C39, 3.66 Å; C17-C36, 3.65 Å). Thus, the benzene rings
thalenoparacyclophanes are known as π-acids and can be
reduced chemically and electrochemically to produce the
corresponding radical anions and dianions,11,12 [3.3]paracy-
clophane behaves as a π-base to form the CT-complex with
tetracyanoethylene (TCNE) in solution and in the solid
state.13 The cyclic oligophenylene 2, like [3.3]paracyclo-
phane, forms CT-complexes with TCNE (λmax ) 638 nm)
and DDQ (λmax ) 790 nm) in CH2Cl2. Interestingly, the
oxidation potential of 2 measured by cyclic voltammetry is
fairly low (E1/2(1) ) 0.85 V vs Fc/Fc+),14 whereas 9, 10, and
12 show no oxidation peak under similar conditions.
stand nearly parallel in contrast to 1,8-diphenylnaphthalene
8
2
2
9. Each benzene carbon’s Csp -Csp contact is 2-12% shorter
than the sum of the van der Waals radii (3.40 Å). On the
other hand, the naphthalene parts indicate a splayed structure,
and the intramolecular distances (C4-C5 and C26-C27) are
2.44 and 2.45 Å, respectively, whereas the C1-C8 and C23-
C30 distances are 2.59 and 2.58 Å, respectively. Therefore,
the structure of the naphthalene parts is almost the same as
that of 3-bromo-1,8-dimethylnaphthalene.9 Noteworthy is the
high coplanarity of the benzene rings, the maximum atomic
deviations from the least-squares planes of the four benzene
rings being 0.02-0.05 Å. In contrast, the X-ray analyses of
[2.2]- and [3.3]paracyclophanes revealed bending of the
benzene rings.10 Therefore, the ring strain in 2 is mainly
released by bending six pivot bonds. The out-of-plane
deformation angles of the C-C bonds between the two
phenyl rings of the biphenyl chains have an average value
of 4.1°, and those between the phenyl and naphthalene groups
have an average value of 2.2° to the phenyl rings. Thus, 2
can be regarded as a very stable strained molecule, melting
at 460-462 °C without decomposition.
The title compound 2 and related compounds (9, 10, and
12) show strong fluorescence in solution and in the solid
state. UV and fluorescence spectra of 2, 9, 10, and 12 in
benzene are summarized in Table 1. The absorption maxima
Table 1. Fluorescence Quantum Yields and Absorption
Coefficients of 2, 9, 10, and 12
UV
fluorescence
compound
λmax/nm
ꢀ 104/M-1 cm-1
λ
max/nm
Φfa
9
12
10
2
302
304
315
313
1.23
4.30
3.49
5.67
377
389
393
427
0.11
0.34
0.41
0.12
Although strained cyclophanes and oligophenylenes such
as 1,2:9,10-dibenzo[2.2]paracyclophane-1,9-diene and naph-
(4) For general reviews, see (a) Balasubramaniyan, V. Chem. ReV. 1966,
66, 567. (b) Ko¨nig, P. Topics Curr. Chem. 1998; 196, 91.
a The quantum yield was calculated in benzene by using a 0.5 M solution
of quinine sulfate as a standard (Φf ) 0.546).
(5) All new compounds were fully characterized by spectroscopic
analyses. The selected data are as follows: 2, colorless cryst, mp 460-462
°C, EI-MS m/z 556 (M+); 1H NMR (CDCl3) δ 6.928 (8H, d, J ) 7.7 Hz),
7.104 (8H, d, J ) 7.7), 7.548 (4H, dd, J ) 7.2 and 1.3), 7.605 (4H, dd, J
) 7.8 and 7.2), 7.985 (4H, dd, J ) 7.8 and 1.3); 13C NMR (CS2:CDCl3 )
3:1) δ 124.99, 125.58, 129.03, 129.08, 130.06, 130.55, 135.35, 138.15,
139.65, 140.97; HRMS m/z calcd for C44H28 556.2191, found 556.2185.
10: colorless cryst, mp 239-240 °C, EI-MS m/z 558 (M+); 1H NMR
(CDCl3) δ 6.939-7.008 (10H, m), 6.973 (4H, d, J ) 8.3), 7.000 (4H, d, J
) 8.3), 7.456 (2H, dd, J ) 7.0 and 1.5), 7.500 (2H, dd, J ) 7.0 and 1.5),
7.580 (2H, dd, J ) 8.0 and 7.0), 7.591 (2H, dd, J ) 8.0 and 7.0), 7.981
(2H, dd, J ) 8.0 and 1.5), 7.984 (2H, dd, J ) 8.0 and 1.5); 13C NMR
(CDCl3) δ 125.14, 125.42, 125.76, 127.08, 128.33, 128.64, 128.66, 129.45,
129.96, 130.10, 130.73, 131.03, 135.44, 138.61, 140.16, 140.51, 141.80,
143.16; HRMS m/z calcd for C44H30 558.2348, found 558.2322.
(6) Ibuki, E.; Ozasa, S.; Fujioka, Y.; Mizutani, H. Bull. Chem. Soc. Jpn.
1982, 55, 845.
of 2, 9, 10, and 12 are similar, whereas 2 shows the largest
Stokes shift (114 nm), presumably due to the dimerized
structure. It is worth noting that 2 shows much lower
fluorescence quantum yield as compared to 10, although the
conformational mobility of 2 seems to be smaller than that
of 10. Further studies on the electronic structure and
properties of 2 are now under way.
Acknowledgment. We thank Dr. Hiroyuki Matsuzaka for
the measurement of X-ray analysis, Mr. Masaki Sugita, and
Prof. Haruo Inoue for the determination of fluorescence
quantum yields. Financial support by a Grant-in-Aid for
Scientific Research on Priority Areas from the Ministry of
Education, Science and Culture, Japan (11119256) is grate-
fully acknowledged.
(7) X-ray intensity data were measured on a Rigaku RAXIS-RAPID
Imaging Plate diffractometer with Mo KR radiations using a crystal with
the dimension of 0.20 × 0.40 × 0.05 mm. A total of 6571 reflections were
collected up to 2θ ) 55.0°, of which 6565 had I > -10.00σ(I), and were
used in the refinement. The crystal structure was solved by a direct method
(SIR92), expanded using Fourier techniques (DIRDIF94), and refined by
the full matrix least-squares method. All the non-hydrogen atoms were
refined anisotropically, and the hydrogen atoms were included but not
refined. Crystal data for 2: C44H28, FW ) 556.71, orthorhombic, space
group Pbca (#61), a ) 24.1982(5) Å, b ) 30.3055(7) Å, c ) 7.8559(2) Å,
V ) 5761.0(2) Å3, Z ) 8, dcalcd ) 1.284 g cm-3, R1 ) 0.044 and wR2 )
0.118 for 397 variables, GOF ) 0.62.
OL0001012
(11) de Meijere, A.; Gerson, F.; Ko¨nig, B.; Reiser, O.; Wellauer, T. J.
Am. Chem. Soc. 1990, 112, 6827; Gerson, F.; Scholz, M.; de Meijere, A.;
Ko¨nig, B.; Heinze, J.; Meerholz, K. HelV. Chim. Acta 1992, 75, 2307.
(12) Bieber, W.; Vo¨gtle, F. Angew. Chem., Int. Ed. Engl. 1977, 16, 175.
Gerson, F.; Heckendorn, R.; Mo¨ckel, R.; Vo¨gtle, F. HelV. Chim. Acta 1985,
68, 1923.
(8) House, H. O.; Koepsell, D. G.; Campbell, W. J. J. Org. Chem. 1972,
37, 1003; Vo¨gtle, F.; Papkalla, T.; Koch, H.; Nieger, M. Chem. Ber. 1990,
123, 1097.
(9) Jameson, M. B.; Penfold, B. R. J. Chem. Soc. 1965, 528.
(10) Brown, C. J. J. Chem. Soc. 1953, 3265; Lonsdale, D. K.; Milledge,
H. J.; Rao, K. V. K. Proc. R. Soc. 1960, A255, 82; Gantzel, P. K.; Trueblood,
K. N. Acta Crystallogr. 1965, 18, 958; Hope, H.; Bernstein, J.; Trueblood,
K. N. Acta Crystallogr. 1972, B28, 1733.
(13) Sheehan, M.; Cram, D. J. J. Am. Chem. Soc. 1969, 91, 3553.
(14) Cyclic voltammetric analysis: 1,2-dichlorobenzene, 0.05 M Bu4-
NPF6, glassy carbon working, Pt counter, and Ag/Ag+ reference electrodes,
298 K.
Org. Lett., Vol. 2, No. 14, 2000
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