C O M M U N I C A T I O N S
Figure 2. The pale background drawing shows the structure of the 1‚2
cocrystal diacetylene monomers. The bold foreground drawing shows the
structure of the resulting polydiacetylene. The main motion is a rotation of
the diacetylene accompanied by a pivot of the methylene group. The C1
and C4 atom movements are similar, 1.37 and 1.34 Å.
Figure 3. The pale background drawing shows the structure of the 1‚H2O
terminal diacetylene monomer structure. The bold foreground drawing shows
the structure of the resulting polydiacetylene. The main motion is an inward
swing of the diacetylene unit with a bend at C4. Atom C1 moves inward
2.45 Å. This inward motion of the diacetylene causes a shrinkage of the
unit cell c axis and a 9% increase in crystal density.
Table 1. Crystallographic Data
It is interesting to note that the repeat distance in the 1:2 structure
decreases from 5.090(4) Å for the monomer to 4.925(5) Å for the
polymer. The 1‚H2O structure starts short at 4.725(1) Å and
lengthens to 4.876(1) Å. The polymer repeat distances approach
the ideal 4.9 Å from opposite directions.
In conclusion, molecule 1 has turned out to be an interesting
molecule. It undergoes the first structurally characterized polym-
erization of terminal diacetylene, and it does it twice. In the hydrate,
the diacetylene functionality is “free”, and there is a dramatic
2.45 Å swinging movement of C1. In the designed structure, the
diacetylene polymerization takes place in a triple-helix “cage”, and
the diacetylene movement is much more constrained. A detailed
comparison of these two sets of structural changes offers an
interesting insight into the precise trajectories of polymerization
reactions.
1‚H O
monomer
1‚H O
polymer
1‚2
monomer
1‚2
polymer
2
2
a (Å)
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
vol (Å3)
den. g/cm3
space grp.
4.725(1)
7.878(2)
30.482(8)
90
90.502(5)
90
1134.5(5)
1.371
P21/c
4.876(2)
7.814(3)
27.407(9)
90
87.203(7)
90
1043.0(6)
1.491
P21/c
14.345(1)
5.090(4)
33.38(3)
90
94.83(1)
90
2450(4)
1.318
P21/n
14.607(1)
4.925(5)
33.14(3)
90
91.92(1)
90
2382(4)
1.356
P21/n
We were pleased with our designed structure, but in carrying
out the synthesis we found an unexpected bonus. When pure
resorcinol 1 is recrystallized from a methanol water mixture, large
single crystals formed that showed an unexpected reddish brown
color. These crystals turned black at 85 °C and showed no melting
point up to 300°. A well-formed crystal was selected, and a structure
determination revealed that the molecule had crystallized as a mono-
hydrate with alignment of the diacetylene functionalities in reason-
able agreement with the requirements for a topochemical polym-
erization, Figure 3.
Acknowledgment. We wish to thank the National Science
Foundation (CHE9980350) for support of this work.
Supporting Information Available: Details of the synthetic
procedures and tables of X-ray diffraction data (PDF and CIF). This
The all important repeat distance is a bit short at 4.725(1) Å
with a declination angle of 54.3°; the C1-C4′ intermolecular contact
is 3.95 Å. These parameters are at the fringe of the range normally
associated with crystal-to-crystal polymerizations, but upon heating
the same single crystal at a relatively low temperature of 50 °C for
20 h a smooth single-crystal-to-single-crystal polymerization took
place.
The polymerization of 1‚H2O is accompanied by a significant
change in both unit cell constants and crystal density. The
polymerization occurs along the short a axis. This axis lengthens
from 4.725(1) Å in the monomer crystal to 4.876(1) Å in the
polymer crystal. At the same time, the long c axis of 30.482(8) Å
dramatically contracts to a value of 27.407(8) Å in the polymer
crystal. The density increases by 8.8%. The extreme motion of the
terminal diacetylene groups causes this 3 Å shrinkage of the c axis.
There is a bend at C4 with C1 moving inward by an unprecedented
2.45 Å to approach the C4′ atom of the molecule below.
References
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Ed. 2001, 39, 2132-2134. (b) Hong, T.; Lauher, J. W.; Fowler, F. W. J.
Am. Chem. Soc. 2002, 124, 10656-10657.
(2) For similar work on diene polymerizations, see: Matsumoto, A. Polym.
J. 2003, 35, 93-121.
(3) Wegner, G. Z. Naturforsch 1969, 24b, 824-832.
(4) Allen, F. H.; Motherwell, W. D. S. Acta Crystallogr. 2002, B58, 407-
422.
(5) There have been attempts to polymerize terminal diacetylenes. For
example: Inoue, K.; Koga, N.; Iwamua, H. J. Am. Chem. Soc. 1991, 113,
9803-9810.
(6) Monomers need to be spaced at 4.9 Å with a 45°-declination angle.
Enkelmann, V. Chem. Mater. 1994, 6, 1337-1340.
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