Article pubs.acs.org/crystal
Intermolecular Interactions and Second-Harmonic Generation Properties of (E)‑1,5-Diarylpentenyn-1-ones Published as part of the Crystal Growth & Design Mikhail Antipin Memorial virtual special issue Anna V. Vologzhanina,*,† Alexandr A. Golovanov,‡ Dmitry M. Gusev,‡ Ivan S. Odin,‡ Ruben A. Apreyan,§ and Kyrill Yu. Suponitsky† †
A. N. Nesmeyanov Institute of Organoelement Compounds RAS, 28 Vavilova str., 119991 Moscow, Russian Federation Togliatti State University, 14 Belorusskaya str., 445667 Togliatti, Russian Federation § Institute of Applied Problems of Physics, NAS of Armenia, 25 Nersessyan Str., 0014 Yerevan, Armenia ‡
S Supporting Information *
ABSTRACT: Investigation of crystal structures of eight quasiplanar (E)-1,5-diarylpentenyn-1-ones has been carried out. Five of these compounds crystallize in chiral space groups. Intermolecular interactions responsible for the loss of planarity and steric hindrances that prevent molecules to form centrosymmetric dimers were suggested to be the reasons of the crystallization in chiral groups. Intermolecular bonding has been investigated by means of the Hirshfeld surfaces, and the role of the C−H···O interactions as driving force for crystal structure formation has been demonstrated. Three types of C−H···O bonded synthons have been suggested for this family. Those synthones are found to be in accordance with the charge distribution along the conjugated system estimated with natural population analysis. Nonlinear optical (NLO) properties for five (E)-1,5-diarylpent-2-en-4-yn-1-ones crystallizing in chiral space groups have been investigated both theoretically and experimentally. It was shown that crystalline NLO susceptibility of the Br-derivative is comparable to such an NLO material as N-(4-nitrophenyl)-L-prolinol. The crystal packing effects on calculated NLO properties have been estimated based on the recently proposed Charge Model. Second-harmonic generation measurements of selected (E)-1,5-diarylpent-2-en-4-yn-1-ones confirmed a validity of the Charge Model and demonstrated an efficiency of this family for potential application as materials for nonlinear optics.
1. INTRODUCTION Materials based on compounds that crystallize in acentric and chiral space groups attract an ongoing interest due to their practical meaning. They are prospective for applications in nonlinear optics (NLO),1−6 asymmetric heterogeneous catalysis,7−11 selective separation of (stereo)isomers,11,12 etc. Application of chiral molecules or ligands in the synthesis to obtain chiral materials is an obvious but rather expensive solution, and many efforts have been directed to the synthesis of acentric crystals from achiral ligands. The number of papers devoted to the synthesis of acentric metal−organic crystals from achiral ligands has increased drastically by now. The main reason is the stability of the coordination ability of a node and ligating properties of a ligand, which allow rather reliable prediction of a structure for a compound with selected composition. The ability of achiral small molecules to crystallize in an acentric space group in this case becomes much more intriguing, because the appearance of a given chiral motif based on hydrogen bonding, specific or nonspecific interaction, is unreliable and can be handicapped by the appearance of solvatomorphism or polymorphism. Thus, investigation of factors that enable a family of molecules to crystallize in acentric © 2014 American Chemical Society
or chiral space groups is of great practical and theoretical importance. The presence of the carbonyl group, long conjugated chain, and possibility to functionalize the chain with different donor/ acceptor groups makes the family of arylsubstituted planar (or quasiplanar) alken-1-ones and polyen-1-ones a promising candidate for potential NLO application. Relatively high melting points observed for this family are also advantageous. For instance, synthetic procedures to obtain chalcones (1) are well-known, and a number of their derivatives crystallizes in acentric space groups. Moreover, the chalcone,12,13 4methylchalcone,14 and 3-hydroxychalcone15,16 unambiguously justify possibility of alkenones to form both centric and acentric polymorphs. Investigation of crystal structures of chalcones collected from the Cambridge Structural Database17 revealed that in the absence of the hydroxide or carboxylic group, the C−H···O bonded motifs include synthones (i−iv) (Figure 1). The dimers Received: April 14, 2014 Revised: July 12, 2014 Published: July 15, 2014 4402
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quasiplanar ketones one should try to avoid formation of the C−H···O bonded dimers. It is well-known that the presence of the Ar−CC fragment in a quasiplanar molecule promotes it to adopt a nonplanar, chiral conformation, because of low conjugation between alkyl chain and aryl substituent.20 Elongation of the conjugated chain would hinder formation of dimer structures of type (ii). Thus, we assumed the family of (E)-1,5-diarylpentenyn-1-ones 2 and 3 to be prospective to obtain acentric crystals with secondharmonic generation (SHG) properties.
The synthesis of (E)-1,5-diphenylpent-4-en-2-yn-1-one (3a) was described by Iman et al.,21 although the X-ray investigation has not been carried out. Recently, Golovanov et al.22 synthesized a number of 1,5-diarylpent-2-en-4-yn-1-ones (2) in good yields (up to 90%). These were found to be stable at room temperature with the exception of the furyl-containing compound and characterized by high melting temperatures. X-ray investigation of 2a, 2d, and 2g confirmed that they crystallize in chiral space groups (P212121 and P21).22,23 Herein we discuss features of the crystal structure of seven (E)-1,5diarylpent-2-en-4-yn-1-ones (2a−g) and (E)-1,5-diphenylpent4-en-2-yn-1-one (3a), five of which crystallize in chiral space groups. For these compounds, NLO characteristics were calculated to estimate the potential ability of this family to generate second harmonic. For the most promising candidates (2d and 2g), SHG measurements were carried out, which confirmed their NLO efficiency.
Figure 1. Types of intermolecular interactions observed in the structures of chalcones: schematic representation and molecular view of C−H···O bonded dimers in (i) (E)-1-(4-methoxyphenyl)-3-(3,4,5trimethoxyphenyl)prop-2-en-1-one,18 and in (ii) chalcone (centric polymorph),12 schematic representation and molecular view of C−H···O bonded chains in (iii) calcone (acentric polymorph),12 and in (iv) 4,4′dimethylchalcone.19
2. EXPERIMENTAL SECTION 2.1. Synthetic Procedures. Details of synthetic procedures, 1H and 13C NMR data, elemental analysis, FTIR spectra of 2, and crystal structures of 2a, 2d, and 2g are described earlier.22 (E)-1,5-Diphenylpent-4-en-2-yn-1-one (3a) was prepared by the oxidation of (E)-1,5-diphenylpent-4-en-2-yn-1-ol with active γmanganese oxide in acetone. Carbinol was synthesized by reaction of benzaldehyde with a (E)-1-phenylbut-1-en-3-ynylmagnesium bromide (Iotsich reagent) in a solution of ether.
(i) and (ii) are obtained through an inversion center, so that corresponding compounds crystallize in centric space groups (formation of dimers through the π-stacking and C−H··· π interactions for such conjugated systems is also possible). Alternative C−H···O bonded motifs include formation of infinite chains by means of interactions with (iii) a hydrogen atom of Ar2 moiety, or (iv) with a hydrogen atom of the double bond (formation of the head-to-tail motif). Such chains are observed in both acentric and centric crystals. Therefore, in order to obtain chiral material from highly conjugated
(E)-1,5-Diphenylpent-4-en-2-yn-1-one (3a). To a stirring solution of 0.1 mol of ethylmagnesium bromide (0.1 mol) in 100 mL of anhydrous diethyl ether under cooling was added dropwise solution of (E)-(but-3-en-1-yn-4-yl)benzene (12.5 g, 0.1 mol) in 50 mL of ether. The reaction mixture refluxed for 2 h. Fresh distilled benzaldehyde 4403
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Table 1. Crystallographic Data and Refinement Parameters empirical formula fw color, habit crystal size (mm3) radiation (λ) a (Å) b (Å) c (Å) β (deg) V (Å3) Z crystal system space group dcalc (g·cm−3) μ (mm−1) independent reflections (Rint) obs. refl. /restraints/parameters R,a % [I > 2σ(I)] Rw,b % GOFc F(000) Hooft/Flack a
2b
2c
2e
2f
3a
C18H14O 246.29 colorless, needle 0.32 × 0.09 × 0.07 Cu Kα (1.54178) 5.7118 (2) 15.0846 (4) 15.2666 (4) 90 1315.37 (7) 4 orthorhombic P212121 1.244 0.587 1282 (0.023) 1241/0/173 0.029 0.079 1.00 520 0.1(1)/0.1(1)
C18H14O2 262.29 yellow, needle 0.53 × 0.09 × 0.08 Mo Kα (0.71073) 5.402 (3) 14.878 (8) 16.625 (10) 90 1336.0 (13) 4 orthorhombic P212121 1.304 0.084 2624 (0.058) 1801/0/182 0.048 0.095 1.00 552 −0.1(17)/−1.9(8)
C19H16O 260.32 colorless, plate 0.28 × 0.12 × 0.03 Cu Kα (1.54178) 15.1645 (5) 5.5972 (2) 16.6520 (5) 92.678 (2) 1411.87 (8) 4 monoclinic P21/c 1.225 0.573 2377 (0.053) 2048/0/183 0.036 0.091 1.00 552
C18H13ClO 280.73 colorless, plate 0.42 × 0.27 × 0.03 Cu Kα (1.54178) 14.2242 (7) 5.7666 (3) 34.8348 (16) 90 2857.3 (2) 8 orthorhombic Pbcn 1.305 2.288 2504 (0.074) 2019/0/182 0.055 0.143 1.00 1168
C17H12O 232.27 colorless, needle 0.54 × 0.09 × 0.09 Mo Kα (0.71073) 15.186 (2) 10.284 (1) 16.045 (2) 90 2506.0 (5) 8 orthorhombic Pbca 1.231 0.075 2734 (0.050) 2033/0/163 0.042 0.100 1.01 976
R = Σ ||Fo| − |Fc|| / Σ |Fo|. bRw = [Σ(w(Fo2 − Fc2)2)/Σ(w(Fo2))]1/2. cGOF = [Σw(Fo2 − Fc2)2/(Nobs − Nparam)]1/2.
(11.7 g, 0.11 mol) was added dropwise to the obtained solution of (E)-1-phenylbut-1-en-3-ynylmagnesium bromide (Iotsich reagent) under vigorous stirring. After 12 h, the reaction mixture was treated with saturated solution of ammonium chloride (150 mL) and ethereal layer was separated. Aqueous layer was extracted with diethyl ether (3 × 50 mL) and added to a ethereal layer. The ether solution was washed with 5% sodium carbonate solution and water and dried with magnesium sulfate. Ether was removed under a vacuum, and residue was dissolved in acetone (200 mL) and treated with active γmanganese oxide (90 g, 1 mol) for 4 h. After that, γ-manganese oxide was filtrated and washed with acetone, and extract was combined with the acetone solution of residue. Acetone was removed under a vacuum, and remaining oil was crystallized from aqueous ethanol. The single crystal was recrystallized from methanol solution. M.p. 338−339 K (Iman et al. data21 is 341 K). IR (KBr), ν/cm−1: 3058, 3033, 3012, 2180, 1632, 1606, 959, 935. 1H NMR (400 MHz, CDCl3, 303 K): δ = 6.38 (d, 1H, J = 16.2), 7.33−8.20 (m, 11H). 13C NMR (100 MHz, CDCl3, 303 K): δ = 89.1, 93.1, 105.4, 127.1, 128.7, 129.1, 129.7, 130.3, 134.2, 135.3, 137.0, 148.0, 178.0. Anal. Calcd for C17H12O, %: C, 87.89; H, 5.26. Found, %: C, 87.75; H, 5.63. 2.2. Single-Crystal Structure. X-ray diffraction data were collected at T = 100 K with Bruker APEX II CCD diffractometer using Mo Kα (graphite monochromator) or Cu Kα (microfocus tube with multilayer optics) radiation. The structures were solved by the direct method and refined by full-matrix least-squares method against F2 of all data, using SHELXTL24 and OLEX225 software. Nonhydrogen atoms were found on difference Fourier maps and refined with anisotropic displacement parameters. The positions of hydrogen atoms were calculated and included in refinement in isotropic approximation by the riding model with the Uiso(H) = 1.5Ueq(Ci) for methyl groups and 1.2Ueq(Cii) for other atoms, where Ueq(C) are equivalent thermal parameters of parent atoms. Details of data collection and refinement are listed in Table 1. Molecular views of investigated compounds in representation of atoms with thermal ellipsoids are given as Supporting Information (Figure 1S). Specific features of intermolecular interactions were investigated by means of the Hirshfeld partitioning26−28 using the CrystalExplorer3.029 software. A range of 1.0 (red) and 2.5 (blue) for mapping de on the Hirshfeld surfaces was employed; shape index is mapped between −1.0 (red) and +1.0 (blue) and curvedness varies from −4.0 (red) to
Table 2. Selected Geometrical Parameters of Molecules 2a−g, 3a (Å, °) and Molecular Hyperpolarizabilities (in au × 103) as obtained for X-ray (βX-Ray) and Optimized (βM052X) Molecular Geometry within M052X/6-31+G(d) Approximationa
experimental geometry 2a 2b 2c 2d 2e 2f 2g 3a
βX‑ray
βM052X
0 5.0 0 4.8
2.8 2.1 2.0 1.6
3.0 2.5 1.9 1.9
6.2
3.0
4.2
optimized geometry
α1
α2
α1
α2
6.2 8.5 2.6 1.7 14.7 19.1 19.9 7.7
10.8 26.5 10.5 69.4 22.1 18.9 33.0 15.8
0 14.0 0 11.6
14.1
a The atom numbering and the α1 and α2 angles (the angles between O1−C1−C2−C3 central fragment and phenyl cycles) are depicted in the scheme above.
+0.4 (blue). Colors in 2D fingerprint plots range from blue (few points) to red (many points). 2.3. SHG Properties. NLO activity was measured by the modified powder technique30 with the setup described in detail earlier,31 using a pulsed YAG:Nd laser with passive Q-switching (duration of pulses 20 ns, repetition rate 8 Hz) operating at 1064 nm. 2.4. Computational Details. Geometry optimization and calculation of the molecular properties was carried out using the 4404
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Figure 2. Hirshfeld surfaces for pentenyn-1-ones. The molecules are shown with the Hirshfeld surface mapped with (a) de, (b) shape index, and (c) curvedness. Gaussian program.32 The atomic charges were obtained with the natural population analysis (NPA) method33 as implemented in the Gaussian program. The first hyperpolarizability tensor components (βijk) were calculated as the negative third derivatives of the energy (W) with respect to the applied field (E): ∂ 3W (E) βijk = − ∂Ei∂Ej∂Ek
The M052X/6-31+G(d) level of theory was used throughout this study. Both functional and basis set were successfully used earlier for calculations of conjugated molecules36−38 as well as for the study of intermolecular interactions.39−43
3. RESULTS AND DISCUSSION 3.1. Molecular and Crystal Structures of Compounds. Selected geometric parameters as well as the atom numbering scheme of ketones 2a−g and 3a are listed in Table 2. The bond lengths and angles for aryl moieties and Ar−C bonds coincide to normally observed.44 Deviation of the Ar1 and Ar2 moieties from the meanplane of the pentenyn-1-one fragment achieves 68° and provides an appearance of chirality for a molecule. The shortening of the single C3−C4 bond (it does not exceed 1.425(2) Å) and planar disposition of pent-2-en-4-yn-1-one moiety is indicative of delocalization of electron density along the alkyl chain. Although the molecules exhibit chirality due to nonplanar disposition of aryl rings, only five of eight compounds crystallize in a chiral space group. Hence, intermolecular interactions not only affect the conformation of the molecule but also influence on the possibility of these compounds to form chiral materials. Intermolecular interactions for these compounds
E=0
For static β, the Polar = EnOnly keyword was used, while dynamic β was calculated with the Polar = DCSHG keyword for 1064 nm wavelength. The crystalline nonlinear susceptibility was calculated according to the formula:34,35
dIJK =
1 f V L
Z
3
3
3
∑ [∑ ∑ ∑ n=1
n cos θiIn cos θjJn cos θkK βijk ]
i=1 j=1 k=1
were V is the unit cell volume, Z is the number of molecules per unit cell, cos θniI are the direct cosines of the angles between molecular and crystal coordinate systems, and f L is the local field correction factor (set here to be equal to 1 for simplicity), and βijk tensor components are taken either for isolated molecules, or for a molecule affected by intermolecular interactions. 4405
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Figure 3. Fingerprint plots of Hirshfeld surfaces for 2a−g, 3a.
one fragment and carbon atom of another fragment are equal to 3.4 and 3.3 Å in the former case, and 3.5 and 3.6 Å in the latter. The most common feature for all fingerprint plots is the presence of prominent “wings” that refer to C−H···π interactions, and “peaks” corresponding to C−H···O contacts (Figures 3and 2S). The former interactions appear at de = 1.1 Å − di = 1.7 Å, and de = 1.7 Å − di = 1.1 Å, although in the structures of 2d and 2g this area overlaps with (de; di) values that correspond to other types of intermolecular interactions. For example, additional sharp “wings” for 2g correspond to C−H···Br interactions. The “peaks” at de = 1.1 Å − di = 1.4 Å and de = 1.4 Å − di = 1.1 Å of 2D plots correspond to the C−H···O contacts. These contacts are elongated for halogen-containing
were investigated by means of the Hirshfeld surfaces and their 2D fingerplots. Figure 2 represents Hirshfeld surfaces for 2a−g, 3a. Although all compounds contain two aryl moieties in their composition, none of the surfaces exhibit features characteristic for aryl···aryl interactions (flat regions observed for curvedness and red and blue triangles on the same region of the shape index surface26). At the same time, the fingerprint plots indicate the presence of weak π···π interactions in the structures of 2d, 2e, and 2g (the light-blue/green regions at de = di ≈ 1.7 ÷ 2.0 Å, Figure 3 and Figure 2S). These π···π interactions appear between CC and Ar1 (2d and 2g) or CC and Ar2 moieties (2e and 2g, Figure 4). The shortest distances between the meanplane of 4406
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Figure 5. (a−c) Fragments of C−H···O bonded chains in the structures of 2a−c. Intermolecular contacts are depicted with dashed lines. Hydrogen atoms that do not take part in C−H···O bonding are omitted for clarity. Figure 4. Stacking molecules (a) 2d, (b) 2e, and (c) 2g. Hydrogen atoms are omitted for clarity.
important role. For instance, in the case of 2f, the Cl···Cl interactions are responsible for bonding between infinite C−H···O bonded chains (Figure 7b), and inversion centers are situated between halogen atoms. In 2g, the C−H···Br contacts connect C−H···O bonded chains into the layers (Figure 7c). To obtain better insight into the electronic properties of these systems, we have investigated NPA atomic charges for the molecules that crystallize in chiral space groups. Oxygen atoms bear negative charge (−0.57 to −0.58 e), while carbon atoms of the carbonyl group are strongly positive (0.54−0.55 e). The atomic charges of hydrogen atoms vary in a narrow range (0.24−0.27 e), but the charges accumulated at -Csp2-H groups are remarkably different and follow the expected electronic properties. Particularly, the charges of (CH) fragments of phenyl rings depend on the position and fall from the orthoposition (0.06−0.08 e) to para (0.02−0.03 e), and meta (
