M. Kato et al. / Journal of Molecular Structure 471 (1998) 139±143
143
The hexyloxy group is in almost the same plane as
the benzene rings except for C(29) and C(30). The
conformation change at the end of the group is caused
by the crystal packing. The plane formed by C(26)±
C(27)±C(28) in the hexyloxy group is tilted from the
mean plane of the two benzene rings at 20.7(6)8 and at
22.4(6)8.
The amide group N(15)±C(16)±O(20) forms a
plane tilted by 38.6(3)8 from the mean plane of
the two benzene rings. Thus the amide group is
located between molecules stacked parallel along
the b-axis, permitting formation of the hydrogen
bond (Fig. 3). The distance between O(20) and
N(15) of the neighbor molecule by one unit cell
material 3-n-propylamide-4-(4-hexyloxyphenylethy-
nyl)-nitrobenzene, examined its second-order
nonlinear optical properties, and determined its struc-
ture. Its second-order nonlinear optical susceptibility
was found to be twice as large as that of m-NA, and the
structure was very similar to other tolane derivatives,
which also have large SHG ef®ciency. The intermole-
cular hydrogen bond was found to be formed in the
amide group, suggesting that an amide group is
required for the tolane derivatives to be SH active.
Acknowledgements
We would like to thank Dr. Angel Alvarez-Larena
of Universidad de Autonoma de Barcelona for his
useful discussions.
Ê
along the b-axis is 2.967(5) A. The hydrogen
¼
bond N(15)±H(N15) O(20) is formed between
the neighboring molecules. The angle for the
hydrogen bond was found to be 146.4(4)8. It has
been indicated that tolane derivatives with hydrogen
bonding between molecules tend to have high
nonlinear optical susceptibilities [7] because the
hydrogen bonding is expected to break the centrosym-
metry structure. Thus, for this derivative 1, which
shows large SHG ef®ciency as shown below, hydrogen
bonding plays an important role in its second-order
nonlinear properties.
The mean plane of the tolane structure, which is
formed by the two benzene rings and the triple bond
between C(1) and C(8), is tilted from the ab, ca, and
bc planes at 83.8(1), 42.3(1) and 117.0(1)8, respec-
tively. The mean planes of tolane of the two mole-
cules in symmetry (x, 2 y, z 1 1/2) are tilted 87.7(1)8,
as shown in Fig. 4.
References
[1] D.S. Chemla, J. Zyss (Eds.), Nonlinear Optical Properties of
Organic Molecules and Crystals. Academic Press, Orlando,
1987.
[2] T. Kurihara, H. Tabei, T. Kaino, J. Chem. Soc. Chem.
Commun. 1987 (1987) 959.
[3] A.E. Stiegman, E. Graham, K.J. Perry, L.R. Khundkar, L.-T.
Cheng, J.W. Perry, J. Am. Chem. Soc. 113 (1991) 7658.
[4] M. Nakano, K. Yamaguchi, T. Fueno, Springer Proc. Phys.
Nonlinear Optics Organics Semiconductors 36 (1989) 98.
[5] N. Matsuzawa, D.A. Dixon, J. Phys. Chem. 96 (1992) 6232.
[6] E. Graham, V.M. Miskowski, J.W. Perry, D.R. Coulter, A.E.
Stiegman, W.P. Schaefer, R.E. Marsh, J. Am. Chem. Soc. 111
(1989) 8771.
[7] M. Kato, M. Okunaka, N. Sugita, M. Kiguchi, Y. Taniguchi,
Bull. Chem. Soc. Jpn. 70 (1997) 583.
[8] M. Kato, K. Kobayashi, M. Kiguchi, N. Sugita, M. Okunaka,
Y. Taniguchi, J. Mater. Chem. 7 (1997) 705.
As expected from the SHEW results, the molecular
structure and packing of 1 are very similar to those of
2 [8]. Thus, the molecular packing of 1 and 2, which
contains the intermolecular hydrogen bond, is the key
to have a large second-order nonlinear optical
susceptibility.
[9] M. Kato, M. Kiguchi, J. Appl. Phys. 81 (1997) 550.
[10] M. Kiguchi, M. Kato, N. Kumegawa, Y. Taniguchi, J. Appl.
Phys. 75 (1994) 4332.
[11] P. Main, S.E. Hull, L. Lessinger, G. Germain, J.-P. Declercq,
M.M. Woolfson, MULTAN. A Program for the Automatic
Solution of Crystal Structures from X-ray Diffraction Data,
University of York, England, and Louvain, Belgium. 1978.
[12] T. Sakurai, K. Kobayashi, Rikagaku Kenkyusho Hokoku (in
Japanese) 55 (1979) 69.
4. Conclusion
[13] Handbook of Lasers, Chemical Rubber Co., Cleveland, OH,
1971, p. 497.
We have synthesized the novel nonlinear optical
Kato, Midori
