Article pubs.acs.org/crystal
Unusual Twisting and Bending of Phenyltriene with Methylthiolated Biphenyl Sulfane Group in the Crystalline State Ji-Youn Seo,† Mojca Jazbinsek,‡ Eun-Young Choi,†,# Seung-Heon Lee,† Hoseop Yun,§ Jong-Taek Kim,∥,⊥ Yoon Sup Lee,∥ and O-Pil Kwon*,† †
Department of Molecular Science and Technology, Ajou University, Suwon 443-749, Korea Rainbow Photonics AG, CH-8048 Zurich, Switzerland § Division of Energy Systems Research and Department of Chemistry, Ajou University, Suwon 443-749, Korea ∥ Department of Chemistry, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 305-701, Korea ⊥ Department of Basic Science, Korea Air Force Academy, Cheongju 363-849, Korea ‡
S Supporting Information *
ABSTRACT: We report a series of π-conjugated phenyltriene analogous molecules and crystals having different thiolated building blocks, which significantly influence the molecular ordering in the crystalline state. Whereas a polyene crystal having the methylthiolated phenyl (SM) building block exhibits a zigzag molecular ordering based on head-to-tail hydrogen bonds, the crystals of other analogues having the biphenyl sulfane (SB) block exhibit isomorphic crystal structures with herringbone packing. In one of these isomorphic crystals having both SM and SB building blocks, the herringbone packing is accompanied with head-to-tail hydrogen bonds. As a result of such packing promoted by SM and SB building blocks, the rigid phenyltriene bridge shows an unusual twisting and bending conformation, which is accompanied with a significant change of physical properties, such as fluorescent, linear, and nonlinear optical properties in the solid state. different π-conjugated bridges may result in a change of the electronic transition properties of the crystals and is, therefore, important to understanding the macroscopic material properties. Recently, a series of π-conjugated polyene chromophores have been reported with very promising nonlinear optical properties for photonic applications.7,8,13 SB1 (2-(5,5-dimethyl3-(4-(phenylthio)styryl)cyclohex-2-enylidene)malononitrile; see Figure 1b) crystals having the SB block linked with the πconjugated triene bridge exhibit a herringbone structure.13 Here, in order to examine the packing characteristics of the SB building block in the crystalline state and the accompanying change of the physical properties, a series of analogous phenyltriene crystals having different thiolated building blocks, namely, the methylthiolated phenyl (SM) group, the biphenyl sulfane (SB) group, or the methylthiolated biphenyl sulfane (SBSM) group, are investigated (see Figure 1b). In contrast to the polyene crystals having the SM group, the investigated analogous crystals having the SB or SBSM groups all show isomorphic crystal structures based on the herringbone packing of SB blocks. Interestingly, in the isomorphic crystal with the SBSM block, the rigid π-conjugated phenyltriene bridge shows an unusual twisting and bending conformation, which is accompanied with a significant change of the physical
1. INTRODUCTION Macroscopic physical properties of organic materials depend on the nature of constituting molecules. In the crystalline state, the physical properties depend additionally on isomerization and molecular ordering of constituting molecules, which may be particularly important in the case of π-conjugated crystals. Conformational isomers induced by rotation, bending, and twisting of bonds often show large differences in electronic properties.1−3 Many π-conjugated polyene compounds possessing efficient π-electron delocalization characteristics4 have been widely investigated for photonic and optoelectronic applications.5−8 On the other hand, the influence of conformational variations of the polyene bridge on the physical properties has only been scarcely investigated. Molecular ordering of π-conjugated molecules in the crystalline state may also significantly affect the electronic transition properties, such as fluorescent and nonlinear optical properties.7−10 An interesting approach for predicting and controlling the molecular ordering in the crystalline state is using “supramolecular building blocks”, which often lead to similar supramolecular interactions and molecular packing in the crystalline states.11 Such a building block is, for example, the biphenyl sulfane (SB) group, which often leads to a herringbone packing structure in the crystalline state, even with coexisting strong hydrogen-bond donor and acceptor groups in the molecules (see Figure 1a).12−14 In the crystalline state, ordering of the electron-rich SB block13,14 linked with © 2013 American Chemical Society
Received: April 13, 2012 Published: January 17, 2013 1014
dx.doi.org/10.1021/cg301625d | Cryst. Growth Des. 2013, 13, 1014−1022
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Article
(2-(5,5-Dimethyl-3-(4-(4-(methylthio)phenylthio)styryl)cyclohex2-enylidene)malononitrile) (SBSM1). Yield: 40%. 1H NMR (CDCl3, 400 MHz, δ): 1.00 (s, 6H,−CH3), 2.36 (s, 2H, −CH2−), 2.41 (s, 3H, −SCH3), 2.50 (s,2H, −CH2−), 6.71 (s, 1H, −C−−CH−), 6.80−6.84 (d, J = 16 Hz, 1H, −CH−−CH−), 6.86−6.90 (d, J = 16 Hz, 1H,− CH−−CH−), 7.06−7.08 (d, J = 8.0 Hz, 2H, Ar−H), 7.12−7.14 (d, J = 8.0 Hz, 2H, Ar−H), 7.26−7.28 (d, J = 8.0 Hz, 2H, Ar−H). 13C NMR (CDCl3, 400 MHz, δ): 169.2, 153.7, 140.3, 139.8, 133.9, 133.5, 128.9, 128.7, 128.1, 127.1, 123.6, 113.6, 112.9, 43.3, 39.5, 32.3, 28.3, 15.8. Elemental analysis for C26H24N2OS2 Calcd: C, 72.86; H, 5.64; N, 6.54; S, 14.96. Found C, 72.05; H, 5.63; N, 6.12; S, 15.24. 2.2. Single X-ray Crystal Structures. The crystal structure of SB1 was previously reported;13 the other crystal structures for SM1, SB2, and SBSM1 compounds were determined by single-crystal X-ray analysis as listed below. SM1. C20H20N2S, Mr = 320.44, monoclinic, space group P21/c, a = 6.2408(5) Å, b = 17.2380(14) Å, c = 16.7115(16) Å, β = 91.427(3)°, V = 1797.2(3) Å3, Z = 4, T = 293(2) K, μ(MoKα) = 0.072 mm−1. Of 7125 reflections collected in the θ range of 3.51−23.12° using ω scans on a Rigaku R-axis Rapid S diffractometer, 3106 were unique reflections (Rint = 0.049, completeness = 99.8%). The structure was solved and refined against F2 using SHELX97,15 307 variables, wR2 = 0.1115, R1 = 0.0428 (Fo2 > 2σ(Fo2)), GOF = 0.968, and max/min residual electron density 0.332/−0.206 e·Å−3. CCDC-875566. SB2. C24H20N2S, Mr = 368.50, monoclinic, space group P21/n, a = 5.7277(3) Å, b = 43.616(2) Å, c = 8.0965(5) Å, β = 91.1839(17)°, V = 2022.2(2) Å3, Z = 4, T = 293(2) K, μ(MoKα) = 0.170 mm−1. Of 7125 reflections collected in the θ range of 3.13−23.99° using ω scans on a Rigaku R-axis Rapid S diffractometer, 3182 were unique reflections (Rint = 0.0605, completeness = 99.7%). The structure was solved and refined against F2 using SHELX97,15 307 variables, wR2 = 0.1739, R1 = 0.0541 (Fo2 > 2σ(Fo2)), GOF = 1.409, and max/min residual electron density 0.346/−0.201 e·Å−3. CCDC-875564. SBSM1. C26H24N2S2, Mr = 428.59, monoclinic, space group P21/n, a = 5.6649(2) Å, b = 44.2183(15) Å, c = 9.2378(4) Å, β = 97.1237(12)°, V = 2296.14(15) Å3, Z = 4, T = 290(1) K, μ(MoKα) = 0.072 mm−1. Of 22 587 reflections collected in the θ range of 3.20−27.48° using ω scans on a Rigaku R-axis Rapid S diffractometer, 5259 were unique reflections (Rint = 0.0302, completeness = 99.8%). The structure was solved and refined against F2 using SHELX97,15 307 variables, wR2 = 0.1209, R1 = 0.0434 (Fo2 > 2σ(Fo2)), GOF = 1.128, and max/min residual electron density 0.189/−0.280 e·Å−3. CCDC-875565. 2.3. Absorption and Fluorescence Measurements. The absorption and fluorescent spectra in methylene chloride solution were recorded by a JASCO V-550 and FP-6500 spectrometers, respectively. The absorption spectra in the solid state have been evaluated by measuring transmission through thin layers of ground crystalline powders using a Perkin-Elmer λ9 UV−visible spectrophotometer. Because of the large contribution of background powder scattering, the results have been normalized individually for each measurement. The exact shape of the absorption band measured like this depends on the powder size and thickness, but the position of the main absorption peaks does not vary considerably with powder preparation. The fluorescent spectra in the solid state were recorded by a homemade fluorescence spectrophotometer with OceanOptics NIRQuest 512 spectrometers at an excitation wavelength of 365 nm from a UV lamp.
Figure 1. (a) Examples of herringbone structures of biphenyl sulfane (SB) blocks in the crystalline state: N,N-dimethyl-4-(4nitrophenylthio)benzenamine and 4,4′-thiodiphenol from refs 12a and 12b, respectively. The shadow highlights the herringbone packing of SB blocks. (b) Chemical structures of the investigated phenyltriene analogues.
properties, such as fluorescent, linear, and nonlinear optical properties in the solid state.
2. EXPERIMENTAL SECTION 2.1. Synthesis. The synthesis of SM1 (2-(5,5-Dimethyl-3-(4(methylthio)styryl)cyclohex-2-enylidene)malononitrile) and SB1 compounds was previously reported.13 SB2 and SBSM1 compounds were synthesized in a similar manner according to the literature.13 2-(5-Methyl-3-(4-(phenylthio)styryl)cyclohex-2-enylidene)malononitrile (SB2). Yield: 35%. 1H NMR (CDCl3): 1.17 (s, 3H,− CH3), 2.11−2.19 (m, H, −CH−), 2.25−2.35 (m, 4H, −CH2−), 6.79 (s, 1H, −C−−CH−), 6.89−6.93 (d, J = 16 Hz, 1H, −CH−−CH−), 6.98−7.02 (d, J = 16 Hz, 1H,−CH−−CH−), 7.21−7.23 (d, J = 8.0 Hz, 2H, Ar−H), 7.33−7.42 (m, 7H, Ar−H). 13C NMR (CDCl3): 169.8, 155.3, 139.7, 136.3, 133.8, 133.7, 132.9, 129.7, 128.7, 128.3, 124.6, 124.6, 113.7, 112.9, 37.7, 33.8, 29.1, 21.4. Elemental analysis for C24H19N2S (%) Calcd: C, 75.34; H, 5.56; N, 7.03; S, 12.07. Found: C, 75.29; H, 5.54; N, 7.38; S, 8.89. 4-(4-(Methylthio)phenylthio)benzaldehyde. Yield: 70%. 1H NMR (CDCl3, 400 MHz, δ): 2.52 (s, 3H, −SCH3), 7.18 (d, 2H, J = 8.4 Hz, Ar−H), 7.26 (d, 2H, J = 8.0 Hz, Ar−H), 7.43 (d, 2H, J = 8.0 Hz, Ar− H), 7.69 (d, 2H, J = 8.0 Hz, Ar−H), 9.87 (1H, s, −CHO). 13C NMR (CDCl3, 400 MHz, δ): 191.2, 147.8, 141.1, 135.2, 133.6, 130.2, 127.0, 126.7, 126.5, 15.6.
3. RESULTS AND DISCUSSION 3.1. Design of Polyene Analogues. Figure 1b shows the chemical structures of the investigated polyene analogues. The SB1 molecule has been previously reported13 and consists of the hexatriene bridge linked between the biphenyl sulfane (SB) and dicyano groups. To investigate the packing characteristics, we modified the chemical structure of SB1 slightly: instead of two methyl groups on the non-π-conjugated part of the cyclohexene, only one methyl group is introduced for the SB2 molecules (see Figure 1b). Such a modification of polyene 1015
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molecules with the dicyanomethylidene electron acceptor often leads to a considerably different crystal packing; for example, phenolic polyene analogues having a different number of methyl groups on the cyclohexene ring showed different crystal structures with monoclinic Cc and orthorhombic Pna21 space group symmetries.8a,b For comparison, the analogous polyene SM1 chromophore having a methylthiolated phenyl (SM) group13 is also characterized. To extend our hypothesis, we newly designed a bigger polyene analogous SBSM1 chromophore possessing the methylthiolated biphenyl sulfane (SBSM) group, which has both SM and SB building blocks in the electron-donor part of the molecule. 3.2. Single-Crystal Structure. For analyzing the X-ray single-crystal structures, single polyene crystals are grown in solution. SM1 single crystals are grown by a rapid cooling method in methanol. SB2 single crystals are grown by a slow evaporation method at 35 °C in acetonitrile solution, similarly as SB1 crystals reported previously.13 SBSM1 single crystals are also grown by a slow evaporation method at 40 °C in methanol. We have newly analyzed the crystal structures of SM1, SB2, and SBSM1 crystals in this work, whereas the SB1 crystal structure has been previously reported.13 Whereas SM1 crystals exhibit monoclinic P21/c space group symmetry, SB1, SB2, and SBSM1 crystals exhibit monoclinic P21/n space group symmetry. The crystallographic details are described in the Experimental Section and are listed in Table 1. Table 1. Summary of Crystallographic Data for the Investigated Polyene Crystals formula formula wt cryst syst space group a (Å) b (Å) c (Å) α (deg.) β (deg.) γ (deg.) V (Å 3) Z
SM1
SB113
SB2
SBSM1
C20H20N2S 320.44 monoclinic P21/c
C25H22N2S 382.53 monoclinic P21/n
C24H20N2S 368.50 monoclinic P21/n
C26H24N2S2 428.59 monoclinic P21/n
6.2408(5) 17.2380(14) 16.7115(16) 90 91.427(3) 90 1797.2(3) 4
5.9245(4) 45.446(3) 7.7993(6) 90 94.178(2) 90 2094.3(2) 4
5.7277(3) 43.616(2) 8.0965(5) 90 91.1839(17) 90 2022.2(2) 4
5.6649(2) 44.2183(15) 9.2378(4) 90 97.1237(12) 90 2296.14(15) 4
Figure 2. Crystal packing diagrams of SM1 crystals along the crystallographic a axis. The dotted lines present hydrogen bonds (
