Hydrogen-bonding induced cooperative effect on the energy transfer in helical polynorbornenes appended with porphyrin-containing amidic alanine linkers

Article abstract of DOI:10.1002/asia.200900567

Polynorbornenes appended with porphyrins containing a range of different linkers are synthesized. The use of bisamidic chiral alanine linkers between the pending porphyrins and the polymeric backbone has been shown to bring the adjacent porphyrin chromoph

Full text of DOI:10.1002/asia.200900567

DOI: 10.1002/asia.200900567
Hydrogen-Bonding Induced Cooperative Effect on the Energy Transfer in
Helical Polynorbornenes Appended with Porphyrin-Containing Amidic
Alanine Linkers
Zhi-Chang Liu,[a, b] Chih-Hsien Chen,[b] Hsian-Wen Wang,[b] Yen-Chin Huang,[b]
Ming-Jui Kao,[b] Tsong-Shin Lim,[c] and Tien-Yau Luh*[b]
Abstract: Polynorbornenes appended
with porphyrins containing a range of
different linkers are synthesized. The
use of bisamidic chiral alanine linkers
between the pending porphyrins and
the polymeric backbone has been
shown to bring the adjacent porphyrin
chromophores to more suitable orien-
tation for exciton coupling owing to hy-
drogen bonding between the adjacent
linkers. The hydrogen bonding between
the adjacent pendants in these poly-
mers may induce a cooperative effect
and therefore render single-handed
helical structures for these polymers.
Such a cooperative effect is reflected in
the enhancement of FRET efficiencies
between zinc–porphyrin and free base
porphyrin in random copolymers.
Keywords: energy transfer · helical
structures
·
hydrogen bonds
·
porphyrinoids · ring-opening poly-
merization
Introduction
arrays appended on polyisocyanides,[6] polypeptides,[7] cellu-
lose,[8] poly(N-propargylamide)s,[9] polyacrylates,[10] and poly-
norbornenes[11] have been explored.
Numerous model systems containing porphyrin donor–ac-
ceptor arrays have offered a platform to mimic biological
light harvesting process.[1] Fluorescence resonance energy
transfer (FRET) between zinc–porphyrin and free base por-
phyrin dyads with covalent[2] or noncovalent[3] linkers is well
documented. Oligomers having linear, two-dimensional, as
well as dendritic arrangements of chromophores have been
adopted to simulate this important process.[4,5] Porphyrin
Polynorbornenes (PNBs) with a variety of pendant groups
have been extensively investigated for photoinduced elec-
tron transfer,[12] liquid crystal,[13] nonlinear optical,[14,15] and
possible molecular switching[16] applications. The relatively
rigid polymeric backbone of PNBs provides a supporting
framework for the pending groups coherently aligned to-
wards the same direction.[11–16] We recently established that
PNBs having endo-fused N-arylpyrrolidene pendants, ob-
tained by Grubbs I catalyst mediated ring-opening metathe-
sis polymerization[17] of the corresponding norbornene deriv-
atives, adopt comblike structures with homogeneous tactici-
ty and all double bonds in trans configuration.[11a,15] The cor-
responding double-stranded poly(bisnorbornene)s or ladder-
phanes were prepared accordingly,[18] single-handed helical
polymers[19] being obtained when the chiral substituents are
incorporated into these polymers. Each of the monomeric
units spans about 5.5 ꢀ in these polymers.[15a] Exciton cou-
pling,[11a,18c] excimer formation,[18c] fluorescence quenchin-
g,[11a] or enhancement in second-order optical nonlinearity[15]
readily occurs in these polymers when photoactive chromo-
phores are used as pendants or linkers. For example, PNBs
with certain porphyrin pendants exhibit Soret band splitting
and significant fluorescence quenching owing to interactions
between these chromophores.[11a,18c] It is envisaged that
[a] Dr. Z.-C. Liu
Shanghai Institute of Organic Chemistry
Chinese Academy of Sciences
354 Fenglin Lu, Shanghai 200032 (China)
[b] Dr. Z.-C. Liu, Dr. C.-H. Chen, H.-W. Wang, Y.-C. Huang, M.-J. Kao,
Prof. T.-Y. Luh
Department of Chemistry
National Taiwan University
Taipei, 106 (Taiwan)
Fax : (+886)2-2364-4971
E-mail: tyluh@ntu.edu.tw
[c] Prof. T.-S. Lim
Department of Physics
Tung Hai University
Taichung, 407 (Taiwan)
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/asia.200900567.
Chem. Asian J. 2010, 5, 1425 – 1438
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FULL PAPERS
PNBs containing both donor and acceptor pending chromo-
phores may undergo efficient energy and electron transfer
between these photoactive species.
Hydrogen bonding offers a powerful arsenal to assemble
different kinds of connectivity so that an intrinsically flexi-
ble structure can be transformed into a more ordered robust
motif.[20] The amidic linkage is particularly attractive to fur-
nish a range of new classes of folded oligomers. Abiotic
supramolecular scaffolds with well-defined secondary struc-
tures can thus be designed and executed. Oligoamides de-
rived from enantiomerically pure amino acid residues have
been the archetype of helical foldamers[21] as well as sheet-
like architectures.[22] Amalgamations of amino acid or pep-
tide pendants onto polyisocyanides[23] and poly(phenylacety-
lene)s[24] are known to induce single-handed helicity of the
polymers. The use of hydrogen bonding to form supramolec-
ular systems can bring the attached chromophores into close
proximity so that FRET or photoinduced electron transfer
can readily take place.[25]
The relative distance and orientation of the porphyrin
moieties may dictate the photophysical behavior of a light-
harvesting system.[26] We envisioned that the introduction of
chiral amino acid linkers between the pendant chromo-
phores and the PNB backbone would increase the robust-
ness of the polymer as a result of hydrogen bonding be-
tween amino acid residues. Strong interactions between
chromophores might be expected because hydrogen bonding
may bring the adjacent chromophores into a more suitable
orientation for exciton coupling. Herein, we report a system-
atic study on the intramolecular energy transfer in a series
of zinc–porphyrin and free base porphyrin-appended
random copolymers with a range of different linkers.
Results and Discussion
Synthesis
mers 2c–f) were much broader than those without hydrogen
bonded linkers. Apparently, hydrogen bonding between
pendants would make the polymers more rigid, leading to
broader signals in the 1H NMR spectra. Similar behavior
was found in rigid double-stranded ladderphanes with por-
phyrin linkers.[18c]
It is interesting to note that the chemical shifts of a-meth-
ylene (next to the oxygen atom) protons on the para-alkoxy
substituents of the two phenyl groups at the C10 and C20 po-
sitions were very sensitive to hydrogen bonding in the pend-
ants. They appeared at d=3.12, 3.81, and 3.93 ppm for 2d
(with two hydrogen bonds per monomeric unit), 2h (with
one hydrogen bond per monomeric unit), and 2j (no hydro-
gen bonds), respectively. Hydrogen bonding might bring two
adjacent porphyrin pendants closer so that the relevant pro-
tons appeared at higher field owing to the anisotropic
shielding. However, the chemical shift of similar a-methyl-
ene protons on the phenyl substituent at C15 was less sensi-
tive. The ratios of monomeric units with zinc–porphyrin and
free base porphyrin pendants in 3–7 were determined by in-
A series of porphyrin-appended PNBs 2 incorporated with
and without l-, d-alanine, or l-lactate linkers were synthe-
sized. Random copolymers 3–7 containing zinc–porphyrin
and free base porphyrin pendants with and without chiral
linkers described above were used for energy transfer inves-
tigations. The details are summarized in Scheme 1 and the
results are outlined in Table 1.
The H NMR spectra of monomers 1 and polymers 2–7
are worthy of comment. The olefinic protons in the poly-
meric backbones appeared in the H NMR spectra around
1
1
d=5.2 ppm as a broad symmetrical peak, which is similar to
those of related polymers.[11a,15] These results indicate that
the alkenes in the polymer backbone have trans configura-
tion. Similar to those of homopolymer 2a reported previous-
ly,[11a] certain H NMR signals in 2b–l and 3–7 appeared at
1
higher field and with significant broadening relative to those
of the corresponding monomers 1. Presumably, the aniso-
tropic shielding arising from the adjacent porphyrin moiety
1
may be responsible for such shifts. The H NMR signals of
ꢀ
the porphyrin pendants with amidic alanine linkers (poly-
tegration of the N H protons in the pyrrole rings (d=
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Chem. Asian J. 2010, 5, 1425 – 1438

Energy Transfer in Helical Polynorbornenes
relative to those of the corresponding monomers 1a and 1b.
Polymers 2i–l behaved similarly. In contrast, when the ala-
nine linker was employed, a shoulder was observed in the
Soret band at 410 nm for polymers with free base porphyrin
pendants 2d and 2 f. In addition, significant broadening of
the Soret band was observed for 2c and 2e. Presumably, ex-
citon coupling between the adjacent pending porphyrins
may occur in these homopolymers. These polymers have the
bisamidic alanine linkers between the porphyrin chromo-
phores and the PNB backbone. As mentioned earlier, the
span occupied by each of the monomers would be around
5.5 ꢀ.[15b] It seems likely that hydrogen bonding between the
adjacent bisamidic chiral alanine moieties in these polymers
may play an important role to bring the porphyrin chromo-
phores to more suitable orientation for exciton coupling.
Even with monoamidic l-lactate linkers (polymers 2g and
2h), in which only one hydrogen bond is available for each
of these linkers, the Soret bands of their polymers were
somewhat broader than those of the corresponding mono-
mers 1g and 1h.
The Q-band absorptions of zinc–porphyrin-appended
polymers 2c, 2e, and 2g also appear to be slightly sensitive
to hydrogen bonding in the linkers. For example, 2c and 2e
absorb at 557 and 600 nm, whereas the corresponding mono-
mers 1c and 1e exhibit absorption maxima at 551 and
591 nm. The Q-band absorptions for 2g (554 and 598 nm)
also exhibit a slight red shift relative to those of 1g (551 and
592 nm).
Scheme 1. a) Boc-alanine (8l or 8d), EDCI/DMAP, 95% for both 10l
and 10d; b) TFA, 98% for 11l and 93% for 11d; c) (COCl)2; d) 13,
Et3N, 90% for 1d and 92% for 1 f; e) 13, Et3N, 85%; f) LiOH, THF/H2O
(10:3), 85%; f) 9 or 16, EDCI/DMAP, 95% for 1h and 90% for 1j;
h) Zn
ACHTUNGTRENNUNG
As can been see from Table 1, the lem bands for free base
porphyrin-appended PNBs 2 are almost the same as those
for the corresponding monomers 1. Intriguingly, the emis-
sion maxima of polymers 2c and 2e showed bathochromic
shifts (11 nm) relative to the emission of the corresponding
monomers 1c and 1e. The shifts became less prominent for
polymers 2g and 2i relative to 1g and 1i, respectively. Fur-
thermore, the decrease of quantum yields from monomers
to polymers also depends on the nature of the linkers. Thus,
the quantum yields for zinc–porphyrin-appended polymers
2c and 2e were significantly lower than those of 1c and 1e,
respectively. The quantum yield of polymer 2i appeared to
be affected much less than that of 1i. Again, hydrogen
bonding will bring the two adjacent porphyrins closer so
that interactions between these chromophores may lead to a
red shift in their emission profiles and a reduction in quan-
tum yields.
Random copolymers 3–7: The photophysical properties of
random copolymers 3–7 are also tabulated in Table 1 and
the absorption of these polymers are shown in the Support-
ing Information (Figure S3). The Q bands were essentially a
superposition of the spectra of a mixture of the correspond-
ing monomeric zinc–porphyrin and the free base porphyrin
components of same ratios. It is interesting that the full
width at half maximum (fwhm) values of the Soret band for
random copolymers 4–6 decreased with the availability of
hydrogen bonding in the linkers (Table 1).
i) [Cl2ACHTUNGTRENNUNG
2 f, 90% for 2g, 98% for 2h, 87% for 2i, 95% for 2j, 85% for 3 (m/n=
1.5:1), 93% for 4 (m/n=1:1), 98% for 5 (m/n=1:1), 93% for 6 (m/n=
1:1), 92% for 7 (m/n=1:1).
ꢀ2.8 ppm) and the protons at the b positions (around d=
1
8.8 ppm) in the H NMR spectra.
Dimers 16 and 17 were synthesized to compare the helici-
ty of the polymers 2c–f (Scheme 2). The observation of two
nonequivalent sets of the 13C NMR signals for the two ring-
opened norbornene moieties in 23 indicates that the mole-
cule may adopt C1 symmetry and therefore have isotactic
stereochemistry with trans double bonds and the two pend-
ants in syn conformation.[14c] Since further transformations
of 23 into 16 and 17 may not affect the stereochemistry of
the double bonds and the asymmetric centers, it seems rea-
sonable to suggest that both 16 and 17 may have similar ste-
reochemistry to that of 23.
Photophysical Properties
Homopolymers 2: The photophysical properties of mono-
mers 1 and homopolymers 2a–l are also outlined in Table 1.
The absorption spectra of 1c,d,g–i and 2c,d,g–i are shown in
Figure 1 and the absorption spectra of the rest of monomers
and polymers together with the emission spectra of 1 and 2
are included in Figures S1 and S2 in the Supporting Infor-
mation. As described previously,[11a] the Soret band of poly-
mers 2a,b showed neither splitting nor bathochromic shifts
The emission profiles of random copolymers 3–7 and of a
mixture of the corresponding homopolymers 2 of same
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T.-Y. Luh et al.
FULL PAPERS
Table 1. Photophysical properties of 1–7.
Compd
Mn (PDI)
Soret band[a,b]
lmax [nm] (log e)
Q-bands[a]
lmax [nm] (log e)
Emission
Lifetime t [ps]
(rel. wt.)[e]
h
lmax [nm][c]
Ff[d]
ACHTUNGTRENNUNG
1b
2b
1d
2d
1 f
2 f
1h
2h
1j
–
421 (5.65) [790]
422 (5.50) [1129]
422 (5.54) [845]
423 (5.27) [1658]
422 (5.54) [846]
423 (5.26) [1653]
422 (5.66) [730]
422 (5.54) [1038]
422 (5.55) [734]
422 (5.48) [957]
418 (5.49) [659]
418 (5.34) [1033]
518 (4.19), 554 (4.08),
593 (3.73), 650 (3.73)
518 (4.17), 555 (4.05),
592 (3.70), 650 (3.70)
518 (4.00), 556 (3.86),
594 (3.52), 650 (3.58)
520 (4.04), 557 (3.90),
595 (3.55), 651 (3.55)
518 (4.01), 554 (3.87),
592 (3.52), 650 (3.56)
520 (4.03), 557 (3.90),
595 (3.53), 651 (3.55)
519 (4.22), 556 (4.08),
595 (3.74), 651 (3.81)
519 (4.25), 557 (4.10),
595 (3.77), 650 (3.80)
518 (4.12), 555 (3.94),
594 (3.60), 650 (3.64)
519 (4.15), 556 (3.97),
595 (3.63), 651 (3.63)
518 (4.15), 554 (3.95),
598 (3.60), 655 (3.78)
519 (4.04), 555 (3.85),
599 (3.48), 656 (3.70)
550 (4.34), 589 (3.91)
552 (4.31), 592 (3.89)
551 (4.27), 591 (3.81)
557 (4.17), 600 (3.87)
551 (4.28), 591 (3.81)
557 (4.18), 600 (3.87)
551 (4.35), 592 (3.91)
554 (4.28), 598 (3.93)
551 (4.19), 591 (3.69)
552 (4.18), 592 (3.72)
554 (4.15), 593 (3.78)
557 (4.08), 596 (3.78)
518 (3.90), 553 (4.15),
593 (3.78), 651 (3.30)
520 (3.90), 557 (4.04),
598 (3.70), 651 (3.30)
520 (4.04), 556 (4.20),
597 (3.85), 651 (3.48)
518 (4.00), 553 (4.18),
593 (3.78), 650 (3.48)
520 (3.78), 556 (3.85),
599 (3.48), 656 (3.30)
656
0.033
8400
–
–
–
–
–
–
–
–
–
–
28367 (1.40)
658
0.030
0.037
0.030
0.036
0.029
0.028
0.021
0.031
0.029
0.015
0.012
860 (17%) 8400 (83%)
8450
–
655
14820 (1.11)
656
480 (52%), 8450 (48%)
8600
–
655
11460 (1.11)
656
560 (57%), 8600 (43%)
8420
–
654
17600 (1.09)
655
1300 (34%), 8400 (66%)
8800
–
656
2j
16490 (1.19)
–
656
2400 (21%), 8800 (79%)
8450
1l
656, 714
658, 716
2l
11000 (1.13)
2200 (24%) 8450 (76%)
1a
2a
1c
2c
1e
2e
1g
2g
1i
–
423 (5.68) [841]
423 (5.52) [1225]
423 (5.67) [669]
425 (5.36) [1486]
423 (5.66) [669]
424 (5.37) [1485]
423 (5.74) [669]
424 (5.51) [1188]
423 (5.59) [700]
424 (5.49) [919]
420 (5.51) [613]
407 (5.19), 420 (5.29) [1749]
422 (5.51) [1124]
602
610
600
611
600
611
600
604
601
604
600
605
0.040
0.025
0.029
0.009
0.030
0.009
0.029
0.017
0.030
0.022
0.036
0.007
0.018
1340
34200 (1.50)
–
14190 (1.13)
–
13670 (1.13)
–
15500 (1.12)
–
12760 (1.14)
–
228 (72%), 1350 (28%)
1650
230 (73%), 1650 (27%)
1600
215 (79%), 1600 (21%)
1510
190 (66%), 1510 (34%)
1340
–
–
–
–
–
–
–
–
–
–
0.47
0.85
0.69
0.21
0.46
2i
221 (45%), 1340 (55%)
1420
182 (72%), 1420 (28%)
1k
2k
3
17000 (1.19)
14390 (1.12)
613, 663
43 (35%), 207 (53%), 1350 (12%)
29 (87%), 202 (10%), 1600 (3%)
40 (53%), 270 (43%), 1510 (4%)
58 (11%), 242 (55%), 1340 (34%)
50 (45%), 182 (42%), 1420 (13%)
4
5
6
7
13400 (1.11)
18000 (1.12)
17500 (1.11)
11600 (1.24)
423 (5.31) [1477]
423 (5.54) [1110]
423 (5.54) [953]
419 (5.20) [1330]
612, 661
0.021
0.018
0.017
0.007
603, 654, 710
602, 654, 711
604, 657, 717
[a] Molar extinction coefficients (log
bracket are the fwhm values (cmꢀ1) of the Soret band. [c] Excitation at lex =550 nm. [d] With reference to [Zn
weights were fitted based on the formula Sai exp
(ꢀt/ti).
ACHTUNGTRENNUNG
AHCTUNGTRENNUNG
AHCTUNGTRENNUNG
ratios are compared in the Supporting Information (Fig-
ure S4). In these random copolymers 3–7, the relative inten-
sities of the emission around 600–610 nm, attributed to the
emission of the zinc–porphyrin complex, were much lower
than those of the luminescence around 654–660 nm arising
from the emission of the free base porphyrin, where the
fluorescence intensities of these two chromophores were
comparable in the mixture of homopolymers. Again, the rel-
ative intensities of the emission around 600 nm and 655 nm
in 4–6 appeared to be dependent on the number of hydro-
gen bonds between adjacent pendants. Since there were no
changes in emission wavelength in these two systems, these
results suggest that FRET from zinc–porphyrin to free base
porphyrin might occur.
Time-Resolved Fluorescence Spectroscopy
A femtosecond laser equipped with a streak camera was
employed to measure the time-resolved fluorescence spectra
of monomers 1, polymers 2, and copolymers 3–7 in CH2Cl2.
The emission at 590–610 nm was monitored, and the decay
curves are shown in the Supporting Information (Figure S5).
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Chem. Asian J. 2010, 5, 1425 – 1438

Energy Transfer in Helical Polynorbornenes
within the same range as that for self-quenching between
adjacent chromophores in homopolymers 2. Different
weightings of each component were contributed by the com-
petition among FRET, self-quenching, and intrinsic emission
[Eq. (1)].[28] The energy transfer efficiencies (h) for FRET
were calculated accordingly [(Eq. (2)].
As can be seen from Table 1, the relative weighting of the
shorter lifetime in copolymer 4 was higher than that in 5,
which in turn was higher than that in 6. As mentioned
before, the diamidic alanine linker in each pendant in 4
would form two hydrogen bonds with the next adjacent
pendant. Such hydrogen bonding would bring two adjacent
pending chromophores to more suitable orientation for in-
teractions. Consequently, when a zinc–porphyrin and a free
base porphyrin are well oriented next to each other, more
efficient FRET might be expected.
As described earlier, all pendants of PNBs 2–7 may be es-
sentially aligned in a similar direction. Nevertheless, the ad-
jacent pendants would not be in the eclipsed conformation,
but rather in a gauche conformation like that of an ethane
molecule.[15] The dihedral angle between adjacent pendants
would depend on the nature of interactions between these
moieties. Thus, the distance between the adjacent appended
chromophores would be controlled. The lengths of the pend-
ants for 4–6 were similar. The energy transfer efficiency, h,
for 4 was higher than that for 5, which, in turn, was even
higher than that for 6. The presence of hydrogen bonding
would better orientate adjacent chromophores so that h
would be enhanced. In addition, the h values for 3 and 7
were somewhat higher than that of 6, in which all pendant
groups in these copolymers are not involved in hydrogen
bonding. Since the pendants in 3 and 7 were shorter than
that of 6, more efficient energy transfer would be expected
because the interactions between the adjacent chromo-
phores in 3 and 7 might be somewhat better than those in 6.
Scheme 2. a) [PhCH=CH2, Cl2ACHTNUTRGNE(UNG PCy3)2Ru=CHPh], 75%; b) LAH, 84%;
c) (i) nBuLi, CO2(g), 71%; d) (COCl)2, then MeOH, 92%; e) 24, 28%;
f) NaOH, MeOH/THF; g) (COCl)2, then 11l. Et3N, 72% in two steps;
h) ZnACHTUNGTRENNUNG(OAc)2, 89%.
The lifetimes of 1–7 obtained by fitting are also summarized
in Table 1.
Multiexponential fitting (S ai exp
N
solve two decay lifetimes for homopolymers 2 and three
decay lifetimes for copolymers 3–7. The amplitude-weighted
lifetimes (tDA) were calculated from a summation of the
products of the lifetimes (ti) and the amplitudes (ai) ob-
served for copolymers 3–7, and tD values were obtained sim-
ilarly for homopolymers 2 [Eq. (1)]. The efficiencies of
energy transfer (h) were estimated according to Equa-
tion (2).[27]
Helicity and Hydrogen Bonding
Homopolymers 2c–h: As described above, hydrogen bond-
ing between the amidic linkers in copolymers 4 and 5 brings
the pending porphyrin chromophore into a more suitable
orientation for interactions so that FRET becomes more ef-
ficient than in those systems without hydrogen bonding
(e.g., 3, 6, and 7). In this study, both d- and l-alanines were
used as linkers in homopolymers 2c–f and copolymer 4. The
incorporation of amino acid pendants onto a polymer may
induce the helicity of the polymer.[9] Accordingly, 2c–f were
subject to circular dichroism (CD) measurements (Figure 2).
The CD properties of 2g and 2h are also shown in Figure 2
for comparison. In comparison, the CD curves for mono-
mers 1c–j were very weak (Supporting Information, Fig-
ure S6).
tD ðor tDAÞ ¼ Saiti
h ¼ 1ꢀðtDA=tDÞ
ð1Þ
ð2Þ
As shown in Table 1, three components of the fluores-
cence decay lifetimes were involved in the observed fluores-
cence decay signal from the zinc–porphyrin moiety in co-
polymers 3–7. The long decay lifetimes (larger than 1000 ps)
were assigned to the intrinsic fluorescence lifetimes for the
emission of the zinc–porphyrin chromophore. The shorter
lifetimes (less than 100 ps) might be mainly from FRET be-
tween the donor zinc–porphyrin and the acceptor free base
porphyrin. It is noteworthy that the fluorescence lifetimes
ranging from 200 to 270 ps in random copolymers 3–7 fall
Homopolymers with zinc–porphyrin pendants (2c and 2e)
and with free base porphyrin pendants (2d and 2 f) exhibit-
ed mirror image CD curves with very prominent intensities
in the Soret band region. The Cotton effect in this Soret
band region appeared to be opposite to that of the shorter
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T.-Y. Luh et al.
FULL PAPERS
Figure 1. Absorption spectra of 1c,d,g–j and 2c,d,g–j in CH2Cl2.
wavelength region (280–330 nm) for the absorption of the
aminobenzamide chromophores. Similar behavior was found
in substituted polyacetylenes.[9] The intensities of the CD
curves of 2c and 2d slightly decreased with increasing tem-
perature and were recovered upon cooling to ambient tem-
perature (Supporting Information; Figure S7a,b). The fwhm
and lmax values remain essentially unchanged with variation
of the temperature. These results suggest that polymers 2c–f
may adopt single-handed helical structures and significant
exciton coupling between orderly oriented adjacent porphy-
rin chromophores might take place. A strong CD response
of 2c–f suggests that these polymers, like other related
PNBs reported earlier,[15] may adopt homogeneous tacticity
and that all double bonds would be in trans configuration.
The helicity of the polymers 2c–f can be understood
within the framework of the exciton chirality method.[28] In
other words, the exciton coupling between the appended
porphyrins and aminobenzamide moieties would be respon-
sible for the helicity of the complexes. Since the porphyrin
moiety has a much higher extinction coefficient than that of
the aminobenzamide group, the intensity of the CD curves
at 360–460 nm was much higher than that around 300 nm. In
addition, the exciton couplet amplitudes among these poly-
mers would be related to the interchromophore distance as
1430
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Chem. Asian J. 2010, 5, 1425 – 1438

Energy Transfer in Helical Polynorbornenes
Figure 2. CD curves of homopolymers 2c–j in CH2Cl2.
well as the dihedral angle of the interacting moments. As
mentioned earlier, all pendants in 2–7 would align coherent-
ly towards the same direction, and the spacing occupied by
each of the monomeric units in PNBs would be about 0.5–
0.6 nm.[11a,14] The dihedral angle of the interacting chromo-
phores would likely offer a platform to dictate the intensity
of the couplet. The De value could therefore be estimated
by the summation of the contribution from each interacting
pair of these complexes. The uniformity of the orientation
of these interacting chromophores in these complexes would
determine the amplitude of the CD curves.
As shown in Figure 2, the intensity of the CD curve for
2g with zinc–porphyrin pendants was similar to those of 2c.
The temperature dependent CD profile for 2g is also shown
in the Supporting Information (Figure S7c). In contrast to
the cases of 2c and 2d, the intensities decreased more signif-
icantly as temperature increased with more than 80% re-
duction at 808C. Since there is only one hydrogen bond be-
tween adjacent lactamide linkers, it seems likely that 2g
might be easier to be “denatured” to give disordered struc-
ture, which would be CD-inactive.
the same Cotton effect as that of 2c and 2d. Even in the
presence of chiral linkers, simple p–p interactions between
adjacent pendants might not lead to single-handed helicity
of the polymer. Increases in the fwhm values of the Soret
bands of 2h–j, relative to the corresponding monomers 1h–
j, were much less than those of other homopolymer ana-
logues shown in Table 1. Presumably, the exciton coupling
would be relatively weak, and, hence, the CD intensities
were comparatively low.
Dimers 16 and 17: Dimers 16 and 17 were subject to CD
measurements to verify the nature of the exciton coupling
between adjacent chromophores in polymers (Figure 3). The
absorption and emission spectra of 16 and 17 (Figure S8 in
the Supporting Information) were comparable to those of
the corresponding monomers 1d and 1c and of the corre-
sponding polymers 2d and 2c, respectively. The CD curves
for 16 and 17 showed similar Cotton effects in the amino-
benzamide absorption region (300–350 nm) as those for 2d
and 2c, respectively. Both 16 and 17 exhibited strong CD re-
sponse in the Soret band region, but, surprisingly, opposite
Cotton effects to those for 2d and 2c.
Surprisingly, the CD intensity for 2h with the free base
porphyrin pendants was low. Polymers 2h exhibited an op-
posite Cotton effect to that of 2d. Polymers 2i and 2j,
having the lactate linker without hydrogen bonding between
adjacent pendants, exhibited very low CD intensities with
Density functional theory (DFT) calculations were carried
out to examine the possible conformation of model dimer
25 containing two additional alanine-based units to avoid in-
trapendant hydrogen bonding between the two amidic spe-
cies. The optimized geometries of 25 are shown in Figure 4.
Chem. Asian J. 2010, 5, 1425 – 1438
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1431

T.-Y. Luh et al.
FULL PAPERS
packing in polymers such as 2c–f and those in dimers 16 and
17 might be different. Nevertheless, the present results indi-
cate that there might be strong exciton coupling between
adjacent porphyrin pendants in these dimers and polymers
leading to a strong CD response.
Random copolymers 4–6: The CD profiles of 4–6 are
shown in Figure 5. Again, copolymer 4 having two hydrogen
Figure 5. CD curves of 4–6 in CH2Cl2.
bonds between the adjacent pendants exhibited a fairly
strong CD response with the same Cotton effect as that of
the corresponding homopolymers 2c and 2d. Copolymer 5
containing only one hydrogen bond between adjacent pend-
ants behaved similarly. However, the shape of the CD pro-
file of 5 was somewhat different from that of 4, while both
copolymers showed similar absorption spectra. When a lac-
tate was employed as the linker through the ester bonds for
6, the CD intensity was relatively weak.
Figure 3. CD curves of 16 (solid) and 17 (dotted) in CH2Cl2.
Conclusions
In summary, we have addressed an interesting feature on
the nature of linkers on the photophysical properties of por-
phyrin-appended PNBs. The use of bisamidic chiral alanine
linkers between the pending porphyrins and the polymeric
backbone has been shown to bring the adjacent porphyrin
chromophores to more suitable orientation for exciton cou-
pling because of hydrogen bonding between adjacent link-
ers. The hydrogen bonds between the adjacent pendants in
these polymers may induce a cooperative effect and there-
fore render single-handed helical structures for these poly-
mers (e.g., 2c–f). Such a cooperative effect is reflected in
the enhancement of FRET efficiencies between the zinc–
porphyrin and free base porphyrin in the random copoly-
mers 4 and 5.
Figure 4. DFT-calculated structures of 25 in a) helical form (torsional
angles 138 and 108) and b) sheet form (torsional angles 18 and 48).
The helix form was found to be 5.2 kcalmolꢀ1 more stable
than the sheet form. The two adjacent alanine moieties form
hydrogen bonds with an average distance around 2 ꢀ. For
the helix form, the projected torsional angle of two pendants
defined by two lines from the chiral center of the alanine
and the center of the porphyrin was 138 with right-handed
rotation. The two lines defined from the chiral center of the
amino acid and the center of the aminobenzamide moiety
for the helix form also yielded a right-handed torsional
angle of 108. These right-handed rotations for torsional
angles described above are consistent with the negative
Cotton effect in the CD spectrum for 16 shown in Figure 3.
The discrepancy of the Cotton effect between dimers 16,
17, and polymers 2c–f is striking. It is known that p–p inter-
actions between porphyrin rings are strong.[29] The mode of
Experimental Section
General: Gel permeation 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=
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Chem. Asian J. 2010, 5, 1425 – 1438

Energy Transfer in Helical Polynorbornenes
1.0 mLminꢀ1). Waters Styragel HR2, HR3, and HR4 columns (7.8ꢂ
300 mm) were employed for determination of relative molecular weight
using polystyrene as standard (Mn values ranged from 375 to 3.5ꢂ106).
Absorption spectra were measured on a Hitachi U-3310 spectrophotome-
ter and emission spectra on a Hitachi F-4600 fluorescence spectropho-
tometer. Quantum yield was obtained using ZnTPP (TPP=tetraphenyl-
porphyrin) in toluene as the reference (F=0.033). CD spectra were re-
corded on a JASCO J-815 spectropolarimeter.
and triethylamine in vacuo, the residue was purified by column chroma-
tography (silica gel, CH2Cl2/CH3OH=100:1, v/v), to give a purple solid
1d (350 mg, 90%): m.p.: 156–1578C; 1H NMR (300 MHz, CDCl3): d=
ꢀ2.78 (s, 2H), 0.92 (t, 3J (H,H)=6.5 Hz, 9H), 1.35–1.49 (m, 24H), 1.52–
1.62 (m, 8H), 1.71 (d, 3J (H,H)=7.1 Hz, 3H), 1.91–2.00 (m, 6H), 2.93–
2.95 (m, 4H), 3.04–3.06 (m, 2H), 3.24–3.28 (m, 2H), 4.17 (t, 3J (H,H)=
6.5 Hz, 4H), 4.23 (t, 3J (H,H)=6.5 Hz, 2H), 5.10 (quint, 3J (H,H)=
7.1 Hz, 1H), 6.13 (s, 2H), 6.43 (d, 3J (H,H)=8.9 Hz, 2H), 6.61 (d, 3J
(H,H)=7.2 Hz, 1H), 7.15 (d, 3J (H,H)=8.1 Hz, 2H), 7.18 (d, 3J (H,H)=
8.1 Hz, 2H), 7.25 (d, 3J (H,H)=8.4 Hz, 2H), 7.77 (d, 3J (H,H)=8.9 Hz,
2H), 7.97 (d, J (H,H)=8.4 Hz, 2H), 7.99 (d, J (H,H)=8.1 Hz, 2H), 8.01
(d, 3J (H,H)=8.1 Hz, 2H), 8.09 (d, 3J (H,H)=8.4 Hz, 2H), 8.14 (d, 3J
(H,H)=8.4 Hz, 2H), 8.78–8.85 (m, 8H; b-H), 9.58 ppm (s, 1H);
13C NMR (100 MHz, CDCl3): d=14.2, 18.1, 22.7, 26.21, 26.23, 29.3, 29.46,
29.47, 31.9, 45.3, 46.5, 50.2, 50.4, 52.0, 68.2, 68.3, 111.2, 112.47, 112.52,
112.7, 118.3, 119.1, 119.4, 119.8, 128.8, 130–132 (br), 134.2, 134.4, 135.0,
135.4, 135.6, 135.7, 137.9, 149.9, 158.8, 158.9, 168.2, 171.4 ppm; IR (KBr):
n˜ =3313, 2924, 2853, 1702, 1606, 1502, 1469, 1401, 1377, 1349, 1284, 1245,
1174, 1108, 966, 801, 734 cmꢀ1; MS (MALDI): m/z: 1322.8 (C87H99N7O5,
[M++H]); elemental analysis calcd (%) for C87H99N7O5: C 79.00, H 7.54,
N 7.41; found: C 79.12, H 7.78, N 7.10.
Compound 10l: To a solution of 9[11a] (507 mg, 0.5 mmol) in CH2Cl2
(50 mL) were added sequentially Boc-l-alanine (113 mg, 0.6 mmol;
Boc=tert-butyloxycarbonyl) and 1-ethyl-3-(3-dimethylaminopropyl)car-
bodiimide hydrochloride (EDCI) (115 mg, 0.6 mmol) and a catalytic
amount of 4-methylaminopyridine (DMAP; 7 mg, 0.06 mmol), and the
mixture was stirred at room temperature overnight. The mixture was
washed with water (100 mL) and brine (100 mL). The organic phase was
evaporated in vacuo to give the residue, which was purified by chroma-
tography (silica gel, CH2Cl2/CH3OH=100:1, v/v) to give 10l as a purple
solid (570 mg, 95%): m.p.: 201–2028C; 1H NMR (300 MHz, CDCl3): d=
ꢀ2.78 (s, 2H; NH), 0.95 (t, 3J (H,H)=6.3 Hz, 9H), 1.35–1.50 (m, 24H),
1.50–1.70 (m, 18H), 1.87–1.99 (m, 6H), 3.97 (br, 4H), 4.23 (t, 3J (H,H)=
3
3
3
6.3 Hz, 2H), 4.59 (br, 1H), 5.27 (br, 1H), 6.79 (d, J (H,H)=7.2 Hz, 2H),
7.04 (d, 3J (H,H)=7.2 Hz, 2H), 7.26 (d, 3J (H,H)=7.2 Hz, 2H), 7.64 (d,
3J (H,H)=7.2 Hz, 2H), 7.86 (d, 3J (H,H)=7.2 Hz, 2H), 7.97 (d, 3J
(H,H)=7.2 Hz, 2H), 8.10 (d, 3J (H,H)=7.2 Hz, 2H), 8.18 (d, 3J (H,H)=
7.2 Hz, 2H), 8.63 (s, 2H; b-H), 8.79–8.85 (m, 6H; b-H), 9.15 ppm (s, 1H;
CONH); 13C NMR (100 MHz, CDCl3): d=14.2, 17.4, 22.7, 26.2, 28.4,
29.3, 29.5, 31.9, 51.2, 53.4, 68.21, 68.3, 80.9, 112.5, 112.60, 112.69, 118.0,
119.1, 119.8, 120.0, 130.9 (br), 134.3, 134.4, 135.1, 135.5, 135.6, 137.6,
138.2, 158.9, 159.0, 173.9 ppm; IR (KBr): n˜ =3317, 2928, 2856, 1683, 1606,
1509, 1469, 1351, 1287, 1245, 1174, 966, 802, 738 cmꢀ1; HRMS (MALDI):
m/z: calcd for 1185.7185 (C76H93N6O6, [M++H]); found: 1185.7151.
Compound 1 f was obtained in a similar manner in 92% yield. HRMS
(MALDI): m/z: calcd for 1322.7807 (C87H100N7O5, [M++H]); found:
1322.7780.
Compound 15: To a solution of ethyl l-lactate (472 mg, 4 mmol) and trie-
thylamine (202 mg, 2 mmol) in CH2Cl2 (10 mL) cooled at 08C under
argon was added a CH2Cl2 solution (5 mL) of 13 freshly prepared from
12 (510 mg, 2 mmol) and oxalyl chloride (1.7 mL, 20 mmol) as described
above. The mixture was allowed to warm to room temperature and
stirred for an additional 4 h. Solvent and excess Et3N were removed in
vacuo and the residue was chromatographed on silica gel (CH2Cl2) to
give a white solid (603 mg, 85%), which was treated with a solution of
lithium hydroxide monohydrate (74 mg, 1.8 mmol) in water (1.5 mL) and
THF (5 mL). The mixture was stirred at 08C for 1.5 h. Removal of THF
in vacuo followed by the addition of water (10 mL) gave an aqueous so-
lution, which was acidified to pH 2 to afford 15 as a white powder
(445 mg, 85%): m.p.: 185–1868C; [a]D =+34.38 (c=0.40m, CHCl3);
1H NMR (400 MHz, CDCl3): d=1.56 (d, 2J (H,H)=8.4 Hz, 1H), 1.62 (d,
3J (H,H)=7.2 Hz, 3H), 1.66 (dt, 2J (H,H)=8.4 Hz, 1H), 2.90–3.00 (m,
4H), 3.15–3.16 (m, 2H), 3.37–3.42 (m, 2H), 5.29 (q, 3J (H,H)=7.2 Hz,
1H), 6.20 (s, 2H), 6.59 (d, 3J (H,H)=8.4 Hz, 2H), 7.93 ppm (d, 3J
(H,H)=8.4 Hz, 2H); 13C NMR (100 MHz, CDCl3): d=17.4, 45.6, 46.3,
52.8, 68.3, 113.1, 118.2, 131.2, 135.7, 148.4, 165.2, 175.0 ppm; IR (KBr):
n˜ =3056, 2968, 2942, 2847, 1701, 1603, 1527, 1473, 1451, 1388, 1343, 1302,
1270, 1175, 1106, 1042, 824, 770, 726 cmꢀ1; HRMS (EI): m/z: calcd for
327.1474 (C19H21NO4, [M+]); found: 327.1471.
In a similar manner, 10d was obtained in 95% yield from 9 (710 mg,
0.7 mmol) and Boc-d-alanine (159 mg, 0.84 mmol); HRMS (MALDI):
m/z: calcd for 1184.7030 (C76H92N6O6, [M+]); found: 1184.7073.
Compound 11l. A mixture of 10l (474 mg, 0.4 mmol) and trifluoroacetic
acid (TFA; 10 mL) in CH2Cl2 (40 mL) was stirred for 2 h. After evapora-
tion of the solvent and TFA in vacuo, the residue was dissolved in
CH2Cl2 (50 mL) and washed with an aqueous 10% sodium bicarbonate
solution (50 mL), water (100 mL), and brine (100 mL). The organic phase
was evaporated in vacuo and the residue was chromatographed on silica
gel (CH2Cl2/CH3OH=25: 1, v/v) to give 11l as a purple solid (425 mg,
98%): m.p.: 221–2238C; 1H NMR (300 MHz, CDCl3): d=ꢀ2.77 (s, 2H;
NH), 0.93 (t, 3J (H,H)=6.3 Hz, 9H), 1.35–1.50 (m, 24H), 1.50–1.57 (m,
9H), 1.90–2.20 (m, 8H), 3.70–3.90 (m, 1H), 4.12 (t, 3J (H,H)=6.3 Hz,
4H), 4.20 (t, 3J (H,H)=6.3 Hz, 2H), 7.16–7.26 (m, 6H), 7.98–8.07 (m,
6H), 8.10 (d, 3J (H,H)=8.4 Hz, 2H), 8.18 (d, 3J (H,H)=8.4 Hz, 2H),
8.84–8.86 (m, 8H; b-H), 9.90 ppm (s, 1H); 13C NMR (100 MHz, CDCl3):
d=14.2, 21.6, 22.7, 26.2, 29.3, 29.5, 31.9, 51.2, 68.2, 112.6, 117.6, 119.3,
119.9, 120.0, 130–132 (br), 134.3, 134.4, 135.1, 135.5, 135.6, 137.5, 138.0,
158.90, 158.92, 173.9 ppm; IR (KBr): n˜ =3313, 2924, 2853, 1693, 1606,
Compound 1h: A mixture of 9 (202 mg, 0.2 mmol), 15 (98 mg, 0.6 mmol),
EDCI (115 mg, 0.6 mmol), and DMAP (7 mg, 0.06 mmol) in CH2Cl2
(20 mL) was stirred overnight and then washed with water (50 mL) and
brine (50 mL). The organic phase was dried (MgSO4), filtered, and
evaporated in vacuo to give the residue which was purified by column
chromatography (silica gel, CH2Cl2) to give 1h as a purple solid (250 mg,
95%): m.p.: 209–2218C; 1H NMR (400 MHz, CDCl3): d=ꢀ2.73 (s, 2H),
0.96 (t, 3J (H,H)=7.2 Hz, 9H), 1.37–1.68 (m, 32H), 1.81 (d, 3J (H,H)=
1519, 1506, 1468, 1402, 1349, 1284, 1244, 1174, 1101, 966, 801, 735 cmꢀ1
;
HRMS (MALDI): m/z: calcd for 1085.6646 (C71H85N6O4, [M++H]);
found: 1085.6627.
In a similar manner, 11d was obtained in 93% yield from 10d (780 mg,
0.65 mmol) and TFA (25 mL); HRMS (MALDI): m/z: calcd for
1085.6636 (C71H85N6O4, [M++H]); found: 1085.6627; elemental analysis
calcd (%) for C71H84N6O4: C 78.56, H 7.80, N 7.74; found: C 78.13,
H 7.83, N 7.62.
3
6.4 Hz, 3H), 2.00 (quint, J (H,H)=7.2 Hz, 6H), 3.01–3.04 (m, 4H), 3.10–
3.13 (m, 2H), 3.32–3.37 (m, 2H), 4.23–4.27 (m, 6H), 5.77 (q, 3J (H,H)=
6.8 Hz, 1H), 6.19 (t, 3J (H,H)=1.6 Hz, 2H), 6.49 (d, 3J (H,H)=8.8 Hz,
2H), 7.25–7.29 (m, 6H), 7.95 (d, 3J (H,H)=8.8 Hz, 2H), 8.03 (d, 3J
(H,H)=8.8 Hz, 2H), 8.09 (d, 3J (H,H)=8.4 Hz, 4H), 8.11 (d, 3J (H,H)=
8.4 Hz, 2H), 8.18 (d, 3J (H,H)=8.4 Hz, 2H), 8.44 (s, 1H), 8.81–8.88 ppm
(m, 8H; b-H); 13C NMR (100 MHz, CDCl3): d=14.3, 18.0, 22.8, 26.3,
28.5, 29.4, 29.6, 32.0, 45.4, 46.7, 50.5, 52.1, 68.3, 70.5, 111.1, 112.6, 114.7,
118.1, 118.9, 119.8, 119.9, 130–132 (br, embodied a sharp peak at 131.5),
134.17, 134.24, 134.9, 135.37, 135.42, 135.6, 136.8, 138.4, 150.7, 158.7,
165.6, 169.3 ppm; IR (KBr): n˜ =3420, 3316, 3031, 2930, 2863, 1707, 1675,
1606, 1525, 1514, 1467, 1378, 1347, 1277, 1249, 1176, 1099, 1036, 970, 799,
770, 739 cmꢀ1; HRMS (FAB): m/z: calcd for 1323.7626 (C87H99N6O6, [M+
+H]); found: 1323.7606.
Compounds 1d and 1 f: To a solution of 12 (115 mg, 0.45 mmol) in
CH2Cl2 (10 mL) at 08C was added oxalyl chloride (0.13 mL, 1.5 mmol).
The mixture was gradually warmed to room temperature and stirred for
30 min. The solvent was removed in vacuo to give the corresponding acid
chloride, which was used for the next reaction without further purifica-
tion. To a CH2Cl2 (10 mL) solution of 11l (326 mg, 0.3 mmol) and trie-
thylamine (0.05 mL, 0.45 mmol) cooled to 08C under argon was added
dropwise a solution of the freshly prepared acid chloride described above
in CH2Cl2 (5 mL). The mixture was allowed to warm to room tempera-
ture and stirred for an additional 4 h. After evaporation of the solvent
Chem. Asian J. 2010, 5, 1425 – 1438
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T.-Y. Luh et al.
FULL PAPERS
3
3
Compound 1j: In a manner similar to that described for 1h, 16 (202 mg,
0.2 mmol) and 15 (98 mg, 0.6 mmol) were converted into 1j as a purple
solid (238 mg, 90%): m.p.: 118–1208C; 1H NMR (400 MHz, CDCl3): d=
ꢀ2.75 (s, 2H), 0.96 (t, 3J (H,H)=6.8 Hz, 9H), 1.37–1.68 (m, 32H), 1.92
(d, 3J (H,H)=6.8 Hz, 3H), 2.00 (quint, 3J (H,H)=6.8 Hz, 6H), 3.02 (br,
4H), 3.11–3.13 (m, 2H), 3.31–3.37 (m, 2H), 4.26 (t, 3J (H,H)=6.8 Hz,
6H), 5.62 (q, 3J (H,H)=6.8 Hz, 1H), 6.19 (s, 2H), 6.45 (d, 3J (H,H)=
8.8 Hz, 2H), 7.25–7.29 (m, 6H), 7.53 (d, 3J (H,H)=8.4 Hz, 2H), 8.03 (d,
3J (H,H)=8.4 Hz, 2H), 8.10 (d, 3J (H,H)=8.4 Hz, 6H), 8.20 (d, 3J
(H,H)=8.0 Hz, 2H), 8.81–8.87 ppm (m, 8H, b-H); 13C NMR (100 MHz,
CDCl3): d=14.3, 17.4, 22.8, 26.4, 29.4, 29.6, 29.8, 32.0, 45.4, 46.7, 50.5,
52.1, 68.3, 68.7, 110.9, 112.6, 115.1, 118.4, 119.5, 119.9, 120.0, 131.0, 131.6,
134.16, 134.22, 135.1, 135.4, 135.6, 139.9, 150.2, 150.5, 158.8, 166.3,
170.1 ppm; IR (KBr): n˜ =3316, 3031, 2923, 2847, 1780, 1708, 1606, 1511,
1498, 1467, 1377, 1343, 1274, 1249, 1172, 1100, 970, 802, 739 cmꢀ1; HRMS
(FAB): m/z: calcd for 1324.7466 (C87H98N5O7, [M++H]); found:
1324.7471.
2H), 7.68 (d, J (H,H)=8.8 Hz, 2H), 8.15 (d, J (H,H)=8.4 Hz, 6H), 8.26
(d, 3J (H,H)=8.0 Hz, 2H), 9.00 (d, 3J (H,H)=4.8 Hz, 2H; b-H), 9.04–
9.05 ppm (m, 6H; b-H); 13C NMR (100 MHz, CDCl3): d=14.6, 17.5, 23.1,
26.6, 29.65, 29.78, 29.80, 30.0, 32.2, 45.4, 46.7, 50.5, 52.2, 68.3, 68.5, 110.5,
112.3, 114.4, 119.1, 119.2, 120.3, 120.5, 120.7, 131.0, 131.2, 131.5, 131.7,
134.6, 134.7, 135.0, 135.3, 140.2, 149.5, 149.91, 149.94, 150.04, 158.0, 165.6,
169.4 ppm; IR (KBr): n˜ =3063, 3034, 2955, 2923, 2850, 1780, 1704, 1606,
1527, 1508, 1492, 1470, 1378, 1337, 1280, 1248, 1175, 1106, 998, 796, 770,
720 cmꢀ1; HRMS (FAB): m/z: calcd for 1385.6523 (C87H95N5O7Zn, [M+
]); found: 1385.6531.
Polymer 2d: A solution of 1d (79 mg, 0.06 mmol) and [(Cy3P)2Cl2Ru=
CHPh] (4.8 mg, 0.006 mmol) in CH2Cl2 (2 mL) was stirred under argon at
room temperature for 2 h. The mixture was quenched with ethyl vinyl
ether (0.2 mL) and then poured into MeOH (10 mL). The solid was col-
lected, redissolved in CH2Cl2 (1 mL), and reprecipitated by adding
MeOH (10 mL). This procedure was repeated twice, and the solid was
collected to afford 2d as a dark purple solid (79 mg, 99%); 1H NMR
(300 MHz, CDCl3): d=ꢀ2.85 (2H), 0.90 (s, 9H), 1.29–1.96 (m, 41H),
2.20–3.60 (m, 12H), 4.22 (s, 2H), 5.00–5.70 (m, 3H), 5.70–7.00 (m, 7H),
7.25 (s, 2H), 7.50–9.00 (m, 20H; phenyl and b-H), 10.01 ppm (br, 1H;
CONH); 13C NMR (100 MHz, CDCl3): d=14.1, 17.6, 22.7, 26.1, 29.3,
29.4, 31.8, 43–45 (br), 49–51 (br), 67.3, 68.2, 110–113 (br, embodied a
sharp peak at 112.6), 117–120 (br), 127–136 (br, embodied three sharp
peaks at 133.1, 134.4 and 135.5), 157.8, 158.9 ppm; IR (KBr): n˜ =3313,
2926, 2854, 1691, 1606, 1509, 1470, 1401, 1377, 1351, 1285, 1245, 1174,
1108, 966, 801, 735 cmꢀ1; GPC (THF): Mn =14820; Mw =16470; PDI=
1.11.
Compounds 1c and 1e: To a solution of 1d (132 mg, 0.1 mmol) in chloro-
form (30 mL) was added a methanolic solution (10 mL) of Zn acetate di-
hydrate (219 mg, 1 mmol), and the mixture was stirred at room tempera-
ture overnight, poured into water, and extracted with chloroform. The
chloroform extract was washed three times with water. The solvent was
evaporated and the residue was purified by column chromatography
(silica gel, CH2Cl2/CH3OH=100:1, v/v) to give a purple solid 1c (130 mg,
94%): m.p.: 156–1588C; 1H NMR (400 MHz, CDCl3): d=0.91 (t, 3J
(H,H)=6.4 Hz, 9H), 1.35–1.62 (m, 35H), 1.94 (quint, 3J (H,H)=6.4 Hz,
6H), 2.84 (d, 3J (H,H)=10.4 Hz, 2H), 2.94 (br, 2H), 3.00–3.01 (m, 2H),
3.12–3.17 (m, 2H), 4.00 (br, 1H; CHCO), 4.17–4.22 (m, 6H), 6.10 (s,
2H), 6.17–6.19 (m, 3H), 7.07 (d, 3J (H,H)=7.2 Hz, 2H), 7.17–7.28 (m,
2 f: (93%): GPC (THF): Mn =11460; Mw =12660; PDI=1.11.
2c: (96%): 1H NMR (300 MHz, CDCl3): d=0.93 (s, 9H), 1.30–1.96 (m,
41H), 2.20–3.60 (m, 8H), 4.22 (br, 6H), 5.00–6.00 (m, 3H), 6.00–7.26 (m,
9H), 7.27–7.50 (br, 2H), 7.60–8.40 (m, 10H), 8.40–9.50 ppm (m, 9H; b-H
and CONH); 13C NMR (100 MHz, CDCl3): d=14.2, 22.7, 26.2, 29.4, 29.5,
31.9, 35.3, 42–52 (v br), 67–69 (br), 110–114 (br), 119–121 (br), 128.6,
130–133 (br), 133–136 (br), 149–151 (br), 157–159 ppm (br); IR (KBr):
n˜ =2925, 2854, 1698, 1606, 1525, 1509, 1492, 1473, 1377, 1339, 1245, 1174,
1108, 1068, 998, 798, 719 cmꢀ1; GPC (THF): Mn =14190; Mw =16080;
PDI=1.13.
3
3
6H), 7.70 (d, J (H,H)=7.2 Hz, 2H), 8.03 (d, J (H,H)=8.0 Hz, 4H), 8.08
(d, 3J (H,H)=8.0 Hz, 4H), 8.75 (s, 1H), 8.90–8.94 ppm (m, 8H; b-H);
13C NMR (100 MHz, CDCl3): d=14.1, 17.1, 22.7, 26.2, 29.3, 29.5, 31.9,
45.3, 46.5, 49.2, 50.3, 52.0, 68.2, 110.7, 112.4, 117.6, 117.8, 120.2, 120.6,
120.7, 128.1, 131.7, 131.8, 134.8, 135.2, 135.3, 135.4, 135.7, 137.1, 138.7,
149.6, 150.1, 150.4, 150.5, 158.6, 167.3, 170.4 ppm; IR (KBr): n˜ =2926,
2854, 1698, 1606, 1525, 1509, 1493, 1473, 1378, 1339, 1245, 1174, 1108,
1068, 998, 797, 720 cmꢀ1; HRMS (MALDI): m/z, calcd for 1383.6850
(C87H97N7O5Zn, [M+]); found: 1383.6837.
2e: (95%): GPC (THF): Mn =13670; Mw =15440; PDI=1.13.
In a similar manner, reaction of 1 f (132 mg, 0.1 mmol) and a solution of
Zn acetate dihydrate (219 mg, 1 mmol) furnished 1e (125 mg, 91%) as a
purple solid: HRMS (MALDI): m/z: calcd for 1383.6862 (C87H97N7O5Zn,
[M+]); found: 1383.6837; elemental analysis calcd (%) for
C87H97N7O5Zn: C 75.38, H 7.05, N 7.07; found: C 74.95, H 7.20, N 7.00.
2h: (98%): 1H NMR (400 MHz, CDCl3): d=ꢀ2.76 (s, 2H), 0.88 (br,
9H), 1.28–1.90 (m, 41H), 2.37 (br, 4H), 2.91 (br, 4H), 3.81 (br, 4H), 4.11
(br, 2H), 5.09 (br, 2H), 5.58 (br, 1H), 6.30 (br, 2H), 6.87 (br, 4H), 7.15
(br, 2H), 7.50–8.20 (m, 12H), 8.50–8.80 ppm (m, 9H; NH and b-H);
13C NMR (100 MHz, CDCl3): d=14.1, 17.8, 22.7, 26.1, 26.9, 29.3, 31.8,
35.6, 36.9, 44.2, 46.1, 49.2, 68.2, 70.8, 111.5, 112.6, 115.7, 118.2, 119.0,
119.8, 131.6, 134.1, 134.9, 135.4, 137.0, 138.4, 151.1, 158.9, 165.9,
169.4 ppm; IR (KBr): n˜ =3420, 3316, 3028, 2920, 2847, 1704, 1606, 1525,
Compound 1g: In a manner similar to that described for 1c, 1h (132 mg,
0.1 mmol) was converted into 1g as a purple solid (126 mg, 91%): m.p.:
209–2118C; 1H NMR (400 MHz, CDCl3): d=1.00 (t, 3J (H,H)=6.8 Hz,
9H), 1.39–1.50 (m, 25H), 1.57–1.65 (m, 10H), 1.95 (quint, 3J (H,H)=
6.8 Hz, 6H), 2.84 (d, 3J (H,H)=10.4 Hz, 2H), 2.94–2.98 (m, 4H), 3.08–
3.15 (m, 2H), 4.14–4.19 (m, 6H), 4.83 (q, 3J (H,H)=6.8 Hz, 1H), 6.12 (s,
1507, 1470, 1375, 1347, 1277, 1239, 1169, 1096, 1030, 966, 799, 732 cmꢀ1
GPC (THF): Mn =17600; Mw =19300; PDI=1.09.
;
3
3
2H), 6.23 (d, J (H,H)=8.8 Hz, 2H), 7.22 (d, J (H,H)=8.8 Hz, 4H), 7.24
(d, 3J (H,H)=8.8 Hz, 2H), 7.58 (d, 3J (H,H)=8.0 Hz, 2H), 7.63 (d, 3J
(H,H)=8.8 Hz, 2H), 8.04 (s, 1H), 8.12 (d, 3J (H,H)=8.8 Hz, 4H), 8.15
(d, 3J (H,H)=8.0 Hz, 4H), 8.95 (d, 3J (H,H)=4.8 Hz, 2H; b-H), 9.01 (d,
3J (H,H)=4.8 Hz, 2H; b-H), 9.02 ppm (s, 4H; b-H); 13C NMR (100 MHz,
CDCl3): d=14.6, 17.8, 23.1, 26.6, 29.6, 29.8, 32.2, 45.4, 46.7, 50.5, 52.2,
68.3, 70.0, 110.6, 112.2, 114.0, 117.6, 119.6, 120.5, 120.6, 130.9, 131.2,
131.5, 134.4, 134.7, 135.0, 135.2, 135.8, 149.5, 149.9, 150.0, 150.1, 158.0,
164.7, 168.2 ppm; IR (KBr): n˜ =3417, 3329, 3031, 2925, 2851, 1704, 1679,
1603, 1524, 1508, 1489, 1467, 1381, 1338, 1270, 1239, 1169, 1090, 995, 796,
720 cmꢀ1; HRMS (FAB): m/z: calcd for 1384.6683 (C87H96N6O6, [M+]);
found: 1384.6677.
2g: (90%): 1H NMR (400 MHz, CDCl3): d=0.88 (br, 9H), 1.28–1.90 (m,
41H), 2.49 (br, 4H), 2.87 (br, 4H), 3.91 (br, 7H), 5.07 (br, 2H), 6.11 (br,
2H), 7.04 (br, 6H), 7.26–7.50 (m, 4H), 7.94 (br, 9H), 8.70–9.00 ppm (m,
8H; b-H); 13C NMR (100 MHz, CDCl3): d=14.1, 17.1, 22.7, 26.1, 29.4,
31.8, 35.3, 37.0, 44.2, 46.1, 49.2, 68.1, 69.9, 111.3, 112.5, 115.2, 117.7, 119.8,
120.7, 131.9, 134.8, 135.4, 139.3, 150.0, 150.5, 158.6, 165.3, 168.5 ppm; IR
(KBr): n˜ =3411, 3031, 2925, 2853, 1708, 1603, 1525, 1507, 1377, 1337,
1264, 1239, 1175, 1093, 995, 799, 717 cmꢀ1; GPC (THF): Mn =15500;
Mw =17400; PDI=1.12.
1
2j: (95%): H NMR (400 MHz, CDCl3): d=ꢀ2.76 (s, 2H), 0.91 (br, 9H),
1.28–1.90 (m, 41H), 2.56 (br, 4H), 3.11 (br, 4H), 3.94–4.20 (m, 6H), 5.16
(br, 2H), 5.52 (br, 1H), 6.41 (br, 2H), 7.02–7.26 (m, 6H), 7.41 (br, 2H),
7.80–8.00 (m, 10H), 8.68 ppm (br, 8H; b-H); 13C NMR (100 MHz,
CDCl3): d=14.3, 17.3, 22.8, 26.3, 29.4, 29.5, 29.6, 29.8, 32.0, 35.8, 36.2,
44.4, 46.4, 49.3, 68.1, 68.8, 111.3, 112.5, 115.8, 118.3, 119.5, 119.8, 120.0,
131.0, 131.6, 134.0, 135.1, 135.3, 139.8, 150.1, 150.9, 158.7, 166.1,
169.9 ppm; IR (KBr): n˜ =3313, 3028, 2930, 2851, 1770, 1708, 1603, 1511,
1473, 1372, 1343, 1274, 1242, 1176, 1100, 967, 802, 736 cmꢀ1; GPC (THF):
Mn =16490; Mw =19630; PDI=1.19.
Compound 1i: In a manner similar to that described for 1c, 1j (66 mg,
0.05 mmol) was transformed into 1i as a purple solid (67 mg, 97%): m.p.:
119–1208C; 1H NMR (400 MHz, CDCl3): d=1.02 (t, 3J (H,H)=6.8 Hz,
9H), 1.37–1.65 (m, 32H), 1.84 (d, 3J (H,H)=6.8 Hz, 3H), 1.91–1.99 (m,
6H), 2.85 (d, 3J (H,H)=11.2 Hz, 2H), 2.96 (br, 4H), 3.07–3.10 (m, 2H),
4.13–4.18 (m, 6H), 5.14 (q, 3J (H,H)=6.8 Hz, 1H), 6.15 (s, 2H), 6.22 (d,
3J (H,H)=8.8 Hz, 2H), 7.20–7.25 (m, 6H), 7.46 (d, 3J (H,H)=8.4 Hz,
1434
www.chemasianj.org
ꢁ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Asian J. 2010, 5, 1425 – 1438

Energy Transfer in Helical Polynorbornenes
2i: (87%): 1H NMR (400 MHz, CDCl3): d=0.92 (br, 9H), 1.33–1.83 (m,
41H), 2.63 (br, 4H), 3.02 (br, 4H), 4.08 (br, 6H), 5.20 (br, 3H), 6.28 (br,
2H), 7.14 (br, 6H), 7.34 (br, 2H), 7.69 (br, 2H), 8.03 (br, 8H), 8.91 ppm
(br, 8H; b-H); 13C NMR (100 MHz, CDCl3): d=14.1, 17.1, 22.7, 26.2,
29.3, 29.4, 29.7, 31.8, 44.4, 46.3, 49.4, 68.2, 68.6, 111.3, 112.5, 115.7, 119.4,
120.8, 121.0, 125.9, 128.5, 131.6, 131.9, 132.0, 135.0, 135.4, 140.6, 145.2,
149.9, 150.4, 150.7, 151.0, 158.7, 166.2, 170.0 ppm; IR (KBr): n˜ =3037,
2955, 2923, 2854, 1771, 1711, 1606, 1520, 1505, 1489, 1470, 1375, 1340,
1271, 1245, 1175, 1100, 998, 799, 770, 723 cmꢀ1; GPC (THF): Mn =12760;
Mw =14500; PDI=1.14.
added dropwise into MeOH (20 mL). The solid was collected and redis-
solved in CH2Cl2 (2 mL) and reprecipitated by adding MeOH (10 mL).
This procedure was repeated twice, and the solid was collected to afford
7 as a purple solid (108 mg, 92%): 1H NMR (500 MHz, CDCl3): d=
ꢀ2.97 (br, 2H), 0.7–0.9 (br, 18H), 0.9–1.7 (br, 88H), 1.7–2.2 (br, 14H),
2.1–2.8 (br, 18H), 2.8–3.4 (br, 8H), 4.0–4.9 (br, 10H), 4.9–5.4 (br, 4H),
5.4–5.8 (br, 4H), 6.2–6.8 (br, 4H), 7.5–7.8 (br, 4H), 7.8–8.2 (br, 8H), 8.5–
9.5 ppm (br, 14H); IR (KBr): n˜ =3313, 3120, 3028, 2949, 2923, 2851,
1705, 1605, 1522, 1479, 1466, 1375, 1271, 1178, 1097, 967, 790, 767 cmꢀ1
;
GPC (THF): Mn =11600; Mw =14400; PDI=1.24.
1
2b (94%): H NMR (400 MHz, CDCl3): d=ꢀ2.77 (s, 2H), 0.83 (br, 9H),
2-(4-Bromophenyl)-4-b-styryl-6-vinyloctahydrocyclopenta[c]pyrrole (19):
A solution of 18 (10.0 g, 31.43 mmol), styrene (9.0 mL, 78.6 mmol), and
Grubbs I catalyst (1.29 g, 1.57 mmol) in CH2Cl2 (150 mL) was stirred
under argon for 24 h and quenched with ethyl vinyl ether (10 mL). Re-
moval of the solvent in vacuo, followed by chromatographic purification
(silica gel, hexane/CH2Cl2 =1:1) afforded 19 (9.96 g, 75%): m.p.: 131–
1.22–1.98 (m, 38H), 2.00–3.50 (br, 8H), 3.72–4.25 (br, 6H), 5.24 (br, 2H),
6.51–7.26 (m, 8H), 7.58 (br, 2H), 7.77 (br, 4H), 8.00–8.20 (m, 6H), 8.71–
8.81 ppm (m, 8H; b-H); 13C NMR (100 MHz, CDCl3): d=14.1, 22.7, 26.1,
26.2, 29.2, 29.3, 29.5, 29.7, 30.2, 31.8, 39.8, 44.4, 46.7, 47.5, 49.2, 67.9, 68.3,
111.6, 112.4, 112.7, 116.2, 118.8, 119.9, 120.2, 126.1, 128.6, 131.0, 132.2,
134.0, 135.3, 135.9, 139.4, 151.2, 158.7, 158.9, 165.6 ppm; IR (KBr): n˜ =
3315, 2924, 2853, 1726, 1606, 1559, 1507, 1469, 1378, 1351, 1311, 1265,
1245, 1205, 1175, 1165, 1059, 966, 800, 760, 734 cmꢀ1; GPC (THF): Mn =
28367; Mw =39764; PDI=1.40.
1
1328C; H NMR (CDCl3, 400 MHz): d=1.56–1.66 (m, 1H), 2.08–2.14 (m,
1H); 3.04–3.20 (m, 2H), 3.39–3.47 (m, 2H), 5.17–5.22 (m, 2H), 6.05–6.13
(m, 1H), 6.45–6.54 (m, 2H), 7.16 (d, 3J (H,H)=8.7 Hz, 2H), 7.20–7.41
(m, 5H), 7.58 ppm (d, 3J (H,H)=8.7 Hz, 2H); 13C NMR (CDCl3,
100 MHz): d=35.9, 45.7, 46.2, 48.7, 49.4, 116.0, 122.2, 126.3, 127.4, 127.8,
127.9, 128.5, 130.8, 131.0, 132.2, 136.0, 137.0, 175.2, 175.3 ppm; IR (KBr):
n˜ =3085, 3056, 3025, 2956, 2923, 2854, 1776, 1712, 1490, 1449, 1377, 1178,
1071, 1013, 964, 924, 804, 749, 695 cmꢀ1; HRMS (FAB): m/z: calcd for:
422.0756 (C23H21NO2Br, , [M++H]); found: 422.0759.
2l: (92%): 1H NMR (400 MHz, CDCl3): d=ꢀ2.84 (br, 2H; NH), 0.7–0.9
(br, 9H; CH3), 0.9–1.4 (m, 44H; CH2), 1.4–1.9 (m, 12H; CH2), 2.1–2.8
(m, 8H), 2.8–3.3 (m, 4H), 4.5–4.8 (m, 6H), 5.0–5.1 (m, 2 H), 5.6 (br,
2H), 6.4 (br, 2H),7.6 (br, 2H), 7.9 (br, 2H), 8.1 (br, 2H), 8.6 (br, 2H),
9.0–9.4 ppm (m, 6H); 13C NMR (100 MHz, CDCl3): d=14.1, 22.6, 29.28,
29.34, 29.6, 29.7, 30.4, 30.6, 31.9, 35.2, 38.5, 38.9, 44.8, 49.2, 65.8, 111.4,
118.9, 125.9, 131.6, 134.4, 136.1, 142.1, 166.9 ppm; IR (KBr): n˜ =3316,
3126, 2955, 2923, 2852, 1705, 1606, 1522, 1479, 1373, 1270, 1177, 1096,
966, 791, 767, 733 cmꢀ1; GPC (THF): Mn =11000; Mw =12000; PDI=
1.13.
To a slurry of LiAlH4 (7.2 g, 189 mmol) in Et2O (100 mL) was added
slowly 19 (10.0 g, 23.68 mmol) in CH2Cl2 (100 mL), and the mixture was
stirred at room temperature for 1 h. Ethyl acetate was carefully added,
water (1 mL) was then introduced, and the resulting suspension was fil-
tered, and the organic layer was evaporated in vacuo to give a residue,
which was triturated with CH2Cl2 repeatedly. The CH2Cl2 solution was
dried (MgSO4) and filtered. The solvent was removed in vacuo to give 20
as a colorless liquid (7.84 g, 84%): 1H NMR (400 MHz, CDCl3): d=1.64
(q, 2J (H,H)=12.0 Hz, 1H), 1.96 (dt, 2J (H,H)=12.4; 3J (H,H)=6.0 Hz,
1H), 2.80–2.86 (m, 1H), 2.91–3.04 (m, 3H), 3.15–3.21 (m, 4H), 5.08 (dd,
Copolymer 3:
A solution of 1a (40 mg, 0.030 mmol), 1b (26 mg,
0.020 mmol) and [(Cy3P)2Cl2Ru=CHPh] (4 mg, 0.005 mmol) in CH2Cl2
(2 mL) was stirred under argon at room temperature for 2 h. The reac-
tion was quenched with ethyl vinyl ether (0.5 mL), and the solution was
added dropwise into MeOH (10 mL). The solid was collected and redis-
solved in CH2Cl2 (1 mL) and reprecipitated by adding MeOH (10 mL).
This procedure was repeated twice, and the solid was collected to afford
3 as a purple solid (55 mg, 85%): 1H NMR (400 MHz, CDCl3): d=ꢀ2.78
(s, 0.79H; NH), 0.84 (br, 9H), 1.25–1.90 (m, 38H), 2.20–3.50 (br, 8H),
3.74 (br, 4H), 4.15 (br, 2H), 5.22 (br, 2H), 6.41 (br, 2H), 6.83 (br, 4H),
7.19 (br, 2H), 7.53 (br, 2H), 7.80–8.19 (m, 10H), 8.41–8.90 ppm (m, 8H;
b-H); IR (KBr): n˜ =2925, 2854, 1725, 1605, 1525, 1508, 1469, 1379, 1339,
1272, 1245, 1205, 1175, 1165, 1061, 998, 966, 799, 720 cmꢀ1; GPC (THF):
Mn =14390; Mw =16200; PDI=1.12.
4: (93%): 1H NMR (400 MHz, CDCl3): d=ꢀ2.81 (s, 2H; NH), 0.93 (br,
18H), 1.34–1.99 (m, 82H), 2.20–3.60 (m, 24H), 4.25 (br, 4H), 5.31 (br,
6H), 6.40–7.26 (m, 18H), 7.26–8.30 (m, 25H), 8.56–8.90 (m, 8H; b-H),
9.79 ppm (br, 1H); IR (KBr): n˜ =3310, 3034, 2927, 2851, 1695, 1679,
1605, 1527, 1508, 1467, 1379, 1331, 1280, 1239, 1175, 1106, 1061, 995, 966,
802, 723 cmꢀ1; GPC (THF): Mn =13400; Mw =14900; PDI=1.11.
5: (98%): 1H NMR (400 MHz, CDCl3): d=ꢀ2.77 (s, 2H; NH), 0.87 (br,
18H), 1.27–1.99 (m, 82H), 2.20–3.60 (m, 16H), 3.86–4.10 (br, 12H), 5.06
(br, 6H), 6.19 (br, 4H), 6.94–7.26 (m, 12H), 7.51–8.10 (m, 26H), 8.80–
8.86 ppm (m, 16H; b-H); IR (KBr): n˜ =3414, 3316, 3034, 2927, 2847,
1704, 1605, 1525, 1511, 1470, 1381, 1339, 1274, 1245, 1205, 1175, 1099,
998, 963, 799, 726 cmꢀ1; GPC (THF): Mn =18000; Mw =20300; PDI=
1.12.
6: (93%): 1H NMR (400 MHz, CDCl3): d=ꢀ2.77 (s, 2H; NH), 0.90 (br,
18H), 1.28–2.00 (m, 82H), 2.40–3.40 (m, 16H), 3.97–4.08 (br, 12H), 5.18
(br, 6H), 6.33 (br, 4H), 7.04–7.26 (m, 12H), 7.37 (br, 4H), 7.60–8.20 (m,
20H), 8.79–8.88 ppm (m, 16H; b-H); IR (KBr): n˜ =3310, 3028, 2925,
2854, 1774, 1709, 1605, 1523, 1506, 1469, 1379, 1339, 1272, 1245, 1205,
1175, 1102, 997, 966, 799, 767, 732 cmꢀ1; GPC (THF): Mn =17500; Mw =
19500; PDI=1.11.
2
3
2
3J (H,H)=9.4 Hz, J (H,H)=1.6 Hz, 1H), 5.09 (dd, J (H,H)=17.2 Hz, J
(H,H)=1.6 Hz, 1H), 5.85 (ddd, 3J (H,H)=17.2 Hz, 3J (H,H)=9.4 Hz, 3J
(H,H)=7.2 Hz, 1H), 6.20 (dd, 3J (H,H)=16.0 Hz, 3J (H,H)=7.6 Hz,
1H), 6.43 (d, 3J (H,H)=16.0 Hz, 1H), 6.69 (d, 3J (H,H)=8.8 Hz, 1H),
7.19–7.34 ppm (m, 7H); 13C NMR (100 MHz, CDCl3): d=35.2, 45.3, 46.0,
46.2, 46.7, 50.2, 50.3, 108.5, 114.8, 115.4, 126.0, 127.1, 128.5, 130.6, 130.9,
131.6, 137.4, 138.9, 147.4 ppm; IR (KBr): n˜ =3078, 3024, 2943, 2834, 1638,
1593, 1494, 1479, 1366, 1184, 1075, 996, 964, 913, 807, 747, 693 cmꢀ1
;
HRMS (FAB): m/z: calcd for 393.1092 (C23H24NBr, [M++H]); found:
393.1098.
4-(4-Styryl-6-vinylhexahydro-cyclopenta[c]pyrrol-2-yl)benzoic acid meth-
AHCTUNGERTGyNNUN l ester (22): To a solution of 20 (9.24 g, 23.43 mmol) in THF (250 mL)
cooled to ꢀ788C was added dropwise nBuLi (11.3 mL, 2.5m in hexane,
28.1 mmol) under argon. The reaction mixture was stirred at ꢀ788C for
1 h, and then excess CO2 gas was bubbled into the solution until white
solid was precipitated. The mixture was gradually warmed to room tem-
perature, poured into a mixture of Et2O (200 mL) and H2O (200 mL),
and filtered, and then the filter cake was washed with Et2O (2ꢂ100 mL).
The combined filtrates were acidified with 10% HCl (until pH 6). The
solid was filtered and washed with Et2O (2ꢂ50 mL) to give 21 as a white
solid (5.98 g, 71%): m.p.: 198–1998C; 1H NMR (400 MHz, DMSO): d=
1.60 (q, 2J (H,H)=12.6 Hz, 1H), 1.99 (dt, 2J (H,H)=12.6 Hz; 3J (H,H)=
6.3 Hz, 1H), 2.80–2.87 (m, 1H), 2.91–3.03 (m, 3H), 3.17–3.24 (m, 2H),
3.27–3.34 (m, 2H), 5.04 (d, 3J (H,H)=10.3 Hz, 1H), 5.08 (d, 3J (H,H)=
17.3 Hz, 1H), 5.81 (ddd, 3J (H,H)=7.2 Hz; 3J (H,H)=10.3 Hz; 3J
(H,H)=17.3 Hz, 1H), 6.27 (dd, 3J (H,H)=7.2 Hz, 15.9 Hz, 1H), 6.44 (d,
3J (H,H)=15.9 Hz, 1H), 6.58 (d, 3J (H,H)=8.7 Hz, 2H), 7.18 (t, 3J
(H,H)=6.5 Hz, 1H), 7.25–7.29 (m, 2H), 7.36 (d, 3J (H,H)=8.0 Hz, 2H),
7.72 (d, 3J (H,H)=8.7 Hz, 2H), 12.06 ppm (brs, 1H); 13C NMR
(100 MHz, DMSO): d=34.7, 44.5, 45.1, 45.6, 46.2, 49.3, 49.4, 111.7, 115.4,
119.0, 125.9, 127.0, 128.5, 130.0, 130.8, 131.2, 137.1, 139.3, 150.5,
168.1 ppm; IR (KBr): n˜ =3430, 3069, 3028, 2930, 2857, 2664, 2537, 1654,
Copolymer 7: A solution of k (57 mg, 0.05 mmol), l (60 mg, 0.05 mmol)
and [(Cy3P)2Cl2Ru=CHPh] (4 mg, 0.005 mmol, 10 mol%) in CH2Cl2
(5 mL) was stirred under argon at room temperature for 2 h. The reac-
tion was quenched with ethyl vinyl ether (1.0 mL) and the solution was
Chem. Asian J. 2010, 5, 1425 – 1438
ꢁ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemasianj.org
1435

T.-Y. Luh et al.
FULL PAPERS
1599, 1525, 1417, 1383, 1289, 1181, 1124, 963, 919, 774 cmꢀ1; HRMS
46.1, 46.4, 49.8, 50.1, 65.2, 67.4, 67.5, 68.3, 111.5, 112.1, 112.6, 118.6, 118.9,
119.1, 119.2, 119.3, 119.6, 120.1, 120.7, 125.80, 125.87, 125.91, 126.8, 127.1,
127.4, 128.33, 128.36, 128.40, 129.3, 129.7, 130.3, 130.6, 130.7, 131.1, 133.2,
133.3, 134.3, 134.9, 135.4, 137.0, 137.1, 137.7, 138.2, 150.3, 150.4, 150.5,
157.8, 157.9, 158.7, 168.4, 172.2, 172.4 ppm; IR (KBr): n˜ =3316, 3113,
3056, 3025, 2926, 2854, 1679, 1606, 1508, 1470, 1376, 1350, 1284, 1245,
(FAB): m/z: calcd for 360.1964 (C24H26NO2, [M++H]); found: 360.1962.
To a solution of 21 (3.0 g, 8.3 mmol) in CH2Cl2 (30 mL) at 08C was
added oxalyl chloride (0.9 mL, 10.5 mmol) and DMF (one drop). The
mixture was gradually warmed to room temperature and stirred for 1 h.
The solvent was removed in vacuo to give the crude acid chloride, which
was used for the next reaction without further purification. To a mixture
of dry methanol (20 mL) and dry THF (30 mL) was added acid chloride
in THF (10 mL) at 08C. The mixture was stirred at room temperature for
8 h. Saturated NaHCO3 was added and the solution was washed with
water and brine and then dried (MgSO4). The solvent was removed in
vacuo, and the residue was chromatographed on silica gel (hexane/
CH2Cl2 =2:1) to give 22 as light yellowish liquid (2.87 g, 92%): 1H NMR
(400 MHz, CDCl3): d=1.62 (q, 2J (H,H)=12.0 Hz, 1H), 1.97 (dt, 2J
(H,H)=12.0 Hz, 3J (H,H)=6 Hz; 1H), 2.80–2.87 (m, 1H), 2.92–3.02 (m,
3H), 3.26–3.35 (m, 4H), 3.84 (s, 3H), 5.05–5.11 (m, 2H), 5.81 (ddd, 3J
(H,H)=17.2 Hz; 3J (H,H)=10.4 Hz; 3J (H,H)=7.2 Hz, 1H), 6.15 (dd, 3J
(H,H)=15.6 Hz; 3J (H,H)=7.6 Hz, 1H), 6.42 (d, 3J (H,H)=15.6 Hz,
1H), 6.54 (d, 3J (H,H)=9.0 Hz, 2H), 7.16–7.22 (m, 1H), 7.26–7.32 (m,
4H), 7.87 ppm (d, 3J (H,H)=9.0 Hz, 2H); 13C NMR (100 MHz, CDCl3):
d=35.2, 45.1, 45.8, 46.2, 46.7, 49.5, 49.6, 51.4, 111.5, 115.5, 116.9, 125.8,
127.0, 128.3, 130.5, 130.6, 131.0, 137.0, 138.6, 150.7, 167.2 ppm; IR (KBr):
n˜ =3075, 3053, 3024, 2945, 2917, 2850, 1705, 1606, 1522, 1480, 1434, 1379,
1280, 1180, 1107, 970, 914 cmꢀ1; HRMS (FAB): m/z: calcd for 374.2120
(C25H28NO2, [M++H]); found: 374.2119.
1174, 1108, 966 cmꢀ1
; HRMS (MALDI): m/z: calcd for 2826.8442
(C188H211N14O10, [M++H]); found: 2826.8452.
.
Dimer 17: A mixture of 16 (110 mg, 0.039 mmol) and ZnACTHNUGTRNEUNG(OAc)2 2H2O
(180 mg, 0.80 mmol) in methanol (10 mL) and CH2Cl2 (20 mL) was
stirred at room temperature in the dark for 3 h and then washed with
NaHCO3 and brine, and dried (MgSO4). The solvent was removed in
vacuo to give
a residue, which was chromatographed on silica gel
(hexane/CH2Cl2/NEt3 =1:2:0.05) to afford 17 (102 mg, 89%): m.p.: 215–
2168C; 1H NMR (400 MHz, CDCl3): d=0.92–0.96 (m, 18H), 1.17–2.05
(m, 82H), 2.84–3.52 (m, 24H), 4.17–4.25 (m, 4H), 5.50–5.64 (m, 2H),
6.03–6.59 (m, 16H), 6.85–7.37 (m, 18H), 7.88–8.35 (m, 20H), 8.52–
8.92 ppm (m, 18H); 13C NMR (100 MHz, CDCl3): d=14.3, 22.9, 26.3,
29.46, 29.52, 29.58, 29.63, 29.8, 32.0, 44.4, 45.2, 46.3, 46.7, 49.8, 67.7, 68.2,
111.6, 112.4, 118.2, 118.6, 119.8, 120.3, 120.5, 125.8, 125.9, 127.1, 128.3,
128.4, 130.3, 130.7, 131.5, 134.3, 134.6, 135.1, 135.3, 137.0, 139.0, 149.7,
149.9, 150.0, 157.8, 158.4, 166.8, 167.3, 171.0 ppm; IR (KBr): n˜ =3037,
2955, 2918, 2850, 1733, 1605, 1524, 1508, 1467, 1244, 1174, 996, cmꢀ1
;
HRMS (MALDI): m/z: calcd for 2953.6050 (C188H207N14O1065Zn2, [M+
+H]); found: 2953.6060.
Time-resolved fluorescence experiments:
A mode-locked Ti:sapphire
Dimer 23: A solution of 22 (1.62 g, 4.33 mmol) and Grubbs II catalyst 24
(187 mg, 0.22 mmol) in CH2Cl2 (40 mL) was heated at reflux under nitro-
gen for 24 h, cooled to room temperature, and quenched with ethyl vinyl
ether (5 mL). Removal of the solvent in vacuo, followed by chromato-
graphic purification (silica gel, hexane/CH2Cl2 =1:2) afforded 23 (870 mg,
28%): m.p.: 190–1918C; 1H NMR (400 MHz, CDCl3): d=1.53–1.63 (m,
2H), 1.92–1.97 (m, 2H), 2.80–2.85 (m, 2H), 2.94–3.02 (m, 6H), 3.19–3.37
(m, 8H), 3.84 (s, 3H), 3.85 (s, 3H), 5.44–5.49 (m, 2H), 6.16 (dd, 3J
(H,H)=7.0 Hz; 3J (H,H)=14.2 Hz, 1H), 6.20 (dd, 3J (H,H)=7.2 Hz; 3J
(H,H)=14.2 Hz, 1H), 6.41 (d, 3J (H,H)=14.2 Hz, 1H), 6.42 (d, 3J
laser (wavelength: 850 nm; repetition rate: 76 MHz; pulse width:
<200 fs) was passed through an optical parametric amplifier to produce
425 nm pulse laser. The fluorescence of sample was reflected by a grating
(150 gmmꢀ1; 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 1ꢂ10ꢀ5 m concentration in CH2Cl2, and using
ultramicrocuvette with 1 mm pathlength to maintain the excitation at the
same time. The signal was collected 50 times to increase the signal to
noise ratio.
DFT calculations: DFT calculations[30] at the GGA/BLYP/DNP level im-
plemented with the DMol3 program package were used for geometric op-
timization of 25.[31] The electronic configuration of the molecular systems
was described by a double-numerical plus polarization (DNP) basis set
comparable to the Gaussian 6-31G** basis sets.[31] The local exchange-
correlation potential[32] was augmented in a self-consistent manner with
Becke exchange[33] and Lee–Yang–Parr correlation[34] gradient correc-
tions, giving a generalized gradient approximation (GGA/BLYP) for the
evaluation of energies and geometries. Convergence criteria for geometry
optimizations were, generally, the threshold values: 2ꢂ10ꢀ5 Hartree,
0.004 Hartree/ꢀ, 0.005 ꢀ, and 1ꢂ10ꢀ5 Hartree for energy, force, displace-
ment, and self-consistent field (SCF) density, respectively. In order to
obtain precise results, neither direct inversion of iterative subspace
(DIIS) to accelerate convergence of the SCF algorithm nor smearing
techniques were used.
3
3
(H,H)=14.2 Hz, 1H), 6.51 (d, J (H,H)=9.0 Hz, 2H), 6.56 (d, J (H,H)=
9.0 Hz, 2H), 7.20–7.25 (m, 2H), 7.26–7.33 (m, 8H), 7.88 (d, 3J (H,H)=
9.0 Hz, 2H), 7.90 ppm (d, 3J (H,H)=9.0 Hz, 2H); 13C NMR (100 MHz,
CDCl3): d=35.7, 35.9, 44.6, 44.8, 45.1, 45.2, 46.2, 46.5, 46.8, 46.9, 49.4,
49.55, 49.59, 51.4, 111.40, 111.43, 116.9, 117.0, 125.8, 127.0, 128.32, 128.34,
130.3, 130.4, 130.6, 131.1, 131.56, 131.62, 137.0, 150.6, 150.7, 167.1 ppm;
IR (KBr): n˜ =3053, 3025, 2945, 2917, 2851, 1702, 1605, 1522, 1479, 1434,
1380, 1280, 1180, 1107, 970 cmꢀ1; HRMS (FAB): m/z: calcd for 718.3771
(C48H50N2O4, [M++H]); found: 718.3768.
Dimer 16: To a solution of 23 (450 mg, 0.62 mmol) in THF (20 mL) and
MeOH (5 mL) at 08C was added NaOH (55 mg, 1.37 mmol). The mix-
ture was heated at reflux for 4 h and cooled to room temperature. After
most of the solvent was removed, Et2O (20 mL) and H2O (30 mL) was
added, and the aqueous layer was acidified with 10% HCl (until pH 6).
The solid was filtered to give the diacid as a white solid, which was used
for the next reaction without further purification.
To a solution of diacid (60 mg, 0.09 mmol) in CH2Cl2 (10 mL) at 08C was
added oxalyl chloride (0.2 mL) and DMF (one drop). The mixture was
gradually warmed to room temperature and stirred for 1 h. The solvent
was removed in vacuo to give crude acid chloride, which was taken up in
CH2Cl2 (10 mL) and added to a cooled (08C) solution of 11l (200 mg,
0.18 mmol), NEt3 (0.5 mL), and a trace amount of DMAP in CH2Cl2
(10 mL). The mixture was stirred at room temperature for 17 h. Saturat-
ed NaHCO3 was added and the solution was washed with water and
brine and then dried (MgSO4). The solvent was removed in vacuo, and
the residue was chromatographed on silica gel (hexane/CH2Cl2/NEt3 =
1:2:0.05) to give 16 (183 mg, 72%): m.p.: 179–1808C; 1H NMR
(400 MHz, CDCl3): d=ꢀ2.80 (s, 4H), 0.86–1.22 (m, 18H), 1.25–1.80 (m,
70H), 1.81–2.12 (m, 12H), 2.78–3.59 (m, 24H), 4.29 (m, 4H), 5.41–5.47
(m, 2H), 5.64–5.78 (m, 2H), 5.94–6.00 (m, 4H), 6.14–6.26 (m, 2H), 6.40–
6.50 (m, 2H), 6.57–6.65 (m, 4H), 6.72–6.77 (m, 2H), 7.05–7.38 (m, 18H),
7.74–8.78 (m, 40H), 9.85–9.95 ppm (m, 2H); 13C NMR (100 MHz,
CDCl3): d=14.3, 22.9, 26.3, 26.4, 29.5, 29.6, 32.0, 44.2, 45.0, 45.1, 45.9,
Acknowledgements
We thank Shanghai Institute of Organic Chemistry, the National Science
Council, Taipei, National Taiwan University, and the National Science
Foundation of China, Beijing, for support. We are grateful to the Com-
puter and Information Networking Center, National Taiwan University,
for the support of high-performance computing facilities and thank Pro-
fessor Huan-Cheng Chang of the Institute of Atomic and Molecular Sci-
ence, Academia Sinica for helpful discussion.
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1436
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ꢁ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Asian J. 2010, 5, 1425 – 1438

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