Synthesis and redox behavior of Wurster blue cyclophanes

Article abstract of DOI:10.1002/ejoc.200400289

Two cyclophanes composed of two p-phenylenediamine (PPD) units connected by methylene chains of different lengths (1c, n = 3; 2c, n = 5) have been synthesized. The PPD unit of cyclophane 1c was oxidized by a two-electron transfer process to give 1c²⁺ at the first oxidation potential. In contrast, 2c was oxidized by a one-electron transfer process to give 2c ⁺ and then 2c²⁺. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.

Full text of DOI:10.1002/ejoc.200400289

FULL PAPER
Synthesis and Redox Behavior of Wurster Blue Cyclophanes
[a]
[a]
[b][‡]
ˆ
Hiroyuki Takemura,* Ko Takehara, and Masafumi Ata
Keywords: Cyclophane / Wurster blue radical / Cyclic voltammetry / CT complex
Two cyclophanes composed of two p-phenylenediamine
(PPD) units connected by methylene chains of different
lengths (1c, n = 3; 2c, n = 5) have been synthesized. The PPD
trast, 2c was oxidized by a one-electron transfer process to
give 2c+ and then 2c2+
.
unit of cyclophane 1c was oxidized by a two-electron transfer ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
process to give 1c2+ at the first oxidation potential. In con-
Germany, 2004)
Introduction
Results and Discussion
Synthesis of 1a؊c and 2a؊c
The Wurster radical, generated by the oxidation of
N,N,NЈ,NЈ-tetramethyl-p-phenylenediamine (TMPD), is a
well-known stable radical, and TMPD itself is a good elec-
tron donor and forms CT complexes with various ac-
ceptors.[1] Recently, several new TMPD analogs have been
synthesized and their properties as electron donors have
been widely studied.[2] During our investigations into CT
interactions and electrochemical properties of azacyclo-
phanes,[3] we became interested in TMPD as a cyclophane
unit. CT interactions are of interest in cyclophane chemis-
try and remains an important subject.[4] An example of a
TMPD-based cyclophane was reported by Staab et al., who
incorporated a TMPD unit into a [3.3]paracyclophane skel-
eton and determined its electrochemical properties and its
ability to form CT complexes.[5] We have synthesized an-
other type of PPD-containing cyclophane in order to inves-
tigate the effect of distance between the two PPD units on
the electrochemical properties of the cyclophanes (Fig-
ure 1). Thus, we wish to report here the synthesis and redox
properties of cyclophanes 1c and 2c.
The synthesis of 2a and 2b has been reported previously
by Stetter and Roos.[6] We improved the yields by employing
a modified one-step procedure without using a high-di-
lution technique. N,NЈ-Ditosyl-p-phenylenediamine in
DMF was allowed to react with the corresponding di-
bromoalkanes using sodium hydride as a base. After the
usual work up, 1a and 2a were obtained in 25 and 56%
yields, respectively (Scheme 1). Cleavage of the tosyl groups
of 1a and 2a was readily achieved by employing 90% H2SO4
(100 °C, 5 min) to yield 1b and 2b. Compounds 1b and 2b
were sensitive to air, particularly under moist conditions;
therefore, these materials were alkylated without further
purification. Methylation of 1b and 2b to give 1c and 2c
could be achieved by the EschweilerϪClarke procedure, but
it is preferable to carry out this reaction under milder con-
ditions because 1b is more sensitive to air than 2b. There-
fore, we employed a NaBH4/aq. HCHO/H2SO4 mixture for
the methylation of 1b.[7]
The solutions of compounds 1c and 2c were gradually
oxidized by exposure to air, and they turned blue just like
the Wurster blue radical solution. UV light irradiation also
generated the blue species. Oxidation of 1c and 2c with an
equal amount of AgBF4 afforded dark-blue crystals which
Ϫ
were less stable than the Wurster blue salt (TMPDϩ·BF4
)
[a]
Department of Chemistry, Faculty of Science, Kyushu
University,
prepared similarly. The solution of 2c oxidized by AgBF4
was more stable than that of 1c: the blue solution of the
oxidized 2c turned dark-blue in a day, but that of 1c turned
pink in half a day. These oxidation phenomena were investi-
gated in detail by an electrochemical method as described
below.
Ropponmatsu 4-2-1, Chuo-ku, Fukuoka 810-8560, Japan
Fax: (internat.) ϩ 81-92-726-4755
E-mail: takemura@chem.rc.kyushu-u.ac.jp
[b]
Department of Chemistry, Faculty of Science, Kyushu
University,
Hakozaki 6-10-1, Higashi-ku, Fukuoka 812-8581, Japan
[‡]
Present address: Research Institute of Innovative Technology
for the Earth, Sony Corporation Research Center, 174
Fujitsuka-cho, Hodogaya-ku, Yokohama 240-031, Japan.
Supporting information for this article is available on the
WWW under http://www.eurjoc.org or from the author.
Unfortunately, the crystals of 1c, 2c, and their oxidized
species were not suitable for crystallographic analysis and
thus we cannot discuss the molecular structure of the cyclo-
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DOI: 10.1002/ejoc.200400289
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Synthesis and Redox Behavior of Wurster Blue Cyclophanes
FULL PAPER
Figure 1. Structures of TMPD and TMPD-based cyclophanes
Scheme 1. Synthetic scheme for the preparation of cyclophanes
phanes in the solid state.[8] In the case of [n.n]paracyclo- try. Figure 2 shows the cyclic voltammograms of TMPD, 1c,
phanes, an energy minimum is found when n is an odd num- and 2c, and the oxidation potentials thus obtained are given
ber and the two benzene rings are in a face-to-face confor- in Table 1. Cyclophane 2c showed two clear peaks at
mation.[9] This is true for the [7.7]paracyclophane system, Ϫ0.184 and ϩ0.432 V (E/V vs Ag/AgNO3), which corre-
as revealed by crystallographic analysis, which is reported spond to the first and second oxidation processes, and are
to be almost strain-free. Therefore, the aza analog of very similar to those of TMPD. Coulometry showed that
[7.7]paracyclophane, 2c, should have similar structural both oxidation processes took place by a one-electron
properties. Because attempts at crystallographic analyses transfer process (Figure 3). In contrast, 1c was oxidized in
were unsuccessful, conformational information about 1c, a different manner to that of 2c or TMPD; two irreversible
2c, and 1c2ϩ was obtained from Conflex calculations (see redox waves were observed in 1c, and coulometry indicated
Supporting Information, for Supporting Informations see that the first oxidation step occurred by a two-electron
also the footnote on the first page of this article).[10] Ac- transfer process. This is also easily seen from the cyclic vol-
cording to the results of these calculations, the two benzene tammetry results, in which the current of the first oxidation
rings of 2c are in a face-to-face geometry and the distance step is about twice that of TMPD and 2c, as shown in Fig-
˚
between the two PPD units is 7.6 A. In contrast, the two ure 2. Furthermore, the one-step-two-electron mechanism
benzene rings of 1c are slightly twisted and the distance can be understood in terms of the peak separation of the
˚
between the two PPD units is 5.2 A. These values agree very first redox couple of the cyclic voltammograms. According
closely with those of the [5.5]- and [7.7]paracyclophanes; to the equation, ∆Ep ϭ 60 (mV)/n, where ∆Ep is the peak
Wartini et al. determined the structures of these cyclo- separation of a redox couple and n is the number of elec-
phanes by crystallographic analysis, and they referred to the trons, we found that n ϭ 2 in the case of 1c2ϩ. The results
flexibility of [5.5]- and [7.7]paracyclophanes.[11]
of the coulometric analysis of 1c at the second potential
In the case of 1c2ϩ, the four nitrogen atoms are sp2 hy- were not clear because an unknown oxidation process oc-
bridized and conjugated with the benzene rings. The two curred and insoluble materials precipitated on the electrode.
PPD units adopted a stair-shaped geometry in order to The peaks at ϩ0.81 and ϩ0.95 V (shown by arrows) seem
avoid repulsion between the two positive charges, and to originate from the oxidation of the by-products gener-
consequently, the distance between the two benzene rings is ated by electrolysis.
˚
about 3.4 A.
The UV spectra of the oxidized species were recorded
with a platinum mesh electrode fitted into a quartz cell at
controlled potentials which were the same as those used in
Cyclic Voltammetry and Coulometry
In order to investigate the electrochemical properties, the the CV experiments (Figure 4). The UV spectrum of the
redox potentials were measured by cyclic voltammetry oxidized species of cyclophane 2c at the first peak is very
(CV), and each oxidation process was analyzed by coulome- similar to that of TMPDϩ. In contrast, the spectrum of
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H. Takemura, K. Takehara, M. Ata
FULL PAPER
Figure 3. The results of coulometry of cyclophanes 1c and 2c at
the first oxidation potential (5.0 ϫ 10Ϫ4 mol·dmϪ3 in CH3CN)
Figure 2. Cyclic voltammogram of TMPD, 1c, and 2c (1.0 ϫ 10Ϫ3
mol·dmϪ3 in CH3CN at a scan rate of 100 mV·sϪ1). Ag/AgNO3
(0.01 ) was used as the reference electrode
served one, the spectra of 1c2ϩ (A) and 1c2ϩ (B) did not
accurately coincide with the experimental spectrum; each
had structure in common with the experimental spectrum.
Therefore, the dication species could not be specified as
either 1c2ϩ (A) or 1c2ϩ (B).
Table 1. Oxidation potentials of TMPD and the cyclophanes, 1c,
2c, and 3
Eox1 [V]
Ϫ0.154
Eox1,2 ϭ Ϫ0.232
Ϫ0.184
Ϫ0.242
Eox2 [V]
ϩ0.420
Eox3 [V]
Eox4 [V]
Because the two PPD units of cyclophane 1c are close to
each other (5.2 A), effective CT interactions can be ex-
˚
TMPD
Ϫ
Ϫ
pected and an electron can easily transfer from one PPD
unit to another by a through-space interaction. Thus, a di-
cation is generated at the first oxidation potential. In con-
1c
2c
3
Eox3 and/or 4 ϭ ϩ0.668
Ϫ Ϫ
ϩ0.432
Ϫ0.102
Eox3,4 ϭ ϩ0.249
˚
trast, each PPD unit of 2c is sufficiently separated (7.6 A)
so that electron transfer from the neutral PPD unit to the
cyclophane 1c2ϩ is quite different. From the results of CV, PPDϩ unit rarely occurs. Therefore, one-electron transfer
coulometry, and UV spectroscopy, 1c2ϩ can be assigned to occurred and the oxidation potentials are similar to those
either a singlet dication 1c2ϩ (A) or a quinonediimine-PPD of TMPD.
structure 1c2ϩ (B), as shown in Scheme 2, rather than to a
Interestingly, these redox processes and oxidation poten-
triplet bis-monoradical form.[12] This was further supported tials are quite different from those of Staab’s cyclophane 3,
by ESR measurements, in which 1c2ϩ showed no ESR sig- although the experimental conditions were the same as
nal. In the case of 2cϩ, broad temperature-dependent sinus- those used by Staab and co-workers.[5] Namely, the first and
oidal signals were observed in the ESR spectra. Figure 5 second oxidation peaks were observed independently, but
shows the ESR spectra of 2cϩ along with that of TMPDϩ. the third and fourth oxidation peaks could not be dis-
The UV/Vis spectra of 1c, 1c2ϩ (A), and 1c2ϩ (B) were pre- tinguished. These phenomena can be related to the struc-
dicted by ZINDO calculations based on their Conflex-opti- tures of the cyclophanes. Cyclophane 3 is a [3.3]paracyclo-
mized structures (Supporting Information). Although the phane system in which the PPD unit is rigidly fixed in a
calculated spectrum of 1c coincided very well with the ob- face-to-face conformation. The two units are almost paral-
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Eur. J. Org. Chem. 2004, 4936Ϫ4941

Synthesis and Redox Behavior of Wurster Blue Cyclophanes
FULL PAPER
Figure 4. UV spectra of oxidized species at the first oxidation potentials
Scheme 2. Proposed scheme for the oxidation of cyclophanes 1c and 2c
described above. Only the distance between the two PPD
units affects the redox potentials.
Further evidence for this property of unimolecular or bi-
molecular behavior of the PPD units of cyclophanes 1c and
2c is inferred from CT complex formation as follows. Cyclo-
phane 2c formed a deep-blue CT complex with 1,3,5-trini-
trobenzene (TNB), and the ratio of the components of the
complex 2c/TNB was 1:2, as determined by elemental
analysis. In contrast, cyclophane 1c formed a 1:1 CT com-
plex with TNB (Figure 6), even though a large excess of
TNB was added. The UV spectra of these complexes
(CH3CN) were similar to that of TMPDϩ obtained by elec-
trolysis. The specific bands at λ Ͼ 300 nm are as follows:
1c·TNB; λ ϭ 326, 535, 575, 625 nm, TMPDϩ; λ ϭ 326, 528,
562, 612 nm. Thus, the structures of the CT complexes can
be regarded as being of D·ϩ·A·Ϫ type. In the case of 1c, the
spectrum in the range of 300Ϫ700 nm did not change even
in the presence of an excess of TNB; so the complex
1c·2TNB seems to be a very weak complex. Therefore, 1c
acts as a single donor to electron acceptor. However, the
intensities of the absorption bands of 1c·TNB and 2c·2TNB
Figure 5. ESR spectra of (A) TMPDϩ and (B) 2cϩ at (a) 293 K,
(b) 253 K, and (c) 223 K
˚
lel and the PPD units are much closer (3.49 A) together complexes in the range of 300Ϫ700 nm were quite weak
than in 1c.[5] From the crystallographic analysis of 3 the compared with those of TMPDϩ and 2cϩ, which suggests
distortion of the two benzene rings was considered to result that the complexes dissociate easily in dilute solution. The
from the steric repulsion between the facing four dimeth- differences in the ratios of the components of the complexes
ylamino groups. Thus, the distortion and the distance be- were attributed to the donor properties of the cyclophanes.
tween the PPD units affect the oxidation potentials of the The distance between the two PPD units of 1c is short en-
cyclophane. In contrast, 1c and 2c are almost strain-free, as ough for interactions to occur, thus, intramolecular interac-
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H. Takemura, K. Takehara, M. Ata
FULL PAPER
Variable temperature measurements (Ϯ1°C) were made by using
a temperature control apparatus (JEOL, UTC-2AX/JES-VT-3AT).
Radical solutions of 1c and 2c were prepared by electrolysis with
gold electrodes in CH3CN in the presence of tetrabutylammonium
perchlorate as a supporting electrolyte. The preparations were car-
ried out after deaeration by several freeze-pump-thaw cycles. In the
optical measurements, the radical solutions of 1c and 2c were se-
aled in quartz cells of 2 mm path length. The Conflex calculations
were carried out on CAche system and ZINDO calculations were
calculated based on the Conflex-optimized structures.
tions cause 1c to be a single donor. In contrast, each PPD
unit of 2c independently acts as a donor because the units
are sufficiently separated. This explanation coincides with
those based on the electrochemical properties.
N,NЈ,NЈЈ,NЈЈЈ-Tetratosyl-1,5,12,16-tetraaza[5.5]paracyclophane
(1a): N,NЈ-Ditosyl-p-phenylenediamine (20 g, 48 mmol) and so-
dium hydride (60% in mineral oil, 4.2 g) were dispersed in DMF
(1 L) and stirred at 50 °C. After an hour, the temperature was
raised to 120 °C and a solution of 1,3-dibromopropane (9.70 g,
48 mmol) in DMF (200 mL) was added dropwise over a period of
4 h; the resultant solution was stirred for another 2 h. The solution
was then poured into hot brine, and the precipitates were collected
by suction filtration. Recrystallization of the tan powder thus ob-
tained from dichloromethane yielded 1a as a colorless powder
(11.1 g, 25%). Further recrystallization from a benzene/dichloro-
methane mixture gave the analytically pure benzene adduct. M.p.
323.3Ϫ324.2 °C. 1H NMR (CDCl3): δ ϭ 7.42, 7.28 [ABq,
3J(H,H) ϭ 8 Hz, 16 H, Ts-Ar-H], 6.70 (s, 8 H, Ar-H), 3.52 [t,
3J(H,H) ϭ 7 Hz, 8 H, N-CH2-], 2.45 (s, 12 H, Ts-CH3), 1.27 [quint,
3J(H,H) ϭ 7 Hz, 4 H, N-CH2-CH2-] ppm. C46H48N4O8S4·C6H6:
calcd. C 63.01, H 5.49, N 5.65; found C 62.79, H 5.41, N 5.55.
Figure 6. CT complexes of the cyclophanes 1c and 2c with 1,3,5-tri-
nitrobenzene
Conclusions
By altering the distances between the two PPD units in
the cyclophane skeleton, significant differences in the redox FAB-MS: m/z ϭ 912.3 [Mϩ].
properties and CT complex formation were observed.
1,5,12,16-Tetraaza[5.5]paracyclophane (1b): Compound 1a (5 g,
Cyclophane 1c, in which two PPD units are connected by
shorter methylene chains, acts as a single donor. In con-
trast, the PPD units in cyclophane 2c behave independently.
This simple molecular design has shown that the interac-
tions and changes in the properties of the redox unit depend
upon the distance separating the two PPD units.
5.48 mmol) was mixed with 90% sulfuric acid (10 mL), and the mix-
ture was maintained at 100 °C for 5 min. The solution was poured
into water (100 mL) and made alkaline with potassium carbonate.
The resultant mixture was extracted with dichloromethane (5 ϫ
25 mL), and the aqueous layer was saturated with sodium chloride
and extracted with dichloromethane (4 ϫ 25 mL). The organic layers
were combined and dried with potassium carbonate. Evaporation of
the solvent gave almost pure reddish-brown prisms (1.11 g, 68%).
This material was used for the synthesis of 1c without further purifi-
Experimental Section
1
cation. M.p. 239.2Ϫ240.6 °C. H NMR (CDCl3): δ ϭ 6.37 (s, 8 H,
Ar-H), 3.40 (s, 4 H, NH), 3.17 [t, 3J(H,H) ϭ 7 Hz, 8 H, N-CH2-
CH2-], 1.61 [quint, 3J(H,H) ϭ 7 Hz, 4 H, N-CH2-CH2-] ppm.
HRMS (FAB): calcd. for C18H24N4: 296.2001; found: 296.1988.
General Procedure: All melting points were measured in Ar-sealed
1
tubes and are uncorrected. H NMR spectra were recorded with a
JEOL GSX-270 spectrometer (270 MHz). The electrochemical
measurements were performed with a polarograph (Fuso, Model
312) connected to a function generator (NF Circuit Design Block
Co., Model FG-121B). The working electrode was a platinum wire,
while the counter electrode was a platinum plate, the reference elec-
trode being Ag/0.01  AgNO3. The scan rate was 100 mV·sϪ1. The
solvent used was CH3CN, and dissolved oxygen was removed by
passing CH3CN-saturated nitrogen gas through the liquid prior to
measurement. Tetrabutylammonium perchlorate was used as a sup-
porting electrolyte (0.1 mol·dmϪ3 in CH3CN). All measurements
were carried out at 25 Ϯ 0.5 °C. Coulometry was performed under
constant-potential conditions with a high current potentiostat. A
copper anode and a platinum mesh cathode were used. During the
electrolysis, the anode compartment was stirred continuously with
a magnetic stirrer. ESR spectra were recorded with an X-band ESR
spectrometer (Echo Electronics) combined with an electromagnet
N,NЈ,NЈЈ,NЈЈЈ-Tetramethyl-1,5,12,16-tetraaza[5.5]paracyclophane
(1c): Sodium borohydride (408 mg, 10.8 mmol) and 1b (223 mg,
0.752 mmol) were suspended in THF (10 mL), and the mixture was
added to a cold solution of 3 mol·dmϪ3 H2SO4 (1.22 mL) and 37%
formalin (0.75 mL). The THF layer was separated and the aqueous
layer was extracted with dichloromethane (3 ϫ 10 mL). The com-
bined extracts were dried with potassium carbonate. After evapor-
ation of the solvent, the residual material was passed through an
alumina column with dichloromethane as the eluent to yield 1c
(105 mg, 40%) as a pale yellow powder. M.p. 148Ϫ150 °C. 1H
3
NMR (CDCl3): δ ϭ 6.53 (s, 8 H, Ar-H), 3.22 [t, J(H,H) ϭ 7 Hz,
8 H, N-CH2-], 2.81 (s, 12 H, N-CH3), 1.49 [quint, 3J(H,H) ϭ 7 Hz,
4 H, N-CH2-CH2-] ppm. EI-MS: m/z ϭ 352 [Mϩ]. C22H32N4: calcd.
C 74.96, H 9.15, N 15.89; found C 74.74, H 9.00, N 15.58.
(JEOL, JM-360) with 100 kHz modulation; care was taken to avoid N,NЈ,N",NЈЈЈ-Tetratosyl-1,7,14,20-tetraaza[7.7]paracyclophane
power saturation and the modulation amplitudes were at most (2a): Compound 2a was prepared similarly to compound 1a.
0.01 mT. The time constant of the spectrometer was 0.5 s and the Recrystallization of the crude material from a dichloromethane/
sweep rate was as slow as 2 h per spectrum. The magnetic fields
were measured with a proton NMR gaussmeter (JEOL, JMF-3).
benzene mixture afforded fine pale brown crystals (56%). M.p.
1
312.3Ϫ313.6 °C (ref.[6], 311 °C, corrected). H NMR (CDCl3): δ ϭ
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Synthesis and Redox Behavior of Wurster Blue Cyclophanes
FULL PAPER
7.28, 7.44 [ABq, 3J(H,H) ϭ 8 Hz, 16 H, Ts-Ar-H], 6.84 (s, 8 H, Ar-
H), 3.41 [t, 3J(H,H) ϭ 7 Hz, 8 H, N-CH2-], 2.45 (s, 12 H, Ts-CH3),
1.25 (m, 8 H, N-CH2-CH2-CH2-), 1.01 (m, 4 H, N-CH2-CH2-CH2-)
ppm. FAB-MS: m/z ϭ 968.3 [Mϩ].
senko, G. V. Shilov, O. A. Dyachenko, Mol. Cryst. Liq. Cryst.
[1g]
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[1h]
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pared similarly to compound 1b as brown crystals in 47% yield.
This material was used in the subsequent methylation reaction
without further purification. M.p. 174.6Ϫ176.3 °C (ref.[6], 178.5 °C,
corrected). 1H NMR (CDCl3): δ ϭ 6.44 (s, 8 H, Ar-H), 3.06 [t,
[2b]
5928Ϫ5930.
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3
3J(H,H) ϭ 7 Hz, 8 H, N-CH2-], 1.57 [quint, J(H,H) ϭ 7 Hz, 8 H,
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[2g]
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[2h]
N,NЈ,NЈЈ,NЈЈЈ-Tetramethyl-1,7,14,20-tetraaza[7.7]paracyclophane
(2c): A solution of 2b (760 mg, 2.16 mmol), HCOOH (90%, 3 mL,
70.4 mmol), and aq. HCHO (37%, 3 mL, 39.9 mmol) was heated at
100 °C with stirring for 2 h. After adding concd. HCl (0.5 mL), the
solution was concentrated to dryness by heating. To the resultant
mixture was added an excess of aq. K2CO3 and the aqueous layer
was extracted with CH2Cl2 (3 ϫ 20 mL). The combined extracts
were dried with K2CO3 and the solvent evaporated. Recrystallization
of the resultant material from a methanol/dichloromethane mixture
gave 2c as a white powder (419 mg, 48%). M.p. 136Ϫ138 °C. 1H
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3
[3c]
NMR (CDCl3): δ ϭ 6.72 (s, 8 H, Ar-H), 3.17 [t, J(H,H) ϭ 7 Hz, 8
myozu, Tetrahedron 2003, 59, 427Ϫ431.
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3
H, N-CH2-], 2.80 (s, 12 H, N-CH3), 1.62 [quint, J(H,H) ϭ 7 Hz, 8
[3e]
3
Res. Dev. Org. Chem. 2000, 4, 201Ϫ225
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H, N-CH2-CH2-CH2-], 1.46 [quint, J(H,H) ϭ 7 Hz, 4 H, N-CH2-
CH2-CH2-] ppm. EI-MS: m/z ϭ 408 [Mϩ]. C26H40N4: calcd. C 76.42,
[3f]
N. Kon, H. Take-
H 9.87, N 13.71; found C, 76.43, H 9.83, N 13.58.
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of 1,3,5-trinitrobenzene in benzene was added to a solution of the
cyclophane in benzene. Heptane was added to the resultant deep-
blue solution which was then concentrated. The dark blue crystals
were collected and recrystallized from benzene/heptane.
[3g]
65, 3708Ϫ3715.
H. Takemura, H. Kariyazono, N. Kon, T.
[3h]
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[3j]
H. Takemura, N. Kon, K. Tani, K. Takehara, J. Kimoto,
1
1c·TNB: M.p. 119Ϫ120 °C (dec). H NMR (CDCl3): δ ϭ 9.39 (s,
T. Shinmyozu, T. Inazu, J. Chem. Soc., Perkin Trans. 1 1997,
3
3 H, Ar-H), 6.53 (s, 8 H, Ar-H), 3.23 [t, J(H,H) ϭ 7 Hz, 8 H, N-
[3k]
239Ϫ246.
H. Takemura, T. Shinmyozu, T. Inazu, Coord.
[3l]
CH2-], 2.81 (s, 12 H, N-CH3), 1.50 (m, 4 H, N-CH2-CH2-CH2-)
ppm. C28H35N7O6: calcd. C 59.46, H 6.24, N 17.33; found C 59.43,
H 6.22, N 17.32.
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[3m]
H. Takemura, S. Osada, T. Shinmyozu, T.
[3n]
G.
1
2c·2TNB: M.p. 166Ϫ166.1 °C (dec). H NMR (CDCl3): δ ϭ 9.38
3
[3o]
(s, 6 H, Ar-H), 6.71 (s, 8 H, Ar-H), 3.17 [t, J(H,H) ϭ 7 Hz, 8 H,
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N-CH2-], 2.80 (s, 12 H, N-CH3), 1.62 [quint, 3J(H,H) ϭ 7 Hz, 8 H,
N-CH2-CH2-], 1.46 [quint, 3J(H,H) ϭ 7 Hz, 4 H, N-CH2-CH2-
CH2-] ppm. C38H46N10O12: calcd. C 54.67, H 5.55, N 16.78; found
C 54.88, H 5.54, N 16.70.
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Supporting Information: x,y,z files of the Conflex-optimized struc-
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One of the reviewers of this article recommended the use of
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