Versatility in Complexation of Aprotic Guest Molecules by Terphenyl

Article pubs.acs.org/crystal

Versatility in Complexation of Aprotic Guest Molecules by Terphenyl-Based Bisfluorenol Hosts. Structural Modes in the Crystalline Inclusions and of a Guest-Free Host Compound Henrik Klien, Wilhelm Seichter, and Edwin Weber* Institut für Organische Chemie, Technische Universität Bergakademie Freiberg, Leipziger Strasse 29, D-09596 Freiberg, Sachsen, Germany S Supporting Information *

ABSTRACT: Crystalline inclusion compounds of diol hosts 1 and 2 typical of a basic 2,2″-[1,1′:4′,4″]-terphenyl moiety with two attached 9-fluorenol or tertbutyl-substituted 9-fluorenol units and a variety of aprotic guest molecules have been prepared and studied with reference to their crystal structures. Common and differing structural features among one another and including previously described host−guest complexes of 1 and 2 with protic instead of aprotic guest species are distinguished, indicating potential uses in promising supramolecular inclusion formation and underscoring solvent inclusion.

■

INTRODUCTION The design of crystalline inclusion compounds1−4 is one of the most promising challenges in supramolecular chemistry,5 including the field of crystal engineering,6−8 because of the potential use in a variety of fundamental and practical issues such as compound separation and storage.9−12 Host compounds allowing this behavior pattern have been developed in various kinds of structural types adhering to particular lines of structural design.13−16 One of these has given rise to a prototype host molecule featuring two 9-hydroxy-9-fluorenyl residues attached at positions 2 and 2′ to a biphenyl unit,17 being distinguished by a wide-ranging property of inclusion formation.18 Nevertheless, as a characteristic of all the structures of the respective inclusion compounds, an intramolecular hydrogen bond between the host hydroxy groups is found exercising an obvious influence on the host−guest interaction. To eliminate this internal mode of binding, a change in the central 2,2′-biphenyldiyl unit for an elongated 2,2″-[1,1′:4′,1″]-terphenyldiyl unit, as presented with compounds 1 and 2 (Scheme 1), has recently been considered as a powerful method for the conformational alteration of the host molecule.19 Implicated by this operation, correspondingly modified inclusion structures have been obtained, showing 2fold proton donor behavior of the host molecules with a preferred 1:2 host:guest stoichiometric ratio in complex formation and clearly different packing modes in the range of protic guest inclusions, i.e., infinite-chain type hydrogenbonded host−guest association versus discrete hydrogenbonded host−guest units as for the prototype compound.20,21 As an extension of ref 19, we became interested in the ability of 1 and 2 with regard to their complexation with aprotic guest molecules in a crystalline state. Hence, we now report our © 2014 American Chemical Society

results obtained from a corresponding inquiry, including a description of no fewer than nine different crystal structures of respective inclusion compounds that involve complexes of 1 with 1,4-dioxane (1:2), acetone (1:1), and dimethylformamide (DMF) (1:2) (1a−c, respectively) and of 2 with tetrahydrofuran (THF) (1:2), 1,4-dioxane (1:2.5), acetone (1:2), ethyl acetate (1:1), DMF (1:1), and chloroform (1:2) (2a−f, respectively) (Scheme 1). As a supplement to the previous study, we also discuss the crystal structure of the unsolvated host compound 2 that, after all, has now been determined.

■

RESULTS AND DISCUSSION Host Synthesis. Host compounds 1 and 2 were prepared following a synthetic route described previously.19,22 Inclusion compounds 1a−c and 2a−f were obtained by recrystallization of 1 and 2, respectively, from the respective solvents. X-ray Structural Study. To gain more information about the ability of 1 and 2 to form complexes with aprotic guest molecules, a number of crystalline host−guest inclusion compounds involving a broad range of aprotic solvents with different shapes and polarities were studied via X-ray structural analysis. They refer to the inclusions of 1 formed with 1,4dioxane (1:2, 1a), acetone (1:1, 1b), and DMF (1:2, 1c) and the inclusions of 2 with THF (1:2, 2a), 1,4-dioxane (1:2.5, 2b), acetone (1:2, 2c), ethyl acetate (1:1, 2d), DMF (1:1, 2e), and chloroform (1:2, 2f). Growing crystals of the solvent-free hosts suitable for an X-ray structural study failed for a long time. Received: April 11, 2014 Revised: July 2, 2014 Published: July 30, 2014 4371

dx.doi.org/10.1021/cg500497g | Cryst. Growth Des. 2014, 14, 4371−4382

Crystal Growth & Design

Article

Scheme 1. Formulae of Compounds Studied in This Paper

Figure 1. Representation of the framework structure of 1 and 2, including atom numbering and ring specification. This molecule was extracted from the crystal structure of 1a. Dashed lines represent hydrogen bonds, while π···π interactions are marked by dashed double lines.

forces explain the strong twist between the rings of the terphenyl unit [∠mpln(B)···mpln(C) = 71.3(1)−87.3(1)°]. In the crystal structures, only one half of the host molecule is crystallographically unique, with the other half being symmetry-generated. In those cases in which the molecules adopt inversion symmetry, the outer rings of the terphenyl part as well as the fluorenyl units are strictly coplanar. In the case in which the molecule is located on a 2-fold symmetry axis (2e), the molecular structure adopts a distortion along the terphenyl element and an arrangement of fluorenyl residues deviating from coplanarity. Packing Structures. The 1:2 inclusion compound of 1 with 1,4-dioxane (1a) crystallizes in monoclinic space group P21/n. The asymmetric part of the unit cell contains one half of the host and one molecule of dioxane that is associated with a strong hydrogen bond [O(1)−H(1)···O(1A), 2.05 Å, 166°] to the hydroxy group of the host molecule (Figure 2a). The second oxygen of the dioxane is situated in a way that it is not able to participate in a strong hydrogen bond. The crystal structure of 1a is composed of 1:2 complex units (Figure 6a) that are further associated with hydrogen bonds of the C−H···O type23 [C(3)−H(3)···O(1), 2.65 Å, 132°] and weak C−H···π contacts25 [C(9)−H(9)···C(2), 2.75 Å, 141°]. Crystallization of 1 from acetone yields a 1:1 inclusion complex (1b) in space group P1̅ with the unit cell containing two crystallographically independent host molecules and two molecules of acetone; i.e., the host molecules are located on symmetry centers (Figure 2b). According to the distinctive acceptor activity of the guest species, the crystal structure of 1b is constructed of infinite O−H···O bonded strands of host molecules [O(1A)−H(1A)···O(1), 2.00 Å, 165°] extending along the cell’s body diagonal with a lateral attachment of guest molecules [O(1)−H(1)···O(1B), 1.82 Å, 166°] (Figure 6b). The oxygen of acetone acts as a bifurcated acceptor as it is in contact with one of the methyl hydrogens of a symmetryrelated guest molecule [C(3B)−H(3B1)···O(1B), 2.40 Å, 167°], thus creating a cyclic C−H···O bonded structure motif of graph set R22(8) according to Etter’s definition.26,27 The 1:2 complex of 1 with DMF (1c) crystallizes in monoclinic space group P21/c with the asymmetric part of the

Finally, we succeeded with 2, which allowed us to describe and coherently discuss its structure (below). Crystal and refinement data for the studied compounds are summarized in Table 1. The conformation of the host molecules can be depicted best by the calculation of interplanar angles between the aromatic fragments. These geometric parameters together with relevant distances and torsion angles are listed in Table 2. Information regarding noncovalent interactions in the crystals is given in Table 3. The numbering scheme of the molecular backbone of 1 and 2 is presented in Figure 1. To simplify the structural characterization, the rings of the molecules are marked by capital letters (A−C) in the illustrations of the molecular structures (Figures 2−5). The packing diagrams are presented in Figures 6−9. Molecular Structures. As is evident from the geometrical parameters listed in Table 2, host molecules 1 and 2 reveal restricted conformational flexibility that is reflected by similar dihedral angles between the plane molecular parts. Obviously, the presence of two 9-fluoren-2-ol units attached at positions 2 and 2″ of the terphenyl element induces a “folded” molecular geometry that is stabilized by two types of intramolecular interactions (Figure 1). That is, in all crystal structures, the OH oxygens of the host molecule form relatively strong hydrogen bonds of the C−H···O type23 [d(H···O) = 2.22−2.28 Å; ∠(C− H···O) = 104° and 105°], which enforces a nearly orthogonal orientation of the fluorenyl parts with respect to the terphenyl rings to which they are connected (Figures 2−5). The interplanar angles between these molecular fragments range from 79.0(1)° to 87.8(1)°. Moreover, the location of the central terphenyl ring between the fluorenyl moieties [centerto-center distances (A′/C) of 3.454(3)−3.615(2) Å and interplanar angles (A/C) of 15.8(2)−22.3(1)°] suggests the presence of π···π interactions.24 These cooperative intramolecular 4372


4373

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

empirical formula C44H30O2·2 C4H8O2 formula weight 766.89 crystal system monoclinic space group P21/n a (Å) 9.9877(2) b (Å) 15.4374(4) c (Å) 12.8383(3) α (deg) 90.0 β (deg) 96.610(1) γ (deg) 90.0 1966.30(8) V (Å3) Z 2 F(000) 812 1.295 Dc (μg m−3) 0.084 μ (mm−1) data collection temperature (K) 100(2) no. of reflections collected 13389 within the θ limit (deg) 2.1−27.4 index ranges (±h, ±k, ±l) −12/12, −19/16, −16/13 no. of unique reflections 4447 0.0285 Rint refinement calculations, full-matrix leastsquares on all F2 values σ2(Fo2) + (0.0465P)2 + weighting expression wa (0.5783P)−1 no. of refined parameters 263 no. of F values used [I > 2σ(I)] 3432 final R indices 0.0389 R (=∑|ΔF|/∑|Fo|) 0.0993 wR on F2 1.013 S (goodness of fit on F2) 0.32/−0.28 final Δρmax/Δρmin (e Å−3)

1a C60H62O2·2.5 C4H8O2 1035.36 triclinic P1̅ 10.9784(5) 14.2909(6) 19.6702(9) 98.144(2) 95.506(2) 107.769(2) 2877.3(2) 2 1116 1.195 0.075

2b C60H62O2·2C3H6O 931.25 triclinic P1̅ 10.6432(3) 11.3772(3) 22.7292(7) 80.527(1) 80.408(1) 87.917(2) 2676.68(13) 2 1004 1.155 0.070

2c

0.0500 0.1361 1.024 0.48/−0.42 C60H62O2·C4H8O2 903.20 triclinic P1̅ 10.8003(6) 11.0836(6) 24.7588(13) 89.734(3) 95.506(3) 63.611(2) 2583.8(2)

0.0383 0.1060 0.997 0.37/−0.27 2d

σ2(Fo2) + (0.0571P)2 + (0.6442P)−1 256 3630 0.0497 0.1653 1.024 0.43/−0.26

0.0551 0.1354 1.003 0.30/−0.25 2e

σ2(Fo2) + (0.0517P)2 + (0.8994P)−1 663 7809

C60H62O2·C2H7NO 888.19 monoclinic C2/c 26.9959(12) 24.2344(11) 18.7233(8) 90.0 120.515(1) 90.0 10552.8(8)

σ2(Fo2) + (0.0893P)2 + (0.5623P)−1 573 7535

0.0544 0.1590 0.937 0.32/−0.49

σ2(Fo2) + (0.0895P)2 + (0.4738P)−1 715 7589

2f C60H62O2·2 CHCl3 1053.83 monoclinic P21/c 10.2087(2) 11.8640(2) 22.6390(4) 90.0 98.310(1) 90.0 2713.16(8)

0.0588 0.1630 1.015 0.54/−0.52

σ2(Fo2) + (0.0774P)2 + (2.4622P)−1 648

C60H62O2·2C4H8O 959.30 triclinic P1̅ 10.6569(2) 11.2177(3) 23.0926(5) 79.945(1) 80.684(1) 87.827(1) 2682.24(11) 2 1036 1.188 0.072

2a

σ2(Fo2) + (0.0616P)2 + (0.9700P)−1 455 6496

C60H62O2 815.10 triclinic P1̅ 11.6011(4) 13.1095(5) 15.2093(5) 88.122(2) 87.395(2) 84.615(2) 2299.50(14) 2 876 1.177 0.069

2

100(2) 47771 0.9−27.6 −13/13, −14/14, −29/29 12372 0.0228

C44H30O2·2C3H7NO 736.87 monoclinic P21/c 13.9048(3) 13.6994(3) 10.1484(2) 90.0 93.781(1) 90.0 1928.93(7) 2 780 1.269 0.080

1c

100(2) 100(2) 100(2) 100(2) 100(2) 31802 14745 41986 50323 42463 2.5−28.4 1.5−27.4 1.6−28.1 0.9−27.8 2.1−27.2 −13/15, −17/17, −16/17 −18/17, −17/17, −13/13 −15/14, −17/17, −20/20 −13/13, −14/14, −26/30 −14/7, −16/18, −25/25 8478 4361 11187 12664 12410 0.0287 0.0221 0.0491 0.0642 0.0536

C44H30O2·C3H6O 648.76 triclinic P1̅ 11.3706(2) 13.0603(3) 13.1504(3) 97.421(1) 107.212(1) 109.961(1) 1694.76(6) 2 684 1.271 0.078

1b

Table 1. Crystallographic and Structure Refinement Data of the Compounds Studied

Crystal Growth & Design Article


4374

a

P = (Fo2 + 2Fc2)/3.

no. of refined parameters no. of F values used [I > 2σ(I)] final R indices R (=∑|ΔF|/∑|Fo|) wR on F2 S (=goodness of fit on F2) final Δρmax/Δρmin (e Å−3)

Z F(000) Dc (μg m−3) μ (mm−1) data collection temperature (K) no. of collected reflections within the θ limit (deg) index ranges (±h, ±k, ±l) no. of unique reflections Rint refinement calculations, full-matrix least-squares on all F2 values weighting expression wa

Table 1. continued 8 3824 1.118 0.067 100(2) 63721 2.1−29.1 −35/36, −32/33, −25/22 14160 0.0346

σ2(Fo2) + (0.0841P)2 + (6.6336P)−1 647 10233 0.0486 0.1534 1.013 0.40/−0.30

100(2) 41105 0.9−27.3 −13/13, −13/14, −31/31 11375 0.0505

σ2(Fo2) + (0.1029P)2 + (0.0000P)−1 660 7240 0.0546 0.1726 1.000 0.43/−0.33

2e

2 972 1.161 0.070

2d

0.0399 0.1022 1.018 0.56/−0.53

σ2(Fo2) + (0.0406P)2 + (1.8799P)−1 336 5429

100(2) 49675 1.8−28.5 −13/7, −15/15, −30/30 6785 0.0314

2 1108 1.290 0.360

2f



177.0(1)

−176.9(1) 93.9(1)

3.615(2) 3.612(2)

85.2(1) 82.5(1) 21.3(1)

84.2(1) 81.2(1) 20.3(2)

1b

3.489(2)

86.0(1) 81.7(1) 18.1(2)

1a

180.0(1)

3.513(2)

87.7(1) 87.3(1) 19.9(2)

1c

176.7(1)

−175.4(1)

3.479(2) 3.540(2)

82.9(1) 81.1(1) 17.6(2)

84.8(1) 80.5(1) 16.3(2)

2

174.4(2)

−177.6(3)

3.463(3) 3.476(3)

82.6(1) 79.5(1) 15.8(2)

87.8(1) 86.4(1) 17.5(2)

2a

176.2(2)

−179.7(2)

3.491(3) 3.454(3)

86.7(1) 85.2(2) 18.5(2)

86.6(1) 84.0(2) 17.6(2)

2b

177.4(1)

−172.9(1)

3.501(3) 3.501(3)

86.3(1) 86.3(1) 18.5(1)

82.0(1) 78.6(1) 18.0(1)

2c

165.8(2)

−169.9(2)

3.484(3) 3.479(3)

88.1(1) 86.0(1) 19.7(3)

87.2(1) 82.7(2) 17.3(2)

2d

150.7(1)

67.9(1)

3.516(2) 3.574(2)

79.0(1) 71.3(1) 22.3(1)

87.3(1) 84.1(1) 22.3(1)

2e

177.5(1)

3.544(2)

81.2(1) 76.4(1) 18.9(1)

2f

mpla means best plane through the aromatic units: ring A, C(1)−C(13); ring B, C(14)−C(19); ring C, C(20)−C(22) and C(20′)−C(22′); ring A′, C(1A)−C(13A); ring B′, C(14A)−C(19A); ring C′, C(20A)−C(22A) and C(20A′)−C(22A′). bMeans the center of the ring: ring A1, C(1), C(6), C(7), C(12), and C(13); ring C, C(20)−C(22) and C(20′)−C(22′); ring A1′, C(1A), C(6A), C(7A), C(12A), and C(13A); ring C′, C(20A)−C(22A) and C(20A′)−C(22A′).

a

dihedral angles (deg) mpla(A)/mpla(B) mpla(B)/mpla(C) mpla(A)/mpla(C) mpla C/mpla D mpla D/mpla E mpla C/mpla E mpla A′/mpla B′ mpla B′/mpla C′ mpla(A′)/mpla(C′) distances (Å)b centroid(C)···centroid(A1) centroid(C′)···centroid(A1′) torsion angles (deg) C(14)−C(13)−O(1)−H(1) C(31)−C(32)−O(2)−H(2) C(14A)−C(13A)−O(1A)−H(1A)

a

Table 2. Relevant Conformational Parameters of Diol Molecules 1 and 2 in Their Crystal Structures


4375



Article

Table 3. Noncovalent Interactions in the Studied Crystal Structures atoms (D−H···A)

symmetry

D···A distance (Å)

H···A distance (Å)

D−H···A angle (deg)

O(1)−H(1)···O(1A) C(15)−H(15)···O(1) C(3)−H(3)···O(1) C(9)−H(9)···C(2)a

x, y, z x, y, z −0.5 + x, 0.5 − y, −0.5 + z −0.5 + x, −0.5 + y, 1.5 − z

2.869(1) 2.673(2) 3.359(2) 3.537(3)

2.05 2.28 2.65 2.75

166 104 132 141

O(1)−H(1)···O(1B) O(1A)−H(1A)···O(1) C(3B)−H(3B1)···O(1B) C(15)−H(15)···O(1) C(15A)−H(15A)···O(1A) C(3)−H(3)···centroid(B′)b C(3A)−-H(3A)···centroid(B)b

x, −1 + y, z x, 1 + y, z 1 − x, 2 − y, −z x, y, z x, y, z 1 − x, 1 − y, 1 − z −x, 1 − y, −z

2.642(2) 2.820(2) 3.364(3) 2.627(2) 2.699(2) 3.776(3) 3.587(3)

1.82 2.00 2.40 2.23 2.29 2.88 2.67

166 165 167 104 105 157 162

O(1)−H(1)···O(1A) C(15)−H(15)···O(1) C(16)−H(16)···O(1A) C(17)−H(17)···C(9)a

x, y, 1 + z x, y, z 2 − x, −y, −z x, y, −1 + z

2.707(1) 2.628(2) 3.378(2) 3.640(3)

1.88 2.22 2.45 2.90

169 104 167 136

O(1)−H(1)···C(5A)a O(1A)−H(1A)···C(9)a C(15)−H(15)···O(1) C(15A)−H(15A)···O(1A)

x, x, x, x,

y, y, y, y,

3.372(2) 3.367(2) 2.632(2) 2.638(2)

2.65 2.58 2.24 2.25

146 157 104 104

O(1)−H(1)···O(1B) O(1A)−H(1A)···O(1C) C(15)−H(15)···O(1) C(15A)−H(15A)···O(1A)

x, x, x, x,

−1 + y, z y, z y, z y, z

2.853(2) 2.789(2) 2.650(2) 2.632(2)

2.02 1.95 2.25 2.24

173 175 104 104

O(1)−H(1)···O(1E) O(1A)−H(1A)···O(1B) C(4A)−H(4A)···O(1D) C(8A)−H(8A)···O(2D) C(15)−H(15)···O(1) C(15A)−H(15A)···O(1A)

x, y, z x, 1 + y, z 1 + x, 1 + y, z 1 − x, 1 − y, −z x, y, z x, y, z

2.823(2) 2.896(2) 3.370(3) 3.349(3) 2.643(2) 2.649(2)

1.99 2.06 2.53 2.45 2.24 2.25

169 174 148 158 104 104

O(1)−H(1)···O(1CA) O(1A)−H(1A)···O(1B) C(15)−H(15)···O(1) C(15A)−H(15A)···O(1A)

x, x, x, x,

2.884(4) 2.840(2) 2.626(2) 2.632(2)

2.05 2.01 2.23 2.23

173 172 104 104

O(1A)−H(1A)···O(1B) O(1)−H(1)···C(9)a C(16A)−H(16A)···O(2B) C(15)−H(15)···O(1) C(15A)−H(15A)···O(1A)

x, −1 + y, z 1 − x, −y, 2 − z −1 + x, y, z x, y, z x, y, z

2.727(3) 3.227(3) 3.518(3) 2.640(2) 2.624(3)

1.89 2.44 2.69 2.24 2.23

174 156 147 104 104

O(1)−H(1)···O(1A) O(1A)−H(1A)···O(1B) O(1A)−H(1A)···O(1BA) C(2B)−H(2B2)···O(1) C(15)−H(15)···O(1) C(15A)−H(15A)···O(1A) C(1B)−H(1B)··· centroid(A2′)b

0.5 − x, 0.5 − x, 0.5 − x, x, y, z x, y, z x, y, z 0.5 − x,

2.764(1) 2.678(2) 2.566(2) 3.422(2) 2.723(2) 2.631(2) 3.540(3)

1.92 1.87 1.75 2.53 2.33 2.24 2.67

178 159 165 152 104 104 153

O(1)−H(1)···C(9)a C(15)−H(15)···O(1) C(1A)−H(1A)···C(18)a C(1B)−H(1B)···C(17)a C(26)−H(26C)···Cl(3A) C(28)−H(28C)···Cl(3B)

1 − x, 1 − y, 1 − z x, y, z x, y, z x, y, z x, −1 + y, z 1 − x, 1 − y, 1 − z

3.219(3) 2.621(2) 3.600(3) 3.165(3) 3.834(3) 3.779(3)

2.48 2.22 2.63 2.25 2.88 2.87

147 104 163 156 164 155

1a

1b

1c

2 z z z z

2a

2b

2c y, z 1 + y, z y, z y, z

2d

2e −0.5 + y, 1.5 − z 0.5 − y, 1 − z 0.5 − y, 1 − z

0.5 − y, 1 − z

2f

a

To achieve a reasonable hydrogen bond geometry, we chose an individual atom instead of the ring center as an acceptor site. bCentroid means the center of the respective aromatic ring: ring A2′, C(1A)−C(6A); ring B, C(14)−C(19); ring B′, C(14A)−C(19A). 4376



Article

Figure 2. Illustration of the molecular structures of 1a (a), 1b (b), and 1c (c), including numbering of relevant atoms and ring specification. Oxygens are displayed as dotted circles and nitrogens as hatched circles. Dashed lines represent hydrogen bond interactions.

Figure 3. Illustration of the molecular structures of 2 (a), 2a (b), and 2b (c), including numbering of relevant atoms and ring specification. Oxygens are displayed as dotted circles. Broken lines represent hydrogen bond interactions.

unit cell containing one half of the host and one molecule of DMF (Figure 2c). The crystal of 1c is constructed of parallel supramolecular strands running along the crystallographic a-axis. Within a given strand, each solvent molecule is associated in an asymmetric fashion with two different host molecules by forming a strong hydrogen bond [O(1)−H(1)··· O(1A), 1.88 Å, 169°] and a weaker C−H···O hydrogen bond [C(16)−H(16)···O(1A), 2.45 Å, 167°]. According to the bifurcated coordination mode of the solvent oxygen, the host molecules are interlinked by pairs of solvent molecules, thus creating cyclic hydrogen bond motifs [R24(16) organized by the symmetry center] leading to a chain structure (Figure 6c). Interstrand association is accomplished by weak edge-to-face arene interactions28,29 [C(17)−H(17)···C(9), 2.90 Å, 136°]. As mentioned above, in the course of our experimental work, we were unsuccessful in growing good-quality crystals of 1 in a solvent-free state. Contrary to expectations,19 recrystallization of 2 from ethanol yields a solvent-free crystal structure in space

group P1̅ with two crystallographically independent molecules within the unit cell (Figure 3a). Because of the steric influence of the 2,7-disubstituted fluorenyl moieties, the crystal structure lacks strong hydrogen bonding. Instead, the OH groups are engaged in weak intermolecular O−H···π interactions23 with the fluorenyl units acting as acceptors. With this kind of intermolecular interaction taken into account, the crystal structure is composed of molecular chains extending along the direction of the body diagonal (Figure 7a). Neither other directed noncovalent bonding nor arene stacking is observed in the crystal structure of 2, so that interchain association is reduced to weak van der Waals forces. Crystals of 2a obtained from crystallization of 2 from THF are in space group P1̅ with the unit cell containing two crystallographically independent host molecules and four molecules of THF that are connected via hydrogen bonding to the OH groups of the host molecules [O(1)−H(1)···O(1B), 4377



Article

Figure 4. Illustration of the molecular structures of 2c (a) and 2d (b), including numbering of relevant atoms and ring specification. Oxygens are displayed as dotted circles. Broken lines represent hydrogen bond interactions.

that can be regarded as being constructed of O−H···O bonded 1:2 host−guest units [O(1A)−H(1A)···O(1B), 2.06 Å, 174°] that are further associated by pairs of solvent molecules via C−H···O hydrogen bonding [C(4A)−H(4A)··· O(1D), 2.53 Å, 148°; C(8A)−H(8A)···O(2D), 2.45 Å, 158°]. Both types of supramolecular strands extend parallel to the crystallographic a−b plane. Unlike that of 1b, crystallization of 2 from acetone gives a 1:2 solvent complex (2c) in space group P1̅ with the asymmetric part of the unit cell containing two halves of host molecules and two molecules of acetone, one of them being disordered over two positions (SOFs of 0.54 and 0.46) (Figure 4a). Obviously, the presence of bulky substituents in 2 weakens host−host association, so that the crystal structure of 2c is composed of discrete 1:2 complex units (Figure 8a). Crystals of 2·ethyl acetate (1:1) (2d) are in space group P1̅ with the asymmetric part of the unit cell containing two halves of host molecules and one molecule of solvent (Figure 4b). Because of the given host:guest stoichiometry, the packing structure of 2d is constructed of two different types of supramolecular aggregates (Figure 8b). Only one of the host molecules is engaged in formation of 1:2 host−guest units via O−H···OC hydrogen bonding [O(1A)−H(1A)···O(1B),

2.02 Å, 173°; O(1A)−H(1A)···O(1C), 1.95 Å, 175°] (Figure 3b). Consequently, the crystal structure of 2a is constructed of discrete 1:2 host−guest units (Figure 7b). As in the aforementioned case, the crystal structure appears to be stabilized by van der Waals forces. The 2:5 host:guest stoichiometric ratio in the inclusion structure of 2 with 1,4-dioxane (2b) (space group P1̅) indicates structural differences compared with 2a. The asymmetric part of the unit cell of 2b contains two halves of the host molecules and two complete molecules and one half-molecule of dioxane; i.e., the symmetries of the host molecules and one molecule of solvent coincide with the crystallographic symmetry (Figure 3c). One of the solvent molecules located in general positions adopts two disorder sites (SOFs of 0.87 and 0.13), with the major disorder component hydrogen bonded and the minor component uncoordinated. As is evident from the packing structure (Figure 7c), the solvent molecules participate in a different way in molecular association, thus creating different types of supramolecular entities. The solvent molecule located on a symmetry center is involved in the formation of chainlike aggregates with an alternating order of host and guest molecules [O(1)−H(1)···O(1E), 1.99 Å, 169°]. The remaining solvent molecules participate in a more complex chain structure 4378



Article

Figure 5. Illustration of the molecular structures of 2e (a) and 2f (b), including numbering of relevant atoms and ring specification. Oxygens are displayed as dotted circles, nitrogens as hatched circles, and chlorines as cross-hatched circles. The two disorder positions of the solvent molecules in 2f are marked by different bond types. Dashed lines represent hydrogen bond interactions.

of solvent molecules (Figure 9a). Within a given strand, independent host molecules are linked in alternating order but participate in a different way in guest binding. One equivalent of the host molecules (host 1) utilizes the OH hydrogens for guest association via conventional hydrogen bonding [O(1A)− H(1A)···O(1B), 1.87 Å, 159°; O(1A)−H(1A)···O(1BA), 1.75 Å, 165°], while in the second equivalent, the OH oxygens are involved in the formation of weaker C−H···O hydrogen bonds with one of the methyl hydrogens of DMF acting as a donor [C(2B)−H(2B2)···O(1), 2.53 Å, 152°]. According to this interaction pattern, the crystal components are cross-linked to two-dimensional networks extending parallel to the crystallographic a−c plane. The 1:2 complex of 2 with chloroform (2f), the structure of which is depicted in Figure 5b, is in monoclinic space group P21/c with one half of the host molecule and one disordered solvent molecule in the asymmetric part of the unit cell. The short distance from the solvent hydrogen to an individual atom of ring B of the host molecule [C(1A)−H(1A)···C(18), 2.63 Å, 163°] indicates the presence of a C−H···π interaction.

1.89 Å, 174°]. The second host molecule is self-assembled by relatively strong O−H···πfluorenyl interactions [O(1)−H(1)··· C(9), 2.44 Å, 156°], resulting in the formation of molecular strands extending along the b-axis. Weak hydrogen bonds of the C−H···O type [C(16A)−H(16A)···O(2B), 2.69 Å, 147°] complete the pattern of directed noncovalent interactions. The crystal of 2 growing from DMF yields a 1:1 solvent complex (2e) as colorless prisms. Crystals are in monoclinic space group C2/c with the asymmetric part of the unit cell consisting of two halves of host molecules and one molecule of solvent that is disordered over two positions with occupancies of 0.57 and 0.43. One of the host molecules (Figure 5a, molecule 1) adopts inversion symmetry, whereas the second (molecule 2) is located on the 2-fold rotation axis. This latter molecule shows a considerable distortion along its terphenyl element with its outer rings being inclined at an angle of 20.0(2)°. The fluorenyl units of this molecule deviate 11.5(2)° from coplanarity. The crystal structure of 2e is characterized by infinite O−H···O bonded strands of host molecules [O(1A)−H(1A)···O(1B), 1.92 Å, 178°] with a lateral attachment 4379



Article

Figure 6. Packing excerpts of 1a (a), 1b (b), and 1c (c). Oxygens are displayed as light gray circles and nitrogens as dark gray circles. The hydrogens of the host molecule excluded from hydrogen bonding have been omitted for the sake of clarity. Dashed lines represent hydrogen bond interactions.

Figure 7. Packing diagrams of 2 (a), 2a (b), and 2b (c). Oxygens are displayed as light gray circles. With the exception of OH hydrogens, all other hydrogens of the host molecule have been omitted for the sake of clarity. Dashed lines represent hydrogen bond interactions.

Furthermore, C−H···Cl hydrogen bonds30,31 involving one chlorine atom of each disorder position of CHCl3 [C(26)− H(26C)···Cl(3A), 2.88 Å, 164°; C(28)−H(28C)···Cl(3B), 2.87 Å, 155°] stabilize the host−guest complex. The crystal structure of 2f lacks conventional hydrogen bonding. Instead, the hydroxy groups of the host molecule contribute to the formation of relatively strong C−H···π interactions with the fluorenyl units acting as acceptors [O(1)−H(1)···C(9), 2.48 Å, 147°]. Taking this kind of intermolecular interactions into consideration, we assembled the 1:2 complex units into infinite chains extending along the b-axis (Figure 9b).

compounds formed of hosts 1 and 2 with protic guest molecules reveals some interesting features as specified below. One particularly obvious observation is that both in the inclusion structures of host molecules 1 and 2 shown here and in the unsolvated structure of 2, the host molecules adopt a unique folded conformation with the central ring of the terphenyl unit located between the fluorenyl moieties, which is totally in accordance with the previously published findings.19 Thus, the restricted conformational flexibility of the host molecular framework attributed to intramolecular C−H···O hydrogen bonding and π···π arene interactions being unaffected not by the presence of protic or nonprotic guest solvents becomes apparent as a true structural characteristic of this host type. Whether it will ever be possible to break open this seemingly resistant host conformation under the influence of a

■

COMPARATIVE DISCUSSION AND CONCLUSION A comparative inspection of the presently studied crystal structures and also previously described crystal structures of inclusion 4380



Article

Figure 8. Packing diagrams of 2c (a) and 2d (b). Oxygens are displayed as light gray circles. All arene hydrogens have been omitted for the sake of clarity. Dashed lines represent hydrogen bond interactions.

Figure 9. Packing excerpts of of 2e (a) and 2f (b). Oxygens are displayed as light gray circles, nitrogens as dark gray circles, and chlorines as cross-hatched circles. All arene hydrogens have been omitted for the sake of clarity. Dashed lines represent hydrogen bond interactions.

particularly strong interacting guest species remains to be seen. Another remarkable feature is revealed by the inclusion structures of 1 and 2 with 1,4-dioxane, acetone, and DMF, indicating that the bulkiness of the tert-butyl substituents specifically affects the host:guest stoichiometric ratio and thus the mode of host−guest interaction. According to the 1:2 host:guest stoichiometry of the 1·1,4-dioxane complex (1a), the crystal structure is composed of 1:2 complex units; i.e., only one of the dioxane oxygens is involved in molecular association. The same type of supramolecular entity is found in the crystal structure of the 2·THF complex (1:2, 2a). In contrast, a more complicated pattern of noncovalent intermolecular bonding is observed in the crystal of the 2·1,4-dioxane complex (1:2.5, 2b). In this case, one of the crystallographically independent host molecules creates 1:2 host−guest aggregates, whereas the second host molecule takes part in the formation of infinite O−H···O bonded strands with an alternating order of host and guest molecules. The remaining solvent molecules are located on interstitial places of the crystal lattice. In the 1:1 complex of 1 with acetone (1b), strands of host molecules are linked by inversion symmetric cyclic dimers of C−H···O bonded acetone molecules, resulting in the formation of two-dimensional supramolecular networks. Unlike that of 1b, the stoichiometric

ratio of the crystal components of the 2·acetone complex (2c) is 1:2. According to this, the crystal is constructed of 1:2 host− guest units via O−H···O bonding. A structural situation, different from that of 1b, is found in the inclusion compound of 1 with DMF (1:2, 1c). Here, the crystal components form infinite strands in which the solvent oxygen is linked in an asymmetric fashion via O−H···O and C−H···O hydrogen bonds to two crystallographically independent host molecules. This means that the host molecules within a given strand are separated by pairs of guest molecules. The presence of bulky tert-butyl substituents in the 2·DMF complex (1:1, 2d) changes the mode of molecular cross-linkage compared with that of 1c. The crystal structure can be regarded as being composed of strands of host molecules with a lateral attachment of guest molecules via O−H···O bonding. The acceptor/donor behavior of the guest gives rise to aggregation of the supramolecular chains via C−Hguest···Ohost interactions to form two-dimensional networks. With regard to the solvent-free crystal of 2 and the inclusion structure of 2 with chloroform (1:2, 2f), they are dominated by intermolecular O−H···πfluorene and C−Hguest···π contacts, respectively. Obviously, here the steric demand of the tert-butyl groups prevents the formation of conventional 4381



Article

(8) Braga, D., Creponi, F., Eds. Making Crystals by Design: Methods, Techniques and Applications; Wiley-VCH: Weinheim, Germany, 2007. (9) MacNicol, D. D., Toda, F., Bishop, R., Eds. Comprehensive Supramolecular Chemistry; Elsevier: Oxford, U.K., 1996; Vol. 6. (10) Hertzsch, T.; Hulliger, J.; Weber, E.; Sozzani, P. In Encyclopedia of Supramolecular Chemistry; Atwood, J. L., Steed, J. W., Eds.; CRC Press: Boca Raton, FL, 2004; pp 996−1005. (11) Toda, F., Ed. Organic Solid State Reactions; Topics in Current Chemistry; Springer-Verlag: Berlin, 2005; Vol. 254. (12) Gillivray, L. R., Ed. Metal-Organic Frameworks: Design and Application; Wiley: Hoboken, NY, 2010. (13) Bishop, R. Chem. Soc. Rev. 1996, 25, 311−319. (14) Desiraju, G. R. In Comprehensive Supramolecular Chemistry; MacNicol, D. D., Toda, F., Bishop, R., Eds.; Elsevier: Oxford, U.K., 1996; Vol. 6, pp 1−22. (15) Weber, E. In Inclusion Compounds; Atwood, J. L., Davies, J. E. D., MacNicol, D. D., Eds.; Oxford University Press: Oxford, U.K., 1991; Vol. 4, 188−262. (16) Weber, E.; Czugler, M. In Molecular Inclusion and Molecular Recognition: Clathrates II; Weber, E., Ed.; Topics in Current Chemistry; Springer-Verlag: Berlin, 1988; Vol. 149, pp 45−135. (17) Weber, E.; Skobridis, K.; Wierig, A.; Stathi, S.; Nassimbeni, L. R.; Niven, M. L. Angew. Chem., Int. Ed. 1993, 32, 606−608. (18) Weber, E. In Comprehensive Supramolecular Chemistry; McNicol, D. D., Toda, F., Bishop, R., Eds.; Elsevier: Oxford, U.K., 1996; pp 535−592. (19) Klien, H.; Seichter, W.; Weber, E. CrystEngComm 2013, 15, 586−596. (20) Skobridis, K.; Theodorou, V.; Seichter, W.; Weber, E. Cryst. Growth Des. 2010, 10, 862−869 and references cited therein. (21) Skobridis, K.; Theodorou, V.; Alivertis, D.; Seichter, W.; Weber, E.; Csöregh, I. Supramol. Chem. 2007, 19, 373−382. (22) Poriel, C.; Liang, J.-J.; Rault-Berthelot, J.; Barrière, F.; Cocherel, N.; Slawin, A. M. Z.; Horhant, D.; Virboul, M.; Alcaraz, G.; Audebrand, N.; Vignau, L.; Huby, N.; Wantz, G.; Hirsch, L. Chem.Eur. J. 2007, 13, 10055−10069. (23) Desiraju, G. R.; Steiner, T. The Weak Hydrogen Bond in Chemistry and Structural Biology; IUCR Monographs on Crystallography; Oxford University Press: New York, 1999; Vol. 9, pp 29−121. (24) James, S. L. In Encyclopedia of Supramolecular Chemistry; Atwood, J. L., Steed, J. W., Eds.; CRC Press: Boca Rato, FLn, 2004; pp 1093−1099. (25) Nishio, M.; Umezawa, Y.; Honda, K.; Tsuboyama, S.; Suezawa, H. CrystEngComm 2009, 11, 1757−1788. (26) Etter, M. C. J. Phys. Chem. 1991, 95, 4601−4610. (27) Bernstein, J.; Davies, R. E.; Shimoni, L.; Chang, N.-L. Angew. Chem., Int. Ed. 1995, 34, 1555−1573. (28) Salonen, L. M.; Ellermann, M.; Diederich, F. Angew. Chem., Int. Ed. 2011, 50, 4808−4842. (29) Adams, H.; Carver, F. J.; Hunter, C. A.; Morales, J. C.; Seward, E. M. Angew. Chem., Int. Ed. 1996, 35, 1542−1544. (30) Brammer, L.; Bruton, E. A.; Sherwood, P. Cryst. Growth Des. 2001, 1, 277−290. (31) Thallapally, P. K.; Nangia, A. CrystEngComm 2001, 3, 114−119. (32) SAINT; Bruker AXS Inc.: Madison, WI, 2008. (33) Sheldrick, G. M. SHELXS-97: Program for Crystal Structure Solution; University of Göttingen: Göttingen, Germany, 1997. (34) Sheldrick, G. M. SHELXL-97: Program for Crystal Structure Refinement; University of Göttingen: Göttingen, Germany, 1997.

hydrogen bonding. This is also the case in the inclusion structure of the 2·ethyl acetate complex (1:1, 2d) in which only one of the crystallographically different host molecules is involved in chain formation via O−H···π interaction while the second host creates O−H···O bonded 1:2 complex units. In summary, it is shown that considering also the previously demonstrated inclusion behavior of 1 and 2 with protic guest molecules,19 this particular type of terphenyl host may not only be rated as a simple structural modification of the well-known biphenyl analogues18 but also seem to open up development of a new model of versatile host compound, promising usefulness in practical crystal engineering in particular of supramolecular inclusion formation.

■

EXPERIMENTAL SECTION

■

ASSOCIATED CONTENT

Preparation of Compounds. Host compounds 1 and 2 were synthesized as described in the literature.19 Crystalline inclusion compounds were obtained by crystallization of 1 or 2 from corresponding solvents. Solvent-free 2 was crystallized from an ethanol solution. Crystals of 1a−c, 2, and 2a−f suitable for X-ray diffraction were formed by slowly cooling the respective solutions followed by slow evaporation of solutions as necessary. X-ray Crystallography. The intensity data of the compounds studied were collected on a Kappa APEX II diffractometer (Bruker AXS) with graphite-monochromated Mo Kα radiation (λ = 0.71073 Å) at 100(2) K. Cell parameters were refined with SAINT using all observed reflections. Data reduction was performed with SAINT32 and corrected for background, Lorentz, and polarization effects. Preliminary structural models were derived by application of direct methods33 and were refined by full-matrix least-squares calculation based on F2 for all reflections.34 All hydrogen atoms were included in the models in calculated positions and were refined as constrained to bonding atoms. In the crystal structures of 2c, 2e, and 2f, the refinement of the disordered solvent molecules turned out to be difficult. To obtain acceptable molecular geometries, geometrical restraints using the DFIX instruction of SHELXL have been used.

S Supporting Information *

X-ray crystallographic data in CIF format for the structures reported in this paper. This material is available free of charge via the Internet at http://pubs.acs.org.

■

AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Notes

The authors declare no competing financial interest.

■

REFERENCES

(1) Atwood, J. L., Davies, J. E. D., MacNicol, D. D., Eds. Inclusion Compounds; Oxford University Press: Oxford, U.K., 1991; Vol. 4. (2) Weber, E. In Kirk-Othmer Encyclopedia of Chemical Technology, 4th ed.; Kroschwitz, J. I., Ed.; Wiley: New York, 1995; Vol. 14, pp 122−154. (3) Nangia, A. In Nanoporous Materials; Lu, G. Q., Zhao, X. S., Eds.; Series on Chemical Engineering; Imperial College Press: London, 2004; Vol. 4, pp 165−187. (4) Herbstein, F. H. Crystalline Molecular Complexes and Compounds; Oxford University Press: Oxford, U.K., 2005; Vol. 1, pp 421−513. (5) Steed, J. W.; Atwood, J. L. Supramolecular Chemisty, 2nd ed.; Wiley: New York, 2009. (6) Vittal, J. J., Zaworotko, M., Tiekink, E. R. T., Eds. Organic Crystal Engineering; Wiley: New York, 2010. (7) Desiraju, G. R. Angew. Chem., Int. Ed. 2007, 46, 8342−8356. 4382


Versatility in Complexation of Aprotic Guest Molecules by Terphenyl

Recommend Documents