DOI: 10.1021/cg900759e
Two-Dimensional Organic Brick-Wall Layers as Hosts for the Inclusion and Study of Aromatics Ensembles: Acid-Pyridine and Acid-Carbonyl Synthons for Multicomponent Materials
2009, Vol. 9 4969–4978
Ramkinkar Santra and Kumar Biradha* Department of Chemistry, Indian Institute of Technology, Kharagpur-721302, India Received July 4, 2009; Revised Manuscript Received August 8, 2009
ABSTRACT: The compound trimesic acid (H3TMA) with 2,6-bis(4-pyridylmethylene)cyclohexanone (1) was shown to form two-/three-/four-component cocrystals or salts depending on the reaction conditions. Crystals of salt were obtained when crystallized H3TMA and 1 from MeOH alone, whereas the crystals of neutral components were obtained when crystallized from MeOH and phenol mixture. Both the structures (salt and cocrystal) exhibited huge cavities which are occupied by the self-interpenetration of the networks. This self-interpenetration of the networks found to be eschewed in favor of guest inclusion when the crystallization reactions are conducted in the presence of suitable aromatic guest molecules such as biphenyl, naphthalene, anthracene, phenanthrene, pyrene, triphenylene, and 1,4-hydroquinone. The crystal structures of cocrystals contain hydrogen-bonded layers with huge cavities, the self-interpenetrated layers have a honeycomb geometry with the cavity dimensions of 23 42 A˚2 and the guest included layers have a brick wall geometry with cavity sizes of 8 23 A˚2. The guest occupied volume of these materials varies from 12 to 38% of crystal volume. In the four-component systems, the adducts of guest molecules were found between pyrene-phenol, pyrene-1,4-hydroquinone, and phenanthrene-o-cresol. In three-component systems, the packing of guest biphenyls is similar to that of the biphenyl crystal structure itself.
Introduction The engineering of novel materials via noncovalent synthesis has developed as a very attractive and potential area of research because of their fascinating assemblies and several applications.1 The microporous and host-guest solids are important in catalysis,2 separations,3 gas storage devices,4 and targeted drug delivery.5 In particular for designing the organic solids with required properties hydrogen bonds act as a master key. The interactions between the various functional groups play a crucial role in assembling the molecules.6 A particular interaction pattern qualifies to be a robust supramoleucular synthon when it appears repeatedly under different environments.7 The homodimer (I) formed by the carboxylic acid and the heterodimer (II) formed by carboxylic acid and pyridine are typical examples of such robust synthons. In particular, the utility of carboxylic acid-pyridine synthon in the preparation of multicomponent systems was very well demonstrated in the literature by exploring the wide variety of examples.8-11 This heteromeric synthon exists in three forms: II in cocrystal (neutral); III (mixed ionization) and IV in ionic salt depending on the acidity and basicity of the acid and pyridine functionalities, which also tend to change with reaction conditions.9 The formation of these three synthons found to depend upon ΔpKa value which is defined as [pKa (PyNHþ) - pKa (COOH)]. The synthon II forms preferably when the ΔpKa < 0; synthon III forms when 0 < ΔpKa < 3.75, synthon IV forms ΔpKa > 3.75. However in practice the pKa values of acids and pyridines bound to vary based on the solvents and other accompany-
ing components in the reaction. Therefore, it is not easy to predict the nature of the resultant crystals.
*Corresponding author. Fax: þ91-3222-282252. Tel: þ91-3222-283346. E-mail:
[email protected].
One of the prototypal and aesthetic examples of the synthon-II is the formation of honeycomb or (6,3) network between 1,3,5-benzene-tricarboxylic acid (trimesicacid, H3TMA) and 4,40 -bipyridine/4,40 -bipyridylethane/4,4’-bipyrdylethylene (2:3) reported by Zaworotko et al.10 It is pertinent to note here that the R-polymorph of H3TMA contains a honeycomb network with huge cavities of dimension 14 14 A˚2 which are filled by self-interpenetration of networks.11 In the cocrystals of H3TMA with bipyridyl derivatives, these cavities were extended up to 39 27 A˚2; however, these cavities are again of no use, as they are filled by the triple and parallel interpenetration of the networks. Later similar results were reproduced by Nangia et al. replacing H3TMA with 1,3,5-cyclohexane-tricarboxylic acid.12 With the exception of H3TMA, none of the above examples were known to include guest molecules by giving away the self-interpenetration.13 On the other hand, Coppens et al. utilized two trigonal molecules namely H3TMA and 1,3,5-tris(4-pyridyl)-2,4,6triazine to generate the similar network architecture via synthon-II.14 Unlike the above-described structures, the cavities in this network have been occupied by the pyrene aggregates. In our present work, we have planned to extend the cavities in the honeycomb network further by using a chemically reactive spacer, such as 3-pentadienone, between the pyridyl groups and utilize such big cavities for the inclusion
r 2009 American Chemical Society
Published on Web 09/10/2009
pubs.acs.org/crystal
4970
Crystal Growth & Design, Vol. 9, No. 11, 2009
of guest aggregations. Accordingly, the ligand considered for this purpose is 2,6-bis(4-pyridylmethylene) cyclohexanone (1). The carbonyl in 1 is anticipated to bind the guest molecules and help the inclusion of aromatics via C-H 3 3 3 O, whereas alcohols via O-H 3 3 3 O hydrogen bonds. We expected that the interpenetration of the networks may be eschewed if the cocrystal formation reactions are carried out in the presence of suitable guest molecules. Our other assumption here is that the carbonyl group does not interfere in the formation of robust synthon II.
We have recently communicated our preliminary studies on the complexation reactions of 1 with H3TMA, which reveal that 1 has an ability to form a cocrystal as well as an ionic complex with H3TMA depending on the crystallization conditions.15 Here, we would like to present our detailed studies on these systems and their guest inclusion properties. In our studies, we found that indeed the interpenetration of networks can be eschewed in favor of guest molecules. However, given the big size of the expected cavities, the guest molecules form ensembles either with itself or with other guest/solvent molecules. Results and Discussion The compound 1 was prepared by the Aldol condensation reaction of cyclohexanone with 4-pyridylaldehyde. The crystallization of the compound 1 with H3TMA in MeOH solution resulted in the crystals of an ionic compound [1-H1][H2TMA-H-TMAH2], 2. The repeat of the same reaction in the presence of phenol; resulted in the cocrystal [1. H3TMA], 3. Both these structures were found to have infinite networks with the self-interpenetration. Therefore, crystallization reactions of 1 with H3TMA were carried out in the presence of guest molecules without phenol and with phenol. The reactions without phenol found to form crystals of two complexes, [H2TMA]4[H21]2 3 naphthalene, 4, and [H2TMA]2[H1]2 3 pyrene, 5, whereas the reactions in the presence of phenol resulted in the crystals of [1 3 H3TMA] 3 biphenyl, 6; [1 3 H3TMA] 3 anthracene, 7; [1 3 H3TMA] 3 phenanthrene, 8; [1 3 H3TMA] 3 triphenylene, 9; [1 3 H3TMA]2 3 pyrene 3 2(phenol), 10; [1.H3TMA]2 3 pyrene 3 2(1,4-hydroquinone), 11; [1 3 H3TMA]4 3 phenanthrene 3 4(o-cresol) 3 2(MeOH), 12. The crystallographic parameters for all the crystal structures were given in Table 1, the CO bond lengths of COOH or COO- were tabulated in Table 2 and hydrogen-bond parameters were tabulated in Table 3. Interpenetrated Networks. The C-O bond lengths of H2TMA in the crystal structure of 2 indicate that the one of the COOH group is deprotonated. In 2, the cationic component is [1-H-1]þ1 and the anionic component is [H2TMA-H-TMAH2]-1; the H-atom bonded to two nitrogens or carboxylates lies on an inversion center. These ionic components assemble via synthon-II to form a three-dimensional network in the crystal lattice (Figure 1). In the network, the
Santra and Biradha
anionic part acts as a six-connected node and the cationic part acts as a long spacer with the length of 28.5 A˚. Four out of six connections from anionic part are utilized for selfassembling with each other to form a corrugated two-dimensional layer of (4,4)-topology (illustrations a and b in Figure 1). The remaining two connections from anionic part are utilized to interconnect the layers by pyridine groups of [1-H-1]þ1 unit via synthon-II. These layers are separated by each other with a distance of 19.1 A˚ (length of a-axis). Two of these three-dimensional networks are interpenetrated to fill the large channels and voids of the network (illustrations c and d in Figure 1). As stated in the introduction our actual aim is to get the cocrystal having a honeycomb network but not the crystals of the salt 2. At this point, it occurred to us that the presence of better solvating component for pyridine moiety in the reaction mixture may stop this deprotonation and may facilitate the formation of anticipated cocrystals. For this purpose, we have selected phenol as an additional solvent because of its ability to have a better interaction with pyridine moiety. Therefore, the above reaction was repeated in the presence of phenol and obtained crystals of complex 3. The asymmetric unit of 3 is constituted by one each of 1, H3TMA, and MeOH (9% of the crystal volume). The C-O bond lengths of -COOH groups indicate that the carboxylic acid groups are not deprotonated. The imbalance between -COOH and pyridine groups (three vs two) was taken care of by the formation of a self-dimer of -COOH groups (synthon-I, C-O bond lengths, 1.252(3) and 1.272(3) A˚). These dimers of H3TMA moieties are linked by the hetero synthon-II to form the anticipated two-dimensional network containing elliptical cavities of dimension 42.4 23.2 A˚2 (Figure 2a). On the whole, this network can best be described as a (6,3) or distorted honeycomb network in which each distorted hexagon is formed by six units of H3TMA and four units of 1. The two-dimensional layer is corrugated which helps in the self-interpenetration of the networks in parallel fashion (b and c in Figure 2). Therefore, three of these networks interpenetrate in parallel fashion to form a triple interpenetrated layer with the thickness of 9 A˚. It is pertinent to note here that Nangia et al. reported similar architecture in the cocrystal of cyclohexane-1,3-cis,5-cis-tricarboxylic acid and 4,40 -bipyridine.8 Further, the formation of the crystals of 2 and 3 does not show any dependency on the initial ratios of components 1 and H3TMA in the crystallization solution. The ratios of components could be the manifestation of the resultant stable architecture for given components in given conditions. The large voids both in 2 and 3 were filled by the 2-fold and 3-fold interpenetration of the networks, respectively. Open Networks with Guest Inclusion. The above results suggested that the interpenetration may give way to the inclusion of guest molecules if the crystallizations are carried out in the presence of guest molecules under similar conditions. To verify this hypothesis, we have repeated the reactions in the presence of large variety of guest molecules out of which some reactions yielded the crystals of 4-12 as we anticipated and in the cases where the guest molecules are 1,4-dibromobenzene, 1,4-diiodobenzene, hexachlorobenzene, 9,10-anthraquinone, 9,10-dibromoanthracene, and 9-anthranaldehyde, the crystals of 2 and 3 reproduced. Guest Inclusion in the Ionic Structures. In the presence of guest molecules, such as pyrene or naphthalene, the ionic
Article
Crystal Growth & Design, Vol. 9, No. 11, 2009
4971
Table 1. Crystallographic Parameters for the Crystal Structures of 2-12 2 C54H44N4O14 mol wt 972.93 T (K) 293(2) cryst syst monoclinic space group P2(1)/c a (A˚) 19.1296(7) b (A˚) 7.7639(3) c (A˚) 15.7687(6) R (deg) 90.00 β (deg) 98.1380(10) γ(°) 90.00 Vol (A˚3) 2318.39(15) Z 2 3 Dcalcd (Mg/m ) 1.394 R1 (I > 2σ(I)) 0.0504 wR2 (on F2, 0.1690 all data) formula
3
4
5
6
7
8
9
10
11
12
C27H22N2O7 486.47 293(2) monoclinic C2/c 23.612(2) 15.0618(12) 17.8456(15) 90.00 128.492(2) 90.00 4967.5(7) 8 1.301 0.0637 0.1565
C82H64N4O26 1521.37 293(2) triclinic P1 10.1180(6) 12.2782(8) 15.1268(10) 74.305(2) 73.489(2) 88.505(2) 1731.92(19) 1 1.459 0.0585 0.1789
C70H54N4O14 1175.17 293(2) monoclinic P2(1)/c 10.0728(8) 18.7475(14) 15.7570(12) 90.00 107.321(2) 90.00 2840.6(4) 2 1.697 0.0590 0.1372
C39H32N2O7 640.67 293(2) triclinic P1 6.8098(10) 14.235(2) 17.338(2) 104.773(4) 91.947(4) 92.244(4) 1622.2(4) 2 1.312 0.0763 0.2323
C37H32N2O7 616.65 293(2) monoclinic P2(1)/m 14.198(3) 6.8688(17) 17.257(4) 90.00 104.890(7) 90.00 1626.4(7) 2 1.259 0.0738 0.2114
C37H32N2O7 616.65 293(2) monoclinic P2(1)/m 14.183(5) 6.875(3) 17.212(6) 90.00 104.955(10) 90.00 1621.4(10) 2 1.263 0.0766 0.2188
C45H34N2O7 714.76 293(2) triclinic P1 9.6986(7) 14.6317(11) 14.7229(11) 61.082(2) 73.527(2) 84.036(2) 1752.3(2) 2 1.355 0.0481 0.1349
C82H66N4O16a 1363.39 293(2) monoclinic C2/c 22.4878(16) 24.9242(18) 14.3780(10) 90.00 122.438(2) 90.00 6801.3(8) 4 1.331 0.0662 0.2137
C82H66N4O18 1395.39 293(2) monoclinic C2/c 22.4015(13) 24.8681(14) 14.4804(8) 90.00 122.680(2) 90.00 6789.8(7) 4 1.365 0.0638 0.1965
C76H69N4O17 1310.35 293(2) triclinic P1 14.1531(15) 16.3725(17) 17.312(3) 110.186(4) 105.113(4) 106.318(3) 3316.3(7) 2 1.312 0.0609 0.2031
Table 2. C-O Bond Lengths of COOH or COO- Group in the Crystal Structures of 2-12 complex 2 3 4 5 6 7 8 9 10 11 12
COOH(1) 1.2032(19); 1.306(2) 1.204(3); 1.307(3) 1.238(3); 1.253(3) 1.234(3); 1.254(3) 1.210(3); 1.312(3) 1.199(4); 1.295(4) 1.182(4);1.328(4) 1.202(2); 1.311(2) 1.202(4); 1.292(4) 1.203(3); 1.283(3) 1.213(3); 1.295(3)
COOH(2)
COOH(3) a
1.1971(19); 1.3103(19) 1.205(3); 1.303(2) 1.194(3); 1.304(3)a 1.208(3); 1.314(3) 1.209(3); 1.306(3) 1.191(4); 1.258(5) 1.191(4); 1.306(4) 1.208(2); 1.308(2) 1.210(4); 1.297(4) 1.213(4); 1.291(4) 1.212(3); 1.294(3)
1.2242(18); 1.2791(16)a 1.252(3); 1.272(3)a 1.202(3); 1.325(4)a 1.203(3); 1.326(3)a 1.205(3); 1.318(3) 1.193(4); 1.332(4) 1.211(5); 1.265(5) 1.197(2); 1.328(3) 1.199(4); 1.314(4) 1.193(4); 1.323(4) 1.200(3); 1.323(3)
a
The COOH(1) and COOH(2) groups are hydrogen-bonded to pyridine, and COOH(3) is hydrogen-bonded to carbonyl. The distances marked with superscript ‘a’ correspond to hydrogen bonds with COOH or COO-.
structures assemble into 2D networks, although 3D network formation was observed in the absence of guest molecules in 2. No interpenetration of the networks observed as expected; however, the 2D network geometries and stoichiometries differ considerably with respect to the guest molecule. The ionic salts able to include two types of guest molecules naphthalene or pyrene to give the crystals of complexes [H2TMA]4[H21]2 3 naphthalene, 4, and [H2TMA]2[H1]2 3 pyrene, 5, respectively. In the case of 4, the ratio between 1 and H3TMA changes to 1:2 and one -COOH from each H3TMA was deprotonated by pyridyl units of 1. The anionic moieties self-assemble via a plethora of O-H 3 3 3 O hydrogen bonds to form a one-dimensional double chain. These double chains linked further into a two-dimensional layer via synthon-III and charge-assisted N-H 3 3 3 O hydrogen bond (Figure 3a). The layers contain rectangular cavities for the inclusion of naphthalene molecules. The naphthalene molecules stay perpendicular to the layer and are bound in the layer via C-H 3 3 3 O(carboxylate) and pyridine-C-H 3 3 3 π (naphthalene) interactions (Figure 3b). Although the layers have a slipped packing, there exist no channels, as some portion of the layers comes between the cavities of the adjacent layers. Therefore, no interactions were found between the guest molecules (Figure 3c). The presence of pyrene changes the ratio between 1 and H3TMA to 1:1 in 5 and increases the proportion of guest molecule in the crystal lattice. Therefore, in 5, only one of the pyridine moieties of 1 was protonated. The anions self-assemble to form a one-dimensional linear chain via
O-H 3 3 3 O hydrogen bonds. These chains are interlinked by the H1 via synthon-II and charge-assisted N-H 3 3 3 O hydrogen bonds (Figure 4a). The major difference between the 2D layers of 4 and 5 is the presence of a double chain of anions in 4, whereas it is the single chain of anions in 5. This difference significantly increased the cavity dimensions in 5 (8.3 18 A˚2 vs 10 24 A˚2 in 4 and 5, respectively) and hence the guest occupied volume in the crystal lattice (12.6% in 4 and 23.3% in 5). The layers pack in a slipped fashion such that there exist continuous channels through which pyrene molecules interact with each other (illustrations b and c in Figure 4). Another interesting and common feature in both the structures is the weak C-H 3 3 3 O hydrogen bonding between the H1 or H21 moieties to form a self-dimer via the interaction between C-H group of pyridine and the O atom of the carbonyl. Although the two salt structures discussed here are unpredictable, one can see some degree of consistency in the form of weak hydrogen bonding and self-assembling of H2TMA moieties. Guest Inclusion in the Cocrystals. The crystallization of 1 with H3TMA in the presence of MeOH, phenol, and an excess of guest molecules resulted in the open two-dimensional layers resembling brick wall. The rectangular grid cavities accommodate the guest molecules such as biphenyl, anthracene and triphenylene to form a three-component crystals. However, the guest molecules such as pyrene and phenanthrene form adducts with phenol or p-hydroquinone or o-cresol to result in the four-component crystals.
4972
Crystal Growth & Design, Vol. 9, No. 11, 2009
Table 3. Some Significant Hydrogen Bond Interactions in the Structures of 2-12
2
3
O-H 3 3 3 N C-H 3 3 3 O O3 3 3H3 3 3O N3 3 3H3 3 3N O-H 3 3 3 O O-H 3 3 3 O O-H 3 3 3 N C-H 3 3 3 O
4
O-H 3 3 3 O O-H 3 3 3 N N-H 3 3 3 O C-H 3 3 3 O
5
N-H 3 3 3 O O-H 3 3 3 O
6
C-H 3 3 3 O O-H 3 3 3 O O-H 3 3 3 N
7
C-H 3 3 3 O O-H 3 3 3 O O-H 3 3 3 N
8
C-H 3 3 3 O O-H 3 3 3 O O-H 3 3 3 N
9
C-H 3 3 3 O O-H 3 3 3 N
10
O-H 3 3 3 O C-H 3 3 3 O O-H 3 3 3 N
11
O-H 3 3 3 O C-H 3 3 3 O O-H 3 3 3 N O-H 3 3 3 O
12
C-H 3 3 3 O O-H 3 3 3 N
O-H 3 3 3 O C-H 3 3 3 O
H 3 3 3 A (A˚) 1.67 2.82 1.56 1.64 1.63 1.64 2.65 2.42 1.70(3) 1.60(3) 1.41(3) 2.603 2.38 1.82(3) 1.65(3) 1.86(3) 1.80(3) 1.74(3) 1.35(3) 2.58 1.78(3) 1.69(3) 1.59(3) 2.59 1.87(4) 1.42(3) 1.41(3) 2.58 1.95(4) 1.61(4) 1.55(3) 2.56 1.61(3) 1.72(3) 1.86(3) 2.56 1.76(3) 1.84(4) 2.03(4) 2.672 1.63(3) 1.44(3) 1.75(4) 1.90(4) 2.67 1.61(3) 1.57(3) 1.58(3) 1.67(3) 1.88(3) 1.95(3) 1.72(3) 2.612 2.58
D 3 3 3 A (A˚) 2.645(2) 3.465(2) 2.438(2) 2.679(2) 2.529(2) 2.625(4) 2.606(3) 2.618(3) 3.292(4) 3.163(5) 2.535(3) 2.604(3) 2.529(3) 3.275 3.234(3) 2.640(4) 2.609(4) 2.636(3) 2.605(3) 2.657(4) 2.487(3) 3.027(4) 2.634(3) 2.610(3) 2.591(3) 3.459(4) 2.642(3) 2.544(4) 2.566(4) 3.457(4) 2.619(3) 2.548(4) 2.569(5) 3.443(4) 2.621(3) 2.701(2) 2.688(2) 3.423(3) 2.593(4) 2.580(4) 2.635(5) 3.530(6) 2.568(3) 2.541(3) 2.703(4) 2.633(4) 3.519(5) 2.571(4) 2.581(4) 2.583(4) 2.606(4) 2.659(3) 2.768(4) 2.606(3) 3.469(4) 3.445(4)
D-H 3 3 3 A (deg) 171 128 180 180 166 179 171 173 127 124 169(3) 175(2) 168(2) 130 152 172(3) 163(3) 166(4) 162(3) 158(3) 177(3) 110 162(3) 160(3) 169(3) 156 163(4) 157(3) 156(3) 157 160(4) 170(3) 145(3) 157 179(4) 174(2) 159(3) 154 165(3) 168(5) 162(5) 154 164(3) 165(3) 166(2) 159(3) 152 160(3) 174(3) 164(2) 173(3) 161(3) 165(3) 162(3) 153 154
Three-Component Crystals. The asymmetric unit of 6 contains one moiety each of 1, H3TMA, and biphenyl. The ratio of 1 and H3TMA is same as the one observed in 3; however, the assembling of these components differs significantly from 3. The one-dimensional chain, which is a part of a two-dimensional layer, formed between 1 and H3TMA also repeated in the crystal structure of 6 with a different geometry. It was a zigzag chain in 3 but almost a linear chain in 6 (Figure 5a). In 6, the chain becomes linear by sacrificing the C-H 3 3 3 O hydrogen bond of the synthon-II and therefore the molecules are linked via only one O-H 3 3 3 N hydrogen bond. In 3, the free COOH groups of the chain were placed alternately onto the both sides of the chain and link them through the centro-symmetric synthon-I to result in
Santra and Biradha
honeycomb network with huge cavities and the carbonyl group does not participated in the network hydrogen bonding . Whereas in 6, the free COOH groups are placed to only one side of the chain and these chains interact via a new hetero synthon-V between COOH group and R,β-unsaturated carbonyl group. Now the chains within the layer are not related by the inversion and related by the translation, all CO or free -COOH groups in the layer point in one direction. This type of arrangement changes the hydrogen bonding and significantly reduced the cavity size (8 23 A˚2 in 6 and 23 42 A˚2 in 3) and shape (rectangular in 6 and hexagonal in 3). In other words the network can be described as a brick wall as both the moieties 1 and H3TMA act as T-shape node (Figure 5a). The cavity formed is good enough to accommodate two biphenyl molecules in succession (Figure 5b). The packing of the layers occur through the inversion center such that the channels size is as wide as the cavity size of the layer. The biphenyl molecules interact via edge-to-edge aromatic interactions in the channel to form a one-dimensional column (Figure 5c). We note here that the interactions between the biphenyls are similar to those observed in the crystal structure of biphenyl itself.16 However, at the molecular level, the geometry of the biphenyl differs significantly: in 6, the biphenyl is not planar and exhibit interplanar angle of 37° between the two C6-rings, whereas it is completely planar in the crystal structure of biphenyl (Figure 5d).
The crystal structures of 7 and 8, with anthracene and phenanthrene as guests, contain similar type two-dimensional layer as well as packing of the layers with a minor difference that the layers sit on mirror symmetry. As a result, the asymmetric unit is constituted by only half a unit each of 1, H3TMA, and guests. The anthracene and phenathrene molecules were found to be highly disordered and could not be located. The bigger guest molecule such as triphenylene has also been included in the crystal structure of 9. The hydrogen bonding of the layer remains the same as the above two structures, with some minor variations. The geometry of the one-dimensional chain formed by 1 and H3TMA is zigzag and the supportive C-H 3 3 3 O hydrogen bond of synthon-II also exists. Because of these geometrical differences in the 1D chain, the joining of the chains via synthon-V resulted in the cavities of pentagonal shape (Figure 6a). The layers pack in slipped fashion such that there exist one-dimensional channels (Figure 6b). The triphenylene molecules form a π-π dimer with centroid-to-centroid distance of 3.64 A˚ and interplanar angle of 0° (Figure 6c and d). Another interesting aspect is that the middle C6-rings of the dimer are perfectly overlap on each other while the peripheral C6 rings arrange in staggered manner. These dimers interact with the neighboring dimers via edge-to-edge π-π interactions to form a one-dimensional column. It is pertinent to note here that triphenylene moieties pack in slipped manner in its crystal structure with the centroid-to-centroid distance of 5.26 A˚, one of the peripheral C6-ring interacts with central C6-ring with a centroid to-centroid distance of 3.73 A˚ (Figure 6e).17
Article
Crystal Growth & Design, Vol. 9, No. 11, 2009
4973
Figure 1. Illustrations for the crystal structure of 2: (a) assembling of anions into corrugated 2D layer (bc-plane); (b) side view of the 2D layer via b-axis; (c) assembling of 2D layers into three-dimensional network by cations (space-filling mode); (d) double interpenetration of 3D networks.
Figure 2. Illustrations for the crystal structure of 3: (a) Hexagonal network via synthon-I and II ; (b) triple and parallel interpenetration of hexagonal networks; (c) side view of the packing of triply interpenetrated networks.
Therefore to the best of our knowledge, the dimer observed between the triphenylene moieties in 9 is first of its kind. The guest molecules occupy the 36.2, 36, 36, and 38% of unit cell volumes of 6, 7, 8, and 9 respectively. Four-Component Crystals. Our trails to include pyrene as a guest in 1 and H3TMA host resulted in the inclusion of adduct between pyrene and phenol in the crystal structure of 10. This reaction encouraged us to try to include some more related adducts; we were successful in obtaining pyrenehydroquinone and phenathrene-o-cresol-MeOH adducts also in the crystal structures of 11 and 12, respectively. The geometry and hydrogen bonding of the layers in the crystal structures of all these complexes are similar to those obtained in complexes 6-8. The guest occupied volume in crystals also remains to be same as above complexes (38, 37.7, and 37.4%
in 10, 11, and 12, respectively). However, the packing of the layers was found to depend on the geometry of the adduct included. The crystal structures of 10 and 11 are isostructural and in both cases the guest molecules form a one-dimensional column that fits in the channels formed by the slightly slipped packing of the layers (Figure 7). In 10 and 11, the repeat of layers occurs for every four layers (along c-axis) and interlayer separation of these layers is as short as 3.5 A˚. The layers interact via π-π interactions between the pyridine moieties of 1 and also between the central ring of H3TMA and carbonyl group of 1. In 10, the pyrene guest molecules are heavily disordered and could not be modeled, whereas the phenol molecules are disordered and modeled. In 11, the disorder 1,4-hydroquinone molecules are modeled,
4974
Crystal Growth & Design, Vol. 9, No. 11, 2009
whereas pyrene molecules are ordered. The guest molecules interact with each other via edge-to-face aromatic interactions. The hydroxyl groups interact with the carboxylate groups of the walls of the channels and pyrene molecules lie perpendicular to the plane of the layers and propagate in the channels. The crystal structure of 12 differs from the above structures as it has two symmetrically independent layers. The hydrogen bonding of the independent layers is same and it is also identical with the above-discussed structures. However, the distinct features of crystal structure 12 are the packing of the layers, guest inclusion, and guest-guest interactions. Four layers have a slipped packing and therefore contain big channels along the cavities of the layers (Figure 8). These channels are not continuous, as for every four layers the channels have offset packing. The guest molecules, unlike the above complexes, form a 2D layer that interpenetrates through the above hydrogen-bonded layers. Here it is important to note that in this reaction the o-cresol was used as a replacement for phenol. Initially, the reaction yields the crystals of complex 8, which has the phenanthrene alone
Figure 3. Illustrations for the crystal structure of 4: (a) 2D layer containing cavities, notice the double chain of H2TMA moieties and the C-H 3 3 3 O hydrogen bond pattern between the moieties of 1; (b) packing of 2D layers such that there exists cavities for the inclusion of napthalene guest (in space filling mode); (c) naphthalene guest molecules in space-filling mode showing no interactions between them.
Santra and Biradha
as a guest. However, on standing, these crystals were found to dissolve gradually to convert into the crystals of the complex 12. Distinguishing Salt or Cocrystal from IR Spectra. The materials containing salt and cocrystals were distinguished from analyzing carbonyl stretching frequencies of H3TMA molecule and C-C and C-N aromatic bond stretching frequencies of pyridine moieties of 1. (Figure 9). In cocrystals, the carbonyl of COOH of H3TMA exhibits a band at 1718 cm-1 or above (maximum observed at 1729 cm-1), whereas the same stretching frequency in ionic salts for H2TMA-1 appears at 1706 cm-1. All the neutral cocrystals exhibit C-C and C-N aromatic bond stretching frequencies of 1420 and 1602 cm-1, respectively, representing the free pyridine moieties of 1. In complex 4, where both the pyridines are potonated, these peaks are shifted to 1496 and 1628 cm-1. The situation with complexes 2 and 5 is not so clear, as they contain both protonated and nonprotonated pyridines. Conclusion The molecular component 1 was shown to form host systems with H3TMA to include variety of guest molecules. The interpenetration of the layers was eschewed in favor of the inclusion of guest molecules with minor variations in network geometries. The change in network geometry could be the result of relatively small size of guest molecules present in the solution when compared to the huge cavities observed in the networks of 3. Our results show that more than the formation of particular robust synthons, such as I-IV, the overall optimization of the interactions between the available components in the crystallization vessel plays a major role in determining the final structure. The presence of phenol in the reaction mixture resulted in the formation of neutral networks. The phenol did not act as a coguest when the guest molecules are biphenyl, triphenylene, and anthracene. It is important to note here that the cyclohexanone moiety of 1 played an important role in the formation of these systems as the similar reactions with cyclopentanone or acetone analogues of 1 did not result in the suitable crystals for single crystal X-ray diffraction. These materials have a great potential as organic zeolites18 due to their consistent layer formations with very short interlayer separation (3.5 to 4.0 A˚) and the guest occupied volumes of 30-38%.19 A new synthon (V), which
Figure 4. Illustrations for the crystal structure of 5: (a) 2D layer containing cavities, notice the single chain of H2TMA moieties and the C-H 3 3 3 O hydrogen bond pattern between moieties of 1; (b) packing of 2D layers creates channels for the inclusion of pyrene guest (in space filling mode); (c) column of pyrene guest molecules included across the channels.
Article
Crystal Growth & Design, Vol. 9, No. 11, 2009
4975
Figure 5. Illustrations for the crystal structure of 6: (a) 2D brick wall network of H3TMA and 1 in space filling model; (b) an inversion related packing of 2D layers (shown in pink and yellow color) containing 1D channel occupied by biphenyl guest (in space filling mode); (c) biphenyl guest packing in cocrystal 6; (d) packing of biphenyl in its molecular crystal.
Figure 6. Illustrations for the crystal structure of 9: (a) 2D network of H3TMA and 1 in space filling mode; (b) slipped packing of the layers (shown without guest); (c) side view and (d) top view of dimeric stacking of triphenylene guest in 9; (e) slipped packing of triphenylene molecule in its molecular crystal.
was observed between -COOH and the R,β-unsaturated carbonyl group, has been reproduced in six structures out of seven neutral structures studied here. The CSD-analysis shows that synthon-V is present in six crystal structures out of 515 structures containing both the fragments in CSD; all six structures are one-component systems. However, the interference of keto group in the formation of synthon-I found to be very high (183 out of 841 structures) compared to the aldehyde group (5 out of 36 structures). Further, these host systems provided an opportunity of studying the aggregation of rare adduct formations such as biphenyl, triphenylene, pyrenephenol, pyrene-1,4-hydroquinone and phenanthrene-o-cresol.
The biphenyl packing in the channels of 6 is similar to that of biphenyl crystal structure, whereas the triphenylene packing in 9 deviates significantly from triphenylene crystal structures. In the four-component systems, it is hard to imagine that the electron-rich components such as pyrene or phenanthrene form adducts with other electron-rich components such as phenol or 1,4-hydroquinone or o-cresol. Our efforts to cocrystallize these guest molecules without the host are in vein. Experimental Section General. FTIR spectra were recorded with a Perkin-Elmer Instrument Spectrum Rx Serial No. 73713. Powder XRD
4976
Crystal Growth & Design, Vol. 9, No. 11, 2009
Santra and Biradha
Figure 7. Illustrations for the crystal structure of 10 and 11: slightly slipped packing of the layers (four layers were shown) with the inclusion of (a) pyrene and phenol (space-filling) and (b) pyrene and 1,4-hydroquinone; one-dimensional columns by (c) pyrene (disordered) and phenol and (d) pyrene and 1,4-hydro quinone.
Figure 8. Illustrations for the crystal structure of 12: offset packing of the quadruple brick-wall layers (a) top view and (b) side view (guest molecules shown in space-fill); (c) two-dimensional layer of disordered phenanthrene, o-cresol, and MeOH; the unit that is occupied in the cavity of the quadruple layer is shown as a blue rectangle.
data were recorded with a PHILIPS Holland PW-1710 defractometer. Melting point measurement was carried out using Fisher Scientific instrument Cat. No. 12-144-1. Preparation of Crystal of Material 2-12. All the crystals suitable for single crystal X-ray diffraction were grown by the slow evaporation technique. A typical procedure includes dissolving 0.0394 g of 1 (0.143 mmol), 0.03 g of H3TMA (0.143 mmol), and a certain amount of guest (specified below) in MeOH and leaving the solution for slow
evaporation at room temperature. The crystals of salts 2, 4, and 5 were grown from 8-10 mL of MeOH, whereas the cocrystals of 3 and 6-11 were grown from 5 mL of MeOH and 1 mL of phenol mixture. For the cocrystals of 12, o-cresol was used in place of phenol. All the crystals were produced in moderate to high yield except in the case of 9 and the purity of the bulk materials has been verified by comparing the experimental and calculated powdered XRD patterns. In the case of 9, the yield of the reaction was increased
Article
Crystal Growth & Design, Vol. 9, No. 11, 2009
4977
Figure 9. IR spectra of the complexes to exemplify the characteristic features of salts and cocrystal.
by seeding with the mother liquor with the crystals of 9. Compounds 2-12 were characterized by IR spectra, X-ray powder diffraction, and single-crystal X-ray diffraction. No clear melting points were observed for any of these crystals; rather, charring of the crystals was observed near or above 300 °C. Crystals of 2. 70-75% yield after 5-6 h. FT-IR (KBr): 3447, 2942, 2460, 1706, 1604, 1406, 1270, 1211, 1169, 1147, 1067, 1017, 936,837, 753, 673, 538 cm-1. Crystals of 3. 60-65% yield after 10-12 h. FT-IR (KBr): 3432, 3167, 1723, 1603, 1420, 1250, 1168, 1032, 972, 828, 746, 695, 550 cm-1. Crystals of 4. Two and half equivalents of naphthalene (0.045 g) was used in the reaction. 45-50% yield after 10-12 h. FT-IR (KBr): 3087, 2523, 1706,1628, 1496, 1264, 1208, 1169, 970, 834, 749, 669, 531 cm-1. Crystals of 5. One equivalent of pyrene (0.029 g) was used in the reaction. 75-80% yield after 1-2 h. FT-IR (KBr): 3448, 3080, 2375, 1707, 1606, 1498, 1420, 1247, 1213, 1165, 1065, 928, 835, 750, 678, 539 cm-1.
Crystals of 6. Two and a half equivalents of biphenyl (0.055 g) was used in the reaction. 60-65% yield after 10-12 h. FT-IR (KBr): 3447, 3154, 2936, 2367, 1722,1602, 1419, 1234, 1211, 1170, 1071, 943, 825, 740, 689, 549 cm-1. Crystals of 7. One equivalent of anthracene (0.025 g) was used in the reaction. 60-65% yield after 10-12 h. FT-IR (KBr): 3421, 3167, 2372, 1725, 1604, 1420, 1249, 1171, 1033, 974, 829, 744, 670, 551 cm-1. Crystals of 8. One equivalent of phenanthrene (0.025 g) was used in the reaction. 60-65% yield after 10-12 h. FT-IR (KBr): 3422, 3167, 2374, 1725, 1604, 1420, 1249, 1170, 1033, 974, 829, 744, 670, 551 cm-1. Crystals of 9. One equivalent of triphenylene (0.033 g) was used in the reaction. 60-65% yield after 10-12 h on seeding the mother liquor by using the crystal of 9 from a previously prepared batch. Without seeding, the yield is too low (20-30%). FT-IR (KBr): 3197, 2912, 2448, 1729, 1601, 1421, 1256, 1202, 1164, 1070, 931, 828, 745, 667, 543 cm-1. Crystals of 10. One eq. of pyrene (0.029 g) was used in the reaction. 65-70% yield after 10-12 h. FT-IR (KBr): 3179,
4978
Crystal Growth & Design, Vol. 9, No. 11, 2009
Santra and Biradha
Scheme 1. Modeled Disorders of Guest Molecules
2941, 2373, 1720, 1602, 1419, 1265, 1172, 1066, 932, 827, 744, 669, 551 cm-1. Crystals of 11. One equivalent of pyrene (0.029 g) and two equivalents of 1,4-hydroquinone (0.031 g) was used in the reaction. 65-70% yield after 10-12 h. FT-IR (KBr): 3184, 2373, 1721, 1602, 1419, 1245, 1171, 1033, 973, 829, 744, 669, 551 cm-1. Crystals of 12. Two and a half equivalents of phenanthrene (0.062 g) was used in the reaction. 60-65% yield after 1-2 days. Here, after 8-10 h, crystals of 9 were found that dissolved gradually in mother liquor, resulting in crystals of 12 after 1-2 days. FT-IR (KBr): 3402, 3162, 2945, 2448, 1718, 1603, 1419, 1249, 1171, 1024, 934, 826, 752, 670, 550 cm-1. Crystal Structure Determination. All the single-crystal data were collected on a Bruker-APEX-II CCD X-ray diffractometer that uses graphite monochromated Mo KR radiation (μ = 0.71073 A˚) at room temperature (293 K) by the hemisphere method. The structures were solved by direct methods and refined by least-squares methods on F2 using SHELX-97.20 Non-hydrogen atoms were refined anisotropically and hydrogen atoms were fixed at calculated positions and refined using a riding model. The H-atoms attached to O-atom or N-atoms are located wherever id possible and refined using the ridging model. The fractional coordinates, full list of bond lengths and angles and the anisotropic displacement parameters have been deposited as Supporting Information. Pertinent crystallographic details were given in Table-1, the C-O bond lengths of -COOH or -COO- are given in Table 2 and hydrogen bond details were given in Table 3. The anthracene and phenathrene molecules in 7 and 8 are heavily disordered and hence Platon squeeze option was used in the final refinement.21 The disorder of phenol in 9, 1,4-hydroquinone in 10, and phenanthrene in 11 were modeled as shown in Scheme 1. Acknowledgment. We gratefully acknowledge financial support from CSIR, DST-FIST for the single-crystal X-ray facility. R.S. thanks UGC for a research fellowship. Supporting Information Available: IR spectra, powder X-ray patterns, and IR spectra and XRPD patterns for guest exchange reactions (PDF); crystallographic information for complexes 2-12 (CIF). This material is available free of charge via the Internet at http://pubs.acs.org.
(2) (3) (4) (5) (6)
(7) (8) (9)
(10)
(11) (12)
(13) (14) (15) (16) (17) (18)
(19)
References (1) (a) Tiekink, E. R. T.; Vittal, J. J. Frontiers in Crystal Engineering; Wiley: West Sussex, U.K., 2006. (b) Braga, D.; Grepioni, F. Making Crystals By Design: Methods, Techniques and Applications; Wiley-VCH: Weinheim, Germany, 2007. (c) Atwood, J. L.; Steed, J. W. Encyclopedia of Supramolecular Chemistry; Dekker, New York, 2004. (d) Jones, W. I.; Rao, C. N. R. Supramolecular Organization and Materials Design; Cambridge University Press, Cambridge, U.K., 2002. (e) Velaga, S. P.; Basavoju, S.; Bostrom, D. J. Mol. Struct.
(20) (21)
2008, 889, 150. (f) Moulton, B.; Zaworotko, M. J. Chem. Rev. 2001, 101, 1629. (g) Trask, A. V.; Jones, W. Top. Curr. Chem. 2005, 254, 41. (h) Macgillivray, L. R.; Papaefstathiou, G. S.; Friscic, T.; Hamilton, T. D.; Bucar, D. K.; Chu, Q.; Varshney, D. B.; Georgiev, I. G. Acc. Chem. Res. 2008, 41, 280. € (a) Zahmakiran, M.; Ozkar, S. Langmuir 2008, 24, 7065. (b) Sawaki, T.; Aoyama, Y. J. Am. Chem. Soc. 1999, 121, 4793. (a) Custelcean, R.; Jiang, D.; Hay, B. P.; Luo, W.; Gu, B. Cryst. Growth Des. 2008, 8, 1909. (b) Kawano, M.; Kawamichi, T.; Haneda, T.; Kojima, T.; Fujita, M. J. Am. Chem. Soc. 2007, 129, 15418. Thallapally, P. K.; McGrail, B. P.; Atwood, J. L.; Gaeta, C.; Tedesco, C.; Neri, P. Chem. Mater. 2007, 19, 3355. Kadri, M.; Djemil, R.; Abdaoui, M.; Winum, J.-Y.; Coutrotb, F.; Montero, J.-L. Bioorg. Med. Chem. Lett. 2005, 15, 889. (a) Rajput, L.; Biradha, K. Cryst. Growth Des. 2009, 9, 40. (b) George, S.; Goldberg, I. Cryst. Growth Des. 2006, 6, 755. (c) Burrows, A. D. Struct. Bonding (Berlin) 2004, 108, 55. (d) Sreekanth, B. R.; Vishweshwar, P.; Vyas, K. Chem. Commun. 2007, 2375. (e) Etter, M. C. Acc. Chem. Res. 1990, 23, 120. (f) Samai, S.; Biradha, K. CrystEngComm. 2009, 11, 482. (g) Shattock, T. R.; Arora, K. K.; Vishweshwar, P.; Zaworotko, M. J. Cryst. Growth Des. 2008, 8, 4533. (h) Aakeroy, C. B.; Desper, J.; Urbina, J. F. Chem. Commun. 2005, 2820. (a) Desiraju, G. R. Angew. Chem., Int. Ed. 1995, 34, 2311. (b) Desiraju, G. R. Angew. Chem., Int. Ed. 2007, 46, 8342. (a) Mohamed, S.; Tocher, D. A.; Vickers, M.; Karamertzanis, P. G.; Price, S. L. Cryst. Growth Des. 2009, 9, 2881. (b) Aakeroy, C. B.; Fasulo, M. E.; Desper, J. Mol. Pharm. 2007, 4, 317. (a) Johnson, S. L.; Rumon, K. A. J. Phys. Chem. 1965, 69, 74. (b) Bhogala, B. R.; Basavoju, S.; Nangia, A. CrystEngComm. 2005, 7, 551. (c) Men, Y. B.; Sun, J.; Huang, Z. T.; Zheng, Q. Y. CrystEngComm 2009, 11, 978. (d) Reddy, L. S.; Bethune, S. J.; Kampf, J. W.; Hornedo, N. R. Cryst. Growth Des. 2009, 9, 378. (a) Weyna, D.; Shattock, R. T.; Vishweshwar, P.; Zaworotko, M. J. Cryst. Growth Des. 2009, 9, 1106. (b) Shattock, T. R.; Vishweshwar, P.; Wang, Z.; Zaworotko, M. J. Cryst. Growth Des. 2005, 6, 2046. (c) Sharma, C. V. K.; Zaworotko, M. J. Chem. Commun. 1996, 2655. (a) Duchamp, D. J.; Marsh, R. E. Acta Crystallogr., Sect. B 1969, 25, 5. (b) Herbstein, F. H. Top. Curr. Chem. 1987, 140, 107. (a) Bhogala, B. R.; Vishweshwar, P.; Nangia, A. Cryst. Growth Des. 2002, 2, 325. (b) Bhogala, B. R.; Nangia, A. Cryst. Growth Des. 2003, 3, 547. (c) Bhogala, B. R.; Basavoju, S.; Nangia, A. Cryst. Growth Des. 2005, 5, 1683. (d) Bhogala, B. R.; Nangia, A. New J. Chem. 2008, 32, 800. Herbstein, F. H.; Kapon, M.; Reisner, G. M. J. Incl. Phenom. 1987, 5, 211. Ma, B.-Q.; Coppens, P. Chem. Commun. 2003, 2290. Santra, R.; Ghosh, N.; Biradha, K. New J. Chem. 2008, 32, 1673. Trotter, J. Acta Crystallogr. 1961, 14, 1135. Ahmed, A. R.; Trotter, J. Acta Crystallogr. 1963, 16, 503. (a) Aoyama, Y. Top. Curr. Chem. 1998, 198, 131. (b) Sozzani, P.; Comotti, A.; Simonutti, R.; Meersmann, T.; Logan, J. W.; Pines, A. Angew. Chem., Int. Ed. 2000, 39, 2695. (c) Ung, A. T.; Gizachew, D.; Bishop, R.; Scudder, M. L.; Dance, I. G.; Craig, D. C. J. Am. Chem. Soc. 1995, 117, 8745. We have tried the guest exchange reactions by soaking the crystals of complexes 6 or 7 in nitrobenzene or benzene solutions. The XRPD patterns, IR spectra and TLC have shown complete exchange of anthracene or biphenyl in case of nitrobenzene. The XRPD patterns before and after exchange remains same with minor differences indicating no major changes in structure occurred during the exchange. The quality of the single crystals that broke during the exchange is not good enough for single-crystal structure studies. Sheldrick, G. M. SHELX-97, Program for the Solution and Refinement of Crystal Structures; University of Gottingen: Gottingen, Germany, 1997. Spek, A. L. PLATON A Multi Purpose Crystallographic Tool; Utrecht University: Utrecht, The Netherlands, 2002.
