 8H, J ) 10.6 Hz, H4′′), 8.20 (d,
8H, J ) 10.6 Hz, H8′′), 7.51 (s, 8H, H2′′), 7.45 (s, 2H, H3,6), 7.15
(dd, 8H, J ) 10.6, 1.7 Hz, H5′′), 7.10 (dd, 8H, J ) 10.6, 1.7 Hz,
H7′′), 6.98 (d, 4H, J ) 3.7 Hz, H3′), 6.75 (s, 4H, CH), 6.41 (d, 4H,
J ) 3.7 Hz, H4′′), 1.47 (s, 72H, 3′′-t-Bu), 1.39 (s, 72H, 6′′-t-Bu);
13C NMR (100 MHz, CDCl3) δ ) 160.5, 154.6, 137.8, 135.5, 134.7,
134.4, 134.3, 133.8, 132.5, 131.9, 129.3, 125.7, 124.2, 120.8, 119.6,
118.6, 91.0, 89.5, 38.2, 37.6, 33.2, 32.2, 31.8. Anal. Calcd for
C178H198S4: C, 86.70; H, 8.09; S, 5.20. Found: C, 86.41; H, 8.12;
S, 5.10.
12a: blue crystals; mp 209.6-211.0 °C (hexane/ethanol); MS
12b: green crystals; mp 201.9-206.4 °C dec (ethanol/water);
(MALDI TOF) m/z 1975.12 (M+), found 1974.86; IR (KBr disk)
ν
MS (MALDI TOF) m/z 1992.99 (M+), found 1992.76; IR (KBr
disk) νmax 2963, 2197 (w, CtC), 1578, 1364 cm-1; UV-vis (CH2-
Cl2) λmax, nm (log ꢀ) 242 (4.95), 284 (5.29), 301 (5.26), 345 (4.89),
356 sh (4.88), 374 (4.82), 413 sh (4.57), 559 sh (3.15), 605 (3.29),
max 2963, 2213 (w, CtC), 1576, 1364, 833 cm-1; UV-vis (CH2-
Cl2) λmax, nm (log ꢀ) 242 (4.93), 286 sh (5.28), 291 (5.28), 303
(5.30), 345 sh (4.81), 355 (4.82), 375 (4.71), 558 sh (3.10), 610
1
1
(3.25), 663 sh (3.16), 741 sh (2.58); H NMR (600 MHz, CDCl3)
661 sh (3.19), 738 sh (2.60); H NMR (600 MHz, CDCl3) δ )
δ ) 8.56 (d, 2H, J ) 10.7 Hz, H4′′), 8.54 (d, 4H, J ) 10.7 Hz,
H4′′), 8.15 (d, 2H, J ) 10.7 Hz, H8′′), 8.12 (d, 4H, J ) 10.7 Hz,
H8′′), 8.00 (s, 1H, H3 or H6), 7.61 (s, 1H, H3 or H6), 7.44 (d, 2H,
J ) 8.3 Hz, H2′,6′), 7.40 (d, 4H, J ) 8.3 Hz, H2′,6′), 7.35 (s, 2H,
H2′′), 7.32 (s, 4H, H2′′), 7.17 (dd, 2H, J ) 10.7, 1.4 Hz, H5′′), 7.16
(dd, 4H, J ) 10.7, 1.4 Hz, H5′′), 7.11 (d, 2H, J ) 8.3 Hz, H3′,5′),
7.09 (d, 2H, J ) 8.3 Hz, H3′,5′), 7.08 (d, 2H, J ) 8.3 Hz, H3′,5′),
7.07 (dd, 2H, J ) 10.7, 1.4 Hz, H7′′), 7.05 (dd, 4H, J ) 10.7, 1.4
Hz, H7′′), 6.64 (s, 1H, CH), 6.61 (s, 1H, CH), 6.60 (s, 1H, CH),
1.49 (s, 18H, 3′′-t-Bu), 1.47 (s, 18H, 3′′-t-Bu), 1.46 (s, 18H, 3′′-
t-Bu), 1.41 (s, 18H, 6′′-t-Bu), 1.40 (s, 36H, 6′′-t-Bu); 13C NMR
(150 MHz, CDCl3) δ ) 160.4 (C6′′), 147.6 (C1′ or C4′), 147.5 (C1′
or C4′), 147.4 (C1′ or C4′), 141.5 (C3 or C6), 137.7 (C3′′), 136.2 (C2′′),
134.7 (1C and/or 1C, C4′′, C8′′a, and/or C3 or C6), 134.6 (3C and/or
8.56 (d, 2H, J ) 10.6 Hz, H4′′), 8.54 (d, 2H, J ) 10.6 Hz, H4′′),
8.53 (d, 2H, J ) 10.6 Hz, H4′′), 8.23 (d, 2H, J ) 10.6 Hz, H8′′),
8.20 (d, 4H, J ) 10.6 Hz, H8′′), 7.85 (s, 1H, H3 or H6), 7.55 (s, 2H,
H2′′), 7.51 (s, 4H, H2′′), 7.43 (s, 1H, H3 or H6), 7.19 (dd, 2H, J )
10.6, 1.6 Hz, H5′′), 7.16 (dd, 4H, J ) 10.6, 1.6 Hz, H5′′), 7.13 (dd,
2H, J ) 10.6, 1.6 Hz, H7′′), 7.11 (dd, 4H, J ) 10.6, 1.6 Hz, H7′′),
7.11 (d, 1H, J ) 3.6 Hz, H3′), 7.00 (d, 2H, J ) 3.6 Hz, H3′), 6.79
(s, 1H, CH), 6.76 (s, 2H, CH), 6.51 (d, 1H, J ) 3.6 Hz, H4′), 6.42
(d, 2H, J ) 3.6 Hz, H4′), 1.51 (s, 18H, 3′′-t-Bu), 1.48 (s, 18H,
3′′-t-Bu), 1.47 (s, 18H, 3′′-t-Bu), 1.41 (s, 18H, 6′′-t-Bu), 1.40 (s,
36H, 6′′-t-Bu); 13C NMR (150 MHz, CDCl3) δ ) 160.6 (2C, C6′′),
160.5 (C6′′), 155.2 (C2′ or C5′), 155.0 (C2′ or C5′), 154.7 (C2′ or
C5′), 140.7 (C3 or C6), 137.8 (C3′′), 135.5 (C2′′), 134.7 (C4′′), 134.4
(C3′′a or C8′′a), 134.3 (C3′′a or C8′′a), 133.7 (C3 or C6), 132.7 (C3′),
132.6 (C3′), 132.5 (C3′), 131.8 (C8′′), 129.3 (C1′′), 129.2 (2C, C1′′),
129.0 (C2, C4, or C5), 125.7 (2C, C4′), 125.6 (C4′), 125.3 (C2, C4,
or C5), 124.8 (C2, C4, or C5), 120.6 (C2′ or C5′), 120.5 (C2′ or C5′),
1C, C4′′, C8′′a, and/or C3 or C6), 134.5 (2C and/or 1C, C4′′, C8′′a
,
and/or C3 or C6), 134.2 (C3′′a), 132.1 (C8′′), 131.6 (2C, C2′,6′), 131.5
(C2′,6′), 129.8 (C1′′), 129.7 (2C, C1′′), 129.3 (C2, C4, or C5), 128.9
J. Org. Chem, Vol. 72, No. 1, 2007 169

Ito et al.
120.3 (C2′ or C5′), 119.6 (C7′′), 118.6 (C5′′), 98.4 (C1), 94.2 (CR or
Câ), 90.4 (CR or Câ), 90.2 (CR or Câ), 90.1 (CR or Câ), 89.3 (CR or
Câ), 89.2 (CR or Câ), 38.2 (s, 6′′-t-Bu), 37.6 (d, CH), 37.5 (2C, d,
CH), 33.2 (s, 3′′-t-Bu), 32.2 (q, 3′′-t-Bu), 31.8 (q, 6′′-t-Bu). Anal.
Calcd for C135H149IS3: C, 81.29; H, 7.53; S, 4.82. Found: C, 81.45;
H, 7.57; S, 4.72.
) 10.6 Hz, H8), 7.51-7.48 (m, 2H, H2′′,6′′), 7.39 (d, 2H, J ) 8.3
Hz, H3′,5′), 7.36 (s, 2H, H2), 7.33-7.26 (m, 3H, H3′′,4′′,5′′), 7.17 (dd,
2H, J ) 10.6, 1.8 Hz, H5), 7.10 (d, 2H, J ) 8.3 Hz, H2′,6′), 7.07
(dd, 2H, J ) 10.6, 1.8 Hz, H7), 6.63 (s, 1H, CH), 1.50 (s, 18H,
3-t-Bu), 1.41 (s, 18H, 6-t-Bu); 13C NMR (100 MHz, CDCl3) δ )
160.4, 146.9, 137.7, 136.2, 134.7, 134.5, 134.2, 132.1, 131.5 (2C),
129.9, 128.8, 128.3, 128.0, 123.5, 120.3, 119.3, 118.4, 89.8, 88.8,
42.0, 38.2, 33.2, 32.2, 31.8. Anal. Calcd for C51H56: C, 91.56; H,
8.44. Found: C, 91.34; H, 8.68.
Bis(3,6-di-tert-butyl-1-azulenyl)[5-(phenylethynyl)-2-thienyl]-
methane (16b). The general procedure was followed by using 9b
(152 mg, 0.254 mmol), 15 (52 mg, 0.25 mmol), CuI (4.5 mg, 0.024
mmol), tetrakis(triphenylphosphine)palladium(0) (15 mg, 0.013
mmol), triethylamine (3 mL), and toluene (6 mL) at room
temperature for 24 h. Chromatographic purification on silica gel
with 50% toluene/hexane and GPC afforded 16b (91 mg, 53%)
and 5,5′-bis[bis(3,6-di-tert-butyl-1-azulenyl)methyl]di(2-thienyl)-
diacetylene (17b) (14 mg, 9%).
1,4-Bis{4-[bis(3,6-di-tert-butyl-1-azulenyl)methyl]-
phenylethynyl}benzene (14a). The general procedure was followed
by using 9a (202 mg, 0.341 mmol), 1,4-diiodobenzene (13) (57
mg, 0.17 mmol), CuI (6.5 mg, 0.034 mmol), tetrakis(triphenylphos-
phine)palladium(0) (20 mg, 0.017 mmol), triethylamine (3 mL),
and toluene (6 mL) at room temperature for 24 h. Chromatographic
purification on silica gel with 50% CH2Cl2/hexane afforded 14a
(163 mg, 76%): blue crystals; mp 243.9-245.7 °C dec (toluene/
hexane); MS (ESI negative) m/z (relative intensity) 1258 (M- -
-
H, 91%); HRMS calcd for C96H106 - H 1257.8222, found
1257.8228; IR (KBr disk) νmax 2965, 2217 (w, CtC), 1576, 1516,
1364, 833 cm-1; UV-vis (CH2Cl2) λmax, nm (log ꢀ) 237 (4.79),
244 sh (4.77), 285 sh (5.09), 290 sh (5.10), 301 (5.12), 330 sh
(4.82), 339 sh (4.78), 356 sh (4.70), 374 sh (4.48), 559 sh (2.95),
16b: blue crystals; mp 137.2-138.4 °C dec (methanol); MS (ESI
negative) m/z (relative intensity) 673 (M- - H, 100%); HRMS
calcd for C49H54S- - H 673.3873, found 673.3873; IR (KBr disk)
νmax 2963, 1576, 1364 cm-1; UV-vis (CH2Cl2) λmax, nm (log ꢀ)
242 (4.42), 283 sh (4.72), 290 sh (4.73), 302 (4.75), 338 sh (4.25),
355 sh (4.05), 374 (3.88), 554 sh (2.66), 604 (2.78), 656 sh (2.71),
1
609 (3.08), 665 sh (2.99), 746 sh (2.49); H NMR (400 MHz,
CDCl3) δ ) 8.56 (d, 4H, J ) 10.7 Hz, H4′′), 8.14 (d, 4H, J ) 10.6
Hz, H5′′), 7.44 (s, 4H, H2,3,5,6), 7.38 (d, 4H, J ) 8.2 Hz, H2′,6′), 7.35
(s, 4H, H2′′), 7.17 (dd, 4H, J ) 10.7, 1.5 Hz, H5′′), 7.10 (d, 4H, J
) 8.2 Hz, H3′,5′), 7.07 (dd, 4H, J ) 10.6, 1.5 Hz, H7′′), 6.63 (s, 2H,
CH), 1.49 (s, 36H, 3′′-t-Bu), 1.40 (s, 36H, 6′′-t-Bu); 13C NMR (100
MHz, CDCl3) δ ) 160.4, 147.1, 137.7, 136.2, 134.7, 134.6, 134.2,
132.1, 131.5, 131.4, 129.8, 128.9, 123.1, 120.1, 119.3, 118.4, 91.6,
88.6, 42.1, 38.2, 33.2, 32.2, 31.8. Anal. Calcd for C96H106‚H2O:
C, 90.23; H, 8.52. Found: C, 90.54; H, 8.73.
1
736 sh (2.24); H NMR (400 MHz, CDCl3) δ ) 8.57 (d, 2H, J )
10.6 Hz, H4), 8.24 (d, 2H, J ) 10.6 Hz, H8), 7.56 (s, 2H, H2),
7.42-7.45 (m, 2H, H2′′,6′′), 7.27-7.29 (m, 3H, H3′′,4′′,5′′), 7.19 (dd,
2H, J ) 10.6, 1.7 Hz, H5), 7.13 (dd, 2H, J ) 10.6, 1.7 Hz, H7),
7.07 (d, 1H, J ) 3.6 Hz, H4′), 6.80 (s, 1H, CH), 6.52 (d, 1H, J )
3.6 Hz, H3′), 1.52 (s, 18H, 3-t-Bu), 1.42 (s, 18H, 6-t-Bu); 13C NMR
(100 MHz, CDCl3) δ ) 160.6, 154.0, 137.8, 135.5, 134.7, 134.4,
134.3, 131.8 (2C), 131.3, 129.4, 128.3, 128.1, 125.3, 123.2, 121.1,
119.6, 118.6, 92.5, 83.5, 38.2, 37.5, 33.3, 32.2, 31.8. Anal. Calcd
for C49H54S: C, 87.19; H, 8.06; S, 4.75. Found: C, 87.21; H, 8.33;
S, 4.60.
1,4-Bis{5-[bis(3,6-di-tert-butyl-1-azulenyl)methyl]-2-
thienylethynyl}benzene (14b). The general procedure was followed
by using 9b (200 mg, 0.334 mmol), 13 (55 mg, 0.17 mmol), CuI
(6.4 mg, 0.034 mmol), tetrakis(triphenylphosphine)palladium(0) (20
mg, 0.017 mmol), triethylamine (4 mL), and toluene (8 mL) at room
temperature for 24 h. Chromatographic purification on silica gel
with 50% toluene/hexane and GPC afforded 14b (113 mg, 54%):
blue crystals; mp 222.8-226.3 °C dec (methanol); MS (ESI
negative) m/z (relative intensity) 1270 (M- - H, 100%); HRMS
17b: green crystals; mp 175.3-178.3 °C dec (hexane/methanol);
MS (ESI negative) m/z (relative intensity) 1194 (M- - H, 100%);
HRMS calcd for C86H98S2- - H 1193.7037, found 1193.7041; IR
(KBr disk) νmax 2963, 2136 (w, CtC), 1578, 1364 cm-1; UV-vis
(CH2Cl2) λmax, nm (log ꢀ) 243 (4.84), 286 (5.18), 296 sh (5.16),
301 (5.17), 340 sh (4.64), 348 sh (4.65), 358 (4.67), 374 (4.59),
392 sh (4.35), 558 sh (2.97), 606 (3.11), 663 sh (3.01), 736 sh
-
calcd for C92H102S2 - H 1269.7350, found 1269.7357; IR (KBr
disk) νmax 2963, 2201 (w, CtC), 1578, 1364, 833 cm-1; UV-vis
(CH2Cl2) λmax, nm (log ꢀ) 241 (4.79), 284 (5.08), 301 (5.06), 344
sh (4.76), 357 (4.82), 374 sh (4.77), 385 sh (4.67), 559 sh (3.04),
1
(2.47); H NMR (400 MHz, CDCl3) δ ) 8.56 (d, 4H, J ) 10.6
1
605 (3.15), 658 sh (3.07), 739 sh (2.57); H NMR (400 MHz,
Hz, H4′), 8.21 (d, 4H, J ) 10.7 Hz, H8′), 7.53 (s, 4H, H2′), 7.18
(dd, 4H, J ) 10.6, 1.8 Hz, H5′), 7.12 (dd, 4H, J ) 10.7, 1.8 Hz,
H7′), 7.08 (d, 2H, J ) 3.8 Hz, H3), 6.76 (s, 2H, CH), 6.46 (d, 2H,
CDCl3) δ ) 8.56 (d, 4H, J ) 10.7 Hz, H4′′), 8.23 (d, 4H, J ) 10.6
Hz, H8′′), 7.56 (s, 4H, H2′′), 7.35 (s, 4H, H2,3,5,6), 7.18 (dd, 4H, J )
10.7, 1.7 Hz, H5′′), 7.13 (dd, 4H, J ) 10.6, 1.7 Hz, H7′′), 7.06 (d,
2H, J ) 3.7 Hz, H3′), 6.79 (s, 2H, CH), 6.52 (d, 2H, J ) 3.7 Hz,
H4′), 1.51 (s, 36H, 3′′-t-Bu), 1.41 (s, 36H, 6′′-t-Bu); 13C NMR (100
MHz, CDCl3) δ ) 160.6, 154.4, 137.8, 135.5, 134.7, 134.4, 134.3,
132.0, 131.8, 131.1, 129.3, 125.4, 122.8, 120.9, 119.6, 118.6, 92.4,
85.4, 38.2, 37.5, 33.2, 32.2, 31.8. Anal. Calcd for C92H102S2: C,
86.88; H, 8.08; S, 5.04. Found: C, 86.63; H, 8.33; S, 5.07.
Bis(3,6-di-tert-butyl-1-azulenyl)[4-(phenylethynyl)phenyl]-
methane (16a). The general procedure was followed by using 9a
(151 mg, 0.255 mmol), iodobenzene (15) (51 mg, 0.25 mmol), CuI
(4.7 mg, 0.025 mmol), tetrakis(triphenylphosphine)palladium(0) (15
mg, 0.013 mmol), triethylamine (3 mL), and toluene (6 mL) at room
temperature for 24 h. Chromatographic purification on silica gel
with 50% toluene/hexane and GPC afforded 16a (107 mg, 64%)
and 17a (12 mg, 8%).
J ) 3.8 Hz, H4), 1.50 (s, 36H, 3′-t-Bu), 1.41 (s, 36H, 6′-t-Bu); 13
C
NMR (100 MHz, CDCl3) δ ) 160.7, 155.7, 137.9, 135.4, 134.8,
134.4, 134.3, 134.2, 131.8, 129.1, 125.5, 120.0, 119.6, 118.7, 77.6,
77.4, 38.2, 37.6, 33.2, 32.2, 31.81. Anal. Calcd for C86H98S2: C,
86.38; H, 8.26; S, 5.36. Found: C, 86.07; H, 8.28; S, 5.19.
General Procedure for the Preparation of Hexafluorophos-
phate Salts (4a4+, 4b4+‚4PF6-, 5a2+, 5b2+‚2PF6-, and 6a+,
6b+‚PF6-). DDQ was added at room temperature to a solution of
the corresponding hydro derivatives (11a, 11b, 14a, 14b, and 16a,
16b) in CH2Cl2. After the solution was stirred at the same
temperature for 30 min, a 60% HPF6 solution was added to the
mixture. After stirring at room temperature for an additional 15
min, water was added to the mixture. The resulting suspension was
filtered with suction. The organic layer was separated, washed with
water, dried with MgSO4, and concentrated under reduced pressure.
The residue was crystallized from CH2Cl2 and Et2O. The precipi-
tated crystals were collected by filtration, washed with Et2O, and
16a: blue crystals; mp 142.5-144.7 °C dec (methanol); MS (ESI
negative) m/z (relative intensity) 667 (M- - H, 100%); HRMS
dried in vacuo to give the corresponding methyl cations (4a4+, 4b4+
5a2+, 5b2+, and 6a+, 6b+) as hexafluorophosphate salts.
,
-
calcd for C51H56 - H 667.4309, found 667.4308; IR (KBr disk)
ν
max 2965, 2217 (w, CtC), 1576, 1509, 1364, 833, 754 cm-1; UV-
vis (CH2Cl2) λmax, nm (log ꢀ) 243 (4.53), 289 (4.90), 296 (4.89),
1,2,4,5-Tetrakis(phenylethynyl)benzene-4′,4′′,4′′′,4′′′′-tetrayl-
tetrakis[bis(3,6-di-tert-butyl-1-azulenyl)methylium] tetrakis-
(hexafluorophosphate) (4a4+‚4PF6-). The general procedure was
followed by using DDQ (27 mg, 0.12 mmol), 11a (60 mg, 0.025
302 (4.90), 339 (4.06), 345 sh (4.05), 356 (4.08), 374 (4.01), 563
sh (2.72), 609 (2.85), 663 sh (2.76), 747 sh (2.25); H NMR (400
1
MHz, CDCl3) δ ) 8.56 (d, 2H, J ) 10.6 Hz, H4), 8.15 (d, 2H, J
170 J. Org. Chem., Vol. 72, No. 1, 2007

Di(1-azulenyl)methylium Ion Based Tetracations
mmol), and 60% HPF6 (1.0 mL) in CH2Cl2 (10 mL). Recrystalli-
3′′-t-Bu), 1.47 (s, 36H, 6′′-t-Bu); 13C NMR (150 MHz, CDCl3) δ
) 169.1 (C6′′), 159.5 (br, C+), 149.3 (C3′′a), 148.4 (br, C8′′a), 147.5
(C3′′), 142.6 (br, C2′′), 141.4 (br, C1′ or C4′), 139.2 (C4′′), 138.6 (C8′′),
134.6 (C2′,6′ or C3′,5′), 132.4 (C5′′), 132.1 (C2′,6′ or C3′,5′ and C7′′),
132.0 (C2,3,5,6), 131.6 (br, C1′′), 127.7 (br, C1′ or C4′), 123.1 (C1,4),
93.7 (CR), 91.1 (Câ), 39.5 (s, 6′′-t-Bu), 33.4 (s, 3′′-t-Bu), 31.6 (q,
6′′-t-Bu), 31.1 (q, 3′′-t-Bu). Anal. Calcd for C96H104P2F12‚H2O: C,
73.64; H, 6.82. Found: C, 73.32; H, 6.95.
-
zation from CH2Cl2/ether gave 4a4+‚4PF6 (59 mg, 80%): black
powder; mp 208.4-209.1 °C dec (CH2Cl2/ether); MS (ESI positive)
m/z (relative intensity) 1363 (M2+ - 2PF6, 13%), 860 (M3+ - 3PF6,
2+
38), 609 (M4+ - 4PF6, 38); HRMS calcd for C186H202P2F12
3+
1362.7540, found 1362.7538; HRMS calcd for C186H202PF6
860.1811, found 860.1812; HRMS calcd for C186H2024+ 608.8946,
found 608.8943; IR (KBr disk) νmax 1478, 1418, 1335, 1314, 1242,
841 (s, PF6-), 558 (m, PF6-) cm-1; UV-vis (CH3CN) λmax, nm
(log ꢀ) 236 (5.21), 268 sh (5.11), 304 (5.19), 314 (5.18), 371 sh
(5.00), 400 (4.97), 425 sh (4.88), 502 (4.87), 644 sh (4.90), 692
1,4-Bis(2-thienylethynyl)benzene-5′,5′′-diylbis[bis(3,6-di-tert-
butyl-1-azulenyl)methylium]bis(hexafluorophosphate)(5b2+‚2PF6-).
The general procedure was followed by using DDQ (21 mg, 0.093
mmol), 14b (50 mg, 0.039 mmol), and 60% HPF6 (0.8 mL) in CH2-
1
(5.17); H NMR (600 MHz, CDCl3, 55 °C) δ )8.97 (d, 8H, J )
-
Cl2 (8 mL). Recrystallization from CH2Cl2/ether gave 5b2+‚2PF6
11.0 Hz, H4′′), 8.09 (dd, 8H, J ) 11.0, 1.4 Hz, H5′′), 8.04 (s, 2H,
H
H
3,6), 7.89 (d, 8H, J ) 11.0 Hz, H8′′), 7.88 (d, 8H, J ) 6.7 Hz,
2′,6′ or H3′,5′), 7.64 (br dd, 8H, J ) 11.0, 1.4 Hz, H7′′), 7.52 (s, 8H,
(46 mg, 75%): black powder; mp 222.5-227.1 °C dec (CH2Cl2/
ether); MS (ESI positive) m/z (relative intensity) 1414 (M+ - PF6,
4%), 634 (M2+ - 2PF6, 84); HRMS calcd for C92H100S2PF+
1413.6903, found 1413.6917; HRMS calcd for C92H100S22+ 634.3628,
found 634.3626; IR (KBr disk) νmax 1476, 1420, 1335, 841 (s, PF6-),
558 (m, PF6-) cm-1; UV-vis (CH3CN) λmax, nm (log ꢀ) 236 (4.91),
268 sh (4.83), 302 (4.82), 333 sh (4.76), 407 (4.49), 436 (4.49),
H2′′), 7.52 (d, 8H, J ) 6.7 Hz, H2′,6′ or H3′,5′), 1.52 (s, 72H, 3′′-t-
Bu), 1.43 (s, 72H, 6′′-t-Bu); 13C NMR (150 MHz, CDCl3) δ )
168.8 (C6′′), 159.6 (br, C+), 149.2 (C3′′a), 148.4 (br, C8′′a), 147.4
(C3′′), 142.8 (br, C2′′), 141.9 (br, C1′ or C4′), 139.0 (C4′′), 138.6 (C8′′),
136.5 (C3,6), 134.8 (C2′,6′ or C3′,5′), 132.3 (C2′,6′ or C3′,5′ and C5′′),
132.0 (C7′′), 131.7 (br, C1′′), 127.1 (C1′ or C4′), 125.4 (C1,2,4,5), 95.9
(Câ), 91.4 (CR), 39.4 (s, 6′′-t-Bu), 33.3 (s, 3′′-t-Bu), 31.5 (q, 6′′-t-
Bu), 31.0 (q, 3′′-t-Bu). Anal. Calcd for C186H202P4F24‚2H2O: C,
73.16; H, 6.80. Found: C, 72.87; H, 6.83.
1
564 (4.85), 650 sh (4.61), 700 (4.86); H NMR (600 MHz, CD3-
CN) δ ) 9.09 (d, 4H, J ) 11.0 Hz, H4′′), 8.16 (dd, 4H, J ) 11.0,
2.1 Hz, H5′′), 7.85 (d, 4H, J ) 10.8 Hz, H8′′), 7.84 (s, 4H, H2′′),
7.67 (dd, 4H, J ) 10.8, 2.1 Hz, H7′′), 7.65 (d, 2H, J ) 4.0 Hz, H3′),
7.56 (s, 4H, H2,3,5,6), 7.53 (d, 2H, J ) 4.0 Hz, H4′), 1.58 (s, 36H,
3′′-t-Bu), 1.39 (s, 36H, 6′′-t-Bu); 13C NMR (150 MHz, CD3CN) δ
) 169.7 (C6′′), 150.4 (C+), 149.6 (C3′′a), 149.2 (C8′′a), 148.1 (C3′′),
147.6 (C2′), 142.6 (C2′′), 140.4 (C4′′), 140.2 (C4′), 139.2 (C8′′), 136.1
(C3′), 135.4 (C5′), 133.1 (C5′′), 132.9 (C7′′), 132.8 (C2,3,5,6), 131.9
(C1′′), 123.7 (C1,4), 99.4 (CR), 85.7 (Câ), 40.0 (s, 6′′-t-Bu), 34.1 (s,
3′′-t-Bu), 31.6 (q, 6′′-t-Bu), 31.3 (q, 3′′-t-Bu). Anal. Calcd for
C92H100S2P2F12: C, 70.84; H, 6.46; S, 4.11. Found: C, 71.04; H,
6.67; S, 3.93.
1,2,4,5-Tetrakis(2-thienylethynyl)benzene-5′,5′′,5′′′,5′′′′-diyltet-
rakis[bis(3,6-di-tert-butyl-1-azulenyl)methylium] tetrakis(hexa-
fluorophosphate) (4b4+‚4PF6-). The general procedure was fol-
lowed by using DDQ (31 mg, 0.14 mmol), 11b (69 mg, 0.028
mmol), and 60% HPF6 (1.1 mL) in CH2Cl2 (11 mL). Recrystalli-
-
zation from CH2Cl2/ether gave 4b4+‚4PF6 (74 mg, 87%): black
powder; mp 247.2-250.4 °C dec (CH2Cl2/ether); MS (ESI positive)
m/z (relative intensity) 1375 (M2+ - 2PF6, 11%), 868 (M3+ - 3PF6,
46), 615 (M4+ - 4PF6, 27); HRMS calcd for C178H194S4P2F12
2+
3+
1374.6668, found 1374.6698; HRMS calcd for C178H194S4PF6
Bis(3,6-di-tert-butyl-1-azulenyl)[4-(phenylethynyl)phenyl]-
methylium hexafluorophosphate (6a+‚PF6-). The general pro-
cedure was followed by using DDQ (20 mg, 0.088 mmol), 16a
(50 mg, 0.075 mmol), and 60% HPF6 (0.8 mL) in CH2Cl2 (8 mL).
868.1230, found 868.1227; HRMS calcd for C178H194S44+ 614.8510,
found 614.8510; IR (KBr disk) νmax 1476, 1418, 1335, 868, 843
(s, PF6-), 558 (m, PF6-) cm-1; UV-vis (CH3CN) λmax, nm (log ꢀ)
240 (5.20), 269 sh (5.15), 304 (5.09), 405 (4.86), 434 sh (4.82),
-
Recrystallization from CH2Cl2/hexane gave 6a+‚PF6 (53 mg,
1
565 (5.07), 652 sh (5.00), 699 (5.15); H NMR (600 MHz, CD3-
87%): black powder; mp 279.6-279.9 °C (CH2Cl2/hexane); MS
(ESI positive) m/z (relative intensity) 667 (M+ - PF6, 100%);
CN, 70 °C) δ ) 9.05 (d, 8H, J ) 11.0 Hz, H4′′), 8.15 (d, 8H, J )
11.0 Hz, H5′′), 7.92 (br s, 2H, H3,6), 7.82 (s, 8H, H2′′), 7.79 (d, 8H,
J ) 10.9 Hz, H8′′), 7.65 (d, 4H, J ) 3.4 Hz, H3′), 7.64 (d, 8H, J )
10.9 Hz, H7′′), 7.38 (d, 4H, J ) 3.4 Hz, H4′), 1.54 (s, 72H, 3′′-t-
Bu), 1.38 (s, 72H, 6′′-t-Bu); 13C NMR (150 MHz, CD3CN, 70 °C)
δ ) 169.4 (C6′′), 149.3 (C+), 149.1 (C3′′a), 148.7 (C8′′a), 147.8 (C3′′),
147.7 (C2′), 141.7 (C2′′), 139.7 (C4′′), 139.1 (C4′), 138.5 (C8′′), 135.7
(C3′), 135.5 (C3,6), 133.5 (C5′), 132.6 (C5′′), 132.2 (C7′′), 131.4 (C1′′),
125.3 (C1,2,4,5), 96.2 (CR), 89.9 (Câ), 39.3 (s, 6′′-t-Bu), 33.3 (s, 3′′-
t-Bu), 30.9 (q, 6′′-t-Bu), 30.6 (q, 3′′-t-Bu). Anal. Calcd for
HRMS calcd for C51H55+ 667.4298, found 667.4298; IR (KBr disk)
-
νmax 1476, 1335, 1314, 1242, 868, 841 (s, PF6-), 558 (m, PF6
)
cm-1; UV-vis (CH3CN) λmax, nm (log ꢀ) 224 sh (4.65), 240 (4.67),
270 (4.63), 301 (4.70), 374 sh (4.24), 398 (4.36), 419 sh (4.27),
493 (4.16), 640 sh (4.36), 687 (4.65); 1H NMR (600 MHz, CDCl3)
δ ) 9.05 (d, 2H, J ) 11.0 Hz, H4), 8.17 (dd, 2H, J ) 11.0, 1.9 Hz,
H5), 7.89 (br d, 2H, J ) 10.7 Hz, H8), 7.75 (br d, 2H, J ) 7.4 Hz,
H2′,6′ or H3′,5′), 7.67 (br dd, 2H, J ) 10.7, 1.9 Hz, H7), 7.62-7.60
(m, 2H, H2′′,6′′), 7.53 (br s, 2H, H2), 7.46 (br d, 2H, J ) 7.4 Hz,
H2′,6′ or H3′,5′), 7.42-7.41 (m, 3H, H3′′,4′′,5′′), 1.58 (s, 18H, 3-t-Bu),
1.46 (s, 18H, 6-t-Bu); 13C NMR (150 MHz, CDCl3) δ ) 169.1
(C6), 159.5 (br, C+), 149.3 (C3a), 148.4 (br, C8a), 147.5 (C3), 142.5
(br, C2), 141.1 (br, C1′ or C4′), 139.3 (C4), 138.6 (C8), 134.6 (C2′,6′
or C3′,5′), 132.5 (C5), 132.1 (C7 and C2′,6′ or C3′,5′), 131.9 (C2′′,6′′),
131.6 (br, C1), 129.1 (C4′′), 128.6 (C3′′,5′′), 128.1 (br, C1′ or C4′),
122.5 (C1′′), 94.2 (Câ), 88.8 (CR), 39.5 (s, 6-t-Bu), 33.4 (s, 3-t-Bu),
31.5 (q, 6-t-Bu), 31.1 (q, 3-t-Bu). Anal. Calcd for C51H55PF6‚1/
2H2O: C, 74.52; H, 6.87. Found: C, 74.64; H, 7.10.
C
178H194S4P4F24‚2H2O: C, 69.47; H, 6.48; S, 4.17. Found: C, 69.34;
H, 6.49; S, 3.83.
1,4-Bis(phenylethynyl)benzene-4′,4′′-diylbis[bis(3,6-di-tert-bu-
tyl-1-azulenyl)methylium] bis(hexafluorophosphate) (5a2+‚2PF6-).
The general procedure was followed by using DDQ (35 mg, 0.15
mmol), 14a (82 mg, 0.065 mmol), and 60% HPF6 (0.6 mL) in CH2-
-
Cl2 (6 mL). Recrystallization from CH2Cl2/ether gave 5a2+‚2PF6
(79 mg, 78%): black powder; mp 248.6-253.4 °C dec (CH2Cl2/
ether); MS (ESI positive) m/z (relative intensity) 1402 (M+ - PF6,
+
4%), 628 (M2+ - 2PF6, 84); HRMS calcd for C96H104PF6
Bis(3,6-di-tert-butyl-1-azulenyl)[5-(phenylethynyl)-2-thienyl]-
methylium hexafluorophosphate (6b+‚PF6-). The general pro-
cedure was followed by using DDQ (18 mg, 0.079 mmol), 16b
(44 mg, 0.065 mmol), and 60% HPF6 (0.7 mL) in CH2Cl2 (7 mL).
1401.7774, found 1401.7793; HRMS calcd for C96H1042+ 628.4064,
found 628.4059; IR (KBr disk) νmax 1476, 1335, 1314, 1242, 870,
841 (s, PF6-), 558 (m, PF6-) cm-1; UV-vis (CH3CN) λmax, nm
(log ꢀ) 231 (4.90), 240 sh (4.89), 268 sh (4.78), 305 sh (4.89), 317
(4.90), 407 (4.62), 420 sh (4.61), 502 (4.57), 643 sh (4.62), 689
-
Recrystallization from CH2Cl2/ether gave 6b+‚PF6 (46 mg,
86%): black powder; mp 209.3-212.2 °C (CH2Cl2/ether); MS (ESI
positive) m/z (relative intensity) 673 (M+ - PF6, 100%); HRMS
calcd for C49H53S+ 673.3862, found 673.3862; IR (KBr disk) νmax
1474, 1420, 1335, 841 (s, PF6-), 558 (m, PF6-) cm-1; UV-vis
(CH3CN) λmax, nm (log ꢀ) 236 (4.66), 270 (4.57), 303 (4.62), 330
sh (4.48), 383 sh (4.08), 407 (4.21), 430 (4.20), 544 (4.47), 649 sh
1
(4.90); H NMR (600 MHz, CDCl3) δ ) 9.04 (d, 4H, J ) 11.0
Hz, H4′′), 8.16 (dd, 4H, J ) 11.0, 1.4 Hz, H5′′), 7.90 (br d, 4H, J )
10.7 Hz, H8′′), 7.77 (br d, 4H, J ) 6.8 Hz, H2′,6′ or H3′,5′), 7.68 (br
dd, 4H, J ) 10.7, 1.4 Hz, H7′′), 7.65 (s, 4H, H2,3,5,6), 7.54 (br s,
4H, H2′′), 7.48 (br d, 4H, J ) 6.8 Hz, H2′,6′ or H3′,5′), 1.58 (s, 36H,
J. Org. Chem, Vol. 72, No. 1, 2007 171

Ito et al.
(4.29), 698 (4.58); 1H NMR (600 MHz, CD3CN) δ ) 9.08 (d, 2H,
J ) 10.9 Hz, H4), 8.15 (dd, 2H, J ) 10.9, 1.1 Hz, H5), 7.85 (d, 2H,
J ) 10.7 Hz, H8), 7.82 (br s, 2H, H2), 7.66 (br d, 2H, J ) 10.7 Hz,
H7), 7.61 (br s, 1H, H4′), 7.55-7.52 (br m, 2H, H2′′,6′′), 7.50 (br s,
1H, H3′), 7.47-7.40 (br m, 3H, H3′′,4′′,5′′), 1.57 (s, 18H, 3-t-Bu),
1.38 (s, 18H, 6-t-Bu); 13C NMR (150 MHz, CD3CN) δ ) 169.7
(C6), 150.6 (C+), 149.5 (C3a), 149.1 (C8a), 148.0 (C3), 147.0 (C5′),
142.7 (C2), 140.3 (C4), 140.2 (C3′), 139.2 (C8), 136.1 (C2′), 135.6
(C4′), 133.0 (C5), 132.8 (C7), 132.5 (C2′′,6′′), 131.8 (C1), 130.8 (C4′′),
129.9 (C3′′,5′′), 122.6 (C1′′), 100.2 (Câ), 83.1 (CR), 40.0 (s, 6-t-Bu),
34.1 (s, 3-t-Bu), 31.6 (q, 6-t-Bu), 31.3 (q, 3-t-Bu). Anal. Calcd for
C49H53SPF6: C, 71.86; H, 6.52; S, 3.92. Found: C, 71.66; H, 6.66;
S, 3.69.
Foundation for Japanese Chemical Research for financial
support. This work was partially supported by a Grant-in-Aid
for Scientific Research (Grant 18550026 to S.I.) from the
Ministry of Education, Culture, Sports, Science, and Technol-
ogy, Japan.
Supporting Information Available: General and electrochemi-
cal measurements details, details of CV data, CV waves of 5a2+
,
,
5b2+ and 6a+, 6b+, spectroelectrograms of 4a4+, 4b4+, 5a2+, 5b2+
1
and 6a+, 6b+, and copies of H and 13C NMR spectra of reported
compounds. This material is available free of charge via the Internet
at http://pubs.acs.org.
Acknowledgment. S.I. thanks Kurata Foundation, Fund for
JO0618324
the Promotion of International Scientific Research, and The
172 J. Org. Chem., Vol. 72, No. 1, 2007