Triple-stranded polymeric ladderphanes

Article abstract of DOI:10.1021/ma100550q

The first triple-stranded polymeric ladderphanes 6 with multilayer planar oligoaryl linkers having C₃ symmetry are synthesized by Grubbs I catalyst-mediated ring-opening metathesis of tris-norbornene derivatives 5. All linkers are coherently al

Full text of DOI:10.1021/ma100550q

5188 Macromolecules 2010, 43, 5188–5194
DOI: 10.1021/ma100550q
Triple-Stranded Polymeric Ladderphanes
Kwang-Wei Yang,† Jun Xu,†,‡ Chih-Hsien Chen,† Hsin-Hua Huang,§
Tony Jian-Yuan Yu,† Tsong-Shin Lim, Chun-hsien Chen,*,† and Tien-Yau Luh*,†
†Department of Chemistry, National Taiwan University, Taipei, Taiwan 106, ‡Department of Chemistry,
University of Science and Technology of China, Hefei, China 230026, §Institute of Polymer Science and
Engineering, National Taiwan University, Taipei, Taiwan 106, and Department of Physics,
Tung Hai University, Taichung, Taiwan 305
Received March 12, 2010; Revised Manuscript Received May 11, 2010
ABSTRACT: The first triple-stranded polymeric ladderphanes 6 with multilayer planar oligoaryl linkers
having C3 symmetry are synthesized by Grubbs I catalyst-mediated ring-opening metathesis of tris-norbornene
derivatives 5. All linkers are coherently aligned perpendicular to the longitudinal axis of the polymer. Inter-
actions between these linkers lead to fluorescence quenching or perturbation of frontier orbitals, resulting in
shift of the emission maximum. These triple-stranded polymeric ladderphanes tend to self-assemble to form
an ordered pattern as revealed by TMAFM.
Scheme 1
Introduction
We recently reported the first polynorbornene-based double-
stranded polymeric ladderphanes 1 with a planar aromatic species
or a ferrocene derivative as covalent linkers.1,2 The key to the
successful synthesis of these supramolecular scaffolds relies on
the stereoselective Grubbs I catalyst-mediated ring-opening meta-
thesis polymerization (ROMP)3 of bis-norbornene modules 2
connected by an relatively rigid linker (Scheme 1).1,2 The presence
of an N-arylpyrrolidine moiety endo-fused to the norbornene
appears to be essential to control the stereoregularity (the
stereochemistry of double bonds and the tacticity) of the double-
stranded polymeric ladderphanes.1,2,4 Presumably, the interac-
tions between these aryl pendents would be responsible for the
selectivity. Triple-stranded oligomers have been intertwined by
means of metal coordination,5,6 van der Waals interactions,7 or
hydrogen bonding.8-10 More recently, triple-stranded DNA
nanotubes are nicely constructed using different sizes of triangu-
lar building blocks covalently linked with three strands of DNA
molecules.11 To the best of our knowledge, triple-stranded poly-
meric ladderphanes with covalent linkers have not been known. It
is envisaged that, with an appropriate design of covalent linkers,
triple-stranded polymeric ladderphanes could be obtained by a
similar strategy.
olefinic carbons shifted from δ 135 in 5a to about δ 131.5 ppm
in 6a. The carbon signals in the high field region (δ35-52 ppm),
attributed to the carbons on the polymeric backbones and the
pending pyrrolidine moieties, are fairly broad, presumably due
to rigidity of the backbone in 6a. Methanolysis of 6a with
NaOMe in MeOH/CHCl3 afforded the single-stranded poly-
mer isotactic 7 with all double bonds in trans configuration4 in
77% isolated yield (Mn=3700, PDI=1.38) corresponding to
13 repetitive units. End-group analysis by 1H NMR of a crude
mixture from the methanolysis of 6a suggests the degree of
polymerization around 14.14 The isolation of 7 in good yield
with relatively narrow dispersity suggests that the polynorbor-
nene strands in 6a may have similar chain lengths and therefore
be consistent with the triple-stranded structure (Schemes 2 and 3).
Furan-Containing Oligoaryl Linkers with C3 Symmetry.
Alternating benzene-furan oligomers have been shown to
be highly fluorescent.15 This kind of oligoaryl has been used
as linkers for double-stranded ladderphanes, and the fluore-
scence of the conjugated chromophores has been signifi-
cantly quenched.1 It is envisaged that similar linkers could be
used for the synthesis of triple-stranded ladderphanes. Thus,
treatment of allenyllithium 11 (obtained from 12 with nBuLi)
with 13 followed by TFA afforded 14 in 46% yield. Further
reaction of 11 with 14 and then with TFA gave 30% yield of
15, which was reduced with DIBAL-H to afford 3b in 94%
Results and Discussion
Synthesis. 1,3,5-Triphenylbenzene Linker. In the beginning
of this research, reaction of 3a12 with 4 under Mitsunobu con-
ditions afforded the corresponding monomer 5a in 57% yield.
ROMP of 5a with 30 mol % of the Grubbs I catalyst3 afforded
the corresponding triple-stranded polymer 6a in 85% yield
(Mn = 13 000, PDI = 1.61) corresponding to 12 repetitive
units.13 In the 1H NMR spectrum, the olefinic protons shifted
from δ 6.18 in 5a to a broad peak centered around δ 5.40
(overlapping with the absorption due to the benzylic protons)
in 6a. The 13C NMR spectrum of 6a is compared with that of
5a in Figure 1. The signals due to aromatic carbons in 6a
appear at similar chemical shifts as those in 5a, whereas the
*To whom correspondence should be addressed.
pubs.acs.org/Macromolecules
Published on Web 05/25/2010
r 2010 American Chemical Society

Article
Macromolecules, Vol. 43, No. 12, 2010 5189
Figure 1. 13C NMR spectra of (a) 5a, (b) 6a, (c) 5b, (d) 6b, (e) 5c, and (f) 6c in CDCl3.
yield. Mitsunobu reaction of 3b with 4 gave 5b in 52% yield
(Scheme 4).
Femtosecond laser equipped with a streak camera was
employed to measure the time-resolved fluorescence decay of
monomers 5 and polymers 6 in CH2Cl2. Single-exponential
decay was observed for monomers 5b and 5c whereas two-
exponential simulation was used to fit the fluorescence decay
of polymers 6b and 6c. The results are summarized in Table 1.
The longer lifetimes (τ) of polymers 6b and 6c are consistent
with the lifetimes of the corresponding monomers 5b and 5c,
and the shorter lifetimes were the major decay pathway
(based on the relative weight) attributed to the self-quenching
of the adjacent chromophores. These results further suggest
that the chromophores aligned in 6b and 6c nicely in a triple-
stranded structure.
The emission of 5a consisted of local emission of both tri-
phenylbenzene and aminobenzoate moieties at 360 nm and
charge separation emission at 464 nm. It would be difficult to
monitor the actual mode of the decay pathway for 5a. The
situation with polymer 6a would be more complicate because
it may involve additional route of decay arisen from the
interactions between adjacent chromophores.
Tapping Mode Atomic Force Microscopic (TMAFM) Images.
Displayed in Figure 3 are TMAFM images of 6c drop-cast
on highly oriented pyrolytic graphite (HOPG). The length of
the rodlike structure is at the scale of several hundred
nanometers, which is much longer than a polymer molecule
(10-mer is about 5 nm). Like those of double-stranded poly-
bisnorbornenes,1,2 the present result indicates that the assem-
bly of the polymeric molecules may place on HOPG due to
π-π attractions between end groups (vinyl and styryl) along
longitudinal axis and van der Waals interactions between the
neighboring polymeric backbones.
In a similar manner, sequential reaction of 1715c with nBuLi,
13, and TFA furnished 3c in overall 21% yield. Monomer 5c
was obtained in 71% yield from the reaction of 3c with 4
under Mitsunobu conditions (Scheme 4). Polymerization of
5b and 5c using Grubbs I catalyst3 and quenched with ethyl
vinyl ether gave polymers 6b and 6c in 66 and 76% yields,
respectively. The 13C NMR spectra of 6b and c are also
compared with those of 5b and c, respectively, in Figure 1.
Photophysical Properties. The photophysical properties of
5a-c and 6a-c are summarized in Table 1, and the emission
spectra of 5a-c and 6a-c are shown in Figure 2. The
quantum yields of the emission for polymers 6b and 6c were
significantly reduced in comparison to those of the corres-
ponding monomers 5b and 5c. These results indicate that,
like double-stranded ladderphanes,1 the adjacent linking
chromophores in 6b and 6c should be in close proximity, and
these polymers would be consistent with a triple-stranded
structure. On the other hand, the quantum yields for 5a and
6a were comparable. It is interesting to note that the fluore-
scence spectrum of monomer 5a was completely different
from that of 8a, but very similar to that of 10 (Figure 2d) due
to 4-aminobenzoate chromophore. The charge transfer emis-
sions of 5a and 10 appeared at longer wavelength than that of
9.16 In addition, the luminescence spectrum of 6a was almost
identical to that of 7, but different from that of 5a. The
emission of the triphenylbenzene linker in 6a may be buried
in the emission of the aminobenzoate moiety. Polymer 7 is
known to have all aminobenzoate pending groups aligned
coherently toward the same direction, and the spacing occu-
4
˚
pied by each of the monomeric units is about 5.5 A. Inter-
Conclusions
actions between adjacent pending aminobenzoate groups in
7 may perturb the frontier orbitals so that the photophysical
properties may be different from those of the corresponding
monomer 10. It seems likely that the aminobenzoate moiety
in 6a may have similar environment to that in 7. In other
words, the aminobenzoate group in 6a may also be in close
proximity to the neighboring aminobenzoate moieties. These
results further suggest that 6a would be a triple-stranded
ladderphane.
In summary, we have extended the strategy for double-stranded
polybisnorbornenes to the synthesis of triple-stranded polymeric
ladderphanes 6 with multilayer planar oligoaryl linkers having
C3 symmetry. Because of the ladderlike structure, all linkers are
coherently aligned perpendicular to the longitudinal axis of
the polymer. Intrachain interactions between these linkers led
to fluorescence quenching or perturbation of frontier orbitals,
resulting in shift of the emission maximum. Like double-stranded

5190 Macromolecules, Vol. 43, No. 12, 2010
Yang et al.
Scheme 2
Scheme 3
Scheme 4. (a) nBuLi, -78 °C; (b) 1,3,5-Benzenetricarboxaldehyde
(13); (c) TFA, 46% (Three Steps); (d) 11, 30% (Three Steps);
(e) DIBAL, 94%; (f) 4, PPh3, DIAD, rt
The use of this strategy for multiple stranded ladderphanes
would be feasible and the application for materials research is
in progress.
Experimental Section
General. High-resolution mass spectrometric measurements
were obtained from JEOL JMS-700 mass spectrometry using
the FAB method in 3-nitrobenzyl alcohol matrix. Gel permea-
tion chromatography (GPC) was performed on a Waters GPC
machine with an isocratic HPLC pump (1515) and a refrac-
tive index detector (2414). THF was used as the eluent (flow rate,
1.0 mL/min) for 9a and 9b, and CHCl3 was used as the eluent
(flow rate, 1.0 mL/min) for 14. Waters Styragel HR2, HR3, and
HR4 columns (7.8 ꢀ 300 mm) were employed for determina-
tion of relative molecular weight using polystyrene as standard
(Mn values ranged from 375 to 3.5 ꢀ 106). Absorption spectra
were measured on a Hitachi U-3310 spectrophotometer and
emission spectra on a Hitachi F-4500.
Synthesis of 5a. To a mixture of 4(128 mg, 0.5 mmol), 3a12 (50mg,
0.13 mmol), and triphenylphosphine (164 mg, 0.63 mmol) in THF
(15 mL) under argon cooled at 0 °C was added diisopropyl azodi-
carboxylate (126 mg, 0.63 mmol) in THF (3 mL) by a syringe pump
over a period of 3 h. The mixture was warmed to room temperature
(rt) and stirred for 36 h. The solvent was evaporated in vacuo, and the
residue was chromatographed on silica gel (CH2Cl2:hexane=2:1) to
polymers, these triple-stranded polymeric ladderphanes can easily
form an ordered pattern by self-assembly as depicted in Figure 3.

Article
Macromolecules, Vol. 43, No. 12, 2010 5191
Table 1. Photophysical Properties of 5 and 6
Mn (PDI) or MWa
λ
max (ε)b
λem
Φfd
τ (wt %)
λem
c
e
substrate
5b
6b
5c
6c
5a
1475
13000 (1.82)
2070
25000 (1.61)
1108
318 (26)
318 (13)
387 (75)
387 (46)
260 (41)
321 (70)
260 (42)
315 (58)
399, 412
406, 427
431, 457
440, 460
360, 464
0.33
0.08
0.90
0.10
0.07
1350
390-410
390-410
430-460
430-460
46 (72%), 1350 (28%)
1100
28 (71%), 1100 (29%)
6a
13000 (1.61)
358, 434
0.08
a Mn for polymers and molecular weight (MW) for monomers. b Absorption maximum and molar absorption coefficient (mM-1 cm-1, based on the
molecular weight of the monomeric unit) measured in CH2Cl2. c Emission maximum in CH2Cl2. d The quantum yields for 5b, 6b, 5c, and 6c in CH2Cl2
were determined using cumarin I as a reference (Φf = 0.99), whereas those for 5a and 6a in CH2Cl2 using 2,5-diphenyloxazole in cyclohexane (Φf = 1.00)
as standard. e Monitoring wavelength for fluorescence decay.
Figure 2. Absorption and emission profiles of (a) 5b and 6b, (b) 5c and 6c, and (c) 5a and 6b in CH2Cl2 (dotted, 5; solid line, 6). (d) Emission profiles of
5a (solid), 8 (dashed), 9 (dotted), and 10 (dash-dotted) in CH2Cl2.
afford 5a as a white solid (79 mg, 57%); mp 190-192 °C. 1H NMR
(300 MHz, CDCl3): δ 1.52 (d, J=8.3 Hz, 3 H), 1.62 (d, J=8.3 Hz,
3 H), 2.95-2.99 (m, 12 H), 3.08-3.10 (m, 6 H), 3.27-3.32 (m, 6 H),
5.38 (s, 6 H), 6.17 (d, 6 H), 6.40 (d, J= 8.9 Hz, 6 H), 7.55 (d, J=
8.1 Hz, 6 H), 7.69 (d, J= 8.1 Hz, 6 H), 7.78 (s, 3 H), 7.94 (d, J=
8.9 Hz, 6 H). 13C NMR (75 MHz, CDCl3): δ 45.4, 46.6, 50.5, 52.0,
65.5, 110.9, 116.1, 125.2, 127.4, 128.4, 131.4, 135.7, 136.3, 140.7, 142.
0, 150.6, 166.9. IR (KBr, cm-1): 3056, 2961, 2848, 1699, 1606, 1558,
1521, 1473, 1378, 1274, 1177, 1079, 985, 825, 767, 721. HRMS
(FABþ) m/z calcd for C75H69O6N3: 1107.5186. Found: 2068.0513.
HRMS (FABþ) m/z calcd for C75H69O6N3: 1107.5186. Found:
1107.5199.
mixture was stirred at -78 °C for 50 min. A solution of 1,3,5-
benenetricarboxaldehyde (164 mg, 1.00 mmol) in THF (10 mL)
was then added at -78 °C, and the mixture was stirred at -78 °C
for 1 h and then gradually warmed to rt. After further stirring for
1 h, TFA (0.5 mL, 6.0 mmol) was added, and the mixture was
stirred at rt for 10 h. The mixture was quenched with saturated
NaHCO3 (30 mL), and the organic layer was extracted with
Et2O (3ꢀ100 mL). The combined organic extracts were washed
with brine (100 mL), dried (MgSO4), filtered, and evaporated in
vacuo to give the residue which was purified by flash column
chromatography (silica gel, EtOAc/hexane 1:10) to afford 14 as
a pale yellow solid (284 mg, 46%); mp 175-176 °C. IR (KBr):
ν 2959, 2927, 2863, 1722, 1711, 1607, 1433, 1275, 1172, 1106,
769, 694 cm-1. 1H NMR (400 MHz, CDCl3): δ 0.97 (t, J=7.3 Hz,
6 H), 1.49 (sext, J=7.3 Hz, 4 H), 1.72 (tt, J=7.7, 7.3 Hz, 4 H),
n
Synthesis of 14. Under nitrogen, BuLi (1.44 mL, 2.5 M in
hexane, 3.6 mmol) was introduced dropwise to a solution of
1215b (1.12 g, 3.50 mmol) in THF (20 mL) at -78 °C, and the

5192 Macromolecules, Vol. 43, No. 12, 2010
Yang et al.
Figure 3. TMAFM images of 6c on HOPG. Left: a 1 μm ꢀ 1 μm image shows that the rodlike feature extends over steps of HOPG. Right: a 300 nm ꢀ
300 nm image exhibits a close-packed monolayer of 6c.
2.79 (t, J=7.7 Hz, 4 H), 3.92 (s, 6 H), 6.84 (s, 2 H), 7.78 (d, J=
8.4 Hz, 4 H), 8.06 (d, J=8.4 Hz, 4 H), 8.10 (s, 2 H), 8.23 (s, 1 H),
10.14 (s, 1 H). 13C NMR (75 MHz, CDCl3): δ 14.1, 22.8, 26.0,
32.1, 52.3, 111.7, 123.5, 124.9, 126.2, 127.5, 128.9, 130.3, 132.8,
134.4, 137.3, 147.6, 151.7, 166.9, 192.1. HRMS (FABþ) m/z
calcd for C39H38O7: 618.2618. Found: 618.2620.
1.3 mmol) under nitrogen at 0 °C was added diisopropyl azodi-
carboxylate (0.26 mL, 1.3 mmol) slowly. The mixture was warmed
to rt and stirred for 24 h. Solvent was removed in vacuo, and the
residue was washed by MeOH and EtOAc to afford 5b (202 mg,
52%); mp 199-201 °C: IR (KBr): ν 3052, 2955, 2929, 1703,
1604, 1469, 1433, 1377, 1271, 1176, 1096, 934, 871, 762, 666
cm-1. 1H NMR (400 MHz, CDCl3): δ 1.01 (t, J=7.6 Hz, 9 H),
1.43-1.62 (m, 12 H), 1.72-1.90 (m, 6 H), 2.84 (t, J = 7.6 Hz,
6 H), 2.94-3.02 (m, 12 H), 3.04-3.11 (m, 6 H), 3.25-3.35 (m,
6 H), 5.32 (s, 6 H), 6.15 (s, 6 H), 6.38 (d, J=8.8 Hz, 6 H), 6.72 (s,
3 H), 7.45 (d, J=8.0 Hz, 6 H), 7.74 (d, J=8.4 Hz, 6 H), 7.91 (d,
J=8.8 Hz, 6 H), 7.93 (s, 3 H). 13C NMR (100 MHz, CDCl3): δ
14.3, 22.9, 26.1, 32.3, 45.4, 46.7, 50.5, 52.1, 65.6, 109.4, 110.8,
116.0, 120.8, 123.6, 124.6, 128.3, 130.5 131.3, 132.0 135.6, 135.7,
147.6, 150.3, 151.7, 166.7. HRMS (FABþ) m/z calcd for C99H99-
O9N3: 1474.7460. Found: 1474.7463.
n
Synthesis of 15. Under nitrogen, BuLi (0.48 mL, 2.5 M in
hexane, 1.2 mmol) was introduced dropwise to a solution of 1215
(352 mg, 1.10 mmol) in THF (15 mL) at -78 °C, and the mixture
was stirred at -78 °C for 50 min. A solution of 14 (618 mg, 1.00
mmol) in THF (10 mL) was added at -78 °C, and the mixture
was stirred at -78 °C for 1 h and then gradually warmed to rt.
After further stirring for 1 h, TFA (0.2 mL, 2.4 mmol) was
added, and the mixture was stirred at rt for 10 h. The reaction
was then quenched with saturated NaHCO3 (30 mL), and the
organic layer was extracted with Et2O (3 ꢀ 100 mL). The com-
bined organic extracts were washed with brine(100 mL), then
dried (MgSO4), filtered, and evaporated in vacuo to give the
residue which was purified by flash column chromatography
(silica gel, EtOAc/hexane 1:10) to give 15 as a pale yellow solid
(254 mg, 30%); mp 224-226 °C. IR (KBr): ν 2952, 2928, 2871,
2851, 1719, 1607, 1434, 1274, 1175, 1107, 933, 769, 697 cm-1. 1H
NMR (300 MHz, CDCl3): δ 0.98 (t, J=7.3 Hz, 9 H), 1.50 (sext,
J=7.3 Hz, 6 H), 1.76 (tt, J=7.7, 7.3 Hz, 6 H), 2.81 (t, J=7.7 Hz,
6 H), 3.92 (s, 9 H), 6.84 (s, 3 H), 7.78 (d, J=8.3 Hz, 6 H), 7.93 (s,
3 H), 8.05 (d, J=8.3 Hz, 6 H). 13C NMR (100 MHz, CDCl3): δ
14.2, 22.9, 26.1, 32.2, 52.2, 111.5, 121.0, 123.0, 125.0, 128.3,
130.0, 131.8, 134.3, 148.4, 150.8, 166.5. HRMS (FABþ) m/z
calcd for C54H54O9: 847.3846. Found: 847.3838.
n
Synthesis of 3c. Under nitrogen, BuLi (3.8 mL, 2.5 M in
hexane, 9.2 mmol) was introduced dropwise to a solution of
1615c (2.1 g, 4.3 mmol) in THF (100 mL) at -78 °C, and the mix-
ture was stirred at -78 °C for 50 min. A solution of 1,3,5-
benenetricarboxaldehyde (164 mg, 1.00 mmol) in THF (10 mL)
was added at -78 °C, andthe mixture was stirredat -78 °Cfor 1h
and then gradually warmed to rt. After further stirring for 1 h,
TFA (1 mL, 12 mmol) was added, and the mixture was stirred at
rt for 10 h. The reaction was then quenched with saturated
NaHCO3 (100 mL), and the organic layer was extracted with
EtOAc (3 ꢀ 100 mL). The combined organic extracts were
washed with brine (100 mL), then dried (MgSO4), filtered, and
evaporated in vacuo to give the residue which was triturated
with Et2O to give 3c as a yellow solid (281 mg, 21%); mp
203-204 °C: IR (KBr): ν 3417, 3041, 2954, 2925, 2858, 1651,
1633, 1621, 1600, 1496, 1486, 1455, 1254, 1178, 1012, 832, 859,
Synthesis of 3b. DIBAL (21.0 mL, 1.0 M in hexane, 21.0
mmol) was added slowly with stirring to a solution of 15 (847 mg,
1.00 mmol) in THF (20 mL) at 0 °C under a nitrogen atmos-
phere. The mixture was stirred for 2 h at rt, and then saturated
NH4Cl (30 mL) was poured in slowly. The gel-like organic layer
was then acidified with HCl (6 M, 30 mL) and extracted with
Et2O (3 ꢀ 200 mL). The combined organic layers were washed
with saturated NaHCO3 (2 ꢀ 30 mL), brine (30 mL), dried
(MgSO4), filtered, and evaporated in vacuo to give 3b as a pale
yellow solid (720 mg, 94%); mp 183-185 °C. IR (KBr): ν 3420,
2954, 2927, 1537, 1495, 1462, 1453, 1415, 1382, 1204, 1110, 1035,
1013, 935, 790 cm-1. 1H NMR (400 MHz, CDCl3): δ 1.01 (t, J=
7.4 Hz, 9 H), 1.45-1.60 (m, 6 H), 1.69-1.82 (m, 6 H), 2.84 (t, J=
7.6 Hz, 6 H), 4.73 (s, 6 H), 6.73 (s, 3 H), 7.40 (d, J=8.0 Hz, 6 H),
7.74 (d, J = 8.0 Hz, 6 H) 7.94 (s, 3 H). 13C NMR (100 MHz,
THF-d8): δ 14.5, 23.7, 26.9, 33.3, 64.7, 109.9, 121.4, 124.3, 125.7,
127.6, 130.4, 133.4, 143.4, 148.3, 153.3. HRMS (FABþ) m/z
calcd for C51H54O6: 762.3920. Found: 762.3926.
1
834, 802, 734, 674, 667 cm-1. H NMR (400 MHz, CDCl3): δ
0.96 (t, J=7.3 Hz, 9 H), 1.04 (t, J=7.2 Hz, 9 H), 1.44-1.49 (m,
6 H), 1.52-1.60 (m, 6 H), 1.67-1.72 (m, 6 H), 1.79-1.85 (m, 6 H),
2.74 (t, J=7.7 Hz, 6 H), 2.88 (t, J=7.5 Hz, 6 H), 4.67 (s, 6 H),
6.68 (s, 3 H), 6.78 (s, 3 H), 7.37 (d, J=8.2 Hz, 6 H), 7.70-7.77
(m, 12 H), 7.84 (d, J=8.3 Hz, 6 H), 7.99 (s, 3 H). 13C NMR (100
MHz, THF-d8): δ 14.6, 14.8, 23.8, 24.0, 27.1, 27.2, 33.3, 33.5,
64.8, 110.1, 110.6, 121.7, 124.3, 124.7, 125.5, 126.0, 126.3, 127.5,
129.9, 130.3, 131.7, 133.4, 143.2, 148.3, 148.7, 153.1, 153.2.
HRMS (FABþ) m/z calcd for C93H96O9: 1356.7054. Found:
1356.7084.
Synthesis of 5c. To a THF solution (12 mL) of 3c (80 mg, 0.06
mmol), 4 (80 mg, 0.3 mmol), and triphenylphosphine (80 mg, 0.3
mmol) under nitrogen at 0 °C was added diisopropyl azodicar-
boxylate (0.06 mL, 0.3 mmol) slowly. The mixture was warmed
to rt and stirred for 24 h. Solvent was removed in vacuo, and
the residue was triturated with MeOH and EtOAc to afford 5c
Synthesis of 5b. To a THF solution (12 mL) of 3b (200 mg,
0.26 mmol), 4(345 mg, 1.3 mmol), and triphenylphosphine (345 mg,

Article
Macromolecules, Vol. 43, No. 12, 2010 5193
(101 mg, 81%); mp 221-222 °C: IR (KBr): ν 3056, 2955, 2928,
2857, 1702, 1603, 1523, 1499, 1474, 1376, 1318, 1272, 1177, 1098,
the residue which was analyzed by 1H NMR for end-group
analysis.14
1
934, 834, 810, 768, 721, 694, 673 cm-1. H NMR (400 MHz,
AFM Characterization. TM-AFM measurements were car-
ried out with a NanoScope IIIa controller (Veeco Metrology
Group/Digital Instruments, Santa Barbara, CA) using a 10 μm
scanner. The nominal curvature and the force constant for the
cantilevers (NCHR, NanoWorld, Switzerland) were 10 nm and
42 nN/m, respectively. The sample, after being drop-cast with an
aliquot of 6c (50 μL, 100 nM in CH2Cl2) on HOPG, was sub-
jected to vacuum-drying and then imaged in a dry-N2(g) purged
Plexiglas to minimize the effect of humidity on imaging.
Time-Resolved Fluorescence Experiments. A mode-locked Ti:
sapphire laser (wavelength: 840 nm; repetition rate: 76 MHz;
pulse width: <200 fs) passed through an optical parametric
amplifier to produce 280 nm pulse laser. The fluorescence of
sample was reflected by a grating (150 g/mm; BLZ: 500 nm) and
detected by an optically triggered streak camera (Hamamatsu
C5680) with a time resolution of about 0.3 ps. The sample was
prepared with 1ꢀ10-5 M concentration in CH2Cl2 and using an
ultra-microcuvette with 1 mm path length to maintain the exci-
tation at the same time. The signal was collected for 20 times to
decrease signal-to-noise ratio.
CDCl3): δ 0.98 (t, J = 7.2 Hz, 9 H), 1.04 (t, J = 7.6 Hz, 9 H),
1.44-1.82 (m, 30 H), 2.74 (t, J=7.6 Hz, 6 H), 2.89 (t, J=7.6 Hz,
6 H), 2.94-3.02 (m, 12 H), 3.04-3.11 (m, 6 H), 3.25-3.33 (m,
6 H), 5.31 (s, 6 H), 6.16 (s, 6 H), 6.39 (d, J=8.8 Hz, 6 H), 6.67 (s,
3 H), 6.78 (s, 3 H), 7.44 (d, J=7.8 Hz, 6 H), 7.71-7.76 (m, 12 H),
7.83 (d, J=8.4 Hz, 6 H), 7.91 (d, J=8.8 Hz, 6 H), 7.99 (s, 3 H).
13C NMR (100 MHz, CDCl3): δ 14.1, 14.3, 22.8, 23.0, 26.1, 26.2,
32.1, 32.4, 45.4, 46.7, 50.5, 52.1, 65.6, 109.4, 109.6, 110.8, 116.0,
123.6, 123.7, 124.4, 124.8, 125.4, 128.2, 128.8, 130.2, 130.3 131.3,
132.1 135.6, 147.6, 150.3, 151.5, 151.7, 166.7. HRMS (FABþ)
m/z calcd for C141H141O12N3: 2068.0515. Found: 2068.0513.
Synthesis of 6a. Under argon atmosphere, a solution of (Cy3P)2-
Cl2Ru=CHPh (41.0 mg, 0.05 mmol) in CH2Cl2 (2 mL) was added
to 5a (184 mg, 0.166 mmol) in CH2Cl2 (10 mL) and stirred at rt for
3 h. The mixture was quenched with ethyl vinyl ether (2 mL). The
mixture was concentrated and redissolved in CH2Cl2 (1 mL). The
solution was poured into MeOH (20 mL). The resulting solid was
collected by centrifuge to give 6a (156 mg, 85%). 1H NMR (300
MHz, CDCl3): δ 1.68-2.10 (br, 6 H), 2.50-3.50 (br, 24 H), 5.4
(brs, 12 H), 6.57 (brs, 6 H), 7.50-7.80 (br, 15 H), 7.97 (brs, 6 H).
13C NMR (75 MHz, CDCl3): δ 44.52, 45.71, 46.29, 46.91, 65.87,
111.56, 116.82, 126.05, 127.42, 128.47, 131.45, 136.31, 140.76, 141.97,
150.87, 150.84, 166.50. IR (KBr, cm-1): 3027, 2933, 2852, 1705,
1605, 1521, 1374, 1270, 1178, 1096, 966, 824, 767, 697. GPC: PDI=
1.61, Mn =13 000, Mw =21 000.
Acknowledgment. We thank the National Science Council
and the National Taiwan University for support. K.W.Y. thanks
the National Science Council for undergraduate research. T.Y.L.
and J.X. thank the Shanghai Institute of Organic Chemistry for
the support.
Synthesis of 6b. Under a nitrogen atmosphere, a solution of
(Cy3P)2Cl2Ru=CHPh (8.2 mg, 0.010 mmol) in CH2Cl2 (1 mL)
was added to 5b (30 mg, 0.02 mmol) in CH2Cl2 (10 mL) and
stirred at rt for 4 h. The mixture was quenched with ethyl vinyl
ether (2 mL). The mixture was concentrated and redissolved in
CH2Cl2 (1 mL). The solution was poured into MeOH (20 mL).
The resulting solid was collected by centrifuge to give 6b (20 mg,
66%). IR (KBr): ν 2953, 2930, 2857, 1720, 1606, 1523, 1497,
1479, 1453, 1433, 1376, 1271, 1178, 1096, 965, 934, 767 cm-1. 1H
NMR (400 MHz, CDCl3): δ 0.70-1.00 (br, 9H), 1.20-1.97 (br,
18H), 2.45-3.60 (br, 30H), 4.80-5.65 (br, 12 H), 6.30-6.80 (br,
9H), 7.30-8.20 (br, 21 H). 13C NMR (125 MHz, CDCl3): δ 4.0,
22.7, 25.9, 32.1, 37.5, 44.8, 46.7, 49.5, 65.7, 109.4, 111.4, 117.0,
123.8, 124.6, 126.1, 128.6, 130.5, 131.5, 135.7, 147.8, 151.0,
151.8, 166.7. Mn = 13 000, PDI= 1.82.
Supporting Information Available: 1H and 13C NMR spec-
tra of all new compounds (including end-group analysis for 7).
This material is available free of charge via the Internet at http://
pubs.acs.org.
References and Notes
(1) A polymeric ladderphane is defined as multiple layers of planar
aromatic ring tethered by two or more tethering chains that are
part of the polymeric backbones. See: Chou, C.-M.; Lee, S.-L.;
Chen, C.-H.; Biju, A. T.; Wang, H.-W.; Wu, Y.-L.; Zhang, G.-F.;
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Huang, S.-L.; Chen, C.-h.; Luh, T.-Y. J. Am. Chem. Soc. 2009, 131,
12579.
Synthesis of 6c. Under a nitrogen atmosphere, a solution of
(Cy3P)2Cl2Ru=CHPh (11.0 mg, 0.013 mmol) in CH2Cl2 (1 mL)
was added to 5c (90 mg, 0.045 mmol) in CH2Cl2 (10 mL) and
stirred at rt for 4 h. The mixture was quenched with ethyl vinyl
ether (2 mL). The mixture was concentrated and redissolved in
CH2Cl2 (1 mL). The solution was poured into MeOH (20 mL).
The resulting solid was collected by centrifuge to give 6c (69 mg,
76%). IR (KBr): ν 2961, 2918, 2849, 1719, 1604, 1519, 1482,
1460, 1376, 1261, 1180, 1096, 1019, 964, 933, 861, 800, 662, 491
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cm-1. H NMR (400 MHz, CDCl3): δ 0.70-1.15 (br, 18 H),
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1.20-1.97 (br, 30 H), 2.35-3.50 (br, 36 H), 4.80-5.75 (br, 12 H),
6.30-6.80 (br, 12 H), 7.30-8.05 (br, 27 H). 13C NMR (125
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Methanolysis of 6a. Under an argon atmosphere, a mixture of
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MeOH (10 mL) was stirred at rt for 20 h. Dichloromethane and
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3.82 (br, 3 H), 5.34 (br, 2 H), 6.49 (br, 2 H), 7.87 (br, 2 H).
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mmol) in CHCl3 (5 mL) and 30% NaOMe in MeOH (2 mL) gave
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