Solid state polymerization of diacetylenes with amide groups

Article abstract of DOI:10.1080/15421400600786306

Two diacetylene derivatives (1, 2) carrying amide groups were prepared in order to control their packing arrangements by intermolecular hydrogen bonds. 1, 6-Bis(4- acetamidomethylphenoxy)-2,4-hexadiyne 1 is a symmetric diamide, which showed no changes by

Full text of DOI:10.1080/15421400600786306

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Solid State Polymerization
of Diacetylenes with Amide
Groups
Tsunehisa Okuno a , Kentaro Yamane a & Daniel J.
Sandman b
a Department of Material Science and Chemistry ,
Wakayama University , Wakayama, Japan
b Department of Chemistry, Center for Advanced
Materials , University of Massachusetts , Lowell,
Massachusetts
Published online: 21 Dec 2006.
To cite this article: Tsunehisa Okuno , Kentaro Yamane & Daniel J. Sandman (2006)
Solid State Polymerization of Diacetylenes with Amide Groups, Molecular Crystals and
Liquid Crystals, 456:1, 45-53, DOI: 10.1080/15421400600786306
To link to this article: http://dx.doi.org/10.1080/15421400600786306
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Mol. Cryst. Liq. Cryst., Vol. 456, pp. 45–53, 2006
Copyright # Taylor & Francis Group, LLC
ISSN: 1542-1406 print=1563-5287 online
DOI: 10.1080/15421400600786306
Solid State Polymerization of Diacetylenes with
Amide Groups
Tsunehisa Okuno
Kentaro Yamane
Department of Material Science and Chemistry, Wakayama University,
Wakayama, Japan
Daniel J. Sandman
Department of Chemistry, Center for Advanced Materials,
University of Massachusetts, Lowell, Massachusetts
Two diacetylene derivatives (1, 2) carrying amide groups were prepared in order to
control their packing arrangements by intermolecular hydrogen bonds. 1, 6-Bis(4-
acetamidomethylphenoxy)-2,4-hexadiyne 1 is a symmetric diamide, which showed
no changes by annealing. p-N-acetyl(6-hydroxy-2,4-hexadiynenyloxy)benzylamine
2 with amide and alcohol groups showed photo and thermal reactivity. Compound
˚
2 crystallized in the monoclinic P21=c space group with a ¼ 17.9162(3) A,
ꢀ
˚
˚
b ¼ 4.8646(2) A , c ¼ 16.106(3) A, b ¼ 105.19(1) . The molecules stacked one-
dimensionally along the b axis and the intermolecular hydrogen bonds of the
amide groups ran along the stacking axis. The hydroxyl group in the other end
of the structure of 2 was also involved in polymeric hydrogen bonds, which also
appear to play an important role in the molecular arrangement.
Keywords: amide; crystal structure; hydrogen bond; polydiacetylene; solid-state
polymerization
INTRODUCTION
Polydiacetylenes (PDAs), which have one-dimensional p-conjugated
systems, are attractive from the viewpoint of their physical properties
such as non-linear optics [1], conductivity [2] and magnetism [3]. It is
This work was partly supported by grants from the Ministry of Education, Culture,
Sports and Technology.
Address correspondence to Dr. Tsunehisa Okuno, Department of Material Science
and Chemistry, Wakayama University, 930 Sakaedani, Wakayama 640–8510, Japan.
E-mail: okuno@sys.wakayama-u.ac.jp
45

46
T. Okuno et al.
well-known that reactivity of solid-state polymerization of diacety-
lenes heavily depends on their crystal packings [4,5]. A schematic
drawing of solid-state polymerization and its conditions of the molecu-
lar arrangement are shown in Figure 1. According to Baughman’s cri-
terion [5], polymerization can proceed when the stacking interval is
˚
˚
from 4.8 A to 5.6 A, and the inclination angle between the molecular
axis and the stacking one is from 40ꢀ to 50ꢀ. It is necessary to control
the molecular arrangements in order to develop novel polydiacety-
lenes. Intermolecular hydrogen bonds are thought to be the most
convenient interaction to control molecular arrangement.
There are many crystal engineering works for PDA systems. TCDU
molecules [6] form intermolecular hydrogen bonds in urethane groups.
The bonds proceed in the same direction to the stacking axis. m-AAPB
molecules [2] also have the same hydrogen bond with TCDU. It is
important in controlling molecular arrangement of diacetylenes that
the hydrogen bonds run along the stacking axis.
Generally, intermolecular hydrogen bonds in an acetanilide moiety
have a tendency to extend within the same plane to the phenyl rings
because of p-conjugation. These bonds have low possibility to make
appropriate one-dimensional stacks. However, the hydrogen bonds
FIGURE 1 A schematic drawing of solid-state polymerization of diacetylenes.

Polymerization of Diacetylenes with Amide Groups
47
in an acetylbenzylamine moiety, where a CH2 group is inserted
between the phenyl ring and the nitrogen atom, have a tendency to
form the perpendicular bonds to the phenyl rings [7]. The bonds are
very convenient to construct a one-dimensional arrangement. We wish
to report here preparation, crystal structure and polymerization reac-
tivity of diacetylene molecules (1, 2) with amide groups.
RESULTS AND DISCUSSION
Preparation of compound 1 and 2 was summarized in Scheme 1. Reac-
tion between 4-cyanophenol and 3-bromo-1-propyne gave 4-(2-propyny-
loxy)benzonitrile [8]. The cyano group was transformed to an
aminomethyl group by a reduction with lithium aluminum hydride.
The amino group was allowed to react with acetic anhydride to give
an amide group. Finally, this compound was coupled with itself to afford
compound 1, and coupled with 2-propyne-1-ol to give compound 2 [9].
Crystals with sufficient quality were obtained for compound 2.
Unfortunately, compound 1 did not give samples that were suitable

48
T. Okuno et al.
SCHEME 1 Syntheses of diacetylene derivatives 1 and 2: (i) 3-Bromo-1-pro-
pyne, K2CO3=NMP (ii) LiAlH4=THF (iii) (CH3CO)2O (iv) O2, CuCl, TME-
DA=Acetone (v) 2-Propyne-1-ol, O2, CuCl, TMEDA=Acetone.
for single crystal X-ray diffraction. Crystal data for compound 2 are
summarized in Table 1 and Figure 2 shows its crystal structure. The
aromatic, diyne and hydroxymethyl portions of the molecule fall in
the same plane, which forms a dihedral angle of 79.4ꢀ [Fig. 2(a)] with
the plane of the amide group.
Figure 2(b) shows the molecular stacking of compound 2. The
˚
molecules stack along the b axis with a spacing of 4.85 A. The incli-
nation angle between the molecular axis and the b axis is ca. 48ꢀ.
TABLE 1 Crystal Data of Compounds 2
2
formula
C15H15O3N1
257.29
monoclinic
P21=c
17.916(2)
4.8646(2)
16.106(3)
90
105.19(1)
90
molar mass [g mol ꢁ 1
crystal system
space group
]
˚
a [A]
˚
b [A]
˚
c [A]
a[ꢀ]
b[ꢀ]
c[ꢀ]
Z
4
3
˚
V [A ]
qcalcd [Mgm ꢁ 3
1349.6(7)
1.266
]
no. of reflections
2780
no. of unique data
2682
R1(I > 3r(I), all data)
wR2(I > 3r(I), all data)
Goof(I > 3r(I), all data)
0.108, 0.253
0.142, 0.210
1.37, 1.25

Polymerization of Diacetylenes with Amide Groups
49
FIGURE 2 Crystal structure of the compound 2: (a) Molecular structure (b)
Molecular stacking along the b axis.
The interatomic distance between adjacent alkynes given by carbon
˚
C(2) of one molecule and C(5) of the other is 3.68 A. This condition
satisfies Baughman’s criterion [5].
It is thought that there are two important interactions. One is the
polymeric hydrogen bond formed by the hydroxyl groups, where the
˚
interatomic distance is 2.73 A. The other is the one-dimensional hydro-
˚
gen bond made by the amide groups, where the distance is 2.97 A.
These two interactions are thought to play a crucial role in fixing
the molecular arrangements.
Compound 2 showed color changes by thermal annealing. The com-
pound gradually turned blue by heating at 90ꢀC. Finally it turned

50
T. Okuno et al.
black and became insoluble. The surface of the compound also turned
blue by UV irradiation. The electronic spectrum of the polymer showed
a broad band around 620 nm, which was assigned to an excitonic tran-
sition [10]. On the other hand, compound 1 did not show polymeriza-
tion reactivity by thermal annealing. The compound was also
expected to form a one-dimensional stack with intermolecular hydro-
gen bonds in the amide groups. However, some significant structural
differences must exist which may the stability of compound 1.
In summary, we prepared two novel diacetylene derivatives (1, 2),
which carried amide groups in their side chains. Unfortunately, we
could not analyze the crystal structure of compound 1 which did not
show any thermal reactivity. However, we succeeded in crystal struc-
tural analysis of compound 2, which showed solid-state polymerization
reactivity. The intermolecular hydrogen bonds in the hydroxyl and
amide groups were found to play a crucial role in forming the crystal
packing. Especially, the intermolecular hydrogen bonds of amide
groups which ran parallel to the stacking direction formed an ideal
stacking for solid state polymerization of diacetylenes.
EXPERIMENTAL PART
General Procedure
Infrared spectra were recorded on a JASCO FT=IR-420 spectrometer
with samples in compressed KBr discs. UV=Visible spectra were mea-
1
sured on a HITACHI U-2010 spectrometer. H and 13C NMR spectra
were measured on a JEOL JNM-AL300. Tetramethylsilane was used
for an internal standard. Melting points were measured on a Yanako
Model MP and temperature was not corrected.
X-ray diffraction data were collected on RIGAKU AFC-5R auto-
matic four-circle diffractmeter using graphite-monochromatic Mo Ka
radiation. The crystal structure was solved by using Texsan. Aniso-
tropic thermal parameters were introduced for all non-H atoms.
Hydrogen atoms were not refined.
Synthesis
4-(2-Propynyloxy)benzonitrile [8]
To a solution of 4-cyanophenol (6.51 g, 54.7 mmol) and 3-bromo-1-
propyne (7.80 g, 65.6 mmol) in 100 ml of N-methyl-2-pyrrodinone was
added K2CO3(22.66 g, 164.0 mmol). The suspension was stirred for 3
hours at 85ꢀC. It was poured into 500 ml of water to precipitate white
powder. The precipitate was filtered off and recrystallized from

Polymerization of Diacetylenes with Amide Groups
51
1
hexane to give 7.52 g (yield 88%) of 4-(2-propynyloxy)benzonitrile. H
NMR (300 MHz, CDCl3): d2.56 (s, 1H), 4.75 (s, 2H), 7.03 (d, J ¼ 9.0 Hz,
Hz, 2H), 7.61 (d, J ¼ 9.0 Hz, 2H), IR (cmꢁ1): 2128 (nCꢂC), 2222 (nCꢂN).
4-(2-Propynyloxy)benzylamine
A solution of 4-(2-propynyloxy)benzonitrile in THF (300ml) was
added dropwise to a suspension of LiAlH4 (3.77 g, 99.3 mmol) in
100 ml of THF. The suspension was stirred for 24 hours at room
temperature. It was poured into ice water and extracted with ether.
The organic layer was washed with brine and dried over Na2SO4. After
filtration, the filtrate was concentrated under a reduced pressure and
dried in vacuo. The residue was purified by column chromatography
(SiO2, ethanol) to afford 8.71 g (66%) of colorless oil. 1H NMR
(300 MHz, CDCl3): d1.72 (s, 2 H), 2.52 (t, J ¼ 2.4 Hz, 1H), 3.81 (s, 2 H),
4.68 (d, J ¼ 2.4 Hz, 2H), 6.95 (d, J ¼ 6 Hz, 2H), 7.24 (d, J ¼ 6 Hz, 2H).
N-acetyl-4-(2-propynyloxy)benzylamine
A solution of 4-(2-propynyloxy)benzylamine (4.00 g, 24.8 mmol) in
18 ml(163.3 mmol) of acetic anhydride was stirred for 20 minutes at
room temperature. The solution was poured into 50 ml of water and
extracted with ether. The organic layer was washed with aqueous
Na2CO3 (5%) and water, and dried over Na2SO4. After the removal
of Na2SO4, the solution was evaporated under a reduced pressure.
The residue was recrystallized from toluene to afford pale pink solid
1
(3.02 g) in 76% yield. H NMR (300 MHz, CDCl3): d2.01 (s, 3H), 2.52
(t, J ¼ 1.8 Hz, 1H), 4.37 (d, J ¼ 5.7 Hz, 2H), 4.68 (d, J ¼ 1.8 Hz, 2H),
5.69 (s, 1H), 6.94 (d, J ¼ 8.4 Hz, 2H), 7.23 (d, J ¼ 8.4 Hz, 2H). 13C
NMR (75 MHz, CDCl3): d23.3, 43.2, 55.8, 75.6, 78.4, 115.1, 129.2,
131.3, 156.9, 169.8, IR (cmꢁ1) : 2127 (nCꢂC), 3235 (nNꢁH).
1, 6-Bis(4-acetamidomethylphenoxy)-2,4-hexadiyne(1) [9]
A suspension of CuCl (0.19 g, 1.93 mmol) in acetone (20 ml) was stir-
red under an argon atmosphere. After an addition of N, N, N0, N0-tetra-
methylethylenediamine (0.070 ml, 0.82 mmol) to the suspension, it was
stirred for 1 hour. The supernatant was added dropwise to an acetone
solution of N-acetyl-4-(2-propynyloxy)benzylamine (2.78 g, 13.7 mmol)
under an argon atmosphere. Then the solution was stirred for 3 days
under an oxygen atmosphere to give white precipitate. It was filtered
1
off and washed with acetone to afford 2.74 g (99%) of white solid. H
NMR (300 MHz, CDCl3): d2.01 (s, 3H), 4.37 (s, 2H), 4.68 (s, 2H), 5.69
(s, 1H), 6.94 (d, J ¼ 8.4 Hz, 2H), 7.23 (d, J ¼ 8.4 Hz, 2H). 13C NMR
(75 MHz, CDCl3): d23.3, 43.2, 56.2, 71.1, 74.5, 115.1, 129.3, 131.6,
156.7, 169.8. IR (cmꢁ1): 1628(nC¼O), 2127 (nCꢂC), 3279 (nNꢁH).

52
T. Okuno et al.
p-N-acetyl(6-hydroxy-2,4-hexadiynenyloxy)benzylamine (2)
A suspension of CuCl (0.19 g, 1.93 mmol) in acetone (28 ml) was
stirred under an argon atmosphere. After an addition of N,N,N0,
N0-tetramethylethylenediamine (0.074 ml, 0.83 mmol) to the suspen-
sion, it was stirred for 1 hour. The supernatant was added dropwise
to an acetone solution of N-acetyl-4-(2-propynyloxy)benzylamine
(1.40 g, 6.89 mmol) and 2-propyne-1-ol (3.90 g, 68.9 mmol) under an
argon atmosphere. Then the solution was stirred for 3 days under
an oxygen atmosphere. It was poured into water and extracted with
dichloromethane. The organic layer was washed with hydrochloric
acid (4.0 M), aqueous Na2CO3 (5%) and water. It was dried over
Na2SO4. After filtration, the filtrate was evaporated to dryness under
reduced pressure. The residue was purified by column chromato-
graphy (SiO2, CH2Cl2-ethanol) and recrystallized from chloroform to
give 0.94 g (39%) of white solid. mp. 118ꢀC. 1H NMR (300 MHz,
CDCl3): d2.01 (s, 3H), 2.04 (t, J ¼ 3.3 Hz, 1H), 4.32 (d, J ¼ 3.3 Hz,
2H), 4.75 (s, 2H), 5.76 (s, 1H), 6.92 (d, J ¼ 8.6 Hz, 2H), 7.21
(d, J ¼ 8.6 Hz, 2H). 13C NMR (75 MHz, DMSO): d23.2, 42.1, 49.9,
56.3, 68.0, 71.1, 75.4, 81.5, 115.3, 129.2, 133.2, 156.4, 169.7. IR
(cmꢁ1): 1631(nC¼O), 3289 (nNꢁH).
Supplementary Data
Supplementary data are available, upon request, from the CCDC, 12
Union Road, Cambridge CB2 1EZ, UK, quoting the deposition number
282617.
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Polymerization of Diacetylenes with Amide Groups
53
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