Effect of Substituents on Molecular Geometry and Self-Aggregation in

Lalit Rajput, Palash Sanphui, and Kumar Biradha*. Department of Chemistry, Indian Institute of Technology, Kharagpur-721302, India. ReceiVed June 18, ...
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Effect of Substituents on Molecular Geometry and Self-Aggregation in the Crystal Structures of Ethylenediamine-N,N,N′,N′-tetraamides Lalit Rajput, Palash Sanphui, and Kumar Biradha* Department of Chemistry, Indian Institute of Technology, Kharagpur-721302, India

CRYSTAL GROWTH & DESIGN 2007 VOL. 7, NO. 9 1872-1880

ReceiVed June 18, 2007; ReVised Manuscript ReceiVed June 29, 2007

ABSTRACT: The derivatives of ethylenediamine-N,N,N′,N′-tetraamides were prepared, and their crystal structures were analyzed in order to understand the variations in their molecular and supramolecular geometries with respect to the substituents. The crystal structures of these compounds indicated that these moieties can exhibit four types of molecular geometries. These geometries contain a minimum of two intramolecular N-H‚‚‚N hydrogen bonds between the amine N-atom and N-H group of the amide. The p-bromophenyl, p-chlorophenyl, 3-pyridyl, and 4-pyridyl derivatives exhibit H-shape geometry, p-iodophenyl, p-toloyl, and 4-pyridyl derivatives exhibit similar geometrical shape, the 4-pyridyl derivative exhibited the geometry of the Greek character π, and the benzyl derivative exhibited the geometry of a swastika. Among the halogen derivatives, the iodo derivative was found to behave differently from bromo and chloro derivatives. The amide-to-amide hydrogen bonds between the iodo-substituted molecules were sacrificed in favor of inclusion of DMF. Introduction Understanding the relationship between molecular structure and crystal structure is the fundamental aspect in crystal engineering.1-3 Establishing such a relationship becomes quite complicated if the molecules contain flexibility as well as multiple functional groups because of the possibility of several stable conformations and therefore supramolecular architectures for a given molecule. In this situation, it is essential to have a group of crystal structures of the compounds containing almost similar functionalities to understand their molecular conformations and respective supramolecular architectures.4 Hydrogen bonds are the major tools in crystal engineering of molecules containing functional groups such as COOH, OH, amides, amines, and pyridine functionalities.5 In particular, the amide functional groups are ubiquitous in nature, as they are present in small or complex synthetic, natural, or biological molecules.6 Recently we have studied a homologous series of amido(bispyridine)alkanes and rationalized the hydrogen bond patterns observed in these analogues by comparing with those in amido(bisphenyl)alkanes.7 In this contribution, as part of our continuing studies on crystal engineering of molecules containing multiple functional groups, we had chosen to study the tetraamides of EDTA containing various aromatic groups on the amide N-atoms. The Cambridge Structural Database8 search on this compound indicates that there exists only one crystal structure containing 1 (R)H, primary amide) to date.9 Therefore, no crystal structure of secondary amide containing moiety 1 is reported thus far. These molecules are highly flexible, as they contain six CH2 groups. Further, when R is a pyridyl moiety, they contain three potential hydrogen-bonding groups namely amide, amine, and pyridine. As a result, in these molecules, three of the acceptors compete with each other to form a hydrogen bond with the donor N-H atom. When R is 4-halophenyl, the competition for the donor N-H is between two groups, the amide O-atom and the amine N-atom. Moreover, in the case of halo derivatives it is interesting to see whether p-Cl, p-Br, and p-iodophenyl derivatives are isostructural. Also, it is of importance to study how the weak halo-halo interactions assemble the hydrogen-bonded aggregates into higher dimen* Author to whom correspondence should be addressed. Fax:+91-3222282252; tel: +91-3222-283346; e-mail: [email protected].

Scheme 1. Schematic Drawing of Four Molecular Shapes for Moiety 1

sional architectures.10 In the present study, we focus our attention on the conformations of these analogues, the change in the hydrogen-bonding patterns with respect to the conformations, the selectivity in amide-to-amide hydrogen bond formation, and the isostructurality of halide analogues. Accordingly, we have synthesized a series of new compounds 2-10 and crystallized the compounds under various conditions. Indeed, it was found that the moiety 1 is capable of forming four shapes (conformations) as shown in Scheme 1, and each structure is capable of having its own self-aggregation. Molecule 5 with R as 4-pyridyl has shown more versatility to form three of the four conformations and has included the guest molecules such as CCl4 or MeOH and H2O. Results and Discussion We have employed two well-known synthetic procedures for the preparation of these new compounds. The first method is a one-pot synthesis: reaction of EDTA and the corresponding amine in the presence of triphenyl phosphite and pyridine.11 The second method is a two step procedure: preparation of the EDTA ester and treatment of the ester with the corresponding amine.12 The crystallization of the compounds 2-10 in various solvents resulted in single crystals suitable for X-ray diffraction. For compound 8 only cell parameters were determined, and we found that they have cell parameters similar to those of

10.1021/cg0705557 CCC: $37.00 © 2007 American Chemical Society Published on Web 08/11/2007

Structures of Ethylenediamine-N,N,N′,N′-tetraamides

Crystal Growth & Design, Vol. 7, No. 9, 2007 1873

Table 1. Crystallographic Parameters for Compounds 2-7

formula mol wt T (K) system Space Group a (Å) B (Å) c (Å) R (deg) β (deg) γ (deg) vol (Å3) Z Dcalc (mg/m3) R1 (I > 2σ(I)) wR2 (on F2, all data)

2

3

4

5a

5b

5c

6

7

C34H32N6 O4Br4 908.30 293(2) triclinic P1h 7.875(2) 10.483(2) 11.123(2) 79.56(3) 79.79(3) 88.83(3) 888.7(3) 1 1.697 0.0748 0.2246

C40H46N8 O6I4 1242.45 293(2) monoclinic C2/c 41.778(8) 4.777(1) 28.950(6) 90.00 127.83(3) 90.00 4562.9(16) 4 1.809 0.0752 0.1897

C30H32N1 0O4 596.66 293(2) monoclinic P21/c 14.586(3) 9.707(2) 10.554(2) 90.00 97.56(3) 90.00 1481.3(5) 2 1.338 0.0523 0.0964

C61H70N2 0O10 1243.37 293(2) triclinic P1h 8.043(2) 10.949(2) 35.444(7) 83.33(3) 89.78(3) 85.02(3) 3088.3(11) 2 1.337 0.0737 0.2316

C31H34N1 0O5Cl4 768.48 293(2) monoclinic P21/n 14.620(3) 21.030(4) 12.810(3) 90.00 109.43(3) 90.00 3714.2(13) 4 1.374 0.0749 0.3000

C48H58N1 0O23 1143.04 293(2) monoclinic P2/n 12.642(3) 12.786(3) 17.557(4) 90.00 97.56(3) 90.00 2813.3(10) 2 1.349 0.0681 0.2316

C38H44N6 O4 648.79 293(2) monoclinic P21/c 13.402(3) 14.539(3) 9.368(2) 90.00 102.91(3) 90.00 1779.3(6) 2 1.211 0.0659 0.1657

C38H44N6 O4 648.79 293(2) monoclinic P21/c 12.991(3) 12.805(3) 10.283(2) 90.00 95.04(3) 90.00 1703.8(6) 2 1.265 0.0473 0.1161

Table 2. Intramolecular Hydrogen Bonds in Crystal Structures 2-7 hydrogen bonds 2 3

N(21)-H(21)‚‚‚N(1) N(21)-H(21)‚‚‚O(17) N(21)-H(21)‚‚‚N(1) 4 N(2A)-H(2A1)‚‚‚N(1) 5a N(22A)-H(22A)‚‚‚O(16A) N(22A)-H(22A)‚‚‚N(1A) N(22B)-H(22C)‚‚‚O(16B) N(22B)-H(22C)‚‚‚N(1B) N(42A)-H(42A)‚‚‚O(36A) N(42A)-H(42A)‚‚‚N(2A) N(42B)-H(42C)‚‚‚O(36B) N(42B)-H(42C)‚‚‚N(2B) 5b N(22)-H(22)‚‚‚O(16) N(22)-H(22)‚‚‚N(1) N(42)-H(42)‚‚‚O(36) N(42)-H(42)‚‚‚N(2) 5c N(22)-H(22)‚‚‚N(1) 6 N(21)-H(21)‚‚‚O(18) N(21)-H(21)‚‚‚N(31) 7 N(11)-H(11)‚‚‚N(1) N(21)-H(21)‚‚‚N(1)

H‚‚‚A (Å) D‚‚‚A (Å) D-H‚‚‚A (deg) 2.20 2.22 2.24 2.27 2.23 2.35 2.17 2.32 2.25 2.33 2.19 2.27 2.19 2.29 2.23 2.31 2.16 2.07 2.30 2.38 2.37

2.681(8) 3.054(12) 2.717(17) 2.684(3) 2.927(5) 2.782(5) 2.948(5) 2.737(5) 2.902(5) 2.766(5) 2.924(5) 2.710(5) 3.004(7) 2.669(6) 2.965(7) 2.749(8) 2.636(5) 2.872(4) 2.724(4) 2.771(3) 2.762(3)

115 163 115 110 138 111 149 110 133 112 142 111 158 107 143 112 115 156 111 108 108

compound 2.13 We were not successful in obtaining crystals suitable for X-ray analysis for compounds 9 and 10. The crystallographic parameters for all the crystal structures are given in Table 1. Single crystal analyses reveal that compounds 2, 4, 6, 7, and 8 are crystallized as such while 3 and 5 include solvent molecules to form 3‚2(DMF) and 2(5)‚MeOH‚H2O, 5a. In addition, compound 5 has shown an ability to include CCl4 and H2O and forms 5‚CCl4‚H2O, 5b, when crystallized from a mixed solvent containing DMF and CCl4 in a 1:4 ratio. Molecule 5 has also shown an ability to form crystals of a complex (H4-3)(H-TMA)2‚7(H2O), 5c, with trimesic acid (H3-TMA). Although there are four shapes observed in these structures, all of them exhibit perfect anti geometry for the ethylenediamine moiety with the torsional angle N-C-C-N close to 180° except in 5b (169°). Out of the seven structures, three structures (2, 4, 5c) have H-shape molecular geometry (I), whereas the shapes II, III, and IV are exhibited by 3/5a/6, 5b, and 7, respectively. The difference between these shapes can be well described by nonbonded torsion angle θ (Scheme 2). The geometries I, II/III, and IV have the θ values of 176-180°,

Table 3. Intermolecular Hydrogen Bonds in Shape-I Molecules

2 4 5c

hydrogen bond type

H‚‚‚A (Å)

D‚‚‚A (Å)

D-H‚‚‚A (deg)

N(11)-H(11)‚‚‚O(5) C(1)-H(1B)‚‚‚O(5) C(2)-H(2A)‚‚‚O(5) N(2B)-H(2B1)‚‚‚N(1A) C(3A)-H(3A)‚‚‚N(1B) C(2A)-H(2A2)‚‚‚O(5) N(11)-H(11)‚‚‚O(36) N(12)-H(12)‚‚‚O(31) N(21)-H(21)‚‚‚O(33) C(11)-H(11)‚‚‚O(33) C(21)-H(21)‚‚‚O(34) C(3)-H(3B)‚‚‚O(35) C(24)-H(24)‚‚‚O(26) C(25)-H(25)‚‚‚O(26) O(1W)‚‚‚O(5W) O(1W)‚‚‚O(35) O(2W)‚‚‚O(4W) O(3W)‚‚‚O(5W) O(3W)‚‚‚O(34) O(3W)‚‚‚O(4W) O(5W)‚‚‚O(32)

2.17 2.54 2.48 2.15 2.54 2.61 1.75 2.15 1.71 2.60 2.52 2.49 2.55 2.57

3.013(8) 3.514(9) 3.378(9) 3.007(3) 3.431(5) 3.424(4) 2.604(5) 2.867(6) 2.568(6) 3.450(6) 3.189(6) 3.146(6) 3.132(6) 3.166(6) 2.796(7) 2.728(5) 2.24(2) 2.628(9) 2.780(6) 2.708(8) 2.586(6)

169 178 153 179 159 146 174 141 171 152 129 125 121 122

45-49°, and 80°, respectively. The parameters for intramolecular hydrogen bonds are given in Table 2. In the H-shape moieties (I), two of the four amides are involved in the formation of intramolecular N-H‚‚‚N hydrogen bonds with the amine N-atom. In geometries II and III, two of the amide N-H groups exhibit intramolecular N-H‚‚‚N as well as intramolecular N-H‚‚‚O hydrogen bonds, while in shape-IV all the four amide groups are involved in intramolecular N-H‚‚‚N hydrogen bonds.

Scheme 2. Nonbonded Torsion Angle θ between C-Atoms Indicated by • Figure 1. Ball-stick representation of H-shape (I) molecules observed in crystal structures 2, 4, and 5c (N ) blue, O ) red, H ) turquoise, and C ) gray).

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Figure 2. Representations for crystal structure 2: (a) 1D-network (runs along a-axis) via amide-to-amide N-H‚‚‚O hydrogen bonds (blue); (b) joining of N-H‚‚‚O hydrogen-bonded chains via Br‚‚‚Br interactions (blue) to form a 2D-layer (ac-plane).

Figure 3. Representation for crystal structure 4: 2D-layer via long N-H‚‚‚O (red) and N-H‚‚‚N hydrogen bonds (blue) (a) top view; (b) side view. The molecules are shown in two colors to represent the interdigitation of two sets of parallely aligned molecules.

Figure 4. Representation for crystal structure of 5c: (a) 2D-hydrogen-bonded layer containing the zigzag chains of HTMA and H2-5; (b) layer of water molecules (ab-plane) and H-TMA. Notice zigzag chains of water molecules.

H-Shape Molecules. In the H-shape structures, the molecule exhibits an inversion center which lies on the C-C bond of the ethylene moiety (Figure 1). The aromatic moieties on amide groups that are attached to different amine N-atoms interact with each other via intramolecular π-π interactions with centroidto-centroid distance and interplanar angles of 4.17 Å and 17°, 4.46 Å and 20.8°, and 4.18 Å and 23.4° in 2, 4, and 5c, respectively.14

Notably, the similarities in the molecular geometries had not resulted in the similar supramolecular architectures (Table 3). In 2, two of the amides, which do not participate in intramolecular N-H‚‚‚N hydrogen bonds, engage in amide-to-amide N-H‚‚‚O hydrogen bonds and form a one-dimensional chain (Figure 2a). In the chain, two CO groups of the amides which are involved in intramolecular hydrogen bonds form C-H‚‚‚O hydrogen bonds with CH2 moieties. The chains join together

Structures of Ethylenediamine-N,N,N′,N′-tetraamides

Crystal Growth & Design, Vol. 7, No. 9, 2007 1875

Figure 5. Illustrations of molecular geometries in crystal structures of 3, 5a, and 6: ball and stick representations of (a) molecule 3; two independent molecules of 5: (b) A and (c) B in 5a; (d) molecule 6.

via Br‚‚‚Br (3.574(2) Å) interactions to form a two-dimensional layer which has a width of 5.25 Å (Figure 2b). In 4, because of the presence of pyridine moieties the molecules join together via N-H‚‚‚N hydrogen bonds. Each molecule has been connected to four of its neighbors by donating two N-H groups, which are not involved in intramolecular hydrogen bonds, to two pyridine moieties (Figure 3a). The two N-H groups that are involved in intramoleuclar hydrogen bonds also participate in very long N-H‚‚‚O hydrogen bonds (H‚‚‚ O, N‚‚‚O, N-H‚‚‚O: 2.691 Å, 3.430(3) Å, 144.85°) with the amide CO. In fact, this particular CO forms a better C-H‚‚‚O hydrogen bond (H‚‚‚O, C‚‚‚O, C-H‚‚‚O: 2.614 Å, 3.424(4) Å, 145.87°) with aromatic C-H than with N-H. The layers are highly corrugated with approximate thickness of 14.5 Å (Figure 3b). The remaining two pyridine units from each molecule point above and below the layer and connect the layers via C-H‚‚‚N hydrogen bonds. The asymmetric unit of 5c contains a half unit of doubly protonated 5, one unit of HTMA, and four water molecules (two with full and two with half occupancy). The deprotonation of two of the three COOH groups of H3TMA is apparent from the bond lengths of C-O of carboxylates. The deprotonated carboxylates have C-O lengths of 1.276(6) and 1.233(6) Å, and 1.222(6) and 1.300(6) Å, while those of -COOH group are 1.203(7) and 1.308(7) Å. HTMA moiety joins the ligands via a charge-assisted N-H‚‚‚O and C-H‚‚‚O hydrogen-bonded synthon to form a zigzag chain (Figure 4a).15 These chains are linked together by O-H‚‚‚O hydrogen bonds between water and COOH, and C-H‚‚‚O hydrogen bonds between aromatic C-H groups and CO of amides. The moieties of TMA that are involved in the layer are further interconnected to those of neighboring layers to form a layer of TMA and H2O molecules via O-H‚‚‚O hydrogen bonds (Figure 4b). In this layer, the water molecules form a zigzag chain and link the TMA moieties. Two of the amide N-H groups that are not involved in intramolecular hydrogen bonds form N-H‚‚‚O hydrogen bonds with CO of the COOH group.

Table 4. Intermolecular Hydrogen Bonds in Shape-II Molecules hydrogen bond type 3

N(11)-H(11)‚‚‚O(100) C(2)-H(2A)‚‚‚O(100) C(2)-H(2B)‚‚‚O(17) 5a N(12A)-H(12A)‚‚‚N(21A) N(12B)-H(12C)‚‚‚N(21B) N(32A)-H(32A)‚‚‚N(41A) N(32B)-H(32C)‚‚‚N(41B) C(4A)-H(4A1)‚‚‚N(11A) C(6A)-H(6A1)‚‚‚N(11A) C(4B)-H(4B1)‚‚‚N(11B) C(21A)-H(21A)‚‚‚O(46A) C(6B)-H(6B1)‚‚‚N(11B) C(25B)-H(25B)‚‚‚O(46B) C(41A)-H(41A)‚‚‚O(26A) C(41B)-H(41B)‚‚‚O(26B) C(45A)-H(45A)‚‚‚O(26B) C(45B)-H(45B)‚‚‚O(26A) 6 N(11)-H(11)‚‚‚O(28) C(33)-H(33A)‚‚‚O(28)

H‚‚‚A (Å) D‚‚‚A (Å) D-H‚‚‚A (deg) 2.20 2.58 2.53 2.14 2.08 2.09 2.11 2.62 2.53 2.60 2.45 2.58 2.58 2.54 2.49 2.55 2.46 1.94 2.59

3.00(2) 3.44(2) 3.309(14) 3.002(5) 2.930(5) 2.939(5) 2.963(5) 3.435(6) 3.497(6) 3.506(6) 3.353(6) 3.504(6) 3.476(6) 3.463(6) 3.411(6) 3.462(5) 3.342(5) 2.800(4) 3.416(4)

153 147 137 175 169 171 171 142 175 156 164 160 161 170 170 168 159 177 143

Shape-II Molecules. The crystal structures of 3, 5a, and 6 exhibited shape-II (Figure 5) geometry. The structures 3 and 5a include solvent molecules in their crystal lattice. Although the shapes are similar, the crystal packing is obviously different from each other owing to the obvious differences in functional groups ((iodophenyl, 4-pyridyl, and p-tolyl, Table 4). Interestingly, the halo analogue 3 exhibits different molecular and supramolecular geometries from those of the Cl and Br derivatives. For example, 3 has DMF included in its crystal structure but 2 and 8 do not, although all are crystallized from DMF. The asymmetric unit is constituted by a half unit of 3 and one DMF molecule. Surprisingly, the crystal packing in 3 is governed by iodo‚‚‚iodo interactions but not by the conventional N-H‚‚‚O hydrogen bonds between amides. The molecules form a 2D corrugated layer with (4,4)-geometry via I‚‚‚I interactions (Figure 6a). Two of these layers interpenetrate in parallel fashion via weak hydrogen bonds (Figure 6b). The interpenetrated layers contain channels which run parallel to the layers. These channels

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Figure 6. Illustrations for crystal structure 3: (a) 2D-layer via I‚‚‚I interactions with (4,4)-geometry, (b) parallel 2-fold interpenetration of (4,4)networks (magenta and green); (c) side view of the doubly interpenetrated layer containing channels occupied by DMF molecules.

are occupied by the DMF molecules (Figure 6c). Two of the four amide groups are involved in intramolecular N-H‚‚‚O and N-H‚‚‚N hydrogen bonds, while the other two amides bind the DMF moiety in the channels via N-H‚‚‚O hydrogen bonds. The DMF molecules occupy 24% of the unit cell volume.16 The I‚‚‚I interactions observed in this structure can be classified as type-II interactions, as they have a C-I‚‚‚I angle of 170° and I‚‚‚I-C angle of 80°. The Br‚‚‚Br interactions observed in 2 can be classified as type-I, as those angles are nearly equal (C-Br‚‚‚Br: 148.2° and Br‚‚‚Br-C:141.4°).17 The TGA analysis shows that 3 loses DMF from 95 to 115 °C and the compound is stable up to 261 °C. In the crystal structure of 5a, the asymmetric unit contains two independent moieties of 5, one H2O, and one MeOH molecule (Figure 5b and 5c). The difference between the two molecules is the conformation in the horizontal chain. In molecule A, the horizontal unit exhibits all anti conformations with a length of 18.95 Å, whereas in molecule B, the horizontal unit exhibits two gauche conformations and hence has a comparatively shorter length (18.53 Å) than that of A. Accordingly, the C(H2)-N-C(H2)-C(H2) torsions in the horizontal unit of A are 164.9° and 166.2°, whereas in B they are 63.9° and 63.4°. However, in both molecules (A and B), two of the amide N-H groups exhibit intramolecular N-H‚‚‚N as well as intramolecular N-H‚‚‚O hydrogen bonds. Further, both form similar types of N-H‚‚‚N hydrogen-bonded 1D-ladders containing cavities (Figure 7a and 7b). Two of the four pyridine moieties and two of four amide N-H groups engage in the formation of these 1D-chains. The cavities of the chains are filled by the interdigitation of the molecular chains of A and B via π‚‚‚π interactions between the pyridyl groups. These molecular chains interact with each other via C-H‚‚‚N and C-H‚‚‚OdC interactions to form layers AA or BB containing the inversion center. These 2D-layers interdigitate with each other and form AABBAABBAA type crystal packing. This type of packing generates two types of cavities which are occupied by H2O or MeOH molecules via O-H‚‚‚N hydrogen bonds with pyridine moieties. In structure 6, the molecule lies on an inversion center; as a result, the asymmetric unit is constituted by a half unit of 6. Two of the four N-H groups engage in intramolecular

N-H‚‚‚O and N-H‚‚‚‚N hydrogen bonds (Figure 8), whereas the remaining two are involved in intermolecular amide-to-amide hydrogen bonds to form a 2D-layer. Each molecule has been connected to four of its neighbors, and the tolyl groups hang above and below the layer with the thickness of 13.4 Å, the length of the a-axis. Shape-III Molecules. Molecule 5 exhibits shape-III in the crystal structure of 5b (Figure 9). The asymmetric unit contains one molecule of 5 and unidentified solvent molecules. PLATON calculation shows that it has guest available volume of 27% of the crystal volume. The presence of CCl4 is conformed by the IR spectra which shows an intense band at 787 cm-1 corresponding to stretching vibration of C-Cl bond. Further, this band was found to be absent in complex 5a. TGA analysis of 5b shows that one molecule each of CCl4 and H2O are present per formula unit of 5. The horizontal unit contains one gauche conformation with a C(H2)-N-C(H2)-C(H2) torsion of 70.46° and a length of 18.68°. Two of the pyridine rings which are connected to different amine N-atoms interact via π‚‚‚π interactions with a centroidto-centroid distance of 4.175 Å and a plane-to-plane angle of 23.4°. Two amide NH groups interact with two pyridine units via N-H‚‚‚N hydrogen bonds to form 2D-layer containing cavities for guest inclusion (Table 5). Within the layer the pyridine unit which does not participate in the N-H‚‚‚N hydrogen bond interacts via π-π interactions. These layers pack on each other via C-H‚‚‚O hydrogen bonds between the amide CO groups and aromatic C-H groups. Shape-IV Molecules. Molecule 7 is somewhat different from rest of the structures, as it has a benzyl group in place of the phenyl/pyridyl groups. The presence of a benzyl group gives additional freedom to the molecule to exist in a more stable conformation (Figure 10a). Accordingly, the phenyl parts of benzyl groups lie away from each other and exhibit more symmetry in interactions compared to previous structures. The shape of this molecule resembles that of a swastika. In this structure, all four amides participate in intramolecular N-H‚‚‚N hydrogen bonds and intermolecular N-H‚‚‚O hydrogen bonds which lead to the formation of a 2D-layer (Figure 10b and 10c) with a layer thickness of 13 Å, the length of the a-axis. We note here that similar to 7, the crystal structure of

Structures of Ethylenediamine-N,N,N′,N′-tetraamides

Crystal Growth & Design, Vol. 7, No. 9, 2007 1877

Figure 7. Illustrations for the crystal structure of 5a: 1D-ladders formed by N-H‚‚‚N hydrogen bonds by molecules (a) A and (b) B of 5a; (c) the packing of chains of A and B in BBAABBAA fashion; MeOH and water molecules are represented as yellow and blue balls respectively; (d) interdegitation of pyridyl groups of one ladder into another ladder via π‚‚‚π interactions.

Figure 8. Illustrations for crystal structure of 6: (a) 2D-layers assembled via amide-to-amide N-H‚‚‚O hydrogen bonds (bc-plane); tolyl groups are not shown for the sake of clarity; (c) side view of the layer (along b-axis) with p-tolyl groups.

the primary amide of 1 (R ) H) also forms four intramolecular N-H‚‚‚N hydrogen bonds.9 The 2D-layers in 7 interact with each other via C-H‚‚‚O interactions between aromatic C-H groups and the CO of the amide groups.

Conclusions In summary, we have synthesized nine new derivatives and determined crystal structures of nine crystalline materials of 1.

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Figure 9. Illustrations for crystal structure of 5b: (a) shape-III geometry observed for 5 in 5b; (b) 2D-layers assembled by N-H‚‚‚N hydrogen bonds (ab-plane), (c) space-filling representation; notice two type of cavities; (d) side view of the layer (along a-axis).

Figure 10. Illustration for crystal structure 7: (a) the geometry of molecule 7 in its crystal structure; (b) the hydrogen-bonded layer (bc-plane); benzyl groups are not shown for the sake of clarity; (c) side view of the layer; benzyl groups are included (along c-axis). Table 5. Intermolecular Hydrogen Bonds in Shape-III and IV Molecules

5b

6

hydrogen bond type

H‚‚‚A (Å)

D‚‚‚A (Å)

D-H‚‚‚A (deg)

N(12)-H(12)‚‚‚N(21) N(32)-H(32)‚‚‚N(41) C(4)-H(4B)‚‚‚N(31) C(6)-H(6B)‚‚‚N(11) C(21)-H(21)‚‚‚O(46) C(31)-H(31)‚‚‚O(46) C(41)-H(41)‚‚‚O(16) C(45)-H(45)‚‚‚O(26) N(21)-H(21)‚‚‚O(10) N(11)-H(11)‚‚‚O(10) C(27)-H(27A)‚‚‚O(20) C(23)-H(23)‚‚‚O(20)

2.12 2.06 2.55 2.56 2.54 2.53 2.58 2.57 2.53 2.21 2.55 2.57

2.965(8) 2.911(8) 3.437(9) 3.485(9) 3.427(10) 3.402(10) 3.512(10) 3.406(10) 3.312(3) 2.968(3) 3.489(3) 3.478(3)

168 174 152 160 160 156 176 149 153 146 163 165

The crystal structure analyses indicate that the moiety 1 exhibits four shapes when the value of nonbonded torsion θ is varied. Compound 5 has shown more versatility to exhibit three different shapes, depending on the surroundings. Amide-toamide hydrogen bonds are not observed when R ) 3- or 4-pyridyl and 4-iodophenyl. In the case of pyridyl groups, the

structures are assembled via N-H‚‚‚N hydrogen bonds, whereas in the case of iodophenyl they are assembled through I‚‚‚I interactions. The similarities in the shapes do not reflect the similarities in supramolecular architectures except for the case of 2 (p-bromophenyl) and 8 (p-chlorophenyl). Although 4 ((piodophenyl) and 6 (p-tolyl) have similar molecular shapes, they have exhibited different supramolecular architectures. The selfaggregation in structure 4 takes place via I‚‚‚I interactions (2Dlayer), whereas in 6 it takes place via N-H‚‚‚O hydrogen bonds (2D-layer). Further, the ladder structure via N-H‚‚‚N hydrogen bonds was observed in crystal structure 5a (shape-II), whereas 5b (Shape-III) forms a 2D-layer via N-H‚‚‚N hydrogen bonds. Indeed, for both pairs (4 and 6 or 5a and 5b) it is possible to have identical supramolecular architectures given the similarities in functional groups. The existence of 1 in more than one molecular geometry and versatility in the self-aggregation are required qualities for host-guest chemistry, for polymorphism, and also for the exploration of metal-organic hybrid materials. Consequently, these compounds are under active investigation in our laboratory.

Structures of Ethylenediamine-N,N,N′,N′-tetraamides

Experimental Section In addition to single-crystal X-ray studies, the synthesized compounds were characterized by IR, NMR, and UV. In the case of 3 and 5b, TGA was recorded, as they contain guest molecules. All the spectra are available in Supporting Information. Synthesis of 2. 4-Bromoaniline (0.0684 mmol, 6.4465 g) was added to a 50 mL pyridine solution of EDTA (0.0171 mmol, 5 g), and the solution was stirred for 15 min. After the addition of triphenyl phosphite (0.0684mmol, 17.9 mL), the mixture was refluxed for 5 h. The volume of the solution was reduced to 5 mL by distilling out the pyridine, and a white precipitate was obtained. The solid was filtered and washed with acetone. The resultant product was crystallized from a mixed solvent containing DCM and DMF in a 5:2 ratio. Yield: 58%; mp: 260-262 °C. Anal. (C26H32N4O4Br4): Calcd C, 44.93%; H, 3.52%; N, 9.05%; Found: C, 45.05%; H, 3.30%; N, 8.95%. A similar procedure was adopted for the synthesis of 3, 4, 6, 7, 8, 9, and 10. 3: crystallized from MeOH and DMF (5:2 ratio); yield: 91%; mp: 240-242 °C. 4: crystallized from MeOH; yield: 69%; mp: 254-257 °C. Anal. C30H32N10O4: Calcd C, 60.40%; H, 5.37%; N, 23.48%; Found: C, 60.56%; H, 5.13%; N, 23.20%. 6: crystallized from MeOH and DMF (5:1); Yield: 40% Mp: 250252 °C. 7: crystallized from p-xylene and MeOH (5:3 ratio); yield: 51%; pp: 238-240 °C. Anal. (C38H44N4O4): Calcd C, 70.37%; H, 6.79%; N, 12.96%; Found: C, 70.37; H, 6.74%; N, 12.76%. 8: crystallized from DMF, yield: 49%; mp: 252-254 °C. 9: crystallized from MeOH, yield: 32%; mp: 198-200 °C. Anal. (C34H32F4N6O4): Calcd C, 61.44%; H, 4.82%; N, 12.65%; Found: C, 62.20; H, 4.97%; N, 12.32%. 10: crystallized from DMF, Yield: 26%, Mp: 136-138 °C. Anal. (C34H32N10O12): Calcd C, 52.85%; H, 4.15%; N, 18.13%; Found: C, 53.27; H, 4.67%; N, 18.71%. Synthesis of Tetramethyl Ester of EDTA. To the stirred suspension of EDTA (10.6 g, 36.6 mmol) in dry MeOH (400 mL) at 0 °C was added freshly distilled thionyl chloride (25 mL, 343 mmol) dropwise. The resulting turbid solution became clear after stirring for 16-18 h, and then excess MeOH and SOCl2 was distilled off. The colorless oil was suspended in 300 mL of Et2O at 0 °C. To this suspension was added 200 mL of saturated NaHCO3 solution slowly, and stirring was continued for an additional 1 h. The organic layer was separated, and the aqueous layer was further extracted with Et2O (5 × 50 mL). The ether extracts were combined and dried over K2CO3. The removal of ether by a rotavapor resulted in the methyl ester of EDTA (colorless viscous liquid).Yield: 44%. Synthesis of 5. It was synthesized by aminolysis of tetramethylEDTA ester. Freshly distilled DMSO (50 mL), NaH (0.7254 g, 31.35 mM), and 4-aminopyridine (2.6824 g, 28.5 mM) were added to a threenecked flask under an inert atmosphere, and the mixture was cooled to 0 °C. The solution of tetraester (2.0 g, 5.7 mmol) in dry DMSO (30 mL) was added dropwise to allow smooth reaction. After continuous stirring for 19 h, the resulting brown solution was poured into cracked ice under vigorous stirring. The white solid precipitated out after 20 min. It was filtered and washed with water several times and finally with acetone. Yield: 39%. Crystallization of 5a: crystallized from MeOH, mp: 197-200 °C. Crystallization of 5b: Crystallized from DMF and CCl4 (1:4 ratio), mp: 185-188 °C. Crystallization of 5c: Cocrystal was obtained by dissolving 20 mg of amide (5) and 9.4 mg of trimesic acid in 5 mL of DMF:toluene (1:4) solvent. Crystal Structure Determination. The single-crystal data for all the structures were collected on a Bruker-Nonius Mach3 CAD4 X-ray diffractometer that uses graphite monochromated Mo KR radiation (λ ) 0.71073 Å) by ω-scan method. The structures were solved by direct methods and refined by least-square methods on F2 using SHELX97.18 Non-hydrogen atoms were refined anisotropically, and H-atoms were fixed in calculated positions and refined isotopically with thermal parameters based upon the corresponding parental atoms. The fractional coordinates, full list of bond lengths and angles, and the anisotropic displacement parameters have been deposited as Supporting Information. Pertinent crystallographic details are given in Table 1 and hydrogen

Crystal Growth & Design, Vol. 7, No. 9, 2007 1879 bond details are given Tables 2-5. The CCl4 and H2O molecules in 5b could not be located, as they are highly disordered. Therefore, PLATON squeeze option was applied to refine the final structure.19

Acknowledgment. We gratefully acknowledge financial support from the Department of Science and Technology (DST, SR/S1/OC-36/2002) and DST-FIST for the single-crystal X-ray facility. L.R. thanks IIT (Kharagpur) for a research fellowship. Supporting Information Available: (1) Spectral characterization summary, (2) IR spectra, (3) UV spectra, (4) TGA for 3 and 5b, (5) 1H NMR spectra, (6) ORTEP drawings, and (7) crystallographic tables. This material is available free of charge via the Internet at http:// pubs.acs.org.

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1880 Crystal Growth & Design, Vol. 7, No. 9, 2007 (13) Unit cell parameters of compound 8: a ) 7.815(8) Å; b ) 10.193(4) Å; c ) 10.957(4) Å; R ) 80.75(7)°; β ) 79.28(8)°; γ ) 88.13(5)°; volume ) 846.5(10) Å3. (14) (a) Burley, S. K.; Petsko, G. A. AdV. Protein Chem. 1988, 39, 125. (b) Hunter, C. A.; Singh, J.; Thornton, J. M. J. Mol. Biol. 1991, 218, 837. (c) Shetty, A. S.; Zhang, J.; Moore, S. J. J. Am. Chem. Soc. 1996, 1019. (15) (a) Sharma, C. V. K.; Zaworotko, M. J. Chem. Commun. 1996, 2655. (b) Bhogala, B. R.; Vishweshwar, P.; Nangia, A. Cryst. Growth Des. 2002, 2, 325. (c) Bhogala, B. R.; Nangia, A. Cryst. Growth Des. 2003, 3, 547. (d) Walsh, R. D. B.; Bradner, M. W.; Fleischman, S.; Morales, L. A.; Moulton, B.; Hornedo, N. R.; Zaworotko, M. J. Chem. Commun. 2003, 186. (e) Nguyen, T. L.; Fowler, F. W.; Lauher, J. W. J. Am. Chem. Soc. 2001, 123, 11057.

Rajput et al. (16) Spek, A. L. PLATON, Bijvoet Center for Biochemical Research, Vakgroep Kristal-en Structure-Chemie, University of Utrecht, The Netherlands, 2002. (17) A halogen(X)‚‚‚halogen(X) interaction C-X‚‚‚X-C is defined as type-I if the C-X‚‚‚X angle θ1 is equal or nearly equal to the X‚‚‚X-C angle θ2. If θ1 ≈ 180° and θ2 ≈ 90°, the contact is definedas type-II. See: Ramasubbu, N.; Parthasarathy, R.; MurrayRust, P. J. Am. Chem. Soc. 1986, 108, 4308. (18) Sheldrick, G. M. SHELX-97, Program for the Solution and Refinement of Crystal Structures, University of Go¨ttingen, Germany, 1997. (19) Spek, A. L. PLATON - A Multi Purpose Crystallographic Tool, Utrecht University, Utrecht, The Netherlands, 2002.

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