Structural Versatility of Pyrene-2 - ACS Publications - American

Article pubs.acs.org/crystal

Structural Versatility of Pyrene-2-(4,4,5,5-tetramethyl[1,3,2]dioxaborolane) and Pyrene-2,7-bis(4,4,5,5-tetramethyl[1,3,2]dioxaborolane) Andrei S. Batsanov,*,† Judith A. K. Howard,† David Albesa-Jové,† Jonathan C. Collings,† Zhiqiang Liu,‡ Ibraheem A. I. Mkhalid,§ Marie-Hélène Thibault,⊥ and Todd B. Marder*,†,# †

Department of Chemistry, Durham University, South Road, Durham DH1 3LE, U.K. State Key Laboratory of Crystal Materials, Shandong University, 27 Shanda South Road, Jinan, 250100, P. R. China § Department of Chemistry, King Abdulaziz University, Jeddah, Kingdom of Saudi Arabia ⊥ Département de chemie, Université Laval, 1045, avenue de la Médecine, Pavillon Alexandre-Vachon, Québec, G1V 0A6, Canada ‡

S Supporting Information *

ABSTRACT: Three polymorphs of pyrene-2,7-bis(Bpin)2 (1) and two of pyrene-2-(Bpin) (2), where Bpin = 4,4,5,5tetramethyl-[1,3,2]dioxaborolane, two different 1:1 co-crystals of 1 with toluene, and co-crystals of hexafluorobenzene (HFB) with 1 (of highly unusual 2:1 composition) and 2 (of usual 1:1 composition) were isolated, studied by X-ray diffraction and differential scanning calorimetry, and described using Hirshfeld surfaces and two-dimensional fingerprint plots. Centrosymmetric phases β- and γ-1 have densities respectively lower and higher than the chiral α-1; α- and β-2 have different packing modes, both with Z′ = 3. Compound 1 is prone to form channel host−guest structures, for example, α- and β-1·PhMe and 1·2HFB. The drastically different stabilities of α- and β-1·PhMe are discussed. The complex 2·HFB has a mixed-stack packing motif. The structural versatility of 1 and 2 is explained by synthon frustration between structurally incongruent pyrene and Bpin moieties.

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problem emerged from our discovery4 that the C−H borylation reaction between pyrene and B 2pin2 (Bpin = 4,4,5,5tetramethyl-[1,3,2]dioxaborolane) is selectively directed to the 2- and 7-positions by an iridium-based catalyst, yielding pyrene2,7-bis(Bpin)2 (1) or pyrene-2-(Bpin) (2), depending on conditions. The selectivity of this reaction is dominated by steric factors.5 From 1 and 2, a wide variety of 2- and 2,7derivatives have been readily obtained,1,4,6 some of which have shown promising electronic and photophysical properties.6,7 Because molecular packing is always an important factor for the performance of organic electronic devices, and pyrene is particularly well-known for the sensitivity of its emission to its microenvironment,1 we undertook a systematic crystallographic study of the newly synthesized derivatives,4 in the course of

INTRODUCTION The remarkable fluorescent properties of pyrene have made it a promising building block for organic electronics, for use in devices such as light-emitting diodes, field-effect transistors, photovoltaic cells, organic lasers and memory cells, as well as liquid-crystal components.1 In addition, pyrene derivatives have also been used for ionic and molecular recognition,2a−c for hydrogel formation,2d and as biological probes to study the structures of peptides and lipid membranes.3 Numerous pyrene derivatives have been obtained by electrophilic substitution of pyrene itself, which takes place at the 1-, 3-, 6-, and 8-positions. With the exception of tert-butyl substitution, 2- and 7derivatives are not accessible in this way, because both the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) of the pyrene molecule have a nodal plane passing through these positions. Thus, such derivatives are prepared by more cumbersome routes (see bibliography in ref 4a). Recently, a novel solution to this © 2012 American Chemical Society

Received: November 24, 2011 Revised: May 7, 2012 Published: May 7, 2012 2794

dx.doi.org/10.1021/cg201554t | Cryst. Growth Des. 2012, 12, 2794−2802

Crystal Growth & Design

Article

more than half of the electron density, and the “fingerprint plot” of intermolecular contacts.17 While broadly confirming the ideas of Desiraju and Gavezzotti, this approach yielded new criteria for classification, based on the relative frequency of C···H and C···C contacts13,17 which were now possible to determine quantitatively (Figure 1). Here we explore the applicability of this approach to substituted PAHs.

which the “gateway” compounds 1 and 2 themselves displayed unexpectedly rich crystallographic behavior, including polymorphism, co-crystallization, and high numbers of independent molecules (Z′). It has long been recognized8 that crystal packing of polycyclic aromatic hydrocarbons (PAHs) is governed by two types of intermolecular interactions: π−π (or C···C) and σ−π (C−H···π or C−H···C). The former are associated with parallel stacking of molecules (face-to-face or offset) and the latter with edge-toface contacts between molecules forming a large dihedral angle, θ. Desiraju and Gavezzotti9 classified the packing motifs of PAHs into four types, viz. herringbone (HB), sandwichherringbone (SHB), γ and β (Figure 1), with the importance of

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RESULTS Crystallization. For compound 1 we obtained three polymorphs. The α-form, briefly reported earlier,4b crystallized from THF/DCM/hexane or THF/DCM solutions, β-1 was grown from ether, whereas γ-1 was obtained as fine powder with a few small single crystals, by sublimation of crude 1. Slow evaporation of toluene solutions of 1 repeatedly produced the following sequence. At first, plate-like crystals of α-1·PhMe formed, which soon dissolved and recrystallized into oblong blocks of β-1. Alongside the latter, on the final stage of evaporation, a different (β) polymorph of 1·PhMe crystallized as prisms (needles). If, at this stage, the vial is sealed with a sufficient amount of toluene still in it, all of β-1 will gradually recrystallize into β-1·PhMe. Out of the mother liquor, crystals of α-1·PhMe begin to desolvate and crumble within seconds, whereas β-1·PhMe is air-stable at room temperature and, according to differential scanning calorimetry (DSC), even on heating to 150 °C. Two separate crystallizations of compound 2 from hexane yielded solvent-free monoclinic (α) and triclinic (β) polymorphs. Crystallizations of 1 and 2 from a mixture of hexafluorobenzene (HFB) and Et2O yielded co-crystals of different composition, 1·2HFB and 2·HFB, respectively. Molecular Structures. The molecular geometries of 1 and 2 (Figure 2) are in agreement with those of pyrene10−12 and other 2- and 2,7-substituted derivatives thereof.4,6 The pyrene system is planar within experimental error in all cases except α1, where the two substituted six-membered rings form an interplanar angle of 3.5°. In accordance with Kitaigorodsky’s theory of crystal packing,18 the potentially centrosymmetric molecule of 1 occupies a crystallographic inversion center in every case (except in the structure of α-1, which is noncentrosymmetric). The boron atom has a trigonal-planar geometry; the interaction of its vacant pπ orbital with the pyrene system is negligible, due both to the competition of each oxygen atom’s lone pairs and the effect of the nodal plane of the pyrene HOMO (vide supra). Nevertheless, the dihedral angle (τ) between the pyrene and CBO2 planes is usually small (Tables 1 and 2), probably due to steric factors. The dioxaborolane (Bpin) ring adopts the twisted conformation with the two carbon atoms displaced from the BO2 plane by ca. 0.2 Å in opposite directions, except in α-2 where all three independent molecules show an envelope conformation, with

Figure 1. Crystal packing motifs of PAH molecules, showing the regions of π−π (red) and C−H···π (blue) contacts, and the range of ρ = (%C···H)/(%C···C) contact ratio for each motif.15

σ−π interactions decreasing and that of π−π interactions increasing in this succession. Thus, the HB motif is entirely dominated by σ−π interactions; in SHBs each molecule forms π−π contacts on one side and σ−π on the other, in the γ motif molecules form π−π stacks with herringbone-type (edge-toface) contacts between stacks, whereas the β-motif shows a graphitic-type layering of usually puckered molecules with predominant π−π and negligible σ−π interactions. Unsubstituted pyrene in polymorphs I10 and II11 presents a seminal example of the SHB motif, although the high-pressure polymorph III has a denser β-packing.12 Originally, the ranges of stability of each motif were described in terms of the shortest unit cell axis (“defining axis”) and the interplanar angle θ, which were seen as being inversely correlated.9a,12 However, with accumulation of structural data, it became obvious that these ranges in fact overlap, the correlation is not universal, and occasionally the formal criteria can be quite misleading as to the structuredefining type of interactions.12,13 Thus, a fifth packing motif, βHB, was recognized, which resembles the β-motif by the narrow θ angle, but HB by the defining axis.13 Recently, a more robust means of analyzing crystal structures generally,14 and PAHs particularly,12−15 was found in the Hirshfeld surface,16 enclosing the volume where the given molecule contributes

Figure 2. Molecular structures of 1 (in the β-form) and 2 (molecule A in the α-form). Primed atoms are generated by the inversion center. The same numbering scheme was used for other structures. 2795



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Table 1. Properties of Molecule 1 in Crystals: Volume within Hirshfeld (VH) and van der Waals (Vm)a Surface, Percentage of Intermolecular Contacts, Packing Coefficient for All Species (ck), Dihedral Angle between Pyrene and CBO2 Planes (τ) α-1 VH, Å3 H···H, % C···H, % O···H, % C···C, % F···H, % C···F, % Vm, Å3 ck τ, (°) a

β-1

γ-1

β-1·PhMe

1·2HFB

606.6 61.2 27.3 9.3 0.5

618.8 62.8 26.1 8.6 0.0

594.5 63.5 24.6 9.0 0.9

606.5 63.7 25.3 9.1 0.0

598.1 60.3 28.7 9.5 0.4

401.0 0.652 11.5, 9.9/31.5b

402.8 0.641 17.6

397.8 0.659 3.1

402.5 0.668 10.1

399.7 0.651 18.9/6.7b

599.1 40.5 12.1 6.3 4.5 28.4 5.1 402.6 0.678 5.4

van der Waals radii used: H 1.09, B 2.0, C 1.7, O 1.52 Å, all C−H bonds adjusted to 1.08 Å. bBO2 fragment is orientationally disordered.

Table 2. Properties of Molecule 2 in Crystalsa 3

V H, Å H···H, % C···H, % O···H, % C···C, % F···H, % C···F, % Vm, Å3 ck τ, (°) a

α-1·PhMe

α-2, A

α-2, B

α-2, C

β-2, A

β-2, B

β-2, C

2·HFB

432.6 58.2

437.3 61.1

437.7 60.1

439.6 59.0

437.7 56.0

431.8 57.0

440.5 49.7

30.1

25.3

29.4

31.9

35.8

34.4

9.4

6.0

8.0

4.9

4.3

5.8

6.0

3.2

4.1

4.5

4.6

3.7

0.7

1.0

287.2 0.650 7.4

288.8

287.9

289.4

289.6

12.2

12.6

290.5 0.653 6.0

6.3

2.2

6.8 20.9 8.3 286.1 0.664 4.0

this discussion: one should not presume that the known polymorphs are the densest ones. Furthermore, disorder is often taken as an indication of loose packing, but in this case α1 shows conformational disorder in one of the two Bpin groups, while the less dense β-1 has none. It is also noteworthy that the observed differences of density are caused in roughly equal measure by more compact conformation of the molecule (smaller van der Waals volume, Vm) and more efficient packing of molecules (higher packing coefficient, ck). Bulky Bpin substituents preclude any efficient π−π stacking of 1. In β-1, the pyrene moiety is sandwiched between four Bpin groups (two on either side). While such arrangement generates many short CH contacts (Figure 4), it does not achieve high packing density. In α-1, Bpin···pyrene contacts coexist with HB-type pyrene−pyrene interactions (θ = 52.4°), and in γ-1 with a tenuous π−π interaction between fringes of pyrene moieties (Figure 5), although the latter contribute less than 1% of C···C contacts. Crystal Packing of 2. The monoclinic (α) and triclinic (β) forms of 2 have almost equal density. The asymmetric units of either polymorph are comprised of three independent molecules, A, B, and C. Nevertheless, the packing motifs are substantially different (Figure 5). That of α-2 broadly resembles the SHB motif of pyrene-I or pyrene-II, albeit interspersed with Bpin groups. The structure contains two symmetrically nonequivalent “sandwiches”: one is formed by molecule A and its inversion equivalent, the other by molecules B and C (parallel within 8°). The mean pyrene−pyrene separations in both sandwiches equal 3.37 Å, which corresponds to a close van der Waals contact. The inward-looking side of each pyrene moiety presents a substantially flattened Hirshfeld surface (Figure 6), indicative of tight π−π interactions, while the outward side is dominated by C···H contacts. Thus, the fingerprints of all three molecules contain over 4% of C···C contacts (Table 2). In β-2, only molecule A with its inversion equivalent form a (strongly offset) sandwich and have a similar fraction of C···C contacts, while independent molecules B and C form a herringbone motif (θ = 51.2°) dominated by C···H interactions. Structures of Co-Crystals. As mentioned above, the two polymorphs of 1·PhMe drastically differ in their stability toward desolvation. The structures are apparently very similar (Figure 7). In both, molecule 1 lies at a crystallographic inversion center, while the toluene molecule is disordered between two overlapping positions related via another inversion center. In both, packing of the host molecules creates infinite channels, parallel to the crystal axis a, in which toluene molecules are

See Table 1.

one carbon atom deviating from the BO2C plane by 0.39 to 0.46 Å. Note that in the β-2 polymorph, all three independent molecules have the usual twisted conformation. This is another example of the intriguing, and so far unexplained, tendency of symmetrically independent molecules in a crystal to adopt a similar conformation (thus, Zorky19 estimated that only 10% of multiple-Z′ structures contain substantially different conformers). One Bpin group in α-1, as well as those in β1·PhMe, α-2 (in the independent molecule C) and 2·HFB are disordered between two oppositely twisted conformations, in the ratios 1:1, 3:2, 9:1, and 1:1, respectively. In each case except 2·HFB, both oxygen atoms are also disordered; that is, the two conformers also have different τ angles. Crystal Packing of 1. The three polymorphs of 1 show very different packing motifs (Figure 3), so that the transitions between them can only be reconstructive. These differences are clearly revealed by dissimilar fingerprint plots (Figure 4), although the distribution of intermolecular contacts by element types is almost identical (Table 1), H···H, C···H, and O···H contacts comprising ca. 97% of the total in each case. As expected,14 the densest γ-polymorph shows the most compact fingerprint. Note particularly the disappearance of the shortest C···H and O···H contacts which appear as pointed projections in the fingerprints of α- and β-1. According to Wallach’s rule,20 racemic polymorphs must be denser than chiral ones, although recent studies21 suggest that this rule has many exceptions and is correct only on average. Compound 1, where a chiral α-form has intermediate density (1.226 g cm−3) between two different centrosymmetric forms (1.200 g cm−3 for β and 1.249 for γ), gives a useful caveat to 2796



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In 1·2HFB (Figure 10), the molecule of 1 lies at a crystallographic inversion center, while HFB occupies a general position, hence the 1:2 ratio of the components which is highly unusual. Planar arene and perfluoroarene molecules tend to cocrystallize in a 1:1 ratio and form mixed stacks in which parallel, or near-parallel, molecules of the two components alternate.22 This motif is remarkably persistent, even when the component molecules are sterically rather disparate, for example, HFB with pyrene, or triphenylene,22e or even dibenzocyclododecadienetetrayne.23 A notable exception is 1,4-(C6H5CC)2C6H4 (3) and 1,4-(C6F5CC)2C6F4 (4), the equimolar solutions of which reproducibly yield 4·(3)2 co-crystals concomitantly with crystals of pure 4,22f even though the closely similar pair 1,4(C6H5CC)2C6F4 and 1,4-(C6F5CC)2C6H4 duly co-crystallizes in the expected 1:1 alternating stacked structure,22c as do the tolan−perfluorotolan pair and various partially fluorinated tolans.22g Another, recently discovered, exception is the pyrene−1,2-diiodotetrafluorobenzene complex of 1:2 composition,24 which may be due to halogen bonds formed by iodine atoms. In 1·2HFB, the planar aromatic moieties (parallel within 4.4°) are stacked in the -pyrene−HFB−HFB−pyrene−HFB− HFB- sequence, with fairly short interplanar separations: pyrene−HFB 3.41 Å and HFB−HFB 3.23 Å. Although the 1:2 co-crystallization has been realized in the p-tert-butylcalix(4)arene·2HFB and octadecamethoxy-hexabenzocoronene· 2HFB clathrates25 (the former structure also containing diads of parallel HFB molecules sandwiched between arene rings of calixarene molecules), in both cases the host molecule is much larger than 1 and contains substantially non-coplanar arene rings. The out-of-plane orientation of the methyl groups of 1 seems to create suitable pockets for (HFB)2 diads in two dimensions, but in the third dimension (parallel to the cell axis a) these diads form continuous chains; thus, they are not in any real sense trapped by the host (i.e., 1). In fact, co-crystallization yields no gain in the packing density compared to the pure components; subtracting the molecular volume of solid HFB (147.3 Å3 at 120 K) from that of 1·2HFB leaves 624.5 Å3 per molecule of 1, compared to 615.4, 628.3, and 603.75 Å3 in α-, β-, and γ-1, respectively. More important for the stability of the co-crystal may be a drastic change of the contacts pattern (Table 1), with massive replacement of H···H and C···H contacts with much more polar F···H and F···C. The co-crystal of 2 with HFB, on the contrary, has the usual 1:1 composition and arene−perfluoroarene packing motif22 of mixed stacks comprising alternating nearly parallel pyrene moieties and HFB molecules (Figure 11). The 1:1 co-crystal of HFB with unsubstituted pyrene22e shows very similar stacking, including the mode of molecular overlap. Although the monoclinic lattice of pyrene·HFB is very different from that of 2·HFB, which is tetragonal, the shortest cell axes, which in both cases are the stacking direction, have similar lengths, viz. a = 6.95 and c = 6.74 Å, respectively. Surprisingly, stacking in 2·HFB is slightly tighter than in pyrene·HFB, with practically uniform interplanar (pyrene···HFB) separations of 3.33 Å vs 3.39 Å. Variable-Temperature Studies. We explored the stability of different polymorphs by sampling diffraction patterns and measuring the unit cells at variable temperatures, viz. from 100 to 329 K for β-1, from 120 to 290 K for γ-1, and from 120 to 230 K for α- and β-1·PhMe and 1·2HFB. No phase transitions were observed. The unit cell volumes of β- and γ-1 increase with temperature sympathetically, albeit nonlinearly (Figure

Figure 3. Crystal packing of the polymorphs of 1. Arrows show close contacts methyl−pyrene (red), pyrene−pyrene σ−π (blue), and pyrene−pyrene π−π (green).

located (Figure 8). Indeed, the stable β-polymorph has a lower density and packing coefficient (Table 1) than the unstable αform, and a larger solvent-accessible volume, both in absolute terms (187 vs 156 Å3 per formula unit) and in proportion to the unit cell volume (24% vs 20%)! Furthermore, the channel in β-1·PhMe is also wider: it can be penetrated by a sphere of 2.2 Å radius, as against 1.6 Å for α-1·PhMe. Therefore, it is necessary to conclude that the instability of α-1·PhMe is caused by factors other than solvent mobility in the channel. Fingerprint plots of molecule 1 in both structures clearly show (Figure 9) that the apparent similarity of the two structures is deceptive. This problem obviously requires further investigation, possibly by mapping electrostatic potential on the Hirshfeld surface. 2797



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Figure 4. Fingerprint plots of molecule 1 in three polymorphs (distances in Å), indicating the shortest contacts H···H (1), C···H (2), and O···H (3).

Figure 6. Hirshfeld surface (showing curvature) and local environment of molecule A in the structure of α-2. The flattened surface inside the sandwich (top) indicates π−π interactions, while the outer surface (bottom) is dominated by σ−π contacts.

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DISCUSSION AND CONCLUSIONS Both 1 and 2 show polymorphism and propensity to form cocrystals. It has been previously pointed out that the latter property often goes together with the tendency to crystallize with a large number (Z′) of symmetry-independent molecules in the structure of the pure component.26 This indeed seems to be the case for 2 which has Z′ = 3 in both polymorphs. It is also noteworthy that of the 126 fully determined structures of areneBpin derivatives present in the May 2011 issue of the Cambridge Structural Database,27 24 show Z′ > 1  a much higher proportion (19%) than the CSD average (8.4%) and rivaling those of the notoriously high-Z′ classes, such as steroids (19%) and nucleotides/nucleosides (21%).28 One compound, p-MeC6H4Bpin, has Z′ = 4.29 However, all of these derivatives, including 2, are intrinsically non-centrosymmetric molecules. On the contrary, molecule 1, in five out of six structures, occupies a crystallographic inversion center with Z′ = 1/2, as do centrosymmetric molecules of naphthalene-2,6-(Bpin)2 and perylene-2,5,8,11-(Bpin)4.4b It has also been suggested that both high Z′ and co-crystal formation can result from awkward molecular shape30 and “supramolecular synthon frustration” resulting from different

Figure 5. Crystal packing in the polymorphs of 2; π−π stacked sandwiches are highlighted with green arrows.

12), while α- and β-1·PhMe expand differently, so that their (calculated) densities diverge from 1.185 and 1.182 g cm−3 at 120 K to 1.159 and 1.139 g cm−3, respectively, at 230 K. DSC curves of single-crystalline β-1 and β-1·PhMe were recorded by cooling from 30 to −90 °C and subsequent heating to 350 °C (Figure 13). Both solids show a very broad maximum at low temperature, which may be due to the onset of flexibility in the Bpin groups. Upward from −20 °C, β-1 shows no significant features until the sharp melting peak (onset 337.3 °C, maximum 344.2 °C), whereas β-1·PhMe has a featureless curve up to ca. 150 °C followed by a series of transformations (with distinct peaks at 199.2 and 250.6 °C) and a broad melting peak (shoulder at 318.6 °C). 2798



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Table 3. Crystal Data and Experimental Details compound

β-1

γ-1

α-1·PhMe

β-1·PhMe

1·2HFB

α-2

β-2

2·HFB

CCDC number formula M T/K crystal system space group (no.) a (Å) b (Å) c (Å) α (°) β (°) γ (°) volume (Å3) Z (Z′) Dcalc (g/cm3) μ (mm−1) reflns collected unique reflns reflns with I > 2σ(I) R1 [I > 2σ(I)] wR2 (all data)

779129 C28H32B2O4 454.16 120 monoclinic P21/n (14a)

779130 C28H32B2O4 454.16 120 monoclinic P21/n (14a)

779131 C28H32B2O4·C7H8 546.29 120 triclinic P1̅ (2)

779132 C28H32B2O4·C7H8 546.29 120 monoclinic P21/n (14a)

779133 C28H32B2O4·2C6F6 826.28 120 triclinic P1̅ (2)

779140 C22H21BO2 328.20 120 monoclinic P21/n (14a)

779141 C22H21BO2 328.20 120 triclinic P1̅ (2)

779142 C22H21BO2·C6F6 514.26 120 tetragonal P42/n (86)

10.6980(4) 11.0555(6) 11.2465(6) 90 109.137(4) 90 1256.6(1) 2 (1/2) 1.200 0.08 14824 3547 2881

6.4525(1) 11.0823(2) 16.9139(3) 90 93.286(9) 90 1207.50(4) 2 (1/2) 1.249 0.64 6183 2045 1718

7.2546(5) 9.8024(6) 11.9441(8) 107.848(15) 100.289(14) 101.533(15) 765.5(1) 1 (1/2) 1.185 0.08 6951 3503 2316

6.6050(4) 19.8267(12) 11.7290(7) 90 91.997(10) 90 1535.04(16) 2 (1/2) 1.182 0.07 22749 4485 2506

6.9162(3) 11.7567(5) 11.8539(5) 76.707(6) 80.150(6) 81.976(7) 919.14(7) 1 (1/2) 1.493 0.14 16830 5361 4381

25.4025(14) 7.3852(4) 30.8651(15) 90 113.39(1) 90 5314.7(5) 12 (3) 1.231 0.08 50216 9360 7345

6.9518(4) 19.7285(12) 20.8481(12) 70.17(2) 82.02(2) 87.41(2) 2663.6(4) 6 (3) 1.228 0.08 20855 8937 5606

26.578(2) 26.578(2) 6.7405(10) 90 90 90 4761.5(9) 8 (1) 1.435 0.07 24260 4179 2451

0.041 0.121

0.040 0.110

0.067 0.201

0.055 0.168

0.041 0.121

0.036 0.096

0.042 0.094

0.080 0.122

a

Nonstandard setting.

Figure 8. Channels in the structures of α-1·PhMe (top) and β-1·PhMe (solvent is omitted). Note the more uniform width of the latter.

tional rigidity favors high Z′. However, the overall space occupied by different conformers of Bpin is practically identical, hence the ubiquitous disorder of this group in crystals, reported for 20% of structurally studied arene-Bpin27 derivatives and repeatedly observed in this work; therefore, its flexibility contributes nothing to facilitate crystal packing. It can be concluded that the Bpin group may present some interesting possibilities as a crystal engineering tool. It is also noteworthy that dumbbell shaped host molecules (e.g., bisadamantyl- or bis-tert-alkyl oligoalkynes) are apt to produce porous networks with nanometer-sized parallel channels, suited for 1D physical property design.32 Compound 1 has precisely

Figure 7. Crystal packing of α-1·PhMe (top) and β-1·PhMe (bottom), viewed down the toluene-filled channels.

parts of the molecule favoring incompatible packing motifs.31 Both factors obviously apply to 1 and 2 which each comprise a planar and rigid aromatic pyrene moiety with aliphatic and hydrophilic (BO2) parts of Bpin, whose bulk frustrates π−π stacking. Thus, the packing of 1, 2, and their co-crystals shows only a remote semblance of the packing of pyrene in all of its three polymorphs. The remarkable conformational flexibility of Bpin apparently contradicts the conclusion30 that conforma2799



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Figure 9. Fingerprint plots of molecule 1 in α-1·PhMe and β-1·PhMe (distances in Å).

Figure 13. DSC curves for β-1 and β-1·PhMe.

Figure 10. Crystal packing of 1·2HFB.

commercial solvents checked for purity. Sublimation of 1 was performed at 150 °C and 6 × 10−4 Torr (the receiver was cooled with dry ice), and the product was then washed with refluxing hexane. DSC experiments were carried out on a TA Instruments Q1000 device. Single-crystal diffraction experiments (Table 1) were carried out on Bruker 3-circle diffractometers with CCD area detectors SMART 1000 (β-1, 2·HFB), SMART 6000 (1·2HFB, α- and β-1·PhMe, α- and β-2), or PLATINUM135 (γ-1) using graphite-monochromated Kα radiation from a sealed Mo-anode tube (λ̅ = 0.71073 Å) or (for γ-1) a Microstar rotating Cu-anode source with cross-coupled Göbel mirrors (λ̅ = 1.54184 Å). Crystals were cooled using Cobra (for γ-1) or Cryostream 700 (Oxford Cryosystems) open-flow N2 cryostats. The structures were solved by direct methods and refined by full-matrix least-squares against F2 of all data, using SHELXTL33 and Olex234 software. Crystallographic data have been deposited with the Cambridge Crystallographic Data Centre and can be obtained free of charge via www.ccdc.cam.ac.uk/data_request/cif. In the structure of β-1·PhMe, the two alternative positions of the toluene phenyl ring are so close together that resolving them did not produce a stable refinement, although similar elongation of all thermal ellipsoids and the spuriously short exocyclic C(15)−C(18) bond of 1.363(5) Å clearly indicate the disorder. Thus, the phenyl was refined in a single, centrosymmetric position with the methyl group C(18)H3 disordered between two opposite orientations. The crystal of β-2 was non-merohedrally twinned by rotation around the reciprocal [0 1 1] axis (twin law −1 0 0/−0.52 0.07 0.93/−0.53 1.07 −0.07). Of the 23379 measured reflections, 5446 involved component 1 only, 5505 component 2 only, and 12428 were overlapping; the component contributions were refined to 0.6685(4) and 0.3315(4). Reflection intensities from both components, corrected using the TWINABS program,35 were used in the refinement, whereas the uncorrected data from component 1 gave an irreducible R(F) = 0.14. Hirshfeld surfaces were calculated and analyzed using the Crystal Explorer program,36 and for other computations and graphics, Olex234 software was used.

Figure 11. Crystal packing of 2·HFB.

Figure 12. Thermal expansion of the unit cell volumes of β- and γ-1 (Z = 2 for both).

such a shape and, indeed, is proven here to form channel structures.

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EXPERIMENTAL SECTION

Syntheses of 1 and 2 have been described elsewhere.4 Crystallizations were made by slow evaporation at room temperature, using 2800



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Sci. 1972, 28, 2977−2984. (d) Kai, Y.; Hama, F.; Yasuoka, N.; Kasai, N. Acta Crystallogr., Sect. B: Struct. Sci. 1978, 34, 1263−1270. (11) (a) Knight, K. S.; Shankland, K.; David, W. I. F.; Shankland, N.; Love, S. W. Chem. Phys. Lett. 1996, 258, 490−494. (b) Frampton, C. S.; Knight, K. S.; Shankland, N.; Shankland, K. J. Mol. Struct. 2000, 520, 29−32. (12) Fabbiani, F. P. A.; Allan, D. R.; Parsons, S.; Pulham, C. R. Acta Crystallogr., Sect. B: Struct. Sci. 2006, 62, 826−842. (13) Schatschneider, B.; Phelps, J.; Jezowski, S. CrystEngComm 2011, 13, 7216−7223. (14) McKinnon, J. J.; Spackman, M. A.; Mitchell, A. S. Acta Crystallogr., Sect. B: Struct. Sci. 2004, 60, 627−668. (15) Loots, L.; Barbour, L. J. CrystEngComm 2012, 14, 300−304. (16) Spackman, M. A.; Jayatilaka, D. CrystEngComm 2009, 11, 19− 32. (17) (a) McKinnon, J. J.; Jayatilaka, D.; Spackman, M. A. Chem Commun. 2007, 3814−3816. (b) Parkin, A.; Barr, G.; Dong, W.; Gilmore, C. J.; Jayatilaka, D.; McKinnon, J. J.; Spackman, M. A.; Wilson, C. C. CrystEngComm 2007, 9, 648−652. (18) Kitaigorodsky, A. I. Molecular Crystals and Molecules; Academic Press: New York, 1973. (19) Zorky, P. M. J. Mol. Struct. 1996, 374, 9−28. (20) Wallach, O. Liebigs Ann. Chem. 1895, 94, 90−143. (21) (a) Brock, C. P.; Schweizer, W. B.; Dunitz, J. D. J. Am. Chem. Soc. 1991, 113, 9811−9820. (b) Patrick, B. O.; Brock, C. P. Acta Crystallogr., B: Struct. Sci. 2006, 62, 488−497. (c) Jeong, K. S.; Kim, D. E.; Lee, E.; Jhon, Y. H.; Han, H.; Kim, J.; Jeong, N. Tetrahedron Asymmetry 2009, 20, 1736−1741. (22) (a) Dahl, T. Acta Crystallogr., Sect. B: Struct. Sci. 1990, 46, 283− 288. (b) Williams, J. H. Acc. Chem. Res. 1993, 26, 593−598. (c) Dai, C.; Nguyen, P.; Marder, T. B.; Scott, A. J.; Clegg, W.; Viney, C. Chem. Commun. 1999, 2493−2494. (d) Collings, J. C.; Roscoe, K. P.; Thomas, R. Ll.; Batsanov, A. S.; Stimson, L. M.; Howard, J. A. K.; Marder, T. B. New J. Chem. 2001, 25, 1410−1417. (e) Collings, J. C.; Roscoe, K. P.; Robins, E. G.; Batsanov, A. S.; Stimson, L. M.; Howard, J. A. K.; Clark, S. J.; Marder, T. B. New J. Chem. 2002, 26, 1740−1746. (f) Watt, S. W.; Dai, C.; Scott, A. J.; Burke, J. M.; Thomas, R. Ll.; Collings, J. C.; Viney, C.; Clegg, W.; Marder, T. B. Angew. Chem., Int. Ed. 2004, 43, 3061−3063. (g) Smith, C. E.; Smith, P. S.; Thomas, R. Ll.; Robins., E. G.; Collings, J. C.; Dai, C.; Scott, A. J.; Borwick, S.; Batsanov, A. S.; Watt, S. W.; Clark, S. J.; Viney, C.; Howard, J. A. K.; Clegg, W.; Marder, T. B. J. Mater. Chem. 2004, 14, 413−420. (23) Bunz, U. H. F.; Enkelmann, V. Chem.− Eur. J. 1999, 5, 263− 266. (24) Shen, Q. J.; Wei, H. Q.; Zou, W. S.; Sun, H. L.; Jin, W. J. CrystEngComm 2012, 14, 1010−1015. (25) (a) Enright, G. D.; Udachin, K. A.; Ripmeester, J. A. Chem. Commun. 2004, 1360−1361. (b) Wang, Z.; Dötz, F.; Enkelmann, V.; Müllen, K. Angew. Chem., Int. Ed. 2005, 44, 1247−1250. (26) Anderson, K. M.; Probert, M. R.; Whiteley, C. N.; Rowland, A. M.; Goeta, A. E.; Steed, J. W. Cryst. Growth Des. 2009, 9, 1082−1087. (27) Allen, F. H.; Taylor, R. Chem. Soc. Rev. 2004, 33, 463−475. (28) Steiner, T. Acta Crystallogr., Sect. B: Struct. Sci. 2000, 56, 673− 676. (29) Kleeberg, C.; Dang, L.; Lin, Z.; Marder, T. B. Angew. Chem., Int. Ed. 2009, 48, 5350−5354. (30) Anderson, K. M.; Probert, M. R.; Goeta, A. E.; Steed, J. W. CrystEngComm 2011, 13, 83−87. (31) Anderson, K. M.; Goeta, A. E.; Steed, J. W. Cryst. Growth Des. 2008, 8, 2517−2524. (32) Couderc, G.; Hulliger, J. Chem. Soc. Rev. 2010, 39, 1545−1554. (33) Sheldrick, G. M. Acta Crystallogr., Sect. A: Found. Crystallogr. 2008, 64, 112−122. (34) Dolomanov, O. V.; Bourhis, L. J.; Gildea, R. J.; Howard, J. A. K.; Puschmann, H. J. Appl. Crystallogr. 2009, 42, 339−341. (35) Sheldrick, G. M. TWINABS; University of Gö ttingen: Göttingen, Germany, 2008.

ASSOCIATED CONTENT

S Supporting Information *

Tables of variable-temperature unit cell data, ORTEP and fingerprint diagrams and full structural information in CIF format for all crystal structures. This material is available free of charge via the Internet at http://pubs.acs.org.

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected] (A.S.B.), todd.marder@ uni-wuerzburg.de (T.B.M.). Present Address #

Institut für Anorganische Chemie, Julius-Maximilians-Universität Würzburg, Am Hubland, 97074 Würzburg, Germany. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS We thank One NorthEast for funding under the UIC Nanotechnology Program. Z.L. thanks the Royal Society and BP for a China Incoming Fellowship. T.B.M. thanks the Royal Society for a Wolfson Research Merit Award, EPSRC for an Overseas Research Travel Grant, and the Royal Society of Chemistry for a Journals Grant for International Authors. We thank AllyChem Co. Ltd. for a generous gift of B2pin2 and W. Douglas Carswell for performing DSC measurements.

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REFERENCES

(1) Figueira-Duarte, T. M.; Müllen, K. Chem. Rev. 2011, 111, 7260− 7314. (2) (a) Liu, L.; Zhang, D.; Zhang, G.; Xiang, J.; Zhu, D. Org. Lett. 2008, 10, 2271−2274. (b) Choi, J. K.; Kim, S. H.; Yoon, J.; Lee, H.-K.; Bartsch, R. A.; Kim, J. S. J. Org. Chem. 2006, 71, 8011−8015. (c) Hariharan, M.; Karunakaran, S. C.; Ramaiah, D. Org. Lett. 2007, 9, 417−420. (d) Kilbinger, A. F. M.; Grubbs, R. H. Angew. Chem., Int Ed. 2002, 41, 1563−1566. (3) (a) Pap, E. H. W.; Hanicak, A.; van Hoek, A.; Wirtz, K .W. A.; Visser, A. J. W. G. Biochemistry 1995, 34, 9118−9125. (b) Pillot, T.; Goethals, M.; Vanloo, B.; Talussot, C.; Brasseur, R.; Vandekerckove, J.; Rosseneu, M.; Lins, L. J. Biol. Chem. 1996, 271, 28757−28765. (c) Sahoo, D.; Narayanaswami, V.; Kay, C. M.; Ryan, R. O. Biochemistry 2000, 39, 6594−6601. (d) Sahoo, D.; Weers, P. M. M.; Ryan, R. O.; Narayanaswami, V. J. Mol. Biol. 2002, 321, 201−214. (4) (a) Crawford, A. G.; Liu, Z.; Mkhalid, I. A. I.; Thibault, M.-H.; Schwarz, N.; Alcaraz, G.; Steffen, A.; Collings, J. C.; Batsanov, A. S.; Howard, J. A. K.; Marder, T. B. Chem.− Eur. J. 2012, 18, 5022−5035. (b) Coventry, D. N.; Batsanov, A. S.; Goeta, A. E.; Howard, J. A. K.; Marder, T. B.; Perutz, R. N. Chem. Commun. 2005, 2172−2174. (5) Mkhalid, I. A. I.; Barnard, J. H.; Marder, T. B.; Murphy, J. M.; Hartwig, J. F. Chem. Rev. 2010, 110, 890−931. (6) Qiao, Y.; Zhang, J.; Xu, W.; Zhu, D. Tetrahedron 2011, 67, 3395− 3405. (7) Crawford, A. G.; Dwyer, A. D.; Liu, Z.; Steffen, A.; Beeby, A.; Pålsson, L.-O.; Tozer, D. J.; Marder, T. B. J. Am. Chem. Soc. 2011, 133, 13349−13362. (8) (a) Robertson, J. M. Proc. R. Soc. London Ser. A 1951, 207, 101− 110. (b) Hunter, C. A.; Sanders, J. K. M. J. Am. Chem. Soc. 1990, 112, 5525−5534. (9) (a) Desiraju, G. R.; Gavezzotti, A. J. Chem. Soc., Chem. Commun. 1989, 621−623. (b) Desiraju, G. R.; Gavezzotti, A. Acta Crystallogr., Sect. B: Struct. Sci. 1989, 45, 473−482. (10) (a) Robertson, J. M.; White, J. G. J. Chem. Soc. 1947, 358−368. (b) Allmann, R. Z. Kristallogr. 1970, 132 (129−151), 416. (c) Hazell, A. C.; Larsen, F. K.; Lehmann, M. S. Acta Crystallogr., Sect. B: Struct. 2801



Article

(36) Wolff, S. K.; Grimwood, D. J.; McKinnon, J. J.; Turner, M. J.; Jayatilaka, D.; Spackman, M. A. CrystalExplorer, version 3.0; University of Western Australia: Perth, Western Australia, 2010.

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