Hydrogen-bonding Networks in Cocrystal of Melamine and 4-Fluoro-benzoic Acid

Transcription

1 CHEM. RES. CHINESE UNIVERSITIES 2010, 26(5), Hydrogen-bonding Networks in Cocrystal of Melamine and 4-Fluoro-benzoic Acid ZHANG Xiu-lian *, YIN Wei and CAO Man-li Department of Chemistry, Guangdong Institute of Education, Guangzhou , P. R. China Abstract A novel interpenetrating structure [(HMA + )(FB )] 2H 2 O of melamine(ma) with 4-fluoro-benzoic acid (HFB) was synthesized. It crystallized in the monoclinic system with space group P2 1 /c. The complex has a interpenetrating 2D structure with hydrogen-bonded grid networks. Carboxylic acid to melamine proton transfer occurs in the complex. The adjacent HMA + cations related by an inverse center form cationic [HMA + ] ribbons via a pair of N H N hydrogen bonds. Adjacent FB anions are paired by C H F hydrogen bonds to form dimers, which are connected to [HMA + ] ribbons through N H O interactions. The supramolecular features in the complex are guided by control of strong N H N, N H O and O H O hydrogen bonds, as well as highly directional weak C H F interactions and aromatic π π stacking interactions. Keywords Hydrogen bond; Melamine; 4-Fluoro-benzoic acid Article ID (2010) Introduction Organic acid-base complexes have received considerable attention for the predictable assembly of supramolecular architectures and interpenetrating networks [1 6]. The design and synthesis of organic solids are largely based on molecular recognition between complementary partners and self-assembly into hydrogen-bonded architectures, chains, sheets and networks. The well-known interactions involving hydrogen bonds are N H N, N H O, O H N and O H O. Organic fluorine as a hydrogen-bond acceptor is of recent interest [7 10]. Melamine(MA, triaminotriazine) is a weak base and the triazine nitrogen atom of melamine might potentially accept protons from carboxylic acid to form strong N H O interactions. Melamine is an excellent hydrogen donor. We have obtained some melamine acid cocrystals in which strong directional N H O hydrogen bonds play a significant role in directing supramolecular organization [11,12]. In the present article, the interpenetrating structure, which is assembled by cooperative acting of strong N H N, N H O and O H O hydrogen bonds and weak but highly directional C H F interactions in a new cocrystal of MA with 4-fluoro-benzoic acid(hfb), namely, [(HMA + )(FB )] 2H 2 O, is reported. 2 Experimental 2.1 Synthesis All the reagents and solvents were commercially available and used as received without further purification. The FTIR spectrum was recorded from KBr pellets in a range of cm 1 on a Nicolet 5DX spectrometer. Elemental analysis was carried out with a Perkin-Elmer 240 elemental analyzer. Thermal gravimetric analysis(tga) was performed under dinitrogen atmosphere. The title compound was prepared by mixing hot aqueous solution of MA(0.126 g, 1 mmol) and HFB in 1:1 molar ratio, respectively. The hot solution was stirred at room temperature and evaporated in air for a few days to give colorless crystal of [(HMA + )(FB )] 2H 2 O. Yield: 0.27 g, 87%. Elemental anal. calcd. for C 10 H 15 N 6 O 4 F: C 39.73, H 5.00, N 27.81; found: C 39.29, H 5.10, N IR(KBr), /cm 1 : , 3075, 1664, 1652, 1540, 1400, 784, Structure Determination and Refinement The data of the title compound were collected at 293 K on a Bruker SMART Apex CCD diffractometer, and the data reduction was performed with the help of *Corresponding author. zxl@gdei.edu.cn Received August 19, 2009; accepted October 16, Supported by the National Natural Science Foundation of China(No ) and a Grant for Key Research Items in Natural Science of Guangdong Higher Education Institutions of China(No.06Z027).

2 No.5 ZHANG Xiu-lian et al. 703 Bruker SAINT [13]. The structure was solved by direct method and refined with the full-matrix least squares on F 2 with anisotropic displacement parameters for non-h atoms via SHELXTL [14]. Crystal data as well as Table 1 Crystal data and structure refinements Empirical formula C 10 H 15 N 6 O 4 F Formula weight Crystal size 0.48 mm 0.43 mm 0.10 mm Crystal system Monoclinic Space group P2 1 /c a/ (2) b/ (9) c/ (1) β /( ) (2) Cell volume/ (4) Z, D/(g cm 3 ) 8, Absorption coefficient/mm F(000) 1264 Radiation/wavelength Mo Kα radiation/λ= θ range Index ranges 27 h 27, 12 k 12, 15 l 11 Reflections collected Independent/observed refls (R int =0.0243)/4357 Goodness-of-fit Weighting scheme w=1/[σ 2 (F 2 o )+(0.0815P) P], where P=(F 2 o )+2F 2 c ) /3 (Δ/σ) max Final R indices [I >2σ(I)] R=0.0568, wr= (Δρ) max and (Δρ) min /(e 3 ) 221 and 340 Table 2 Hydrogen bond distances and angles D H A d(d H)/ d(h A)/ d(d A)/ DHA/ ( o ) N1 H1A N10# (2) N1 H1B O2W# (2) N3 H3A N8# (2) N3 H3B O (2) N5 H5A O1W# (2) N5 H5B O4W# (2) N7 H7A N4# (2) N7 H7B O3# (2) N9 H9A O2W (2) N9 H9B O3W (2) N11 H11A N6# (2) N11 H11B O1W# (2) O4W H4WA O4# (3) 0.212(3) (3) 172(3) O2W H2WA O (4) 0.207(4) (3) 157(3) O1W H1WA O (3) 0.205(3) (3) 165(3) O3W H3WA O (3) 0.200(3) (2) 165(3) O4W H4WB O (3) 0.190(3) (2) 165(3) N2 H2 O (3) 0.177(3) (2) 174(2) O3W H3WB O2# (3) 0.200(3) (2) 154(2) N12 H12 O4# (2) 0.169(2) (2) 173(2) O2W H2WB O3W# (3) 0.203(3) (3) 174(3) O1W H1WB O4W# (3) 0.215(3) (3) 173(3) C9 H9C F1# (3) 0.250(3) (3) 157(3) C3 H3C F2# (3) 0.246(3) (3) 156(3) * Symmetry code: #1: x, y+1/2, z+1/2; #2: x, y+1/2, z+1/2; #3: x, y+1/2, z 1/2; #4: x, y+1, z+2; #5: x, y 1/2, z+3/2; #6: x, y+1/2, z+1/2; #7: x, y+1, z+2; #8: x, y+1/2, z 1/2; #9: x, y 1/2, z+3/2; #10: x, y+3/2, z 1/2; #11: x, y+1/2, z+1/2; #12: x, y+1, z+2; #13: x+1, y+1, z+2; #14: x, y+1/2, z+3/2, #15: x+1, y+1, z+2. details of data collection and refinement for the complex are summarized in Table 1. Hydrogen atoms of the water molecule and the protonated aromatic nitrogen atoms of MA were located according to the difference Fourier maps, and the other hydrogen atoms were generated geometrically(c H ; N H ) for the complex. Hydrogen bond geometries are listed in Table 2. Selected bond lengths and bond angles are listed in Table 3. Table 3 Selected bond lengths() and bond angles( ) F1 C (2) N5 C (2) F2 C (2) N6 C (2) O1 C (2) N6 C (2) O2 C (2) N7 C (2) O3 C (2) N8 C (2) O4 C (2) N8 C (2) N1 C (2) N9 C (2) N2 C (2) N10 C (2) N2 C (2) N10 C (2) N3 C (2) N11 C (2) N4 C (2) N12 C (2) N4 C (2) N12 C (2) C1 C (3) C8 C (3) C1 C (3) C8 C (3) C2 C (3) C9 C (3) C3 C (3) C10 C (3) C4 C (3) C11 C (3) C5 C (3) C11 C (3) C5 C (3) C12 C (3) C17 N2 C (2) C10 C11 C (2) C15 N4 C (2) C12 C11 C (2) C17 N6 C (2) C11 C12 C (2) C18 N8 C (2) C8 C13 C (2) C20 N10 C (2) O3 C14 O (2) C20 N12 C (2) O3 C14 C (2) C2 C1 C (2) O4 C14 C (2) F1 C2 C (2) N3 C15 N (2) F1 C2 C (2) N3 C15 N (2) C3 C2 C (2) N4 C15 N (2) C2 C3 C (2) N5 C16 N (2) C5 C4 C (2) N5 C16 N (2) C4 C5 C (2) N6 C16 N (2) C4 C5 C (2) N1 C17 N (2) C6 C5 C (2) N1 C17 N (2) C1 C6 C (2) N6 C17 N (2) O2 C7 O (2) N7 C18 N (2) O2 C7 C (2) N7 C18 N (2) O1 C7 C (2) N8 C18 N (2) F2 C8 C (2) N9 C19 N (2) F2 C8 C (2) N9 C19 N (2) C9 C8 C (2) N10 C19 N (2) C8 C9 C (2) N11 C20 N (2) C11 C10 C (2) N11 C20 N (2) C10 C11 C (2) N10 C20 N (2) 3 Results and Discussion 3.1 Description of the Structure In the structure, MA is protonated, resulting in

3 704 CHEM. RES. CHINESE UNIVERSITIES Vol.26 an enhancement of the internal bond angles of C15 N2 C (2) and C18 N12 C (2), which is compared with the internal bond angles[ (2) ] of the neutral MA, also similar to those found in melamine-benzoic acid [15]. HMA + cations are arranged in an inversion-related manner via homomeric DD=AA hydrogen bonds [d(n N)=0.2993(2) (2) ], and two adjacent HMA + cations are not coplanar(dihedral angles: 24.4 and 24.7 o ), the dihedral angles are larger than those of melamine-benzoic acid(dihedral angle: 17.8 ) [15], generating undulate [HMA + ] ribbons as shown in Scheme 1(A) running along the c-axis. Scheme 1 Hydrogen bond synthons in the title compound The [HMA + ] infinite ribbon was observed for a 2:1 complex of melamine-1,5-naphthalenedisulfonic acid [12] and a 1:1 complex of melamine-benzoic acid. In the complexes of melamine with terephthalic acid, isophthalic acid, trimellitic acid, trimesic acid, and 3,5-dinitrobenzoic acid, each pair of HMA + ions is doubly N H N hydrogen bonded into a dimer [11]. In the melamine-4,4 -bipridl adduct, the melamine molecules are connected to one another through water molecules [16]. The dihedral angle between HMA + cation and FB anion is 4.2, which is less than that of melamine-benzoic acid[dihedral angle 5.7 ] [15]. The carboxylic acid moiety in FB anion is engaged in a pair of expected intermolecular heteromeric DA=DA hydrogen bonds[d(n O)=0.2653(2) (2) ] with HMA + cation as shown in Scheme 1(B), similar to the contact observed in the structures of melamine-aromatic carboxylic acid [11]. This motif is one of the 24 most frequently observed bimolecular cyclic hydrogen-bonded synthons in organic crystal structures [17,18]. This observation remains in accordance with the principle that the strongest proton donor forms hydrogen bonds with the strongest proton acceptor [19] and is rationalised in terms of a desire of the system to maximise electrostatic attractions. The distances of N H O hydrogen bonds[d(n3 O2)=0.2906(2) and d(n7 O3)= (2) ] are comparable to those previously reported by us in the complexes of melamine with aromatic carboxylic acid, in which the distances of N H O hydrogen bonds are , but the charge-assisted N H + O hydrogen bonds [d(n2 O1)=0.2689(2), d(n1 O4)=0.2653(2) ] are significantly shorter than those of melamineterephthalic acid[d(n O)=0.2711(2) ], melaminetrimellitic acid[d(n O)=0.2790(2) ], melaminetrimesic acid[d(n O)=0.2726(2) ] [11]. The decrease in the N O distance can be attribute to the influence of fluorin atom substituent on the para position of an aromatic ring which makes carboxylic acid to melamine proton transfer occurring more easily, resulting in strong N H + O hydrogen bonds. This structural feature is very different from that of melaminebenzoic acid, in which benzoic acid anions were connected to the [HMA + ] ribbons on alternate sides to generate 1D tape [16], attributable to F atom introducing, two adjacent FB anions are paired by C H F hydrogen bonds to form dimers as shown in Scheme 1(C), which are interlinked to two adjacent [HMA + ] ribbons via the pairs of N + H O and N H O interactions, resulting in a grid structure. Four water molecules are connected to each cavity via hydrogen bonds[d(o3 O4W)=0.2752(2), d(o2 O3W)=0.2770(2), d(n OW)= (2) (2) ], resulting in the hydrogen-bonded ring motifs of R 2 3 (8) and R 3 4 (10)(Fig.1), which are observed in the MA-1,5-naphthalenedisulfonic acid complexes [12]. Each FB dimer is linked to two adjacent [HMA + ] ribbons on alternate sides to generate 2D layers propagated parallel to the ac plane(fig.2). The most unusual feature is there are two individual 2D grids interpenetrating to fill the void space(fig.3). The stucture shown in Scheme 1(D)

4 No.5 ZHANG Xiu-lian et al. 705 Fig.1 View of grid structure built from [HMA + ] ribbons and FB - anion dimers Fig.2 2D grid networks of title compound For clarity, water molecules are omitted. represents two kinds of different hydrogen-bonding types of water molecules, which participate in four hydrogen bonds in a tetrahedral arrangement. One kind of water molecules(o1w, O2W) forms two acceptor hydrogen bonds[d(o1w N11)=0.2937(2), d(o1w N5)=0.3070(2), d(o2w N1)= (2), d(o2w N9)=0.2987(2) ] to two amino groups from adjacent HMA + cations and two donor hydrogen bonds[d(o1w O4W)=2.989(3), d(o1w O3)=0.2877(3), d(o2w O2)=0.2908(3), d(o2w O3W)=0.2851(3) ] to another water molecule and FB anion, while another kind of water molecules(o3w, O4W) accept two hydrogen bonds from another water molecule and amino group of HMA + cation[d(o3w O2W)= (3), d(o3w N9)=0.2888(2), d(n5 O4W)=0.3027(2), d(o4w O1W)=0.2989(3) ] and donate two hydrogen bonds[d(o3w O1)=0.2814(2), Fig.3 Two-fold interpenetrating networks in [(HMA + ) (FB - )] 2H 2 O(A) and space-filling model to show the net void filled with interpenetrating networks(b) d(o3w O2)=0.2770(2), d(o4w O3)=0.2752(2), d(o4w O4)=0.2906(3) ] to carboxyl groups of FB anions from different layer. Meanwhile, two kinds of different water molecules bridge amino hydrogen atoms of HMA + and carboxylate oxygen atoms of FB, forming a hydrogen bonded pattern with R 4 4 (10). Efficient hydrogen-bonded interactions of water molecules with FB anions, HMA + cations from different layer grids are crucial to promoting the formation of interpenetrated structure as shown in Fig.3(A). After water molecules are omitted, it is shown that the 2D net void is filled with interpenetrating networks as shown in Fig.3(B). The adjacent 2D layers form two-fold interpenetrated networks and the dihedral angle between two adjacent 2D layer grid networks is 56.6 o (Fig.4). Strong hydrogen bonds of water dimers with FB anions, HMA + cations from different layers and π π stacking interactions( ) between HMA + and FB anions generate the 3D structure in the solid. Fig.4 Space filling model with interpenetrating network from adjacent 2D layers

5 706 CHEM. RES. CHINESE UNIVERSITIES Vol TG Analyses The sample was heated at a rate of 10 C/min in flowing N 2. Thermogravimetric(TGA) analysis(fig.5) shows that the total water loss occurs in one step at 102 C. The mass loss of the sample(53.1%, calcd. 53.9%) at 198 C is consistent with the loss of melamine cation. The final mass loss of the sample(99.1%, calcd. 100%) at 320 C is consistent with the loss of 4-fluoro-benzoic acid anion. Fig.5 Thermogravimetric plot of the complex 4 Conclusions In conclusion, by multiple hydrogen-bonded sites of melamine as a weak base reacting with 4-fluorobenzoic acid, we successfully obtained an interpenetrated supramolecular architecture, in which the adjacent MA molecules are doubly N H N hydrogen bonded to a [HMA + ] ribbon, while each pair of FB anion is associated by two C H F weak hydrogen bonded to a dimer. The complex has a 2D interpenetrating architecture. The results indicate that halide substituent on the para position of an aromatic ring has great influence on the resulting structures of this system and also prove C H F is a highly directional hydrogen bonded interaction in the construction of noval materials. References [1] Biradha K., Dennis D., MacKinnon V. A., Sharma C. V. K., Zaworotko M. J., J. Am. Chem. Soc., 1998, 120, [2] Sharma C. V. K., Clearfield A., J. Am. Chem. Soc., 2000, 122, 4394 [3] Jaskólski M., Desiraju G. R., Chem. Commun., 2002, 1830 [4] Aakeröy C. B., Beatty A. M., Helfrich B. A., J. Am. Chem. Soc., 2002, 124, [5] Balakrishna R. B., Ashwini N., Cryst. Growth Des., 2003, 3, 547 [6] Balakrishna R. B., Peddy V., Ashwini N., Cryst. Growth Des., 2002, 2, 325 [7] Steiner T., Cryst. Rev., 1996, 6, 1 [8] Dunitz J. D., Chem. Bio. Chem., 2004, 5, 614 [9] Bohm H. J., Banner D., Bendels S., Kansy M., Kuhn B., Muller K., Sander U. O., Stahl M., Chem. Bio. Chem., 2004, 5, 637 [10] Jeschke P., Chem. Bio. Chem., 2004, 5, 570 [11] Zhang X. L., Chen X. M., Cryst. Growth Des., 2005, 5, 617 [12] Zhang X. L., Ye B. H., Chen X. M., Cryst. Growth Des., 2005, 5, 1609 [13] Sheldrick G. M., SAINT and SMART, Bruker AXS Inc., Madison, Wisconsin, 2001 [14] Sheldrick G. M., SHELXTL, Version 6.10, Bruker Analytical X-ray Systems, Madision, Wisconsin, 2001 [15] Zhang X. L., Chem. Res. Chinese Universities, 2008, 24(4), 396 [16] Sivashankar K., Ranganathan A., Pedireddi V. R., Rao C. N. R., J. Mol. Struct., 2001, 559, 41 [17] Hughes E. W., J. Am. Chem. Soc., 1941, 63, 1737 [18] Stanley N., Sethuraman V., Muthiah P. T., Luger P., Weber M., Cryst. Growth Des., 2002, 2, 631 [19] Etter M. C., Acc. Chem. Res., 1990, 23, 120