Synthesis of sequential poly(1,3-phenyleneethynylene)-based polyradicals and through-space antiferromagnetic interaction of their solid state

Article abstract of DOI:10.1016/j.polymer.2014.01.019

Some 1,3-PPE-based polyradicals with pendent phenoxy radicals whose repeating unit consisted of four 1,3-phenyleneethynylene units were synthesized via polymerization between monomers and trimeric monomers in the presence of the Pd(PPh₃)_4<

Full text of DOI:10.1016/j.polymer.2014.01.019

Polymer 55 (2014) 1097e1102
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Polymer
journal homepage: www.elsevier.com/locate/polymer
Polymer communication
Synthesis of sequential poly(1,3-phenyleneethynylene)-based
polyradicals and through-space antiferromagnetic interaction of their
solid state
,
b
,
c
,
a
a
a,b,c
Takashi Kaneko a
, Kyohei Iwamura , Ryo Nishikawa , Masahiro Teraguchi
,
*
,b,c
Toshiki Aoki a
a Graduate School of Science and Technology, Niigata University, Ikarashi 2-8050, Niigata 950-2181, Japan
b Center for Education and Research on Environmental Technology, Materials Engineering, Nanochemistry, Institute of Science and Technology, Niigata
University, Ikarashi 2-8050, Niigata 950-2181, Japan
c Center for Transdisciplinary Research, Niigata University, Ikarashi 2-8050, Niigata 950-2181, Japan
a r t i c l e i n f o
a b s t r a c t
Article history:
Some 1,3-PPE-based polyradicals with pendent phenoxy radicals whose repeating unit consisted of four
1,3-phenyleneethynylene units were synthesized via polymerization between monomers and trimeric
monomers in the presence of the Pd(PPh3)4 complex catalysts. The ESR spectra of the polyradicals in
dichloromethane showed unimodal broad signals. For the solid samples which were prepared from the
dichloromethane solution by evaporating the solvent and by drying in vacuo, the signal intensity
Received 7 November 2013
Received in revised form
11 January 2014
Accepted 16 January 2014
Available online 4 February 2014
decreased with broadening of peak-to-peak line-width (DHpp). However, the ESR spectra almost recover
to the initial intensity and shapes due to redissolving in dichloromethane. In particular, the decrease of
doubly integrating the ESR signal (IESR) was more remarkable for the polyradical bearing galvinoxyl and
phenoxyl residues than others. This behavior suggests that strong antiferromagnetic interaction partially
arose for the polyradical.
Keywords:
Conjugated polymer
Polyradical
Molecular magnet
Ó 2014 Elsevier Ltd. All rights reserved.
1. Introduction
lead to regulated close packing between monomers, and some
sequential polymers exhibited regulated higher order structure
The magnetic properties of
the most attractive research fields about the new functional poly-
mer materials [1e4]. Numerous -conjugated polymers substituted
with pendent radicals have been synthesized and characterized
[5,6]. Ferromagnetic through-bond interaction between the
pendent spins was theoretically predicted for regioregular head-to-
p
-conjugated polyradicals are one of
[28e31]. Poly(phenyleneethynylene) (PPE) is one of the most
possible backbone structure for magnetic -conjugated poly-
p
p
radicals and various PPE-based polyradicals have been investigated
[15,16,32e39]. PPE would be effective backbone structure for
alignment of polymer chain because the linear ethynylene nature
restricts flexibility of the conformation. Actually, some poly(1,3-
phenyleneethynylene) (1,3-PPE) derivatives formed helical struc-
ture [40e42] and extended-chain structure [42]. In this study, we
synthesized some 1,3-PPE-based polyradicals (1be3b) with
pendent phenoxy radicals whose repeating unit consisted of four
1,3-phenyleneethynylene units, and discussed their magnetic
interaction using ESR.
tail
radicals by using simple polyene models and other
polymers [7e9], and some of them actually exhibited the expected
ferromagnetic behavior through their -conjugated backbone [10e
p
-conjugated macromolecules possessing conjugated pendent
p-conjugated
p
27]. However, the through-space magnetic interaction between the
polyradical chains has not been investigated well. Most of poly-
radicals consisted of one or two monomer species, and variety of
close packing between monomers was limited. Actually, their
magnetic properties between polyradical chains only exhibited
weak antiferromagnetic interaction. Sequential polymers have
repeating unit consisting of some kind of monomers, which would
2. Experimental section
2.1. Materials
(3,5-Diiodophenyl)hydrogalvinoxyl (4) was synthesized ac-
cording to the literature procedures [39]. Tetrakis(-
triphenylphosphine)palladium (0) (Pd(PPh3)4) (Aldrich Co.) was
* Corresponding author. Tel./fax: þ81 25 262 6909.
E-mail address: kanetaka@gs.niigata-u.ac.jp (T. Kaneko).
0032-3861/$ e see front matter Ó 2014 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.polymer.2014.01.019

1098
T. Kaneko et al. / Polymer 55 (2014) 1097e1102
used without further purification. Other conventional reagents
were used as-received or purified by conventional methods.
2H, C^CH), 2.38 (s, 3H, COCH3), 1.42 (s, 18H, C(CH3)3). 13C NMR
(CDCl3; ppm): 171.55, 143.03, 142.22, 136.52, 135.19, 133.16,
d
132.03, 131.93, 130.40, 128.49, 125.34, 123.67, 123.32, 122.55, 89.23,
88.99, 83.11, 77.88, 35.63, 31.51, 22.69. IR (KBr pellet; cmꢀ1): 3295
2.2. Synthesis of monomers and trimeric monomers
(nChCeH), 2968 (nCeH, t-Bu), 1761 (nC¼O).
The monomers and trimeric monomers were synthesized as
shown in Schemes 1 and 2 based on the previously described
procedures [19,39,43,44].
2.2.2. Trimeric monomer 6
The crude product was purified by silica gel column separation
with ethyl acetate/hexane (1/5 v/v) as an eluant to give the trimeric
2.2.1. Trimeric monomer 5
The crude product was purified by silica gel column separation
with chloroform/hexane (3/2 v/v) as an eluant to give the trimeric
monomer 6. 1H NMR (CDCl3, 400 MHz; ppm):
d
7.74 (dd, 2H, J ¼ 1.4,
1.3 Hz, ArH), 7.65 (m, 3H, ArH), 7.54 (ddd, 2H, J ¼ 7.8, 1.4, 1.4 Hz,
ArH), 7.47 (ddd, 2H, J ¼ 7.8, 1.4, 1.4 Hz, ArH), 7.46 (s, 2H, PhH), 7.34
(dd, 2H, J ¼ 7.8, 7.8 Hz, ArH), 3.74 (s, 3H, OCH3), 3.11 (s, 2H, C^CH),
monomer 5. 1H NMR (CDCl3, 400 MHz; ppm):
d
7.70 (dd, 2H, J ¼ 1.4,
1.3 Hz, ArH), 7.67 (t, 1H, J ¼ 1.4 Hz, ArH), 7.66 (d, 2H, J ¼ 1.4 Hz, ArH),
7.54 (ddd, 2H, J ¼ 7.8, 1.4, 1.4 Hz, ArH), 7.52 (s, 2H, PhH), 7.47 (ddd,
2H, J ¼ 7.8, 1.4, 1.4 Hz, ArH), 7.33 (dd, 2H, J ¼ 7.8, 7.8 Hz, ArH), 3.11 (s,
1.50 (s, 18H, C(CH3)3). 13C NMR (CDCl3; ppm):
d 159.74, 144.20,
142.47, 135.18, 135.17, 133.67, 132.01, 131.92, 130.39, 130.22, 128.49,
I
I
I
I
1) n-BuLi
ether
KOHaq
DMSO
O
2)
I
AcO
OAc
O
OH
ether
Yield 34%
4
Si
Si
BrMg
OCH3
Ni(dppp)Cl2
THF
KOH
CH3OH
Br
OCH3
Yield 45%
BrMg
OSi(CH3)3
(CH3CO)2O,
HClO4
Ni(dppp)Cl2
THF
KOH
CH3OH
O
O
Yield 24%
I
R
R
HO
PdCl2(PPh3)2,
CuI, PPh3
Et3N
OZ
OZ
KOHaq
R = C(CH3)2OH
5: R = H
Z = COCH3
Yield 80%
Z = COCH3
Yield 56%
Toluene
NaH
R = C(CH3)2OH
Z = CH3
Yield 46%
6: R = H
Z = CH3
Yield 55%
Toluene
Scheme 1. Synthesis of monomer 4, trimeric monomers 5 and 6.

T. Kaneko et al. / Polymer 55 (2014) 1097e1102
1099
O
O
Br
B
bis(pinacolato)diboron
PdCl2(dppf)2, KOAc
DMSO
O
OH
O
OH
Yield 78%
Si
Si
Pd(PPh3)4,
K3PO4
KOH
O
OH
dioxane
CH3OH
Br
Yield 66%
7
I
I
I
I
PdCl2(PPh3)2,
CuI, PPh3
Et3N
O
O
O
Yield 32%
O
8
Scheme 2. Synthesis of monomer 7 and trimeric monomer 8.
125.44,123.57,122.51, 89.33, 88.86, 82.69, 77.90, 64.35, 35.96, 32.13.
2.3. Synthesis of polymers
IR (KBr pellet; cmꢀ1): 3295 (nChCeH), 2963 (nCeH, t-Bu).
Polymerization and elimination of the protecting acetyl group
was carried out according to the previously described procedure
[19,39]. Analytical data for polymer 1a: 1H NMR (CDCl3, 270 MHz;
2.2.3. Monomer 7
The crude product was purified by silica gel column separation
with chloroform/hexane (1/1 v/v) as an eluant to give the monomer
ppm)
d
7.77 (t, 1H, J ¼ 1.5 Hz, ArH), 7.73 (br, 2H, ArH), 7.64 (d, 2H,
7. 1H NMR (CDCl3, 400 MHz; ppm):
d
7.79 (d, 2H, J ¼ 1.4 Hz, ArH),
J ¼ 1.5 Hz, ArH), 7.61 (t, 1H, J ¼ 1.5 Hz, ArH), 7.53 (ddd, 2H, J ¼ 7.8,
1.4, 1.4 Hz, ArH), 7.50 (ddd, 2H, J ¼ 7.8, 1.4, 1.4 Hz, ArH), 7.42 (d,
2H, J ¼ 1.5 Hz, ArH), 7.39 (s, 2H, ArH), 7.36 (dd, 2H, J ¼ 7.8, 7.8 Hz,
ArH), 7.25 (br, 1H, ArH (quinoid)), 7.06 (br, 1H, ArH (quinoid)),
7.05 (s, 2H, ArH), 5.54 (s, 1H, OH), 5.31 (s, 1H, OH), 1.50 (s, 18H,
C(CH3)3), 1.43 (s, 18H, C(CH3)3), 1.29 (s, 9H, C(CH3)3), 1.26 (s, 9H,
C(CH3)3). IR (KBr, cmꢀ1): 3629 (nOeH), 2956 (nCeH, t-Bu), 1594
7.63 (t, 1H, J ¼ 1.4 Hz, ArH), 7.62 (d, 2H, J ¼ 8.4 Hz, ArH), 7.36 (d, 2H,
J ¼ 8.4 Hz, ArH), 7.25 (d, 1H, J ¼ 2.6 Hz, ArH (quinoid)), 7.16 (d, 1H,
J ¼ 2.6 Hz, ArH (quinoid)), 7.04(s, 2H, ArH), 5.53 (s, 1H, OH), 3.14 (s,
2H, C^CH), 1.42 (s, 18H, C(CH3)3), 1.29 (s, 9H, C(CH3)3), 1.26 (s, 9H,
C(CH3)3). 13C NMR (CDCl3; ppm):
d 186.08, 157.31, 155.56, 146.77,
146.69,140.94,140.76,139.64,135.26,134.54,133.08,132.68,132.36,
131.66, 131.06, 130.11, 129.03, 126.25, 123.09, 82.44, 78.24, 35.30,
35.24, 34.38, 30.27, 29.66, 29.53. IR (KBr pellet; cmꢀ1): 3591 (nOeH),
3292 (nChCeH), 2960 (nCeH, t-Bu), 1590 (nquinoid).
(
nquinoid).
2.4. Oxidation
The polyradicals were prepared by chemical oxidation of the
corresponding hydroxyl precursors with PbO2 or K3Fe(CN)6 under
nitrogen in a glovebox as follows.
2.2.4. Trimeric monomer 8
The crude product was purified by silica gel column separation
with ethyl acetate/hexane (1/5 v/v) as an eluant to give the trimeric
monomer 8. 1H NMR (CDCl3, 400 MHz; ppm):
d
7.93 (dd, 2H, J ¼ 1.6,
1.6 Hz, ArH), 7.69 (ddd, 2H, J ¼ 7.9, 1.6, 1.0 Hz, ArH), 7.65 (s, 3H, ArH),
7.52 (ddd, 2H, J ¼ 7.9, 1.6, 1.0 Hz, ArH), 7.52 (s, 2H, PhH), 7.10 (dd, 2H,
2.4.1. Oxidation using PbO2
A degassed dichloromethane solution of the hydroxyl precursor
(0.5 mM per repeating unit) was treated with 100 equiv of recently
prepared PbO2 and was vigorously stirred for 1 h. After filtration the
solution was used for ESR measurement. The solid sample was
prepared by evaporating the solvent and by drying in vacuo, and
was used for spectroscopic measurement.
J ¼ 7.9, 7.9 Hz, ArH), 2.38 (s, 3H, COCH3), 1.42 (s, 18H, C(CH3)3). 13
C
NMR (CDCl3; ppm):
d 171.55, 148.61, 143.54, 142.74, 140.71, 137.99,
136.92, 133.65, 131.29, 130.93, 130.38, 125.81, 125.48, 124.03, 94.20,
90.28, 88.81, 36.12, 31.99, 23.18. IR (KBr pellet; cmꢀ1): 2962 (nCeH, t-
Bu), 1748 (nC¼O).

1100
T. Kaneko et al. / Polymer 55 (2014) 1097e1102
I
H
n
O
OX
OZ
K3Fe(CN)6
Pd(PPh3)4,
CuI
KOHaq
KOHaq
1a: X = H
1b: X =
1c: X = H
2a: X = H
4 + 5
4 + 6
Z = H
CH2Cl2
Z =
Et3N
Z = COCH3 THF/
DMSO
PbO2
CH2Cl2
Pd(PPh3)4,
CuI
2b: X =
Z = CH3
Et3N
Z = CH3
H
I
n
OZ
O
OX
K3Fe(CN)6
KOHaq
Pd(PPh3)4,
CuI
KOHaq
3a: X = H
3b: X =
3c: X = H
7 + 8
Z = H
CH2Cl2
Z =
Z = COCH3 THF/
DMSO
Et3N
Scheme 3. Synthesis of polymers (1a, 2a and 3a) and polyradicals (1b, 2b and 3b).
2.4.2. Oxidation using K3Fe(CN)6
2.5. ESR spectroscopic measurement
A degassed dichloromethane solution of hydroxyl precursor
(0.5 mM per repeating unit) was treated with 10 equiv of 10% tetra-
butylammonium hydroxide methanol and then 50 equiv of aqueous
K3Fe(CN)6. After vigorously stirring for 0.5 h, the organic layer was
washed with water thoroughly and dried over anhydrous sodium
sulfate. After filtration the solution was used for ESR measurement.
The solid sample was prepared by evaporating the solvent and by
drying in vacuo, and was used for spectroscopic measurement.
Solutions for ESR experiments were prepared under nitrogen in
a glovebox and placed in quartz tubes sealed with septa and Par-
afilm. ESR spectra were taken on a JEOL JES-2XG ESR spectrometer
with 100 kHz field modulation in the X-band frequency region.
Signal positions were calibrated against an external standard of
Mn2þ/MgO (g ¼ 1.981). The spin concentrations of each sample
were determined by careful double integration of the ESR signal
Table 1
Polymerization of monomers (4 and 7) and trimeric monomers (5, 6 and 8) using Pd(PPh3)4 catalyst.a
Yieldb (%)
Mnc (ꢁ104)
Mw/Mn
DPn
c
d
No.
Monomer
Polymer
M1
M2
1
2
3
4
4
7
5
6
8
1c
2a
3c
81
84
82
3.7
4.6
1.1
2.2
2.9
2.2
36
44
10
a
[M1]0 ¼ [M2]0 ¼ 0.25 M, [M1]0/[Pd(PPh3)4]0 ¼ 10, [CuI]0/[Pd(PPh3)4]0 ¼ 4, triethylamine, r.t., 12 h.
Methanol insoluble part. Yield is based on the repeating unit.
Determined by GPC calibrated with polystyrene standard (THF eluant).
Degree of polymerization based on the repeating unit, and estimated from Mn.
b
c
d

T. Kaneko et al. / Polymer 55 (2014) 1097e1102
1101
(IESR
)
calibrated with that of the 2,2,6,6-tetramethyl-1-
(a)
(b)
(c)
(d)
piperidinyloxy (TEMPO) standard solution.
2.6. Other measurements
g = 2.004
8
IR spectra were obtained using a Jasco FTIR 4200 spectrometer.
NMR (1H, 13C) spectra were measured using a Varian FT-NMR
400 MR (400 MHz) spectrometer. Average molecular weights (Mn
and Mw) were evaluated by GPC calibrated by polystyrene standard
at 25 ꢂC on THF eluant using Jasco Liquid Chromatograph in-
struments with PU-2080, DG-2080-53, CO-2060, UV2070, CD-
2095, and polystyrene gel columns (Shodex KF-807L).
0.5 mT
0.5 mT
0.5 mT
0.5 mT
3. Results and discussion
The monomers and trimeric monomers were polymerized in the
presence of the Pd(PPh3)4 complex catalysts, and yellow solid poly-
mers 1c, 2a and 3c were obtained by precipitation from the poly-
merization mixtures into methanol as shown in Scheme 3. The
obtained polymer 1c and 3c was converted to the corresponding
hydroxyl polymer 1a and 3a, respectively, after complete elimination
of the protecting acetyl group by treatment with alkaline solution
followed by precipitation into methanol. The polymerization data for
these resultant polymers are summarized in Table 1. The polymer
was soluble in chloroform, dichloromethane, tetrahydrofuran, and
aromatic solvents, but insoluble in alcohols and aliphatic hydrocar-
bons. It was confirmed by IR and1H NMR spectra of the polymersthat
polymerization proceeded by cross-coupling reaction between a
terminal acetylene and iodo group of trimeric monomers or mono-
mers, i.e., the reduction of the peaks assignable to the ethynyl group
of diethynyl monomer (or trimeric monomer) at 3300 cmꢀ1 (hCeH)
g = 2.004
8
in IR and
peak assignable to the aromatic proton of diiodo monomer (or
d
3.1 ppm (s, 2H, CeH) in 1H NMR, and the reduction of the
g = 2.004
8
trimeric monomer) at
d
8.11 ppm (t, 1H, J ¼ 1.0, ArH) for 4 and 7.70
(dd, 2H, J ¼ 1.4,1.3 Hz, ArH) for 5 in 1H NMR. The alternate structure of
monomer and trimeric monomer in the polymer was confirmed by
1H NMR.
The polyradicals 1b, 2b and 3b were obtained by oxidizing the
polymers 1a, 2a and 3a, respectively, by treatment of the polymer
solution in a degassed dichloromethane with fresh PbO2 or
aqueous alkaline K3Fe(CN)6 solution. The formation of the poly-
radical was supported by the appearance of the ESR signal at
g ¼ 2.004
8
accompanied by the decrease of the peak at 3630 cmꢀ1
attributed to the nOꢀH of the sterically hindered phenolic hydroxyl
group in IR spectrum. The spin concentrations of 1b, 2b and 3b in
dichloromethane were calculated as 1.7, 0.68 and 1.8 spin/
repeating unit, respectively. The ESR spectra of 1b, 2b and 3b in
dichloromethane showed unimodal broad signals slightly deviated
from Lorentzian shape, where disappearance of hyperfine struc-
ture was attributable to the spatial proximity of radicals due to the
intramolecular aggregation of radical units along the main chain.
For the solid samples which were prepared from the dichloro-
methane solution by evaporating the solvent and by drying in
vacuo, the signal intensity decreased with broadening of peak-to-
g = 2.004
8
Fig. 1. ESR spectra of the polyradical (a) 1b, (b) 20wt% 1b diluted with polystyrene, (c)
2b and (d) 3b. Black line: As-prepared samples in dichloromethane. Red line: Solid
samples which were prepared from the dichloromethane solution by evaporating the
solvent and by drying in vacuo. Blue line: Redissolved samples in dichloromethane.
(For interpretation of the references to color in this figure legend, the reader is referred
to the web version of this article.)
peak line-width (DHpp), where the line shapes almost coincided
with Lorentzian shape. However, the ESR spectra almost recover to
the initial intensity and shapes due to redissolving in dichloro-
methane as shown in Fig. 1aed. The IESR of the solid states also
decreased in comparison with that of the dichloromethane solu-
tion, and the IESR also recover to the initial value due to redis-
solving in dichloromethane as shown in Fig. 2. Therefore,
irreversible quenching of radical species was not almost consid-
erable for the solid states, while the decrease of IESR might include
measurement error due to the line shape difference. In particular,
the decrease of IESR was more remarkable for 1b than others. This
behavior suggests that strong antiferromagnetic interaction
partially arose for 1b. This unusual decrease of IESR for 1b was
suppressed by dilution with diamagnetic polystyrene as shown in
Fig. 2. This observation indicates that the decrease of the IESR, prior

1102
T. Kaneko et al. / Polymer 55 (2014) 1097e1102
synthesizing sequential 1,3-PPE bearing phenoxyl and galvinoxyl.
1
0.8
0.6
0.4
0.2
0
The magnetic interaction of 2b only arose between galvinoxyls
because phenoxyl residues were protected by methyl group. On the
other hand, the magnetic interaction of 1b and 3b included the
interaction between galvinoxyl and phenoxyl. The close packing
between galvinoxyl and phenoxyl probably preferred to show strong
antiferromagnetic interaction due to difference of the side group
structures. This feature indicates that sequence-regulated poly-
radicals will lead to control of the interchain magnetic interaction by
inducing helical structure and alignment of polyradical chain.
Acknowledgments
Solution
Solid
Redissolved-
solution
This work was partially supported by a Grant-in-Aid for Scien-
tific Research (B) (No. 24310081) from JSPS, and by a Grant for the
Promotion of Niigata University Research Projects.
Fig. 2. Normalized doubly integrating the ESR signal (IESR) by initial value (IESR0) of 1b
(filled circle), 20wt% 1b diluted with polystyrene (open circle), 2b (filled triangle) and
3b (filled square). Solution: As-prepared samples in dichloromethane. Solid: Solid
samples which were prepared from the dichloromethane solution by evaporating the
solvent and by drying in vacuo. Redissolved-solution: Redissolved samples in
dichloromethane.
References
[1] Lahti PM, editor. Magnetic properties of organic materials. New York: Marcel
Dekker, Inc.; 1999.
[2] Itoh K, Kinoshita M, editors. Molecular magnetism: new magnetic materials.
Tokyo and Amsterdam: Kodansha and Gordon and Breach; 2000.
[3] Rajca A. Chem Rev 1994;94:871.
[4] Rajca A. Chem Eur J 2002;8:4834.
[5] Nishide H. Adv Mater 1995;7:937.
[6] Aoki T, Kaneko T, Teraguchi M. Polymer 2006;47:4867.
[7] Ovchinnikov AA. Theor Chim Acta 1978;47:297.
O
O
[8] Yamaguchi K, Toyoda Y, Fueno T. Synth Met 1987;19:81.
[9] Lahti PM, Ichimura AS. J Org Chem 1991;56:3030.
[10] Kaneko T, Toriu S, Kuzumaki Y, Nishide H, Tsuchida E. Chem Lett 1994;13:2135.
[11] Nishide H, Kaneko T, Toriu S, Kuzumaki Y, Tsuchida E. Bull Chem Soc Jpn
1996;69:499.
[12] Nishide H, Kaneko T, Nii T, Katoh K, Tsuchida E, Yamaguchi K. J Am Chem Soc
1995;117:548.
[13] Nishide H, Kaneko T, Nii T, Katoh K, Tsuchida E, Lahti PM. J Am Chem Soc
1996;118:9695.
I
I
[14] TakahashiM, NakazawaT, Tsuchida E, NishideH. Macromolecules 1999;32:6383.
[15] Nishide H, Takahashi M, Takashima J, Tsuchida E. Polym J 1999;31:1171.
[16] Nishide H, Maeda T, Oyaizu K, Tsuchida E. J Org Chem 1999;64:7129.
[17] Miyasaka M, Yamazaki T, Tsuchida E, Nishide H. Macromolecules 2000;33:
8211.
n
[18] Nishide H, Ozawa T, Miyasaka M, Tsuchida E. J Am Chem Soc 2001;123:5942.
[19] Kaneko T, Matsubara T, Aoki T. Chem Mater 2002;14:3898.
[20] Kaneko T, Makino T, Miyaji H, Teraguchi M, Aoki T, Miyasaka M, et al. J Am
Chem Soc 2003;125:3554.
O
O
O
O
[21] Kaneko T, Makino T, Miyaji H, Onuma A, Teraguchi M, Aoki T. Polyhedron
2003;22:1845.
9
[22] Murata H, Takahashi M, Namba K, Takahashi N, Nishide H. J Org Chem
2004;69:631.
Chart 1. Chemical structure of a 1,3-PPE-based polyradical bearing galvinoxyl side
[23] Murata H, Yonekuta Y, Nishide H. Org Lett 2004;6:4889.
[24] Itoh T, Jinbo Y, Hirai K, Tomioka H. J Am Chem Soc 2005;127:1650.
[25] Kaneko T, Onuma A, Ito H, Teraguchi M, Aoki T. Polyhedron 2005;24:2544.
[26] Fukuzaki E, Nishide H. J Am Chem Soc 2006;128:996.
[27] Oka H, Kiyohara Y, Kouno H, Tanaka H. Polyhedron 2007;26:2059.
groups.
to the dilution of 1b with polystyrene, was probably attributed to
interchain antiferromagnetic interactions.
[28] Papapostolou D, Bromley EHC, Bano C, Woolfson DN.
2008;130:5124.
J Am Chem Soc
[29] David R, Günther R, Baumann L, Lühmann T, Seebach D, Hofmann H, et al.
J Am Chem Soc 2008;130:15311.
4. Conclusions
[30] Ryadnov MG, Bella A, Timson S, Woolfson DN. J Am Chem Soc 2009;131:13240.
[31] Roy L, Case MA. J Am Chem Soc 2010;132:8894.
A poly(1,3-phenyleneethynylene) (1,3-PPE) structure is a cross-
conjugated system, and the corresponding polyradicals bearing
pendent spins at 5-position have disjoint non-bonding molecular
orbital (NBMO) based on the theoretical prediction by Borden and
Davidson [45]. We have already reported a moderately strong
through-space magnetic interaction, which was induced by forming
the folded helical conformation of 1,3-PPE-based polyradicals
bearing galvinoxyl side groups (9) (see Chart 1) [39]. On the other
hand, the static magnetic susceptibility of 9, which probably had the
random conformation in benzene and was prepared by evaporating
solvent from the benzene solution of 9 followed by drying in vacuum,
exhibited the weak antiferromagnetic behavior. We found the rela-
tively strong antiferromagnetic interaction of 1b from IESR by
[32] MiuraY, Ushitani Y, Inui K, Teki Y, Takui T, Itoh K. Macromolecules 1993;26:3698.
[33] Miura Y, Issiki T, Ushitani Y, Teki Y, Itoh K. J Mater Chem 1996;6:1745.
[34] Shultz DA, Hollomon MG. Chem Mater 2000;12:580.
[35] van Meurs PJ, Janssen RAJ. J Org Chem 2000;65:5712.
[36] Akita T, Koga N. Polyhedron 2001;20:1475.
[37] Wautelet P, Turek P, Moigne J Le. Synthesis; 2002:1286.
[38] Kaneko T, Yoshimoto S, Hadano S, Teraguchi M, Aoki T. Polyhedron
1825;2007:26.
[39] Kaneko T, Abe H, Teraguchi M, Aoki T. Macromolecules 2013;46:2583.
[40] Nelson JC, Saven JG, Moore JS, Wolynes PG. Science 1997;277:1793.
[41] Hill DJ, Mio MJ, Prince RB, Hughes TS, Moore JS. Chem Rev 2001;101:3893.
[42] Prest P-J, Prince RB, Moore JS. J Am Chem Soc 1999;121:5933.
[43] Kaneko T, Horie T, Matsumoto S, Teraguchi M, Aoki T. Macromol Chem Phys
2009;210:22.
[44] Shi Z, Murayama Y, Kaneko T, Teraguchi M, Aoki T. Chem Lett 2013;42:1087.
[45] Borden WT, Davidson ER. J Am Chem Soc 1977;99:4587.