Morphology and Polymorphism Control of Organic Polyene Crystals

Configurationally locked polyene crystals grown in the absence and in the presence of their tailor-made auxiliaries, which are slightly modified subst...
0 downloads 0 Views 468KB Size
Download PDF
CRYSTAL GROWTH & DESIGN

Morphology and Polymorphism Control of Organic Polyene Crystals by Tailor-made Auxiliaries O-Pil Kwon,*,† Seong-Ji Kwon,† Mojca Jazbinsek,† Ashutosh Choubey,† Paolo A. Losio,† Volker Gramlich,‡ and Peter Gu¨nter†

2006 VOL. 6, NO. 10 2327-2332

Nonlinear Optics Laboratory and Laboratory of Crystallography, ETH Zurich, CH-8093 Zurich, Switzerland ReceiVed May 18, 2006; ReVised Manuscript ReceiVed July 14, 2006

ABSTRACT: Configurationally locked polyene crystals grown in the absence and in the presence of their tailor-made auxiliaries, which are slightly modified substrate molecules, were investigated. The effects of the tailor-made auxiliaries on the crystal characteristics were investigated by X-ray crystal structure analysis and nonlinear optical and photoluminescent measurements. The substrate crystals of 2-{3-[2-(4-dimethylaminophenyl)vinyl]-5,5-dimethylcyclohex-2-enylidene}malononitrile (DAT2) and 2-{3-[2-(4-pyrrolidinphenyl)vinyl]-5,5-dimethylcyclohex-2-enylidene}malononitrile (PyT1) exhibit a strong powder second harmonic generation signal of about 140 and 80 times that of urea at a fundamental wavelength of 1.9 µm. Although the investigated substrate polyene molecules DAT2 and PyT1 show very similar crystal structures in the absence of auxiliaries, in the presence of the tailor-made additives with the same modification of the corresponding substrate molecules, the DAT2 crystal exhibits a morphological change and the PyT1 crystal exhibits a polymorphic change. Introduction The physical properties of bulk materials are related mainly to the microscopic chemical structure of the molecules and the macroscopic supramolecular arrangement. In crystals, morphologic and polymorphic changes,1 which are defined as the tendency of chemically identical molecules to crystallize into several different crystal shapes (i.e., different crystal surfaces, facets, or habits) and several different crystal structures (i.e., different supramolecular packing), respectively, usually lead to significant changes in their physical properties. Therefore, crystal engineering including the control of morphology and polymorphism is essential to achieve optimized molecular configurations and physical properties and to understand the structure-property relationships of new materials. To modify the crystal morphology and crystal structure, many different approaches have been investigated including conventional methods by altering the crystal growth conditions by changing the solvents, growth temperature, and supersaturation,2 nucleation of one polymorph by another,3 crystallization in the presence of auxiliaries or additives4,5 and in confined geometries,6 and introduction of specific interactions in two-dimensional (2D) surfaces such as Langmuir-Blodgett films and self-assembled monolayers.7 The “tailor-made” auxiliaries, which are defined as having similar chemical structures as the corresponding substrate molecules, can be of advantage to modify the crystal characteristics with a stereoselective target.8,9 In particular, the physical properties such as for example the nonlinear optical10,11 and photoluminescent properties12 are strongly dependent on the arrangement of molecules in the solid state. For second-order nonlinearity, a noncentrosymmetric arrangement of chromophores in the crystals is required. Recently, long π-conjugated polyene molecules have been extensively investigated for nonlinear optical and red organic light-emitting diode (OLED) applications due to their large molecular second-order nonlinearity13,14 and high luminescence efficiency with a good color purity.15 However, there are only * Tel: +41 1 633 3258. Fax: +41 1 633 1056. E-mail: kwon@ phys.ethz.ch. † Nonlinear Optics Laboratory. ‡ Laboratory of Crystallography.

a few reports on the crystalline solid state of polyene molecules.16 Modification of the polyene crystals induced by additives has not been reported yet. Moreover, only a few reports exist on crystal engineering by additives for nonlinear optical applications, even for nonpolyene type chromophores (i.e., general benzenoid and stilbene chromophores).17 Here, we report on the selective growth of polyene crystals with different morphologies and polymorphs induced by their analogous tailor-made auxiliaries, which are slightly modified corresponding substrate molecules. The effects of the tailormade auxiliaries on crystal characteristics were investigated by X-ray crystal structure analysis and nonlinear optical and photoluminescent measurements. Although similar crystal structures of the investigated substrate polyene molecules are found in the absence of auxiliaries, using auxiliaries with the same modification of the corresponding substrate molecules, one polyene crystal with a dimethylamino group exhibits a morphological change and the other with a pyrrolidine group exhibits a polymorphic change in the presence of the tailor-made additives. Experimental Section Materials. The investigated substrate chromophores and their analogous auxiliaries (see Figure 1) were synthesized by two consecutive Knoevenagel condensations we described previously.16 The material for all experiments was purified by recrystallization in methanol (or methylenechloride/methanol mixture) solution several times and characterized by 1H NMR. 2-{3-[2-(4-Dimethylaminophenyl)vinyl]-5,5dimethylcyclohex-2-enylidene}malononitrile (DAT2): 1H NMR (CDCl3, δ): 7.4 (d, 2H, Ar-H), 7.0 (d, 1H, -CHdCH-), 6.8 (d, 1H, -CHd CH-), 6.75 (s, 1H, -CdCH-), 6.7 (d, 2H, Ar-H), 3.0 (s, 6H, N-CH3), 2.6 (s, 2H, -CH2), 2.5 (s, 2H, -CH2), 1.0 (s, 6H, -CH3). 2-{3-[2-(4Dimethylaminophenyl)vinyl]cyclohex-2-enylidene}malononitrile (DAM1): 1H NMR (CDCl3, δ): 7.4 (d, 2H, Ar-H), 7.0 (d, 1H, -CHdCH-), 6.8 (d, 1H, -CHdCH-), 6.75 (s, 1H, -CdCH-), 6.7 (d, 2H, Ar-H), 3.0 (s, 6H, N-CH3), 2.76 (t, 2H, -CH2), 2.63 (t, 2H, -CH2), 1.9 (m, 2H, -CH2). 2-{3-[2-(4-Pyrrolidinphenyl)vinyl]-5,5dimethylcyclohex-2-enylidene}malononitrile (PyT1): 1H NMR (CDCl3, δ): 7.4 (d, 2H, Ar-H), 7.0 (d, 1H, -CHdCH-), 6.8 (d, 1H, -CHd CH-), 6.7 (s, 1H, -CdCH-), 6.5 (d, 2H, Ar-H), 3.4 (t, 4H, N-CH2), 2.6 (s, 2H, -CH2), 2.5 (s, 2H, -CH2), 2.0 (t, 4H, -CH2-), 1.0 (s, 6H, -CH3). 2-{3-[2-(4-Pyrrolidinphenyl)vinyl]cyclohex-2-enylidene)malononitrile (PyM1): 1H NMR (CDCl3, δ): 7.4 (d, 2H, Ar-H), 7.0 (d, 1H,

10.1021/cg060293t CCC: $33.50 © 2006 American Chemical Society Published on Web 08/23/2006

2328 Crystal Growth & Design, Vol. 6, No. 10, 2006

Kwon et al.

Results and Discussion

Figure 1. Chemical structures of the investigated configurationally locked polyene chromophores and their tailor-made auxiliaries. Table 1. Summary of Crystallographic Data for DAT2 and PyT1 Crystals

morphology formula formula weight crystal system space group a (Å) b (Å) c (Å) R (deg) β (deg) γ (deg) V (Å3)

DAT2

PyT1 (I)

PyT1 (II)

plate C21H23N3 317.42 monoclinic P21 6.1303(7) 7.4239(9) 20.258(4) 90 96.75(8) 90 915.6(2)

plate C23H25N3 343.46 monoclinic P21 5.9510(12) 7.5960(15) 21.590(4) 90 96.82(3) 90 969.0(3)

needle C23H25N3 343.46 monoclinic P21/c 12.836(3) 16.930(3) 9.3810(19) 90 95.78(3) 90 2028.3(7)

-CHdCH-), 6.8 (d, 1H, -CHdCH-), 6.7 (s, 1H, -CdCH-), 6.5 (d, 2H, Ar-H), 3.4 (t, 4H, N-CH2), 2.7 (t, 2H, -CH2), 2.6 (t, 2H, -CH2), 2.0 (m, 4H, -CH2-), 1.9 (m, 2H, -CH2). Crystal Growth of DAT2. The single crystals of DAT2 were prepared by the slow evaporation method in mixed solvent of methylenechloride and methanol (∼1:2) at 30 or 40 °C. To investigate the effect of the tailor-made auxiliary, the DAT2 crystals were prepared in the same manner but in the presence of DAM1 auxiliary (DAT2/ DAM1 ) 10:1 weight ratio in solution). Crystal Growth of PyT1. To obtain single crystals, the solution of pure PyT1 in methanol was boiled for 1 h. The solution was cooled and kept for slow evaporation of the solvent at 30 or 40 °C. The PyT1 crystals with the PyM1 auxiliary were prepared with similar procedures (PyT1/PyM1 ) 100:1, 10:1, 5:1 weight ratio in solution). X-ray Crystal Structure Analysis. Single-crystal X-ray diffraction experiments were carried out on a single-crystal X-ray diffractometer equipped with a CCD detector (Xcalibur PX, Oxford Diffraction) with 65-mm sample-detector distance. Data reduction and numerical absorption correction were performed using the software package CrysAlis.18 The crystal structures were solved by direct methods, and the full data sets were refined on F2, employing the programs SHELXS97 and SHELXL-97.19 Single-crystal structures grown in absence and in the presence of the tailor-made auxiliaries are given in Table 1 for platelike DAT2 (CCDC 278087), platelike PyT1 crystal (CCDC 293252), and needlelike PyT1 crystal (CCDC 294862). Absorption and Photoluminescence Measurement. UV-Vis absorption spectra were recorded by a Perkin-Elmer Lambda 9 spectrometer in chloroform solution. Photoluminescence spectra were measured using a custom built luminescence spectrometer based on an OceanOptics USB2000 CCD spectrometer (range: 350-1000 nm) for detection and a Xenon lamp equipped with a grating monochromator for excitation. Wavelength and spectral sensitivity of the detection spectrometer were factory calibrated. The sample excitation assembly allows for illumination of liquid samples (side illumination) in methylenechloride and of crystalline powder samples (top illumination); an optical fiber connected to a detection spectrometer collects the light emitted from the sample. The excitation wavelength is in the range of 520-580 nm. By tuning the excitation wavelength, we can match the absorption maximum of the material under study, thus maximizing the emission intensity without influencing the emission maximum wavelength λem. The position of the optical fiber can be adjusted to maximize the photoluminescence signal and reduce stray excitation light pick up.

The chemical structures of the polyene chromophores investigated are shown in Figure 1 together with their abbreviations. All molecules consist of the configurationally locked polyene (CLP) bridge linked between various electron donor groups and dicyanomethylidene electron acceptor group to improve thermal/ photochemical stability.14,16 The electron donor groups in the substrate molecules are dimethylamino (DA) and pyrrolidine (Py) groups for DAT2 and PyT1, respectively. The substrate DAT2 and PyT1 molecules incorporate the equatorial and axial methyl groups in the non-π-conjugated part of the hexatriene bridge. Their tailor-made auxiliaries with a slightly modified chemical structure compared to the substrate molecules contain two hydrogen atoms instead of the equatorial and axial methyl groups in the non-π-conjugated part of the hexatriene bridge. Substrate Crystals Grown in the Absence of Auxiliary. Single crystals of DAT2 and PyT1 were grown from solution (methylenechloride/methanol or methanol) in the absence of auxiliaries by the slow evaporation method. The morphologies of the crystals grown are rectangular platelike crystals for DAT2 and trapezoidal platelike crystals for PyT1 as shown in Figures 2a and 3a. To investigate the crystal structures, we carried out single X-ray structure analysis. The details of the crystal structures are given in Table 1. Both DAT2 and PyT1 crystals grown in the absence of auxiliaries have noncentrosymmetric structures with monoclinic space group symmetry P21 (point group 2). In general, minor chemical modifications of the molecules lead to large differences in the crystal structures: for example, modifying the counterion parts in 4′-(dimethylamino)N-methyl-4-stilbazolium tosylate (DAST), which links the two ions by strong Coulomb forces.20,21 Also for polyene nonlinear optical crystals with strong molecular asymmetry, the CLP chromophore with the diethylamino group crystallizes in the centrosymmetric orthorhombic Pnma structure,16 while the analogous DAT2 chromophore with the dimethylamino group has the noncentrosymmetric P21 structure. However, in this work, two crystals with a different donor group, the dimethylamino group for DAT2 and the pyrrolidine group for PyT1, show very similar crystal structures (i.e., the same space group symmetry, similar cell parameters, and crystallographic angles as listed in Table 1). Moreover, the molecular arrangements along the polar crystallographic b-axis are also similar as shown in Figure 4a,b. To investigate the macroscopic nonlinearity of the crystals, the Kurtz and Perry powder test22 was performed at a fundamental wavelength of 1.9 µm using a tunable output of an optical parametric amplifier pumped by an amplified Ti:sapphire laser.16 The crystalline powders exhibit very strong second harmonic generation (SHG) signals of 140 times for DAT2 and 80 times for PyT1 with respect to that of urea. The reason for the large difference of the SHG efficiency between DAT2 and PyT1 crystals, despite the very similar crystalline packing, can be related to the order parameter of the polar structure cos θp, where θp is the angle between the molecular charge-transfer axis and the polar crystalline axis. The highest macroscopic second-order nonlinear optical coefficient d333 is often roughly estimated by d333 ≈ Nβf(ω)〈cos3 θp〉, where N is the number of molecules per unit volume, β is the microscopic molecular hyperpolarizability, and f(ω) is the local field factor.10 As illustrated in Figure 4c, the long axis of the DAT2 molecule, which is a favorable direction of charge delocalization, is more aligned along the crystallographic polar b-axis than for PyT1, which can lead to the observed changes in the macroscopic nonlinearity.

Polymorphism Control of Organic Polyene Crystals

Crystal Growth & Design, Vol. 6, No. 10, 2006 2329

Figure 2. Morphologic change of DAT2 crystals grown from solution in the absence (a) and in the presence (b) of DAM1 auxiliary (DAT2/DAM1 ) 10:1 weight ratio in solution) as observed between crossed polarizers in a polarizing microscope.

Figure 3. Polymorphic change of the PyT1 crystals grown from solution in the absence (a) and in the presence (b) of PyM1 auxiliary (PyT1/PyM1 ) 10:1 weight ratio in solution) as observed between crossed polarizers in a polarizing microscope.

Figures 5 and 6 show the absorption and photoluminescence (PL) spectra of DAT2 and PyT1 in solution and in the crystalline solids. In solution, the maximum of the emission wavelength λem increases with increasing wavelength of maximum absorption λabs of the DAT2 and PyT1 chromophores. In general, the red fluorescent molecules in the solid state easily aggregate by dipole-dipole interactions or intermolecular π-stacking due to their large dipole moment and long π-conjugation, which leads to concentration quenching and weak or negligible photoluminescent emission.15 In this work, we observe strong photoluminescence in the crystalline solid states. The maximum of the emission wavelengths λem are near 710 nm for the platelike DAT2 crystal and near 692 nm for the platelike PyT1 crystal, which are shifted to longer wavelengths as compared to the same compounds in solution. As shown in Figure 4a,b, the molecules are stacked along the crystallographic b-axis in a mutually crossed fashion without intermolecular π-stacking and antiparallel aggregation of the molecules, thus avoiding concentration quenching. Tailor-made Auxiliaries. Figure 7 shows, in the absence of auxiliaries, the intermolecular interaction features associated with the substrate polyene molecules in the crystal lattice. In both DAT2 and PyT1 crystals, weak hydrogen bonds of CtN‚‚‚H-C become the main supramolecular interactions. The nitrogen atoms on the CtN groups act as hydrogen-bond acceptors. The C-H groups on the equatorial and axial methyl groups in the non-π-conjugated part of the hexatriene bridge and on dimethylamino group for DAT2 and pyrrolidine group

for PyT1 act as hydrogen-bond donors. The distances of CtN‚‚‚H-C are in the range of 2.8-3.4 Å. Resulting from various hydrogen bonds of CtN‚‚‚H-C, the substrate molecules in the absence of auxiliaries build a three-dimensional weak hydrogen-bonded network in the crystalline solid. In general, stereospecific inhibitors are composed of two moieties, binder and perturber.9 Therefore, the chemical structures of the tailor-made auxiliaries were modified slightly compared to the substrate molecules. In this work, the tailormade auxiliaries DAM1 and PyM1 consist of same phenylhexatriene bridge between dialkylamino and dicyanomethylidene groups as the substrate molecules (DAT2 and PyT1), which can act as a binder. However, they eliminate equatorial and axial methyl groups, which are important hydrogen-bond donor groups, in the non-π-conjugated part of the hexatriene bridge. Therefore, eliminating two hydrogen-bond donor sites can act as a perturber. The investigated polyene auxiliaries are expected to generate stereoselective interactions with the substrate molecules at certain surfaces of the grown crystals. Morphologic Change Induced by Tailor-made Auxiliary. Figure 2 shows microphotographs of DAT2 crystals grown from solution in the absence and in the presence of the DAM1 auxiliary (DAT2/DAM1 ) 10:1 weight ratio in solution) as observed between crossed polarizers using a polarizing microscope. Both crystals show equivalent powder X-ray diffraction patterns, thin layer chromatograms, and thermodiagrams including the melting temperature Tm in differential scanning calorimetry (DSC) experiments. This indicates that the DAT2 crystal

2330 Crystal Growth & Design, Vol. 6, No. 10, 2006

Kwon et al.

Figure 6. Absorption and photoluminescence (PL) spectra (normalized scale) of PyT1 in solution and in the crystalline solids. The photoluminescence intensity of the needlelike PyT1 crystals is lower than that of platelike PyT1 crystals, and therefore the photoluminescence signal of the needlelike PyT1 crystals is noisier. The inset is photoluminescence images of PyT1 polymorphs.

Figure 4. Crystal packing diagram of the DAT2 and PyT1 crystals grown from solution in the absence of auxiliaries (the monoclinic P21 phase): (a) rectangular platelike DAT2 crystal, (b) trapezoidal platelike PyT1 crystal, (c) two superimposed molecules of DAT2 and PyT1 from (a) and (b) to point out the difference in crystalline packing.

Figure 7. Crystal packing diagram projected along the a-axis for P21 phase of DAT2 (a) and PyT1 (b). Molecules are linked with weak hydrogen bonds, which are indicated by dotted lines.

Figure 5. Absorption and photoluminescence (PL) spectra (normalized scale) of DAT2 in solution and in the crystalline solids.

grown in the presence of the DAM1 auxiliary consists of only DAT2 molecules without doping or mixing of the auxiliary molecules and exhibits identical crystal structure with the DAT2 crystal grown in the absence of auxiliary. Therefore, the photoluminescence spectra of two DAT2 crystals without polymorphism are equivalent as expected (see Figure 5). However, the morphology of the DAT2 crystals is different: in the absence of auxiliary it is rectangular platelike, and in the presence of DAM1 auxiliary it is trapezoidal platelike as shown in Figure 2. The DAT2 crystals, either with or without the auxiliary, naturally grow into 2D platelet-like crystals with the large

surface showing (001) facets as shown in Figure 2. However, comparing the facets of crystals, the DAT2 crystals in the presence of the DAM1 auxiliary were retarded to grow along the (110) facets. This stereoselective inhibiting effect can be explained in terms of the tendency of the adsorption of DAM1 auxiliaries on DAT2 crystal surfaces due to the binding part of DAM1 and further inhibiting the growth due to the absence of two hydrogen-bonding donor sites. These site-specific interactions are crucial to overcome the antiparallel dipole-dipole aggregation and allow for a parallel arrangement between the DAT2 molecules in solution and on crystal surfaces. Considering the molecular arrangement of the DAT2 crystal, the most possible way for adsorption with lower steric hindrance is along the (110) faces as shown in Figure 8. Therefore, the DAM1 auxiliary adsorbs and inhibits the growth preferentially on the (110) faces of DAT2 crystals, resulting in the morphologic change as shown in Figure 2. Polymorphic Change Induced by Tailor-made Auxiliary. Microphotographs of PyT1 crystals grown from solution in the absence and in the presence of the PyM1 auxiliary (PyT1/PyM1 ) 10:1 weight ratio in solution) as observed between crossed polarizers in a polarizing microscope are shown in Figure 3.

Polymorphism Control of Organic Polyene Crystals

Crystal Growth & Design, Vol. 6, No. 10, 2006 2331

Figure 8. Schematic representation of selective inhibition (or adsorption) of the DAM1 auxiliary at the crystal (110) facet of the DAT2 crystal.

The morphology is trapezoidal platelike when grown in the absence of auxiliary and needlelike when grown in the presence of the PyM1 auxiliary for all different weight ratios (PyT1/ PyM1 ) 100:1, 10:1, 5:1 weight ratio in solution). In thin-layer chromatography experiments, the PyT1 crystals grown in the presence of the PyM1 auxiliary turned out to be doped with the PyM1 auxiliary, in contrast to the case of DAT2 crystals. The doping level in the crystals increases with increasing the weight ratio of the auxiliary PyM1 molecule in the mother solution but remains below a few percent, even for the highest weight ratio in solution (5:1). The crystal structure of the needlelike PyT1 crystal induced by the PyM1 auxiliary is shown in Figure 9 and details are listed in Table 1. The platelike PyT1 crystals are monoclinic with space group symmetry P21, while the needlelike PyT1 crystals are monoclinic with space group symmetry P21/c. Therefore, in contrast to the morphologic change of the DAT2 crystals in the presence of auxiliary, the PyT1 crystals in the absence and in the presence of auxiliary exhibit a polymorphic change. The reason for the polymorphic change of the PyT1 crystals in the presence of the PyM1 auxiliary may be related to the following. Like in the case of the DAM1 auxiliary of the DAT2, the PyM1 auxiliary without two hydrogen-bond donors of the substrate PyT1 molecule can aggregate with the substrate PyT1 molecules by antiparallel dipole-dipole interaction. This antiparallel aggregation could prevent the nucleation of the noncentrosymmetric polymorph and induce a nucleation of a centrosymmetric polymorph. The probability for inducing another crystallographic packing is related to a tendency of molecules to form polymorphs. In contrast to the dimethylamino group on the DAT2 molecule, the pyrrolidine ring on the PyT1 molecule can possesses various conformations: for example, half-chair form as exists in the platelike PyT1 crystal and planar form in the needlelike PyT1 crystal as shown in Figure 10. Additionally, in the DSC measurements (see Figure 11), platelike PyT1 crystals exhibit a reversible enantiotropic phase transition at Ttr ) 85 °C, which will be discussed elsewhere in detail. The high-temperature polymorph of the red plate is different from the needle-type polymorph, as also indicated by the different

Figure 9. Crystal packing diagram of P21/c phase of needlelike PyT1 grown in the presence of PyM1 auxiliary: (a) one layer of molecules parallel to the (1 0 1h) crystallographic plane, (b) projection along the crystallographic axis b. The acentric layer of molecules above the one shown in (a) has an antiparallel orientation of molecules.

Figure 10. The conformations of pyrrolidine ring in PyT1 crystals as viewed from the nitrogen atom to the π-conjugated bridge: half-chair form for the platelike P21 crystal (a) and the planar form for the needlelike P21/c crystal (b).

melting point. On the other hand, DAT2 crystals do not show any phase transition up to the melting point at about 235 °C.16 Therefore, the PyT1 molecules exhibit a higher tendency to form polymorphs than do DAT2 molecules. Like in the platelike PyT1 crystal with the absence of antiparallel aggregation of chromophores (Figure 4b), the PyT1 molecules in the needlelike crystalline state also are aligned along the crystallographic b-axis and form a polar chain (or

2332 Crystal Growth & Design, Vol. 6, No. 10, 2006

Figure 11. DSC thermodiagrams of platelike and needlelike PyT1 crystals grown from solution in the absence and in the presence of PyM1 auxiliary (PyT1/PyM1 ) 10:1 weight ratio in solution).

layer) as shown in Figure 9a. However, as shown in Figure 9b, the polar chain of molecules shows antiparallel stacking one by one and form intermolecular π-stacking with a distance of about ∼3.4 Å. Therefore, the emission maximum wavelength λem of the needlelike PyT1 crystal grown in the presence of auxiliary is shifted by about 40 nm compared to the platelike PyT1 crystals grown in the absence of auxiliary as shown in Figure 6. Although the photoluminescence quantum efficiency was not measured, we could clearly observe that the needlelike PyT1 crystals exhibit a much weaker photoluminescence intensity than the platelike PyT1 crystals under similar excitation and detection conditions, as a consequence of the intermolecular π-stacking and therefore concentration quenching. Conclusion We have reported on configurationally locked polyene crystals grown in the absence and in the presence of their tailor-made auxiliaries, which are the corresponding slightly modified substrate molecules. The effects of the tailor-made auxiliaries on crystal characteristics were investigated by X-ray crystal structure analysis and nonlinear optical and photoluminescence measurements. The substrate crystals of DAT2 and PyT1 exhibit a strong powder SHG signal of about 140 and 80 times that of urea at a fundamental wavelength of 1.9 µm. Despite the similar crystal structures (monoclinic point group symmetry 2) of substrate polyene molecules in the absence of auxiliary and similar chemical structure changes of the auxiliaries, in the presence of the tailor-made additives, DAT2 crystals exhibit a morphological change, and PyT1 crystals exhibit a polymorphic change. Therefore, crystal engineering by analogous tailor-made auxiliary provides an opportunity to control crystal characteristics including morphology and crystal structure and also to obtain desired physical properties. Acknowledgment. This work was supported by the Swiss National Science Foundation. References (1) (a) Bernstein, J.; Davey, R. J.; Henck, J. O. Angew. Chem. Int. Ed. 1999, 38, 3440. (b) Sharma, C. V. K. Cryst. Growth Des. 2002, 2, 465. (c) Giron, D. Eng. Life Sci. 2003, 3, 103. (d) Giron. D. Thermochim. Acta 1995, 248, 1. (2) (a) Xie, Z.; Liu, L.; Yang, B.; Yang, G.; Ye, L.; Li, M.; Ma, Y. Cryst. Growth Des. 2005, 5, 1959. (b) Gracin, S.; Rasmuson, A. C. Cryst. Growth Des. 2004, 4, 1013. (c) Aitipamula, S.; Nangia, A. Chem. Commun. 2005, 3159.

Kwon et al. (3) Yu, L. J. Am. Chem. Soc. 2003, 125, 6380. (4) (a) Lu, J.; Wang, X. J.; Ching, C. B. Cryst. Growth Des. 2003, 3, 83. (b) Davey, R. J.; Blagden, N.; Potts, G. D.; Docherty, R. J. Am. Chem. Soc. 1997, 119, 1767. (5) (a) Lang, M.; Grzesiak, A. L.; Matzger, A. J. A. Am. Chem. Soc. 2002, 124, 14834. (b) Price, C. P.; Grzesiak, A. L.; Matzger, A. J. A. Am. Chem. Soc. 2005, 127, 5512. (6) (a) Ha, J. M.; Wolf, J. H.; Hillmyer, M. A.; Ward, M. D. J. Am. Chem. Soc. 2004, 126, 3382. (b) Hilden, J. L.; Reyes, C. E.; Kelm, M. J.; Tan, J. S.; Stowell, J. G.; Morris, K. R. Cryst. Growth Des. 2003, 3, 921. (7) (a) Hiremath, R.; Varney, S. W.; Swift, J. A. Chem. Mater. 2004, 16, 4948. (b) Hiremath, R.; Basile, J. A.; Varney, S. W.; Swift, J. A. J. Am. Chem. Soc. 2005, 127, 18321. (8) (a) Weissbuch, I.; Lahav, M.; Leiserowitz, L. Cryst. Growth Des. 2003, 3, 125. (b) Weissbuch, I.; Popovitz-Biro, R.; Lahav, M.; Leiserowitz, L. Acta Crystallogr. 1995, B51, 115. (c) Addadi, L.; Berkovitch-Yellin, Z.; Weissbuch, I.; Mil, J.; Shimon, L. J. W.; Lahav, M.; Leiserowitz, L. Angew. Chem., Int. Ed. 1985, 24, 466. (9) Torbeev, V. Y.; Shavit, E.; Weissbuch, I.; Leiserowitz, L.; Lahav, M. Cryst. Growth Des. 2005, 5, 2190. (10) (a) Bosshard, Ch.; Bo¨sch, M.; Liakatas, I.; Ja¨ger, M.; Gu¨nter, P. In Nonlinear Optical Effects and Materials; Gu¨nter, P., Ed.; SpringerVerlag: Berlin, 2000; Chapter 3. (b) Bosshard, Ch.; Sutter, K.; Preˆtre, Ph.; Hulliger, J.; Flo¨rsheimer, M.; Kaatz, P.; Gu¨nter, P. In Organic Nonlinear Optical Materials, Volume 1 of AdVances in Nonlinear Optics; Gordon and Breach Science Publishers: New York, 1995. (11) (a) Pan, F.; Bosshard, Ch.; Wong, M. S.; Serbutoviez, C.; Schenk, K.; Gramlich, V.; Gu¨nter, P. Chem. Mater. 1997, 9, 1328. (b) Pan, F.; Bosshard, Ch.; Wong, M. S.; Serbutoviez, C.; Follonier, S.; Gu¨nter, P.; Schenk, K. J. Cryst. Growth 1996, 165, 273. (c) Follonier, S., Bosshard, Ch.; Meier, U.; Knopfle, G.; Serbutoviez, C.; Pan, F.; Gu¨nter, P. J. Opt. Soc. Am. B 1997, 14, 593. (12) (a) Davis, R.; Rasth, N. P.; Das, S. Chem. Commun, 2004, 74. (b) Mutai, T.; Satou, H. Araki, K. Nat. Mater. 2005, 4, 685. (13) (a) Marder, S. R.; Beratan, D. N.; Cheng, L. T. Science 1991, 252, 103. (b) Marder, S. R.; Cheng, L. T.; Tiemann, B. G.; Friedli, A. C.; Blanchare-Desce, M.; Perry, J. W.; Skindhoj, J. Science 1994, 263, 511. (14) (a) Shu, C. F.; Tsai, W. J.; Jen, A. K.-Y. Tetrahedron Lett., 1996, 37, 7055. (b) Ermer, S.; Lovejoy, S. M.; Leung, D. S.; Warren, H.; Moylan, C. R.; Twieg, R. J. Chem. Mater. 1997, 9, 1437. (c) Shu, Y. C.; Gong, Z. H.; Shu, C. F.; Breitung, E. M.; McMahon, R. J.; Lee, G. H.; Jen, A. K.-Y. Chem. Mater. 1999, 11, 1628. (d) Staub, K.; Levina, G. A.; Barlow, S.; Kowalczyk, T. C.; Lackritz, H. S.; Barzoukas, M.; Fort, A.; Marder, S. R. J. Mater. Chem. 2003, 13, 825. (e) Lawrentz, U.; Grahn, W.; Lukaszuk, K.; Klein, C.; Wortmann, R.; Feldner, A.; Scherer, D. Chem. Eur. J. 2002, 8, 1573. (15) (a) Chen, C. T. Chem. Mater. 2004, 16, 4389. (b) Li, J.; Liu, D.; Hong, Z.; Tong, S.; Wang, P.; Ma, C.; Lengyel, O.; Lee, C. S.; Kwong, H. L.; Lee, S. Chem. Mater. 2003, 15, 1486. (c) Tao. X. T.; Miyata, S.; Sasabe, H.; Zhang, G. J.; Wada, T.; Jiang, M. H. Appl. Phys. Lett. 2001, 78, 279. (16) Kwon, O. P.; Ruiz, B.; Choubey, A.; Mutter, L.; Schneider, A.; Jazbinsek, M.; Gu¨nter, P. Chem. Mater., 2006, 18, 4049-4054. (17) (a) Weissbuch, I.; Lahav, M.; Leiserowitz, L. Chem. Mater. 1989, 1, 114. (b) Staab, E.; Addadi, L.; Leiserowitz, L.; Lahav, M. AdV. Mater. 1990, 2, 40. (18) http://www.oxford-diffraction.com. (19) (a) Sheldrick, G. SHELXS-97, Program for the Solution of Crystal Structures; University of Go¨ttingen: Germany, 1997. (b) Sheldrick, G. SHELXL-97, Program for the Refinement of Crystal Structures; University of Go¨ttingen: Germany, 1997. (20) Marder, S. R.; Perry, J. W.; Yakymyshyn, C. P. Chem. Mater. 1994, 6, 1137. (21) Yang, Z.; Aravazhi, S.; Schneider, A.; Seiler, P., Jazbinsek, M.; Gu¨nter, P. AdV. Funct. Mater. 2005, 15, 1072. (22) Kurtz, S. K.; Perry, T. T. J. Appl. Phys. 1968, 39, 3798.

CG060293T