Shape-persistent cyclyne-type azamacrocycles: Synthesis, unusual light-emitting characteristics, and specific recognition of the Sb(V) ion

Article abstract of DOI:10.1016/S0040-4039(02)02829-0

Simple members of arene-azaarenecyclynes as a novel family of geometrically-controlled and shape-persistent azamacrocycles have been synthesized. Noteworthy is the specific recognition function for Sb(V). The synthesized azamacrocycles, in particular the

Full text of DOI:10.1016/S0040-4039(02)02829-0

TETRAHEDRON
LETTERS
Pergamon
Tetrahedron Letters 44 (2003) 1469–1472
Shape-persistent cyclyne-type azamacrocycles: synthesis, unusual
light-emitting characteristics, and specific recognition
of the Sb(V) ion
Shigeya Kobayashi,a Yoshihiro Yamaguchi,a Tateaki Wakamiya,a Yoshio Matsubara,a
Kunihisa Sugimotob and Zen-ichi Yoshidaa,*
aFaculty of Science and Engineering, Kinki University, 3-4-1 Kowakae, Higashi-Osaka 577-8502, Japan
bX-Ray Research Laboratory, Rigaku Corporation, 3-9-12 Matsubara, Akishima, Tokyo 196-8666, Japan
Received 30 October 2002; revised 8 December 2002; accepted 13 December 2002
Abstract—Simple members of arene–azaarenecyclynes as a novel family of geometrically-controlled and shape-persistent aza-
macrocycles have been synthesized. Noteworthy is the specific recognition function for Sb(V). The synthesized azamacrocycles, in
particular the Sb(V) complex, have unusually strong light-emitting property. © 2003 Elsevier Science Ltd. All rights reserved.
Structually well-defined macrocycles continue to attract
strong interest, because of the emerging unique proper-
ties (such as specific recognition, selective binding, and
complexation) and the resulting molecular functions.
As such an example, we recently reported a novel
family of cyclynes (oxaarenecyclynes) (1) containing
oxygen atoms and benzene rings, focusing on (1) syn-
thesis, (2) very unique reaction of a simple member
(n=2, m-phenylene system),1 and (3) supramolecular
C60 complexes with higher members (n=4, m- and
p-phenylene system).2
Arene–azaarenecyclynes (2) containing alternately
arranged pyridine and benzene rings in a m-bonding
fashion are more geometrically-controlled and shape-
persistent azamacrocycles than oxaarenecyclynes 1. We
report here (1) synthesis3 of simple members (3a–c), (2)
unusual light-emitting characteristics, and (3) specific
recognition of the Sb(V) ion.
Cyclynes 3 can be effectively synthesized by repeating
the Sonogashira Pd coupling reaction.4 Thus, dimer 6,
which is a key compound in the synthetic route, was
prepared by the Pd coupling reaction between bromo-
derivative 4 prepared from 2,6-dibromopyridine and 5
having a terminal acetylene unit prepared from m-
iodoaniline or methyl 3-nitrobenzoate (Scheme 1). The
obtained 6 was converted to 7 by alkaline hydrolysis of
its TMS group, and to 8 by iodination5 of the triazene
group. The Pd coupling reaction between 7 and 8 gave
compound 9. Finally, 3a and 3b were provided by the
intramolecular Pd-catalyzed cyclization of the precursor
compound obtained by iodination followed by alkaline
hydrolysis of 9a and 9b. The cyclyne 3b with methoxy-
carbonyl groups was converted into 3c with butoxycar-
bonyl groups by treatment with BuONa in almost
quantitative yield. Although the solubility of 3a and 3b
toward the organic solvent was extremely low, that of
3c was much improved.
Keywords: azamacrocycles; antimony pentachloride; coupling reac-
tion; molecular recognition.
* Corresponding author. Tel.: +81-6-6721-2332 (ext. 4121); fax: +81-
6-6723-2721; e-mail: yamaguch@chem.kindai.ac.jp
The structure of 3a–c was confirmed by spectral data
(1H and 13C NMR and HR-FAB MS).6 The 1H and 13
C
NMR spectra of 3a–c are simple, comprising high
0040-4039/03/$ - see front matter © 2003 Elsevier Science Ltd. All rights reserved.
PII: S0040-4039(02)02829-0

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S. Kobayashi et al. / Tetrahedron Letters 44 (2003) 1469–1472
i
Scheme 1. Reagents and conditions: (a) (i) PrMgCl/THF, then I2, (ii) trimethylsilylacetylene/Pd(Ph3P)2Cl2/CuI/Et3N; (b) (i)
Br2/Ag2SO4/conc. H2SO4, (ii) SnCl2·2H2O/EtOH, (iii) NaNO2/conc. HCl, then Et2NH/K2CO3/H2O, (iv) trimethylsilylacetylene/
Pd(Ph3P)2Cl2/CuI/Et3N, (v) KOH/MeOH/CHCl3; (c) (i) NaNO2/conc. HCl, then Et2NH/K2CO3/H2O, (ii) trimethylsilylacetylene/
Pd(Ph3P)2Cl2/CuI/Et3N, (iii) KOH/MeOH/CHCl3; (d) Pd(Ph3P)2Cl2/CuI/Et3N; (e) KOH/MeOH/CHCl3; (f) I2/CH2ClCH2Cl; (g)
Pd(Ph3P)2Cl2/CuI/Et3N–THF (2:1, v/v); (h) BuONa/BuOH/CHCl3.
symmetry of the molecules. The inner protons of 3 are
observed at the lowest field (3a: l 8.67; 3b: l 8.84; 3c:
l 8.85) among the aromatic protons and at lower field
and pyridine rings involving shape-persistent macrocy-
cles. The sp carbon atoms of 3 (3a: l 92.1, 90.6; 3b: l
93.0, 89.6; 3c: l 92.7, 89.6) also resonate at slightly
lower field than those of phenylpyridylacetylene (l 88.9,
88.4) and 1,3-PBP (l 88.8, 88.6), reflecting the ring
strain in the molecule.
than
the
corresponding
proton
of
1,
3-
di(pyridylethynyl)benzene (1,3-PBP) (l 7.82), an acyclic
homologue of arene–azaarenecyclynes. Since the chemi-
cal shifts of the outer protons on the benzene ring of 3
are comparable to those of 1,3-PBP, the low-field shift
of the inner protons is presumably due to greater
anisotropic effects from the neighboring triple bonds
The molecular structure of 3b and 3c was determined
by single-crystal X-ray analysis.7 As shown in Figure 1,
3b has a completely coplanar structure with some bond
Figure 1. ORTEP drawing of 3b (a: front view; b: side view; c: packing structure). Ellipsoids are drawn at 50% probability.

S. Kobayashi et al. / Tetrahedron Letters 44 (2003) 1469–1472
1471
angle strain at CꢀCꢁCꢀC (168.7 and 171.0°).8 This
result is consistent with that obtained from 13C NMR.
The crystal structure of 3c was similar to that of 3b.
Unfortunately, both 3b and 3c did not construct the
assembling layer by p–p stacking in spite of their com-
pletely coplanar structure.
The absorption spectra (including the absorption coeffi-
cients) of 3a–c are very similar to each other. Notewor-
thy is that arene–azaarenecyclynes emit unusually
intense fluorescence (Table 1), different from the acyclic
homologue, 1,3-PBP (uem=329 nm, bem=0.026). It is
very interesting to observe such strong fluorescence in
spite of the interruption of p-electron conjugation by
m-bonding.
Figure 3. Changes in the fluorescence spectrum of 3c (3.31×
10−7 M in CH2Cl2) upon addition of SbCl5 (6.62×10−7 M) at
295 K.
Surprisingly dramatic changes in the UV–vis (Fig. 2)
and fluorescence (Fig. 3 and Table 1) spectra were
observed upon addition of antimony pentachloride to a
CH2Cl2 solution of 3c at ambient temperature. As
shown in Figure 3 and Table 1, fluorescence emission
maximum (uem) is shifted significantly to longer wave-
length and fluorescence yield (bem) greatly increases.
1
From the H NMR spectra9 (appeared at lower field
with very simple structure) and Job plots (Fig. 4), this
luminophor is inferred to be the 1:1 complex (10) with
an antimonyꢀnitrogen bond.10,11
Table 1. Photophysical data of arene–azaarenecyclynes
(3a–c) and 3c–SbCl5 complex (10)
a
Figure 4. Continuous-variation method for the complex
between 3c and SbCl5 in CH2Cl2. Total concentration=3.98×
10−5 M.
Compd
umax (nm)
uem (nm)
bem
3ab,c
277, 292, 316, 322
277, 287, 314, 322
277, 292, 316, 322
286, 293, 301, 323, 382
357
356
355
433
0.27
0.11
0.18
0.41
3bb,c
3cb,d
b,d
3c–SbCl5
a Quantum yield is determined relative to Quinine (bem=0.55 in 0.1
M H2SO4) at 295 K.
b uex=315 nm (3a), 312 nm (3b), 312 nm (3c), 379 nm (3c–SbCl5).
c Solvent: CHCl3.
d Solvent: CH2Cl2.
Other metal salts, for example, antimony trichloride
and zinc halides, did not exert any effects on fluores-
cence. Thus, 3c (3 in general) is very useful for the
specific recognition of the Sb(V) ion. To our knowl-
edge, this is the first example for the recognition of
toxic Sb(V). Since the fluorescence intensity due to the
complex formation varies in proportion to the concen-
tration of the Sb(V) ion (Fig. 5), 3c could serve as a
sensor for the Sb(V) ion. We note that antimony pen-
tachloride does not react with the benzene ring12 and
triple bond13 in 3c, different from Komatsu’s and Swa-
ger’s papers. Investigation on novel functions emerging
from the 3c–SbCl5 complex is currently in progress. The
result will be published in due course.
Figure 2. Changes in the UV–vis spectrum of 3c (1.99×10−5
M in CH2Cl2) upon addition of SbCl5 (0.00, 0.40, 0.80, 1.19,
1.59, 1.99 (×10−5 M)) at 295 K.

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S. Kobayashi et al. / Tetrahedron Letters 44 (2003) 1469–1472
MHz, CDCl3; ring and triple bond carbon chemical
shift): l 144.2, 143.8, 137.0, 129.1, 128.6, 123.4, 122.9,
92.1, 90.6; HR-MS (FAB, positive-ion mode, matrix:
3-NBA) calcd. for C30H15N2 ([M+H]+) 403.1235, found
403.1219.
1
Compound 3b: H NMR (300 MHz, CDCl3; ring-proton
chemical shift): l 8.84 (2H, t, J=1.2 Hz), 8.11 (4H, d,
J=1.2 Hz), 7.73 (2H, t, J=8.0 Hz), 7.38 (4H, d, J=8.0
Hz); 13C NMR (75.4 MHz, CDCl3; ring and triple bond
carbon chemical shift): l 147.8, 143.8, 137.0, 131.3, 130.2,
123.7, 123.6, 93.0, 89.6; HR-MS (FAB, positive-ion
mode, matrix: 3-NBA) calcd. for C34H18N2O4 518.1267,
found 518.1233.
1
Compound 3c: H NMR (300 MHz, CDCl3; ring-proton
chemical shift): l 8.85 (2H, t, J=1.8 Hz), 8.10 (4H, d,
J=1.8 Hz), 7.73 (2H, t, J=7.8 Hz), 7.38 (4H, d, J=7.8
Hz); 13C NMR (75.4 MHz, CDCl3; ring and triple bond
carbon chemical shift): l 147.1, 143.6, 137.2, 131.4, 130.1,
123.8, 123.2, 92.7, 89.6; HR-MS (FAB, positive-ion
mode, matrix: 3-NBA) calcd. for C40H30N2O4 602.2206,
found 602.2181.
Figure 5. Plot of the luminescence intensity (at 433 nm) of the
complex versus concentration of SbCl5 ([3c]=6.64×10−6 M,
[SbCl5]=6.64×10−7 M, 6.64×10−8 M and 6.64×10−9 M) at 295
K.
Acknowledgements
7. Crystal data for 3b·4CHCl3: C38H22N2O4Cl12, M=
(
996.04, triclinic, P1 (c2), a=7.624(2), b=9.677(2), c=
We thank Professor M. Munakata (Kinki University)
3
,
,
15.715(5) A, i=96.927(9)°, V=1071.4(5) A , Z=1,
for the single-crystal X-ray analysis of 3b. This work
D
calcd=1.544 g/cm3, R=0.085, RW=0.225, Quantum
CCD area detector coupled with a Rigaku AFC8 diffrac-
tometer, 15959 measured reflections, Mo Ka, 4896
unique (Rint=0.021), 286 variables [I>2|(I)].
was supported by
a Grant-in-Aid for Scientific
Research (No. 13305062 and 14540507) from the Min-
istry of Education, Science, Sports, and Culture of
Japan.
Crystal data for 3c·2CHCl3: C42H32N2O4Cl6, M=841.44,
(
triclinic, P1 (c2), a=8.743(6), b=9.912(8), c=12.357(9)
3
,
,
A, i=70.27(2)°, V=969.7(13) A , Z=1, Dcalcd=1.441
g/cm3, R=0.103, RW=0.236, Rigaku Mercury, 7723
measured reflections, Mo Ka, 5920 unique (Rint=0.075),
261 variables [I>2|(I)].
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ara, Y.; Yoshida, Z. J. Am. Chem. Soc. 2000, 122,
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3. The carbocyclic system of 3 was reported by Oda and
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[2.2.2.2]metacyclophane-1,9,17,25-tetrayne (see Ref. 3).
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1
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8.10 (4H, d, J=1.2 Hz), 7.77 (2H, t, J=8.0 Hz), 7.41
(4H, d, J=8.0 Hz).
1
3c–SbCl5: H NMR (300 MHz, CD2Cl2): l 9.59 (2H, t,
J=1.2 Hz), 8.58 (2H, t, J=8.0 Hz), 8.40 (4H, d, J=1.2
Hz), 7.99 (4H, d, J=8.0 Hz).
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hold, M. Z. Anorg. Allg. Chem. 2001, 627, 1582–1588.
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1
6. Compound 3a: H NMR (300 MHz, CDCl3; ring-proton
chemical shift): l 8.67 (2H, t, J=1.2 Hz), 7.68 (2H, t,
J=7.5 Hz), 7.43 (4H, dd, J=8.4 and 1.2 Hz), 7.35 (2H,
t, J=8.4 Hz), 7.32 (4H, d, J=7.5 Hz); 13C NMR (75.4
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