The crystal and molecular structure of an asymmetric diacetylene monomer has been determined from x-ray diffraction data. The crystals, obtained from an acetone/pentane solution, are orthorhombic, Fdd2 with Z = 16 in a unit cell having dimensions of a = 42.815(6) A, b = 22.224(5) A, c = 4.996(l) A. The structure was solved by direct methods and refined by least- squares techniques to an R(sub F) of 6.4% for 988 reflections and 171 variables. The diacetylene chains are disposed in the unit cell in a complex manner in order to satisfy the hydrogen- bonding, crystal packing, and symmetry requirements of the system. The solid state polymerization mechanism is discussed with respect to the geometric disposition of the diacetylene chains. These chains are far apart and incorrectly oriented with respect to each other to permit polymerization in the crystal by means of 1,4-addition, consistent with the Baughman mechanistic model

Paley, Mark S.

Vlasse, Marcus

English

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NASA-TM-II2849
y,,v. -y 6- - _/_!
The Crystal and Molecular Structure of an Asymmetric Diacetylene Monomer,
6-(2-methyi-4-nitroanilino)-2,4-hexadiyne- 1-ol
by
Marcus Vlasse* and Mark S. Paleyt
Space Science Laboratory, NASA Marshall Space Flight Center
Marshall Space Flight Center, AL 35812 U.S.A.
tUSRA Research Scientist
https://ntrs.nasa.gov/search.jsp?R=19980210981 2020-06-16T00:00:52+00:00Z
Thecrystalandmolecularstructureof anasymmetricdiacetylenemonomerhasbeen
determinedfrom x-raydiffractiondata.Thecrystals,obtainedfrom anacetone/pentanesolution,
areorthorhombic,Fdd2with Z = 16in aunit cell havingdimensionsof a = 42.815(6)/_,b =
22.224(5),/_, c = 4.996(1)/_. The structure was solved by direct methods and refined by least-
squares techniques to an RF of 6.4% for 988 reflections and 171 variables. The diacetylene
chains are disposed in the unit cell in a complex manner in order to satisfy the hydrogen-
bonding, crystal packing, and symmetry requirements of the system. The solid state
polymerization mechanism is discussed with respect to the geometric disposition of the
diacetylene chains. These chains are far apart and incorrectly oriented with respect to each other
to permit polymerization in the crystal by means of 1,4-addition, consistent with the Baughman
mechanistic model.
Introduction
Diacetylenes and polydiacetylenes (R - C - C- C - - R') are important technological organic
materials that have shown promise as third-order nonlinear optical matrices for applications as
optical switching, four-wave mixing and logic circuits (1).
The unique feature of these compounds is the solid-state polymerization (topotactic
reaction) under the influences of an energetic radiation such as UV, y-rays, and x-rays. The
search for macroscopic single crystals of polymers which can be useful in the study of solid-state
properties and possible applications to technological needs have been conducted for a number of
years. These efforts have been mainly unsuccessful, except for the topochemical polymerization
of certain conjugated compounds (2-4). Several classes of organic compounds can undergo
polymerization when exposed to high-energy radiation. Such reactions provide a means of direct
synthesis of highly crystalline polymers and macromolecular systems. A direct correlation has
been established between the geometry and stereochemistry of the molecules in the crystal and
the crystalline molecular structure of the polymer (5-7). As mentioned above, one of these
reactions is the topochemical polymerization of monomer diacetylenes with conjugated triple
bonds. This reaction is known to proceed as a 1,4-addition to the conjugated triple bonds. Single
crystals of a number of these monomers and polymers have been studied by x-ray and neutron
diffraction and Raman spectroscopy, and their stereochemistry has been established. However,
not all diacetylenes polymerize readily and some do not polymerize at all. At present, no detailed
approach exists that would, a priori, predict which diacetylenes will polymerize to any specific
extent.
Baughman (8) advanced a phenomenological model, based on crystallographic studies and
the principle of least motion, in which he specifies the stereochemical criteria governing the
disposition of the molecules in the monomer crystal required in order to bring about
polymerization. In such a model, the polymerization reaction is described as a rotational motion
of the structural units with a specific spacing of the reactive diacetylene chains along the growth
direction (some lattice vector 8) having a period dl and making an angle YI with vector6 (see
Fig. 1).According to this theory,theidealparametersd2 and_ havevaluesof 5.0 ]_ and 13.0
A. The reactivity of a monomer crystal would depend, therefore, on how close dl and 3'I are to
d2 and 3'2- However, a number of other factors influence reactivity and it is not possible to make
quantitative predictions about specific compounds.
At the same time, computer modeling has been used as a means of screening potentially
interesting polymerizable diacetylenes (9). These computer modeling methods make use of
semiempirical molecular orbital calculations such as MNDO and AM1 (10). These models
attempt to predict how a particular diacetylene monomer will pack in the crystal, which is critical
to its ability to polymerize readily or not. In addition, these computations provide HOMO-
LUMO bandgaps, which are of importance in predicting some of the physical and optical
properties of the diacetyles. Again, these predictions are rather qualitative in nature and cannot
take into account the specific arrangement that the monomer will adopt in the crystalline state.
The accurate crystal structure determination of a greater number of representative
diacetylenes will go a long way toward the establishment of a more accurate model which will
allow the prediction of diacetylene reactivity based on the nature and shape of the functional
R,R" groups attached to the diacetylene backbone.
We propose, therefore, a crystal-chemical investigation of a number of diacetylenes, having
important NLO properties, which will permit to establish a more accurate reactivity model and at
the same time allow to determine the structure-property relationships for optical second-order or
third-order NLO behavior.
Experimental Part
The synthesis of the title compound was carried out by the Cadiot-Chodkiewicz coupling of
N-propargyl-2-methyl-4-nitroaniline with bromopropargyl alcohol, as described previously (11).
The pure compound is a yellow powder with m.p. 160-162 "C, and slowly tums to orange-red
upon exposure to light. Single crystals of this compound, suitable for x-ray analysis, were grown
using the solvent vapor diffusion technique. A solution in acetone was exposed to n-pentane
vapor over a period of about 3 days, upon which, long, thin, needle-shaped crystals were
obtained. These crystals are stable in light and air and showed no apparent decomposition under
x-ray radiation during the experiment. However, easy cleavage or splitting was observed along
the needle axis when an attempt was made to cut them normal to this axis. A small needle in the
form of a hexagonal cylinder (0.077 x 0.138 x 0.015 x 1.090 mm) was used for the data
collection. The crystal symmetry was observed to be orthorhombic with space group Fdd2. The
unit cell constants were obtained from 25 high-angle reflections refined on the diffractometer.
These are: a = 42.815(6), b = 22.224(5), c = 4.996(1) A, V = 4753.72 _,3, Z = 16, dcalc= 1.365
g/cm3, dexp. = 1.33(1) g/cm3 (determined by pycnometry). The diffraction intensities were
measured with a single-crystal diffractometer (E-N CAD4) using 0/20 scans and Cu ka (_. =
1.5418 A) graphite-monochromated radiation up to 20max = 70". A total of 988 independent
reflections with I > 2c_(I) were used for the analysis. No crystal movement or decay was
observed during the data collection. An analytical absorption correction was applied (It = 6.43
cm-1).
The structure was solved by direct methods using MULTAN contained in the EN package
of programs. Refinement by full-matrix least-squares with anisotropic thermal parameters led to
a final R-factor (on F) of 6.3% and a G.O.F. -- 1.669. Data were weighed using non-Poisson
scheme with an instrumental uncertainty factor of 0.05. A secondary extinction correction was
applied to the data (12) and the coefficient was refined to a final value of 2.658 x 10 -6.
Corrections for anomalous dispersion were taken from the compilations of Cramer and
Lieberman (13). The hydrogen atoms positions and their thermal factors were not refined and
were fixed to those determined from difference Fourier. A final Fourier difference map showed
no electron density peaks greater than 0.30 e-//_ 3. The final positional and thermal parameters are
given in Tables 1 and 2*. ORTEP (14) diagrams of the molecule, and the contents of the unit
cell, are given in Figures 2 and 3.
*A list of structure factors may be obtained from M.V.
Results and Discussion
The arrangement of the molecules in the unit cell is shown in Figure 3, and the structure of
the molecule is given in Figure 2. The diagram indicates a complex molecular packing scheme
dictated by the hydrogen bonding, the stereochemical requirements of the molecules and the
crystal symmetry. The atoms C2-C5 which comprise the diacetylene backbone are nearly linear
and even the extended chain C1-C6 is approximately linear with only a very small curvature
toward the benzene ring. This linearity is a common element in all diacetylene derivatives and
only the side-groups are inclined with respect to the chain to accommodate crystal packing and
stereochemical requirements (7). The bond distances and bond angles are given in Table 3. The
triple bonds in the diacetylene backbone (C2-C3 and C4-C5) have values which are comparable
to the average < C = C > = 1.206(4) ]_ and to other diacetylenes (7). As was observed in other
substituted diacetylenes, the triple bonds seem to have a certain effect on the adjoining "single"
bonds resulting in shortened C1-C3 = 1.436 (9) ,/_, C5-C6 = 1.49(8) ,_, and even shorter C3-C4 =
1.367(9) A bonds. This is probably due to resonance effects in the triple-single bond system. All
other bond distances and bond angles in the molecule conform to the general accepted values for
organic compounds. The least-squares plane through the benzene ring shows an average
deviation of 0.0031(50) _,. Of the adjoining atoms to this ring only O2 shows a significant
deviation of 0.157(4) A. The strongest cohesive forces in the crystal are due to hydrogen
bonding of the type O1-H(O1) ...... O1 = 2.768(2) _, and N1-H(N1) .... 02 = 3.03(2) ._,. Several
weaker intermolecular interactions of the type C-H ...... O,N also seem to play a role in the crystal
cohesiveness: O1 .... H (C11) = 2.462(4) _, 02 ...... H'(C13) = 2.803(4) A, O3 ...... H(OI) =
2.72(6) ,_,, N2 ...... H'(C13) = 2.691(5) _,, 03 ...... H'(C1) = 2.993(5) ,_, 03 ...... H'(C13) = 2.979(4)
A.
As a whole the relative disposition of the diacetylene backbone chains in the crystaldoes
not correspond to the conditions necessary for the lattice controlled topochemical solid state
polymerization of diacetylenes in crystals. These conditions formulated by Baughman (8) imply
that (1) vector between the centroids of the adjacent parallel diacetylene chains should be equal
to dl = 4.8 - 5.6 _ and (2) the angle YI between this vector and the diacetylene chain should be
about45" (seeFigure 1).Indeed,nosignificantpolymerizationseemto takeplaceunderUV,
visibleor x-ray irradiationof thisparticularcompoundin accordanceto theBaughman
conditions.
Acknowl¢_tgrnent_;
The authors are grateful to Professor Gary Gray of the University of Alabama at
Birmingham for the data collection and kind help in the completion of this work.
References
1. A.J. Heeger and D. R. Ulrich, Eds. "Nonlinear Optical Properties of Polymers," North
Holland Press: New York (1988).
2. G. Wegner and Z. Naturforschg, 246, 824 (1969).
3. M.D. Cohen and B. S. Green, Chemistry in Britain, 9_,490 (1973).
4. G. Wegner, Chimia, 28, 475 (1974).
5. G. Wegner and W. Schermann, Colloid and Polymer Sci., 252, 655 (1974).
6. D. Bloor and G. C. Stevens, J. Polymer Sci., Polymer Phys., _ 703 (1977).
7. M. Vlasse and T. F. Koetzle, Makromol. Chem., 182, 2241 (1986).
8. R.H. Baughman, J. Polymer Sci., Polymer Phys., 12, 15111 (1974).
9. M. Jalab-Heravi, S. P. McManus, S. E. Zutaut, and J. K. McDonald, Macromolecules, 24,
1055 (1991).
10. J.J.P. Stewart, J. Comput. Chem., 10, 221 (1989).
11. M. S. Paley, D. O. Frazier, S. P. McManus, S. E. Zutaut, and S. E. Sanghadasa, Chem.
Mater., accepted for publication (1993).
12. W. H. Zachariasen, Acta Crystallogr., 18, 104 (1965).
13. D. T. Cramer and D. J. Lieberman, J. Chem. Phys., 53, 1891 (1970).
14. C.F. Johnson, ORTEP: "A Fortran Thermal-Ellipsoid Program for Crystal Structure
Illustrations," Report ORNL-3974, revised. ORNL, Oak Ridge, Tennessee (1965).
Figure Captions
Figure l. Disposition of the diacetylene chains in the monomer and polymer crystals. The
parameters dl and YI are geometric factors for solid state polymerization.
Figure 2. Stereochemical structure of the molecule.
Figure 3. Arrangement of the diacetylene chains in the unit cell (dotted lines indicate hydrogen
bonds).
mt
\
"U
0
r
..<
m
mt
C6
Ol
C2
C3
C4
C12
CII
03
N1
C7
C8
CI0
C9
N2
C13
02
0 w
Table I. Positional Parameters and Their ESDs for C13N203HI2
Atom x Y z B(A2)
__m_--m
Ol 0.7527(1) 0.4737(2) 0.805(1) 5.4(1)
02 0.8744(1) -0.0001(2) 0.855(1) 5.09(9)
03 0.8247(1) -0.0038(2) 0.917(1) 6.4(1)
N1 0.83308(9) 0.1926(2) 0.017(1) 3.67(8)
N2 0.8478(1) 0.0160(2) 0.799(1) 3.96(9)
C1 0.7730(2) 0.4284(3) 0.873(2) 6.7(2)
C2 0.7762(1) 0.3839(2) 0.667(1) 4.6(1)
C3 0.7808(1) 0.3447(2) 0.503(1) 4.1(1)
C4 0.7879(1) 0.3035(2) 0.309(1) 3.8(1)
C5 0.7943(1) 0.2660(2) 0.152(1) 4.0(1)
C6 0.8041(1) 0.2211(2) -0.053(1) 4.2(1)
C7 0.8362(1) 0.1484(2) 0.209(1) 3.02(9)
C8 0.8659(1) 0.1238(2) 0.256(1) 3.11(9)
C9 0.8690(1) 0.0806(2) 0.449(1) 3.18(9)
CI0 0.8432(1) 0.0611(2) 0.597(1) 3.30(9)
Cli 0.8141(1) 0.0855(2) 0.551(i) 3.8(1)
C12 0.8105(1) 0.1288(2) 0.362(1) 3.19(9)
C13 0.8938(1) 0.1437(2) 0.099(1) 4.3(1)
H(NI) 0.851(1) 0.208(2) -0.109(13) 4.8(9)
H(OI) 0.769(1) 0.508(3) 0.673(19) 7.1(9)
H(CI) 0.766 0.410 1.034 8.3*
H'(Cl) 0.793 0.446 0.902 8.3*
_!C6) 0.788 0.191 -0.068 5.5*(C6) 0.806 0.241 -0.221 5.5*
H(C9) 0.889 0.064 0.484 4.2*
H(CII) 0.797 0.072 0.650 4.9*
H(CI2) 0.791 0.146 0.333 4.2*
H"(C13) 0.888 0.148 -0.084 5.6*
H(CI3) 0.910 0.114 0.116 5.6*
H'(CI3) 0.901 0.181 0.165 5.6*
Starred atoms were not refined but were placed in their calculated
positions.
Anisotropically refined atoms are given in the form of the
isotropic equivalent displacement parameter defined as:
(4/3) * [a2*B(l,l) + b2*B(2,2) + c2-B(3,3) + ab(cos gamma)*B(l,2)
+ at(cos beta)*B(l,3) + bc(cos alpha)*B(2,3)].
Table 2. Anisotropic Thermal Parameters (betas) for CI3N203HI2
Name
Ol
O2
O3
N1
N2
C1
C2
C3
C4
C5
C6
C7
C8
C9
CI0
CII
C12
C13
B(I,I) B(2,2) B(3,3)
0.00085(3) 0.00280(9) 0.046(2)
0.00081(3) 0.00246(8) 0.045(2)
0.00099(3) 0.0031(1) 0.058(2)
0.00059(2) 0.00177(7) 0.032(2)
0.00077(3) 0.00170(7) 0.029(2)
0.00131(5) 0.0029(1) 0.048(3)
0.00068(3) 0.0024(1) 0.040(3)
0.00058(3) 0.00194(9) 0.041(3)
0.00055(3) 0.00156(8) 0.043(3)
0.00064(3) 0.00187(9) 0.035(2)
0.00077(3) 0.00177(9) 0.033(2)
0.00054(3) 0.00132(8) 0.025(2)
0.00050(2) 0.00139(8) 0.029(2)
0.00044(2) 0.00167(8) 0.030(2)
0.00057(3) 0.00146(8) 0.029(2)
0.00052(3) 0.0020(1) 0.036(2)
0.00047(2) 0.00146(8) 0.032(2)
0.00059(3) 0.0021(1) 0.044(3)
B(1,2) B(1,3) B(2,3)
0.00108(8)-0.0020(5) -0.0026(9)
0.00062(8)-0.0000(5)
-0.0003(1) 0.0036(5)
0.0O034(7) 0.0010(4)
-o.oooo1(8)-o.ooo8(4)
0.0073(8)
0.0149(8)
0.0035(8)
0.0038(8)
0.0018(I) -0.0078(7) -0.006(i)
0.0007(i) -0.0022(6)
0.00026(9)-0.0008(5)
0.00040(8)-0.0017(5)
0.00034(9)-0.0016(5)
0.0005(1) -0.0008(6)
0.002(1)
0.002(1)
0.0025(9)
o.oo3(1)
0.0022(9)
o.ooo18(8)-o.ooo1(5) -o.ooo7(8)
0.00004(8) 0.0000(4) -0.0002(8)
0.00008(8)-0.0001(4)-0.0016(9)
-0.00004(8)-0.0005(5) 0.0017(8)
-0.00015(9) 0.0012(5) 0.002(1)
0.00032(8)-0.0009(5) -0.0007(8)
-0.0002(1) 0.0018(6) 0.003(1)
The form of the anisotropic displacement parameter is:
exp[-(B(l,l)*h2 + B(2,2)*k2 + B(3,3)*12 + B(l,2)*hk + B(l,3)*hl
+ B(2,3)*ki)].
Table 3. Interatomic distances (A) and angles ( ) for C13N203HI2
Atom I Atom 2 Distance Atom 1 Atom 2 Distance
Ol
02
O3
N1
N1
N2
Cl
C2
C3
C1 1.372(7) C4 C5 1.178(8)
N2 1.225(7) C5 C6 1.491(8)
N2 1.232(7) C7 C8 1.404(7)
C6 1.438(7) C7 Cl2 1.407(7)
C7 1.381(7) C8 C9 1.368(7)
c10 1.438(7) c8 c13 1.494(7)
C2 1.436(9) C9 CI0 1.394(7)
C3 1.211(9) CI0 CII 1.380(7)
C4 1.367(9) CII C12 1.359(8)
Atom 1
C6
O2
O2
O3
O1
C1
C2
C3
C4
N1
N1
Atom 2 Atom 3 Angle Atom 1 Atom 2 Atom 3 Angle
N1 C7 124.6(4) N1 C7 C12 121.4(4)
N2 03 122.3(5) C8 C7 C12 119.9(4)
N2 CI0 119.3(5) C7 C8 C9 118.5(5)
N2 CI0 118.4(5) C7 C8 C13 121.4(47
Cl C2 112.7(6) C9 C8 C13 120.1(4)
C2 C3 175.0(7) C8 C9 CI0 121.0(4)
C3 C4 175.2(6) N2 C10 C9 118.7(4)
C4 C5 176.5(7) N2 CI0 Cll 120.8(5)
C5 C6 176.3(6) C9 CI0 Cll 120.4(5)
C6 C5 111.5(5) CI0 Cll C12 i19.6(5)
C7 C8 118.7(4) C7 C12 Cll 120.5(5)
Numbers in parentheses are estimated standard deviations in
the least significant digits.


The Crystal and Molecular Structure of an Asymmetric Diacetylene Monomer, 6-(2-methyl-4-nitroanilino)-2,4-hexadiyne-1-ol

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