Observing second-order nonlinear optical properties by symmetry breaking in centrosymmetric furan-containing oligoaryl cyclophandienes

Article abstract of DOI:10.1002/chem.200902115

Centrosymmetric furan-containing cyclophandienes 3 and 4, synthesized by our furan annulation protocol, have been shown to exhibit extraordinarily large Stokes shifts and second-order nonlinear optical β values. The β values for 3 and 4 measured at 1.32 m

Full text of DOI:10.1002/chem.200902115

FULL PAPER
DOI: 10.1002/chem.200902115
Observing Second-Order Nonlinear Optical Properties by Symmetry
Breaking in Centrosymmetric Furan-Containing Oligoaryl Cyclophandienes
Hsin-Chieh Lin,[a] Jui-Hung Hsu,*[b] Chao-Kuei Lee,[c] Oliver Yung-Hui Tai,[d]
Chin-Hsien Wang,[d] Chih-Ming Chou,[a] Kuang-Yen Chen,[a] Yi-Lin Wu,[a] and
Tien-Yau Luh*[a]
Abstract: Centrosymmetric furan-con-
taining cyclophandienes 3 and 4, syn-
thesized by our furan annulation proto-
col, have been shown to exhibit extra-
ordinarily large Stokes shifts and
3 and 4 are similar to those of respec-
tive cyclophenes 1a and 7 in which
strong hyperpoarizable interactions be-
tween two twisted p-systems (oligoaryl
and bridging double bond) might take
place. Symmetry breaking due to the
resonance contribution (cf. 2) and the
unique structural features of 3 and 4
has been used to account for this un-
usual photophysical behavior.
Keywords:
oligoaryls
nonlinear
breaking
cyclophandienes
photochemistry
·
·
second-order nonlinear optical
b
·
values. The b values for 3 and 4 mea-
sured at 1.32 mm are 208 and 530ꢀ
10ꢀ30 esu, respectively. The b values of
optics
·
symmetry
Introduction
the excited state of the phenylenevinylene-based conjugated
polymers has been rationalized by a conformational kink
mechanism.[5] In addition, a dynamic equilibrium in the pop-
ulation of a centrosymmetric and a noncentrosymmetric site
has been used to elucidate the excitation properties of di-
phenyloctatetraene in n-tetradecane.[2d]
Whilst symmetry and symmetry breaking are central con-
cepts in contemporary physics from the level of the universe
to the level of elementary particles,[1] symmetry breaking of
molecular systems in condensed matter has been shown to
occur in ground and/or low-lying excited states.[2–4] Cou-
plings between electron and molecular vibrations in cyanine
dyes and related linear conjugated systems are known to
lead to symmetry breaking.[4] The electron localization in
Lack of a center of symmetry in a molecule or a bulk ma-
terial is a general criterion to exhibit second-order nonlinear
optical (NLO) properties.[6] However, molecular materials
with a centrosymmetric structure can be NLO active in the
solid state when a magnetic dipole[7] or an electric quadru-
pole[8] is present. In addition, if the molecules can aggregate
in a noncentrosymmetric manner, molecular species may ex-
perience different interactions at the interface where the in-
version symmetry may be broken.[9] Intermolecular charge
transfer may cause symmetry breaking leading to second-
harmonic generation.[9a] Quadrupolar organic dyes have
been shown to be solvatochromic and symmetry breaking
may take place.[3] Hyper-Rayleigh scattering (HRS) at the
doubled frequency, 2w, has been observed for centrosym-
metric dichloro- and tetrachloroethenes in solution.[10] Al-
though the intensities are relatively low, an involvement of
cooperative scattering by neighboring molecules[10] including
solvent molecules[11] has been suggested to account for these
observations.
[a] Dr. H.-C. Lin, Dr. C.-M. Chou, K.-Y. Chen, Y.-L. Wu, Prof. T.-Y. Luh
Department of Chemistry, National Taiwan University
Taipei 106 (Taiwan)
Fax : (+886)2-2364-4971
E-mail: tyluh@ntu.edu.tw
[b] Prof. J.-H. Hsu
Department of Materials and Optoelectronic Science
National Sun Yat-sen University,
Kaohsiung 804 (Taiwan)
Fax : (+886)7-525-4099
E-mail: jhsu@mail.nsysu.edu.tw
[c] Prof. C.-K. Lee
Department of Photonics, National Sun Yat-sen University
Kaohsiung 804 (Taiwan)
[d] Dr. O. Y.-H. Tai, Prof. C.-H. Wang
Department of Physics, National Sun Yat-sen University
Kaohsiung 804 (Taiwan)
We recently found that furan-containing cyclophenes 1 ex-
hibit “monomer-like” excitation in the absorption spectra,
but have a large Stoke shift in the emission profiles.[12] In ad-
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/chem.200902115.
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dition, 1 showed extraordinary second-order nonlinear opti-
cal properties attributed to the geometric restriction of 1
rendering charge-transfer interactions between two twisted
p-systems.[12a,13] The contribution of the resonance structure,
such as 2, to the charge transfer in 1 may be crucial to this
unusual NLO behavior. The
might be no direct conjugative interactions between the two
oligoaryl moieties in 3 and 4 through the bridging double
bonds. It seems likely that the two oligoaryl moieties in
these cyclophandienes would not be excited at the same
electron delocalization may
take place in their respective
hemisphere in which the elec-
tron-vibration interaction may
be strong enough to induce the
polar character of 1. It is envis-
aged that the more rigid centro-
symmetric cyclophandienes
3
and 4 might lead to symmetry
breaking because of the reso-
nance contribution (cf. 2). We
have tested this viewpoint and
now wish to report the synthe-
sis and photophysical properties
of 3, 4, and related compounds
5–9.
Results and Discussion
Synthesis: The oligoaryl moiet-
ies in 3–9 were synthesized by
using our recently developed
furan annulation protocol[14,15]
(Schemes 1–3) and the details
are described in the Experi-
mental Section. The presence
of the butyl substituents would
ensure the solubility of these
substrates in organic solvents
for physical measurements.
Absorption, emission, and elec-
trochemical properties: The ab-
sorption and emission profiles
of cyclophandienes 3 and 4 are
shown in Figure 1 and the pho-
tophysical properties of 1a and
3–9 are compared in Table 1.
The lmax of 3 and 4 appeared at
comparable wavelengths to
those of the corresponding acy-
clic oligoaryls 8 and 9, respec-
tively. The observation of the
monomer-like absorption spec-
tra in 3 and 4 suggests that the
upper and lower hemispheres in
these cyclophandienes would,
relatively speaking, be inde-
pendent in the photoexcitation
Scheme 1. Synthesis of 3: a) 1) nBuLi, THF, ꢀ788C, 50 min; 2) bis(4-formylbenzyl) sulfide, THF, ꢀ788C, 1 h;
RT, 30 min; 3) TFA, RT, 12 h, 58%; b) DIBAL, THF, 08C, 3 h, 90%; c) PBr3, C6H6, RT, 6 h, 92%;
d) Na2S·9H2O, EtOH, reflux, 12 h, 66%; e) 1) LDA, THF, 08C, 1 h; 2) MeI, RT, 1 h, 80%; f) 1) Me3O·BF4,
CH2Cl2, 08C, 2 h; RT, 12 h; 2) tBuOK, THF, RT, 6 h, 21%; g) 1) nBuLi, THF, ꢀ788C, 50 min; 2) 4,4’-diformyl-
Z-stilbene, THF, ꢀ788C, 1 h; RT, 30 min; 3) TFA, RT, 12 h, 36%; h) DIBAL, THF, 08C, 3 h, 95%; i) MnO2,
CH2Cl2, RT, 6 h, 98%; j) TiCl4, Zn, py, reflux, 16 h, 15%. TFA: CF3CO2H; DIBAL: iBu2AlH; LDA: LiNiPr2;
process. In other words, there py: pyridine.
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Chem. Eur. J. 2009, 15, 13201 – 13209

Centrosymmetric Furan-Containing Oligoaryl Cyclophandienes
FULL PAPER
time upon irradiation. As such
symmetry might be broken
during the course of excitation.
It is noteworthy that both 3
and 4 exhibited, in addition to
the absorptions due to respec-
tive oligoaryl chromophores,
tailing at longer wavelengths,
which could be assigned to a
symmetry-forbidden
transi-
tion.[2d] The observation of the
partially allowed transition
could possibly be attributed to
Scheme 2. Synthesis of 4, 6, and 9: a) MnO2, CH2Cl2, RT, 6 h, 96%; b) TiCl4, Zn, py, reflux, 16 h, 47%; c) H2,
Pd/C, MeOH/THF, 50 psi, 1 h, 93%; d) 1) PBr3, C6H6/THF, RT, 6 h; 2) LiAlH4, THF, 08C, 3 h, 82%.
electron-vibration
interac-
tions.[2d] According to our previ-
ous studies,[12a] this vibronic
transition in 3 and 4 may have
charge-transfer character. The
furan moiety can be considered
as an electron-donating group
+
with a sp value of ꢀ0.39.[16]
Like cyclophenes 1,[12a] the
bridging double bonds in 3 and
4 can serve as an electron ac-
Scheme 3. Synthesis of 7: a) nBuLi, THF, ꢀ788C, 70 min; 2) 4,4’-diformylbibenzyl, THF, ꢀ788C, 1 h; RT, 4 h,
3) TFA, RT, 12 h, 52%; b) MnO2, CH2Cl2, RT, 6 h, 90%; c) TiCl4, Zn, py, reflux, 16 h, 20%.
Table 1. Photophysical and b values of 1a and 3–9 in CHCl3.
[b]
lmax [nm]
lem [nm]
F[a]
b1.32
1a
3
4
325
331
369
361
315
367
325
378
501
550
513
451
389
498
380
448
0.28
0.01
0.26
0.74
0.59
0.42
0.83
0.85
220
208 (195)[c]
530 (542)[c]
n.d.[d]
6
7
8
9
n.d.[d]
506
n.d.[d]
n.d.[d]
[a] Measured in EtOAc by using coumarin I as a reference (F=0.99).
[b] At 10ꢀ30 esu. [c] The b values in parenthesis were measured in cyclo-
hexane. [d] n.d.: not detected.
ceptor. Accordingly, a partial negative charge around a
bridging double bond might be generated after photoexcita-
tion.[3,17] It seems likely that the vibronic coupling might be
responsible for such partially allowed charge-transfer transi-
tions.[2d]
As shown in Figure 1, broad and structureless emissions
with relatively large Stokes shifts were observed for 3 and 4.
Similar to those of 1,[12] the large Stokes shift would presum-
ably be the consequence of a substantial change of the geo-
metric structure from the ground to the excited state. It is
noteworthy that the lem of 3 is more red-shifted than that of
1a and the quantum yield of 3 was very low.[12]
These unusual emission properties may suggest that signif-
icant interactions between the oligoaryl chromophores and
the bridging olefin might take place in the excited states of
3 and 4. The emission maximum of 3 appears at a longer
wavelength than that of 4, and the quantum yield of 4 was
higher than that of 3. Because of the difference in strain of
Figure 1. Absorption and emission spectra of the teraryl system (top) and
pentaaryl system (bottom) in CHCl3. Cyclophandiene 3 and 4: c, cy-
clophene 1a and 7: a, cyclophane 5 and 6: d, and monomer 8 and
9: g.
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T.-Y. Luh, J.-H. Hsu et al.
the oligoaryl moieties in 3 and 4, the relaxation energy in
the lowest excited states may be reduced from 3 to 4.[17]
The first oxidation potential for 3 (533 mV) was compara-
ble with that for 1a (540 mV), but lower than that for 5
(614 mV).[12b] These results suggest that the conjugation in-
teractions between the bridging double bond(s) and the oli-
goaryl moieties in 1a and 3 might occur. Because of longer
conjugation lengths, the oxidation potential for 4 was lower
than that of 3.
cant contributions to the HRS. These results suggest that
the HRS results for 3 and 4 would not be influenced by mul-
tiphoton fluorescence (Figure 3).
Nonlinear optical properties: The hyper-Rayleigh scattering
(HRS) measurements at 1.32 mm in chloroform and in cyclo-
hexane were employed and the results are also summarized
in Table 1. Interestingly, the b values obtained in cyclohex-
ane were comparable to those in chloroform (cf. Figures S2
and S3 in the Supporting Information). These results indi-
cate that solvent may play little role in the second-order
nonlinear properties of 3 and 4 and optical nonlinearity
would be attributed to possible intrinsic properties of these
cyclophandienes.
Figure 3. A plot of PL intensity (IPL) versus incident laser intensity (Iw) in
logarithm scale for 4 in chloroform at 1.32 mm. The line fits IPL /(Iw)n
with power dependence n=2.92. The results confirm the cubic depend-
ence of the multiphoton fluorescence process.
To rule out the possible two-photon fluorescence influ-
ence on the HRS results, Figure 2 shows a plot of the HRS
intensities (I2w) for 4 against log(Iw), in which Iw is the inci-
It is interesting to note that both 3 and 4 have relatively
large b values and cyclophanes without bridging double
bonds (5 and 6) were NLO inactive. The b value of 3 was
similar to that of 1a. This observation suggested that contri-
butions of the twisted interactions between the teraryl chro-
mophore and the acceptor double bond would be alike in
1a and 3. The inversion symmetry of 3 might be broken by
the presence of the butyl substituents, albeit the perturba-
tion arisen from these butyl groups might be small. On the
other hand, centrosymmetric 4 exhibited a HRS response
with b=530ꢀ10ꢀ30 esu and was similar to that of cyclophene
7.
As mentioned earlier, the origin of the second-order opti-
cal nonlinearity in these furan-containing cyclophenes or cy-
clophanedienes may arise from the resonance contribution
(cf. 2). Indeed, the X-ray structure of 1d (see the Figure S5
in the Supporting Information) showed that the bond length
between C1 and the bridging olefinic carbon (C2) was
1.471 ꢂ, that is considerably shorter than the corresponding
carbon–carbon single bonds in trans- or cis-stilbenes (1.481
and 1.489 ꢂ, respectively).[19] In addition, DFT calculations
at the 6-31G** level of 3 and 4 with full geometric optimiza-
tion gave the corresponding bond lengths 1.476 and 1.466 ꢂ,
respectively (see Figures S6 and S7 in the Supporting Infor-
mation). The quantum-chemical calculations and HRS re-
sults suggest that electron delocalization from furan ring to
the bridging double bond might take place so that dipolar
character, such as in 2, might contribute to the ground-state
structures of cyclophandienes 3 and 4. This dipolar character
might lay a foundation to break the symmetry of centrosym-
metric 3 and 4 and, hence, these strained cyclophandienes
might be NLO active. The higher b values for 4 and 7 in
comparison with those of 3 and 1a could be well rational-
ized by conjugation lengths of the oligoaryl moieties.[20]
Figure 2. A plot of representative intensity (I2w) versus incident laser in-
tensity (Iw) in logarithm scale for 4 in chloroform at 1.32 mm. The line fits
I2w /(Iw)n, with power dependence n=2.012. Each data point was the
average value of 300 data points (taken over a period of 5 min, or 1 data
point per second) to avoid intrinsic intensity fluctuations of the optical
parametric amplifier (OPA).
dent laser intensity at 1.32 mm. A slope of 2.01 suggests that
the HRS intensities (I2w) would be quadratic power depen-
dent, or I2w /(Iw)n in which n=2.01.18 It is noteworthy that
,
neither 3 nor 4 exhibited absorption around 660 nm (double
the frequency of the incident laser light at 1.32 mm). There-
fore, no two-photon process would affect the HRS signal.
As for the multiphoton process, the other possibility
would be three-photon emission, which was evidenced by
the cubic power dependence (n=2.92) of the photolumines-
cence intensities of 4. However, no emission intensity at
around 660 nm for 4 was observed and the fluorescence in-
tensity at around 660 nm for 3 was too weak to make signifi-
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Centrosymmetric Furan-Containing Oligoaryl Cyclophandienes
FULL PAPER
[M++H]; found: 271.0799; elemental analysis calcd (%) for C16H14O2S:
C 71.08, H 5.22; found: C 71.05, H 5.15.
As can be seen from Table 1, the b values for 3 and 4 are
unexpectedly large. It is known that b values of multipolar
structures can be comprised of both dipolar and octupolar
terms in the absence of environmental interactions,[21] and a
quadrupolar term would not contribute to b in dilute solu-
tion.[18] Although octupolar character cannot completely be
ruled out at this stage, it is worth to mentioning that neither
3 nor 4 would have pure octupolar symmetry.[21c] As men-
tioned earlier, the second-order nonlinearity of 1a measured
by EFISH and HRS was comparable.[12a] This may reflect
that the dipolar contribution would offer a predominant
role to the NLO properties for 1. As shown in Table 1, the b
values of 1a and 3 (and 4 and 7) are comparable. It seems
likely that the second-order NLO properties of both 1a and
3 (and 4 and 7) might take place by a similar mechanism.
Bis-teraryl diester 11: Under argon, nBuLi (2.5m, 11.0 mL in hexane,
27.5 mmol) was added to a solution of 10[12] (8.00 g, 25.0 mmol) in THF
(180 mL) at ꢀ788C. The mixture was stirred at ꢀ788C for 50 min and
then a solution of bis(4-formylbenzyl) sulfide (2.70 g, 10.0 mmol) in THF
(40 mL) was added to the mixture at ꢀ788C. The mixture was stirred for
1 h at ꢀ788C, and then gradually warmed to RT. After further stirring
for 1 h at RT, TFA (5.5 mL, 60.0 mmol) was added and the mixture was
stirred at RT overnight, quenched with saturated NH4Cl (200 mL), and
the organic layer was separated. The aqueous layer was extracted with
Et2O (150 mLꢀ3). The combined organic layers were washed with satu-
rated NaHCO3 (100 mLꢀ2), brine (100 mL), and then dried (MgSO4),
filtered, and evaporated in vacuo. The resulting residue was triturated
with Et2O and the solid 11 was filtered, washed with a mixture of Et2O/
pentane 1:1, and collected as a fluorescent yellow powder (4.22 g, 58%).
M.p. 150–1528C; IR (KBr): n˜ =2950, 2925, 2869, 1717, 1608, 1506, 1434,
1280, 1176, 1106, 1016, 933, 855, 824, 770, 698 cmꢀ1
;
1H NMR (400 MHz,
(H,H)=7.3 Hz, 6H), 1.44 (sextet,
(H,H)=7.3, 7.8 Hz, 4H), 2.69 (t,
(H,H)=7.8 Hz, 4H), 3.66 (s, 4H), 3.91 (s, 6H), 6.77 (s, 2H), 7.36 (d,
(H,H)=8.2 Hz, 4H), 7.64 (d, 3J(H,H)=8.2 Hz, 4H), 7.74 (d, 3J
(H,H)=
(H,H)=8.3 Hz, 4H); 13C NMR (100 MHz,
CDCl3, 258C, TMS): d =0.95 (t, 3J
A
3J
3J
3J
(H,H)=7.3 Hz, 4H), 1.66 (tt, 3J
ACHUTGTNRENNUG CAHTUNGTRENNUNG
AHCTUNGTRENNUNG
Conclusion
A
R
ACHTUNGTRENNUNG
8.3 Hz, 4H), 8.03 ppm (d, 3J
G
We have depicted that centrosymmetric furan-containing cy-
clophandienes 3 and 4 exhibited extraordinarily large Stokes
shifts and second-order nonlinear optical b values. The b
values were comparable to those of the respective cyclo-
phenes 1a and 7, in which hyperpolarizable interactions be-
tween two twisted p-systems (oligoaryl and a bridging
double bond) might take place. Symmetry breaking due to
the resonance contribution (cf. 2) and the unique structural
features of these molecules may account for this unusual be-
havior.
CDCl3, 258C, TMS): d=13.9, 22.6, 25.7, 32.1, 35.5, 52.0, 111.5, 123.2,
124.4, 125.7, 128.3, 129.3, 130.1, 130.2, 134.7, 137.1, 149.0, 150.8,
166.8 ppm; HRMS (EI): m/z: calcd for C46H46O6S: 726.3015; found:
726.3011; elemental analysis calcd (%) for C46H46O6S: C 76.00, H 6.38;
found: C 75.85, H 6.13.
Bis-teraryl diol 12: A solution of DIBAL (1.0m, 16.5 mL in hexane,
16.5 mmol) was added slowly to a solution of 11 (2.00 g, 2.75 mmol) in
THF (80 mL) stirred under an Ar atmosphere at 08C, and the resulting
mixture was stirred at RT for 3 h. After this time, the mixture was
quenched by pouring it into saturated NH4Cl (100 mL) and the mixture
was stirred for 30 min. After the remaining DIBAL had been completely
quenched, the gel-like organic layer was acidified with HCl (6m, 50 mL)
and extracted with CH2Cl2 (200 mLꢀ3). The combined organic extracts
were washed with saturated NaHCO3 (200 mLꢀ2) and brine (200 mL).
The organic layer was dried (MgSO4), filtered, and evaporated in vacuo
to afford a residue that was recrystallized from CH2Cl2/Et2O to afford 12
as a fluorescent yellow solid (1.75 g, 95%). M.p. 114–1168C; IR (KBr):
n˜ =3355, 3031, 2958, 2933, 2874, 1616, 1510, 1465, 1456, 1425, 1380, 1049,
Experimental Section
Bis(4-formylbenzyl) sulfide: A solution of bis(4-methoxycarbonylbenzyl)
sulfide[22] (47.0 g, 0.14 mol) in THF (150 mL) was added slowly to a sus-
pension of LiAlH4 (21.7 g, 0.57 mol) in THF (250 mL) at 08C. The mix-
ture was stirred for 3 h under a N2 atmosphere, and then quenched care-
fully with water (20 mL). 10% NaOH (20 mL) and water (40 mL) were
then added to afford a white suspension that was filtered through a
silica-gel bed (1 cm), and the filter cake was taken up in CH2Cl2
(500 mL). The organic layer was dried (MgSO4), filtered, and evaporated
in vacuo to give a residue that was recrystallized from CH2Cl2 to yield
bis(4-hydroxymethylbenzyl)sulfide (34.96 g, 91%) as a colorless solid.
M.p. 120–1218C; 1H NMR (400 MHz, CDCl3, 258C, TMS): d=1.76 (s,
2H), 3.58 (s, 4H), 4.65 (s, 4H), 7.22–7.29 ppm (m, 8H); 13C NMR
(100 MHz, CDCl3, 258C, TMS): d=35.5, 65.1, 127.2, 129.2, 137.6,
139.6 ppm; HRMS (EI): m/z: calcd for C16H18O2S: 274.1028; found:
274.1022.
1015, 935, 844, 808 cmꢀ1
0.97 (t, 3J(H,H)=7.4 Hz, 6H), 1.45 (tq, 3J
(quint, 3J(H,H)=7.6 Hz, 6H), 2.70 (t, 3J
ACHTUNGTRENNUNG
;
1H NMR (400 MHz, CDCl3, 258C, TMS): d=
(H,H)=7.4, 7.6 Hz, 4H), 1.68
(H,H)=7.6 Hz, 4H), 3.67 (s,
(H,H)=8.3 Hz, 4H), 7.39 (d,
(H,H)=8.3 Hz, 4H), 7.71 ppm (d,
AHCTUNGTRENNUNG
(H,H)=8.3 Hz, 4H); 13C NMR (100 MHz, CDCl3, 258C, TMS): d=
G
ACHTUNGTRENNUNG
E
4H), 4.71 (s, 4H), 6.66 (s, 2H), 7.36 (d, 3J
G
3J
3J
(H,H)=8.3 Hz, 4H), 7.65 (d, 3J
ACHUTGTNRENNUG CAHTUNGTRENNUNG
14.0, 22.6, 25.8, 32.1, 35.3, 65.1, 109.3, 123.8, 124.1, 125.5, 127.3, 129.2,
130.2, 130.5, 136.6, 139.7, 147.7, 151.6 ppm; HRMS (FAB+): m/z: calcd
for C44H46O4S: calcd: 670.3117; found: 670.3106; elemental analysis calcd
(%) for C44H46O4S: C 78.77, H 6.91; found: C 78.45, H 6.77.
Bis-teraryl dibromide 13: A solution of 12 (4.00 g, 5.96 mmol) in benzene
(150 mL) under N2 was treated with PBr3 (0.45 mL, 4.77 mmol) at RT
and stirred for 6 h. After quenching with water (200 mL), the mixture
was extracted with CH2Cl2 (200 mLꢀ3). The combined organic extracts
were dried (MgSO4), filtered, and evaporated in vacuo to give a residue
that was recrystallized from CH2Cl2/Et2O to afford the 13 as a yellow
solid (4.48 g, 94%). M.p. 108–1108C; IR (KBr): n˜ =3031, 2959, 2932,
2863, 1616, 1509, 1493, 1467, 1229, 1203, 1183, 1098, 935, 842, 815, 681,
A solution of bis(4-hydroxymethylbenzyl) sulfide (33.0 g, 0.12 mol) in
THF (300 mL) was added slowly to a suspension of activated MnO2
(120.9 g, 1.44 mol) in CH2Cl2 (100 mL) at 08C. The reaction mixture was
stirred for 6 h at RT. After passing through a silica-gel bed (5 cm) and
washing with EtOAc (1000 mL), the combined filtrate was evaporated in
vacuo. The residue was recrystallized from MeOH to give bis(4-formyl-
benzyl) sulfide as a white solid (29.93 g, 92%). M.p. 107–1088C; IR
(KBr): n˜ =2959, 2925, 2846, 2745, 1684, 1603, 1577, 1417, 1389, 1302,
601, 499 cmꢀ1
G
;
1H NMR (400 MHz, CDCl3, 258C, TMS): d=0.97 (t,
(H,H)=7.2 Hz, 6H), 1.45 (tq, 3J
(H,H)=7.2, 7.6 Hz, 4H), 1.67 (quintet,
(H,H)=7.6 Hz, 4H), 2.70 (t, 3J
(H,H)=7.6 Hz, 4H), 3.67 (s, 4H), 4.53
(H,H)=8.2 Hz, 4H), 7.41 (d, 3J
(H,H)=
(H,H)=8.2 Hz, 4H), 7.68 ppm (d, 3J
(H,H)=
3J
3J
ACHTUNGTRENNUNG
N
ACHTUNGTRENNUNG
(s, 4H), 6.68 (s, 2H), 7.37 (d, 3J
N
ACHTUNGTRENNUNG
8.2 Hz, 4H), 7.64 (d, 3J
A
ACHTUNGTRENNUNG
1213, 1162, 1103, 854, 832, 780, 739, 694, 611, 513 cmꢀ1
;
1H NMR
(H,H)=
8.2 Hz, 4H); 13C NMR (100 MHz, CDCl3, 258C, TMS): d=14.0, 22.6,
25.8, 32.1, 33.6, 35.4, 109.9, 123.9, 124.2, 125.6, 129.3, 129.5, 130.4, 130.9,
136.4, 136.8, 148.1, 151.2 ppm; HRMS (FAB+): m/z: calcd for
C44H44O279Br2S: 794.1429; found: 794.1442; HRMS (FAB+): m/z: calcd
(400 MHz, CDCl3, 258C, TMS): d=3.63 (s, 4H), 7.40 (d, 3J
N
3
8.1 Hz, 4H), 7.81 (d, J
N
(100 MHz, CDCl3, 258C, TMS): d=35.6, 129.6, 130.0, 135.5, 144.8,
191.6 ppm; HRMS (FAB+): m/z: calcd for C16H15O2S: 271.0793
Chem. Eur. J. 2009, 15, 13201 – 13209
ꢁ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
13205

T.-Y. Luh, J.-H. Hsu et al.
for C44H44O279Br81BrS: 796.1410; found: 796.1403; elemental analysis
calcd (%) for C44H44Br2O2S: C 66.33, H 5.57; found: C 66.23, H 5.71.
4H), 4.71 (d, 3J
(m, 8H), 7.60 (d, 3J
ACHTUNGTRENNUNG
G
ACHTUNGTRENNUNG
4H); 13C NMR (100 MHz, CDCl3, 258C, TMS): d=14.4, 23.0, 26.2, 32.3,
65.2, 109.2, 123.4, 124.0, 124.7, 125.1, 126.3, 126.9, 128.7, 129.5, 129.7,
135.2, 139.2, 151.0 ppm; HRMS (FAB+): m/z: calcd for C44H44O4:
636.3240; found: 636.3235.
TerarylACHTUNGTRENNUNG[3.3]thiacyclophane 14: Na2S·9H2O (282.2 mg, 1.2 mmol) was
added to a suspension of 13 (797.0 mg, 1.0 mmol) in absolute EtOH
(1.5 L) and the mixture was refluxed overnight. After removal of the sol-
vent, the residue was taken up in CH2Cl2 (50 mL). The suspension was
Bis-terarylene dialdehyde 18: A solution of 17 (2.00 g, 3.14 mmol) in
CH2Cl2 (50 mL) was added slowly to a suspension of activated MnO2
(16.35 g, 0.19 mol) in CH2Cl2 (40 mL) at 08C. The reaction mixture was
stirred for 6 h at RT. After passing through a silica-gel bed (5 cm) and
washing with EtOAc (1000 mL), the combined filtrate was evaporated in
vacuo. The residue was recrystallized from CH2Cl2/Et2O to give 18 as a
yellow fluorescent solid (1.95 g, 98%). M.p. 176–1778C; IR (KBr): n˜ =
3015, 2955, 2926, 2869, 2730, 1696, 1603, 1570, 1505, 1482, 1422, 1387,
passed through
a silica-gel bed (1 cm) and washed with CH2Cl2
(100 mLꢀ3). The combined filtrate was evaporated in vacuo to give a
residue that was chromatographed on silica gel (CH2Cl2/hexane 1:4) to
afford 14 as a white solid (440.0 mg, 66%). M.p. 176–1788C; IR (KBr):
n˜ =3032, 2958, 2931, 2862, 1617, 1509, 1492, 1466, 1425, 1104, 936, 846,
1
3
809 cmꢀ1; H NMR (300 MHz, CDCl3, 258C, TMS): d=0.96 (t, J
ACHTUNGTRENNUNG
7.2 Hz, 6H), 1.42 (tq, 3J
T
3
(t, J
G
U
1304, 1213, 1165, 1102, 938, 834 cmꢀ1
;
1H NMR (400 MHz, CDCl3, 258C,
3J
(H,H)=8.0 Hz, 4H), 6.96 (d, 3J
A
ACHTUNGTRENNUNG
TMS): d=0.97 (t, 3J
7.9 Hz, 4H), 1.69 (tt, J
G
ACHTUNGTRENNUNG
8.0 Hz, 4H), 7.30 ppm (d, 3J
AHCTUNGTRENNUNG
3
3
R
ACHTUNGTREN(NUNG H,H)=7.6 Hz,
CDCl3, 258C, TMS): d = 14.0, 22.7, 25.9, 32.0, 37.7, 37.9, 108.4, 123.2,
123.3, 124.8, 129.0, 129.2, 129.9, 136.8, 137.1, 147.3, 151.5 ppm; HRMS
(FAB+): m/z: calcd for C44H44O2S2: 668.2783; found: 668.2772.
4H), 6.65 (s, 2H), 6.85 (s, 2H), 7.40 (d, 3J
ACHTUNGTRENNUNG
3J(H,H)=8.4 Hz, 4H), 7.83 (d, 3J
G
U
ACHTUNGTRENNUNG
8.4 Hz, 4H), 9.97 ppm (s, 2H); 13C NMR (100 MHz, CDCl3, 258C, TMS):
d=14.4, 22.9, 26.1, 32.2, 112.2, 123.2, 124.6, 125.0, 128.8, 129.6, 129.7,
129.9, 134.2, 135.4, 135.7, 148.8, 149.86, 190.6 ppm; HRMS (FAB+): m/z:
calcd for C44H40O4: 632.2927; found: 632.2929.
Teraryl bisthiomethoxycyclophanes 15: LDA (2.0m, 1.9 mL in THF/n-
hexane/ethylbenzene, 3.8 mmol) was added to a solution of 14 (0.90 g,
1.30 mmol) in THF (60 mL) at 08C and the mixture was stirred for 1 h.
MeI (0.34 mL, 5.40 mmol) was then added at 08C, and the reaction mix-
ture was slowly warmed to RT and stirred for a further 1 h. Water
(30 mL) was then added and the mixture was extracted with CH2Cl2
(20 mLꢀ3). The combined organic layers were dried (MgSO4), filtered,
and evaporated in vacuo to give a residue that was chromatographed on
silica gel (CH2Cl2/hexane 1:3) to afford a mixture of 15 as a white solid
(0.75 g, 80%), which was used directly for the next reaction. HRMS (EI):
m/z: calcd for C45H46O2S: 696.3096; found: 696.3085.
TerarylACHTNUTRGNEUNG[2.2]cyclophandiene 3
Method A: Under N2, a well-stirred suspension solution of 15 (557.0 mg,
ꢀ
0.8 mmol) in CH2Cl2 (30 mL) was treated with Me3O+·BF4 (237.2 mg,
1.6 mmol) at 08C. The mixture was stirred for 2 h at 08C, and then gradu-
ally warmed to RT and stirred for an additional 12 h. tBuOK (359.3 mg,
3.2 mmol) was added and the mixture was stirred for 30 min, followed by
the addition of THF (10 mL). The mixture was stirred at RT for a further
12 h. After quenching with saturated NH4Cl (50 mL), the organic layer
was separated and the aqueous layer was extracted with CH2Cl2 (50 mLꢀ
3). The combined organic layers were dried (MgSO4), filtered, and
evaporated in vacuo to give a residue that was purified by flash column
chromatography on silica gel (CH2Cl2/hexane 1:4) to afford 3 as a pale-
yellow solid (101.1 mg, 21%). M.p. 240–2418C.
Bis-terarylene diester 16: Under Ar, nBuLi (2.5m, 29.2 mL in hexane,
73.0 mmol) was added to a solution of 10[12] (19.47 g, 60.8 mmol) in THF
(300 mL) at ꢀ788C. After the reaction mixture had been stirred at
ꢀ788C for 50 min,
a
solution of 4,4’-diformyl-Z-stilbene[23] (5.0 g,
21.4 mmol) in THF (100 mL) was added at ꢀ788C. The mixture was
stirred for an additional 1 h at ꢀ788C, and then gradually warmed to RT.
After further stirring for 1 h at RT, TFA (9.8 mL, 130.0 mmol) was added
and the mixture was stirred at RT overnight, quenched with saturated
NH4Cl (200 mL), and the organic layer was separated. The aqueous layer
was extracted with CH2Cl2 (200 mLꢀ2). The combined organic layers
were washed with saturated NaHCO3 (100 mLꢀ2) and brine (100 mL),
dried (MgSO4), filtered, and then evaporated in vacuo. The residue was
chromatographed (silica gel, CH2Cl2/n-hexane 1:6) to give 16 as a yellow
fluorescent solid (5.26 g, 36%). M.p. 235–2368C; IR (KBr): n˜ =3008,
Method B: A solution of TiCl4 (1.0 mL, 9.4 mmol) was added under N2 to
a suspension of zinc dust (1.23 g, 18.8 mmol) in THF (100 mL) over a
period of 30 min and the suspension was refluxed for 1 h. A solution of
18 (600 mg, 0.9 mol) and pyridine (1.1 mL, 13.3 mol) in THF (200 mL)
was added by syringe to the above gently refluxing suspension. After re-
fluxing for 16 h, the mixture was cooled to RT. A solution of K2CO3
(10%) was carefully introduced and the mixture was filtered. The THF
was removed in vacuo and the mixture was extracted with CH2Cl2
(200 mLꢀ2). The combined extracts were washed with water (200 mLꢀ
2), dried (MgSO4), and evaporated in vacuo to give a residue that was
purified by flash column chromatography (silica gel, CH2Cl2/n-hexane
1:6) to afford 3 as a pale-yellow solid (90 mg, 15%). M.p. 239–2408C; IR
(KBr): n˜ =3085, 3013, 2959, 2932, 2862, 1610, 1503, 1491, 1467, 1103, 935,
2953, 2929, 2860, 1716, 1608, 1434, 1276, 1176, 1107, 935, 852, 817 cmꢀ1
1H NMR (400 MHz, CDCl3, 258C, TMS): d=0.97 (t, 3J
(H,H)=7.2 Hz,
6H), 1.46 (tq, 3J(H,H)=7.2, 7.6 Hz, 4H), 1.68 (tt, 3J
(H,H)=7.6, 8.0 Hz,
4H), 2.72 (t, 3J
(H,H)=8.0 Hz, 4H), 3.93 (s, 6H), 6.65 (s, 2H), 6.80 (s,
2H), 7.39 (d, 3J(H,H)=8.4 Hz, 4H), 7.61 (d, 3J
(H,H)=8.4 Hz, 4H), 7.75
(d, 3J(H,H)=8.4 Hz, 4H), 8.03 ppm (d, 3J(H,H)=8.4 Hz, 4H); 13C NMR
;
AHCTUNGTRENNUNG
N
ACHTUNGTRENNUNG
ACHTUNGTRENNUNG
G
ACHTUNGTRENNUNG
883, 825, 736, 692 cmꢀ1
0.97 (t, 3J(H,H)=7.3 Hz, 6H), 1.46 (tq, 3J
(tt, 3J(H,H)=7.6, 7.7 Hz, 4H), 2.71 (t, 3J
ACHTUNGTRENNUNG
;
1H NMR (400 MHz, CDCl3, 258C, TMS): d=
(H,H)=7.3, 7.6 Hz, 4H), 1.68
(H,H)=7.7 Hz, 4H), 6.53 (s,
(H,H)=8.4 Hz, 4H), 7.11 (d,
(H,H)=8.4 Hz, 4H), 7.55 ppm (d,
AHCTUNGTRENNUNG
(H,H)=8.4 Hz, 4H); 13C NMR (100 MHz, CDCl3, 258C, TMS): d=
A
ACHTUNGTRENNUNG
(100 MHz, CDCl3, 258C, TMS): d=14.4, 22.9, 26.1, 32.3, 52.2, 111.3,
122.8, 122.9, 124.3, 124.9, 127.8, 128.8, 129.6, 129.7, 134.1, 135.5, 148.3,
150.1, 166.1 ppm; HRMS (FAB+): m/z: calcd for C46H44O6: 692.3138;
found: 692.3122.
G
ACHTUNGTRENNUNG
E
2H), 6.64 (s, 2H), 6.68 (s, 2H), 7.06 (d, 3J
G
3J
3J
(H,H)=8.4 Hz, 4H), 7.51 (d, 3J
ACHUTGTNRENNUG CAHTUNGTRENNUNG
Bis-terarylene diol 17: A solution of DIBAL (1.0m, 49.6 mL in hexane,
49.6 mmol) was added slowly to a solution of 16 (5.26 g, 8.26 mmol) in
THF (200 mL) under Ar at 08C. The mixture was stirred at RT for 3 h
and quenched by pouring it into saturated NH4Cl (250 mL). After stirring
for 30 min, the gel-like mixture was acidified with HCl (6m, 130 mL), and
extracted with CH2Cl2 (250 mLꢀ3). The combined organic extracts were
washed with saturated NaHCO3 (250 mL ꢀ 2) and brine (200 mL). The
organic layer was dried (MgSO4), filtered, and evaporated in vacuo to
afford a residue that was recrystallized from CH2Cl2/Et2O to afford 17 as
a yellow fluorescent solid (5.01 g, 95%). M.p. 147–1488C; IR (KBr): n˜ =
3335, 3021, 2955, 2928, 2869, 1619, 1507, 1489, 1457, 1421, 1375, 1210,
14.0, 22.6, 25.5, 32.2, 108.5, 123.8, 124.6, 125.4, 129.5, 129.6, 130.4, 130.65,
130.74, 131.0, 135.6, 135.9, 148.4, 152.6 ppm; UV/Vis (CHCl3): lmax (e)=
330 nm (6.1ꢀ104 molꢀ1 m3 cmꢀ1); emission (CHCl3): lem =550 nm; HRMS
(EI): m/z: calcd (%) for C44H40O2: 600.3028; found: 600.3018.
Pentaaryl
[2.2]cyclophandiene 4:
A
solution of TiCl4 (0.71 mL,
6.50 mmol) was added under N2 to a suspension of zinc dust (850.0 mg,
13.0 mmol) in THF (80 mL) over a period of 30 min, and the suspension
was refluxed for 1 h. A solution of 20[14c] (345.0 mg, 0.7 mmol) and pyri-
dine (0.8 mL, 9.8 mmol) in THF (80 mL) was added to the above gently
refluxing suspension by syringe. After refluxing for 16 h, the mixture was
cooled to RT. A solution of K2CO3 (10%) was carefully introduced with
stirring and the mixture was filtered. The THF was removed in vacuo
and the mixture was extracted with CH2Cl2 (2ꢀ100 mL). The combined
1178, 1099, 1012, 933, 880, 833, 806 cmꢀ1
;
1H NMR (400 MHz, CDCl3,
(H,H)=7.2 Hz, 6H), 1.45 (tq, 3J
(H,H)=7.2,
(H,H)=8.0 Hz,
258C, TMS): d=0.97 (t, 3J
G
ACHTUNGTRENNUNG
3
3
7.6 Hz, 4H), 1.69 (tt, J
(H,H)=7.6, 8.0 Hz, 4H), 2.71 (t, J
U
13206
www.chemeurj.org
ꢁ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2009, 15, 13201 – 13209

Centrosymmetric Furan-Containing Oligoaryl Cyclophandienes
FULL PAPER
3
extract was washed with water (2ꢀ100 mL), dried (MgSO4), and evapo-
rated in vacuo to give a residue that was purified by flash column chro-
matography (silica gel, CH2Cl2/n-hexane 1:4) to afford 4 as a pale-orange
solid (302 mg, 47%). M.p. 167–1688C; IR (KBr): n˜ =2994, 2949, 2913,
(d, JACTHGNUTERNNUG
(H,H)=8.0 Hz, 4H), 9.97 ppm (s, 2H); 13C NMR (100 MHz, CDCl3,
258C, TMS): d=14.1, 14.2, 22.7, 22.8, 25.9, 26.0, 32.1, 32.2, 37.6, 109.6,
112.5, 123.5, 123.6, 123.7, 124.7, 125.4, 125.6, 128.6, 129.3, 129.4, 129.5,
130.2, 134.4, 135.8, 140.2, 148.1, 149.3, 150.2, 151.0, 191.2 ppm; HRMS
(FAB+): m/z: calcd for C72H71O6: 1031.5251 [M++H]; found: 1031.5232.
2851, 1633, 1435, 1409, 1311, 1262, 1029, 955, 874, 837, 739, 702 cmꢀ1
;
1H NMR (400 MHz, CDCl3, 258C, TMS): d=0.95 (t, 3J
12H), 1.36–1.52 (m, 8H), 1.60–1.75 (m, 8H), 2.68 (brt, 3J
AHCTUNGTRENNUNG
ACHTUNGTRENNUNG
PentaarylACTHNUTRGNEUNG
[2.2]cyclophene 7: TiCl4 (0.4 mL, d=1.73 gmLꢀ1, 3.87 mmol)
was added under N2 to a slurry of zinc dust (0.51 g, 7.74 mmol) in THF
(50 mL) over a period of 30 min, and the mixture was refluxed for 1 h. A
solution of 23 (400 mg, 0.387 mmol) and pyridine (0.5 mL, 5.8 mmol) in
THF (50 mL) was then slowly syringed in. After refluxing for 16 h, the
mixture was cooled to RT. K2CO3 (10%, 100 mL) was carefully intro-
duced with stirring and the mixture was filtered. The filtrate was evapo-
rated in vacuo and the residue was dissolved in CH2Cl2 (2ꢀ100 mL),
washed with water (2ꢀ100 mL), and dried (MgSO4). Removal of the sol-
vent in vacuo afforded a residue that was purified by flash column chro-
matography (silica gel, CH2Cl2/n-hexane 1:4) to yield 7 as a pale-yellow
solid (77 mg, 20%). M.p. 160–1618C; IR (KBr): n˜ =2952, 2928, 2856,
8H), 6.56 (s, 4H), 6.69 (s, 4H), 7.41 (d, 3J
ACHTUNGTRENNUNG
3J
ACHTUNGTRENNUNG
258C, TMS): d=14.0, 22.6, 25.6, 32.3, 109.3, 123.5, 124.3, 126.3, 129.3,
129.6, 130.3, 135.9, 148.4, 152.1 ppm; UV/Vis (CHCl3): lmax (e)=369 nm
(3.3ꢀ104 molꢀ1 m3 cmꢀ1); emission (CHCl3): lem =513 nm; HRMS (FAB+):
m/z: calcd for C72H68O4: 996.5118; found: 996.5108.
PentaarylACHTUNGTRENNUNG[2.2]cyclophane 6: A solution of 4 (30.0 mg, 0.03 mmol) and Pd/
C (10%, 5 mg) in MeOH (1 mL) and THF (1 mL) was subject to hydro-
genation for 1 h at 50 psi by using a Parr shaker. After filtration through
Celite and a silica-gel bed (5 cm) and washing with CH2Cl2 (5 mL), the
filtrate was evaporated in vacuo to give 6 (28.0 mg, 93%) as a yellow
solid. M.p. 149–1508C; IR (KBr): n˜ =2954, 2917, 2849, 1959, 1649, 1578,
1602, 1507, 1496, 1458, 933, 839 cmꢀ1
;
1H NMR (400 MHz, CDCl3, 258C,
(H,H)=7.2 Hz,
TMS): d=0.97 (t, 3J(H,H)=7.2 Hz, 12H), 1.45 (sext, 3J
N
ACHTUNGTRENNUNG
1541, 1460, 1384, 1257, 1139, 1093, 1024, 875 cmꢀ1
;
1H NMR (400 MHz,
(H,H)=7.3 Hz, 12H), 1.43 (tq,
(H,H)=7.6, 7.7 Hz, 8H), 2.68 (t,
(H,H)=7.7 Hz, 8H), 2.97 (s, 8H), 6.61 (s, 4 H), 6.96 (d, 3J
(H,H)=
(H,H)=8.3 Hz, 8H), 7.65 ppm (s, 8H); 13C NMR
8H), 1.8 (quint, 3J
ACTHUNGTERNNU(G H,H)=7.2 Hz, 8H), 2.66–2.69 (m, 8H), 3.08 (s, 4H),
CDCl3, 258C, TMS): d=0.95 (t, 3J
A
6.56 (s, 2H), 6.66 (s, 2H), 7.13 (d, 3J
A
3J
3J
G
G
3J
(H,H)=8.0 Hz, 4H), 7.55 (d, J
(H,H)=8.0 Hz, 4H), 7.61–7.66 (m, 8H),
3
N
ACTHNGUTERNNUG
7.73 ppm (d, 3J(H,H)=7.8 Hz, 4H); 13C NMR (100 MHz, CDCl3, 258C,
C
TMS): d=14.1, 14.2, 22.8, 25.8, 32.31, 32.34, 36.3, 109.3, 109.5, 123.5,
123.7, 123.8, 124.2, 125.5, 126.1, 129.03, 129.06, 129.2, 129.3, 129.5, 129.7,
130.1, 135.8, 139.7, 148.28, 148.31, 151.4, 152.0 ppm; HRMS (FAB+):
m/z: calcd for C72H70O4: 998.5274; found: 998.5284.
(100 MHz, CDCl3, 258C, TMS): d=14.1, 22.7, 25.8, 32.4, 37.2, 108.4,
123.4, 124.0, 125.8, 128.4, 129.3, 130.0, 139.8, 147.6, 152.1 ppm; UV/Vis
(CHCl3): lmax (e)=361 nm (3.4ꢀ104 molꢀ1 m3 cmꢀ1); emission (CHCl3):
lem =451 nm; HRMS (FAB+): m/z: calcd for C72H72O4: 1000.5431; found:
1000.5421.
Pentaaryl monomer 9: Under a N2 atmosphere, a solution of diol 19[14c]
(290.0 mg, 0.5 mmol) in benzene/THF (10 mL:1 mL), was treated with
PBr3 (0.06 mL, 0.5 mmol) at RT and the mixture was stirred for 6 h.
After quenching with water (10 mL), the mixture was extracted with
CH2Cl2 (20 mLꢀ3). The combined organic extracts were washed with
brine (20 mL), dried (MgSO4), filtered, and evaporated in vacuo to
afford the crude dibromide. Under a N2 atmosphere, a solution of the
crude dibromide in THF (2 mL) was added slowly to a suspension of
LiAlH4 (37.9 mg, 1.0 mmol) in THF (2 mL) at 08C and the mixture was
stirred for 3 h, and then quenched with water (0.1 mL). 10% NaOH
(0.1 mL) and water (0.2 mL) were added and the mixture was filtered
through a silica-gel bed (0.5 cm). The filter cake was washed with CH2Cl2
(50 mL). The combined filtrate was dried (MgSO4), filtered, and evapo-
rated in vacuo to give a residue that was purified by flash column chro-
matography (silica gel, CH2Cl2/hexane 1:3) to yield 9 (218 mg, 82%) as a
colorless oil. IR (KBr): n˜ =2953, 2917, 2847, 1650, 1633, 1435, 1405, 1029,
Ethylene-bridged bis-pentaaryl diol 22: Under Ar, nBuLi (2.5m, 5.2 mL
in hexane, 13.0 mmol) was added to a solution of propargylic dithioacetal
21[14c] (3.05 g, 6.0 mmol) in THF (200 mL) at ꢀ788C. The mixture was
stirred at ꢀ788C for 70 min and then a solution of 4,4’-diformylbiben-
zyl[12] (596 mg, 2.5 mmol) in THF (50 mL) was added at ꢀ788C. The mix-
ture was stirred for 1 h at ꢀ788C, and then gradually warmed to RT.
After further stirring for 4 h at RT, TFA (1.2 mL, 13.3 mmol) was added
and the mixture was stirred at RT overnight, quenched with saturated
NH4Cl (150 mL), and the organic layer was separated. The aqueous layer
was extracted with Et2O (150 mLꢀ3). The combined organic layers were
washed with saturated NaHCO3 (100 mLꢀ2), brine (100 mL), and then
dried (MgSO4), filtered, and evaporated in vacuo. The crude product was
purified by flash column chromatography (silica gel, EtOAC/hexane 2:3)
to give 22 as a pale-yellow solid (1.34 g, 52%). M.p. 109–1108C; IR
(KBr): n˜ =3390, 2953, 2927, 2857, 2360, 2341, 1613, 1507, 1455, 1376,
956, 935, 837, 804, 702 cmꢀ1
;
1H NMR (400 MHz, CDCl3, 258C, TMS):
1183, 1049, 1013, 933, 837, 807, 668 cmꢀ1
258C, TMS): d=0.99 (t, 3J(H,H)=7.2 Hz, 12H), 1.48 (sext, 3J
7.2 Hz, 8H), 1.71 (quint, 3J
(H,H)=7.2, 8H), 2.71–2.76 (m, 8H), 3.02 (s,
4H), 4.72 (s, 4H), 6.68 (s, 2H), 6.70 (s, 2H), 7.27 (d, 3J
(H,H)=8.4 Hz,
(H,H)=8.4 Hz, 4H), 7.71–
(H,H)=8.4 Hz, 4H); 13C NMR (100 MHz,
;
1H NMR (400 MHz, CDCl3,
d=0.90 (t, 3J
A
ACHTUNGTRENNUNG
3
3
A
U
1.61 (tt, J
A
ACHTUNGTRENNUNG
T
4H), 6.53 (s, 2H), 7.12 (d, 3J
A
ACHTUNGTRENNUNG
A
8.1 Hz, 4H), 7.67 ppm (s, 4H); 13C NMR (100 MHz, CDCl3, 258C, TMS):
d=14.5, 21.7, 23.1, 26.3, 32.5, 108.5, 123.3, 124.0, 125.0, 127.8, 129.0,
129.5, 136.6, 146.8, 151.6 ppm; UV/Vis (CHCl3): lmax (e)=378 nm (2.8ꢀ
104 molꢀ1 m3 cmꢀ1); emission (CHCl3): lem =448 nm; HRMS (FAB+):
m/z: calcd for C36H38O2: 502.2872; found: 502.2880.
3
3
4H), 7.40 (d, J
ACHTUNGTRENNUNG(H,H)=8.4 Hz, 4H), 7.64 (d, JCAHTUNGTRENNNUG
7.74 (m, 8H), 7.78 ppm (d, 3J
AHCTUNGTRENNUNG
CDCl3, 258C, TMS): d=13.99, 14.01, 14.1, 22.7, 25.8, 25.9, 31.6, 32.1,
32.2, 37.6, 65.2, 109.4, 109.5, 123.71, 123.79, 123.82, 124.4, 125.5, 127.4,
128.8, 129.0, 129.5, 130.21, 130.22, 139.7, 140.3, 147.8, 148.2, 151.4,
151.6 ppm; HRMS (FAB+): m/z: calcd for C72H74O6: 1034.5485; found:
1034.5490.
Hyper-Rayleigh scattering (HRS) measurements: The HRS experiments
were similar to those described in the literature.[24] A fundamental laser
source with a wavelength at 1320 nm was generated by an OPA pumped
by a kHz Ti:sapphire regenerative amplifier system (Spectra Physics
OPA-800 and Hurricane). The intensity was controlled by a half-wave
plate followed by one polarizer such that no intensity change due to dam-
aged sample was observed. After having been passed though, a 1000 nm
long pass filter (Thorlabs FEL1000) the laser beam was focused into the
sample solution by a f=100 mm lens. By using the right-angle geometry,
the HRS signal was collected by a f=25 mm condensed lens, passed
through the filters (Chroma HQ 655–65+ESCO S906600) to reject the
wavelength outside the 660ꢁ5 nm range, and then detected by a photo-
sensor module (Hamamatsu H5783–20). The detected intensity was mea-
sured by a Lock-In Amplifier (Stanford Research Systems Inc, SR830)
with a reference channel triggered by the Hurricane SGD sync output.
To obtain b from the HRS measurement, the external reference method
Ethylene-bridged bis-pentaaryl dialdehyde 23: A solution of 22 (600 mg,
0.58 mol) in CH2Cl2 (20 mL) was added slowly to a suspension of activat-
ed MnO2 (1.0 g, 11.6 mol) in CH2Cl2 (30 mL) at RT. The reaction mixture
was stirred for 6 h at RT. After passing through a silica-gel bed (2 cm)
and washing with CH2Cl2 (120 mLꢀ3), the combined filtrate was evapo-
rated in vacuo. The residue was recrystallized from Et2O and CH2Cl2 to
afford 23 as a yellow solid (537 mg, 90%). M.p. 185–1868C; IR (KBr):
n˜ =2953, 2929, 2856, 1696, 1601, 1570, 1505, 1455, 1385, 1213, 1165,
1
3
833 cmꢀ1; H NMR (400 MHz, CDCl3, 258C, TMS): d=1.00 (t, J
7.2 Hz, 12H), 1.48 (sext, 3J
(H,H)=7.2 Hz, 8H), 1.69–1.72 (m, 8H), 2.70–
2.75 (m, 8H), 3.02 (s, 4H), 6.71 (s, 2H), 6.85 (s, 2H), 7.27 (d, 3J
(H,H)=
8.0 Hz, 4H), 7.64 (d, 3J(H,H)=8.0 Hz, 4H), 7.72 (d, 3J
(H,H)=8.0 Hz,
4H), 7.78 (d, 3J(H,H)=8.0 Hz, 4H), 7.83 (d, 3J
(H,H)=8.0 Hz, 4H), 7.88
ACHTUNGTRNE(NUNG H,H)=
AHCTUNGTRENNUNG
AHCTUNGTRENNUNG
G
ACHTUNGTRENNUNG
N
ACHTUNGTRENNUNG
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13207

T.-Y. Luh, J.-H. Hsu et al.
was adopted and used a reliable standard bHRS value to serve as an exter-
nal reference.[24] Since disperse red-1 (DR1) has been shown to follow
the Oudar–Chemlaꢃs two-level model (TLM)[25] at off-resonance region
and has a b value of 22.7ꢀ10ꢀ30 esu at 1907 nm, the b value of DR1 at
1320 nm was used as the reference standard (37.1ꢀ10ꢀ30 esu). Each com-
pound was measured by using chloroform or cyclohexane as the solvent,
and the concentration was in the range of 10ꢀ6–10ꢀ8 m. In the dilute con-
centration limit, the HRS intensity (I2w) is proportional to the square of
the intensity of the fundamental beam and is related to molecular param-
eters as shown in Equation (1):
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I2w ¼ GðNchb2ci þ Nshbs2iÞI2w
ð1Þ
in which Nc (Ns) is the number density of the chromophore (solvent), Iw
is the intensity of the fundamental beam, and G is a constant depending
on experimental geometry, optical constants, and local field factors.hb2ci
(hb2si) is the orientation average of the square of the first molecular hy-
perpolarizability tensor element of the chromophore (solvent). bunknown
can be estimated by Equation (2):
rffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi
qffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi
munknown
mreference
ð2Þ
bunknown
¼
hb2unknowni ¼
ꢂ hb2reference
i
The HRS intensity is measured at various chromophore concentrations.
The slope of the chromophore (munknown) and reference DR1 (mreference
)
can be estimated by the linear dependence of the HRS intensity on the
number density of the chromophore and reference DR1 excited with the
laser radiation at 1320 nm, respectively. Therefore, according to the
above equation, bunknown can be obtained.
Power-dependence HRS experiments: To distinguish the observed signals
not from multiphoton fluorescence, we have performed the excitation
power-dependence measurements. Figure 2 and S4 (see the Supporting
Information) showed quadratic dependence of the signals from 3 and 4.
The absorption and photoluminescence spectra (Figure 1) of 3 and 4. ex-
hibit much higher energy than the second harmonic of excitation laser
wavelength (1320 nm, hence 2w=660 nm); it is expected that the lowest
multiphoton excitation of the molecules would be a three-photon process.
The HRS signal has negligible overlap with the fluorescence range. To
verify this, we perform the power dependence at the emission wave-
length, replacing the optical filters by the filter 595AF60 (Omega Opti-
cal, transmission range 570–644 nm) Our data (Figure 3) indicates that
the fluorescence of 4 has a relation to the excitation power of IPL /(Iw)n,
with power dependence n=2.92. Accordingly, these results suggested
that the observed HRS signal may have no contribution from multipho-
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was employed for electrochemical experiments. The working electrode
was a Pt disc (diameter=2 mm), the reference electrode was a Ag/Ag+
(10 mm AgNO3) electrode, and a Pt wire was used as the counter elec-
trode. Samples were dissolved in dry CH2Cl2 containing tetrabutylammo-
nium hexafluorophosphate (0.1m) as the supporting electrolyte, and the
solutions were purged with Ar for at least 15 min before electrochemical
experiments. The potentials reported were referred to the redox potential
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Acknowledgements
This work was supported by the National Science Council and National
Taiwan University of the Republic of China.
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Chem. Eur. J. 2009, 15, 13201 – 13209

Centrosymmetric Furan-Containing Oligoaryl Cyclophandienes
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Received: July 29, 2009
Published online: October 21, 2009
Chem. Eur. J. 2009, 15, 13201 – 13209
ꢁ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
13209