Influence of O-H‚‚‚OdP Hydrogen Bonding on the Supramolecular Architectures of Phosphorus-Based Hydrazones: Alternate Rightand Left-Handed Fused Helical Chains Based on O-H‚‚‚OdP Hydrogen Bonds in the Crystal Structure of C6H5P(O)[N(CH3)NdCHC6H4-p-OH]2
CRYSTAL GROWTH & DESIGN 2006 VOL. 6, NO. 4 910-914
Vadapalli Chandrasekhar,*,† Ramachandran Azhakar,† Jamie F. Bickley,‡ and Alexander Steiner‡ Department of Chemistry, Indian Institute of Technology, Kanpur-208 016, India, and Department of Chemistry, UniVersity of LiVerpool, LiVerpool-L69 7ZD, U.K. ReceiVed August 18, 2005; ReVised Manuscript ReceiVed January 25, 2006
ABSTRACT: The acyclic phosphorus dihydrazone C6H5P(O)[N(CH3)NdCHC6H4-p-OH]2 (1) forms an alternate right- and lefthanded fused helical chain supramolecular structure in the solid state. The supramolecular architecture of 1 is formed as a result of intermolecular O-H‚‚‚OdP interactions. Variation in the position of the hydroxy group in C6H5P(O)[N(CH3)NdCHC6H4-m-OH]2 (2) leads to the formation of a ladder structure, also mediated by O-H‚‚‚OdP interactions. In contrast to 1 and 2, C6H5[N(CH3)Nd CHC6H4-o-OH]2 (3), which contains an o-hydroxy group on the phenyl substituents, only shows C-H‚‚‚O interactions. The absence of O-H‚‚‚OdP interactions in the latter is attributed to the involvement of the O-H unit in intramolecular O-H‚‚‚N hydrogen bonding. Introduction Hydrazine and its derivatives are commercially important chemicals.1 Apart from their use in rocket fuels, they are also useful reagents for the synthesis of heterocycles in organic chemistry.2 Inorganic chemists have used hydrazines as ligands in coordination compounds.3-5 In particular, the derivatives of N-methyl hydrazine have attracted interest in recent years.4,5 Thus, the reaction of N-methyl hydrazine with phosphorus(V) halides such as P(E)Cl3, RP(E)Cl2, R2P(E)Cl (E ) O, S; R ) alkyl, aryl, aryloxy, etc.), or even inorganic heterocyclic rings such as N3P3Cl6 occurs regiospecifically to afford the corresponding hydrazides, P(E)[N(Me)NH2]3, RP(E)[N(Me)NH2]2, R2P(E)[N(Me)NH2], N3P3[N(Me)NH2]6.6 The terminal -NH2 groups in these hydrazides can be elaborated readily as shown by the conversion of these compounds into hydrazones.4d-4f,5g,7 A further point of interest of these hydrazides is their ability to participate in weak and strong hydrogen bonds to afford interesting supramolecular structures6a-6b It is well-known from literature precedents that the PdO group plays a crucial role in crystal packing.8 To delineate the role of the PdO group in the supramolecular interactions among phosphorus-based hydrazones, we synthesized and structurally characterized C6H5P(O)[N(CH3)NdCHC6H4-p-OH]2 (1), C6H5P(O)[N(CH3)NdCHC6H4-m-OH]2 (2), and C6H5P(O)[N(CH3)NdCHC6H4-o-OH]2 (3). The rationale for the choice of these compounds is as follows. Each of these contains a terminal PdO group that can function as a proton acceptor in a hydrogenbonding interaction. Further, each of these compounds has a phenolic -OH group in slightly different geometric orientations. These features, we reasoned, would allow an assessment of the relative roles of the different structural units in influencing the * Corresponding author. Department of Chemistry, Indian Institute of Technology, Kanpur-208 016, India. Tel: 91-512-2597259, Fax: 91-5122590007/2597436. E-mail:
[email protected]. † Department of Chemistry, Indian Institute of Technology, Kanpur-208 016, India ‡ Department of Chemistry, University of Liverpool, Liverpool-L69 7ZD, U.K.
overall crystal structure. The crystal structure of 1 shows the formation of helical chains with both right- and left-handed chains being fused and present alternately. The crystal structure of 2, on the other hand, shows a ladder structure also mediated by the O-H‚‚‚OdP interaction.8b-8d,9 In contrast to 1 and 2, which show robust O-H‚‚‚OdP interactions, C6H5[N(CH3)NdCHC6H4-o-OH]2 (3) is characterized by their total absence. This is due to the proximity of the phenolic OH with the imino nitrogen atom in the same arm leading to a strong intramolecular O-H‚‚‚N hydrogen bond. Because of this, the supramolecular structure of 3 is formed as a result of C-H‚‚‚OdP interactions. Other weak interactions such as C-H‚‚‚O (phenolic) also augment the supramolecular architecture of 3. Experimental Section Reagents and General Procedures. Solvents were purified and dried by standard methods and distilled prior to use.10 The reagents, p-hydroxy benzaldehyde, m-hydroxy benzaldehyde, o-hydroxy benzaldehyde, and C6H5P(O)Cl2 were purchased from Fluka, Switzerland, and were either distilled or recrystallized before use. N-Methylhydrazine was obtained as a gift from the Vikram Sarabhai Space Research Center, Thiruvananthapuram, India, and was used as received. C6H5P(O)[N(CH3)NH2]2 was prepared by the reaction of C6H5P(O)Cl2 with N-methyl hydrazine as reported in the literature.6c Instrumentation. 1H, 31P{1H}, and 13C{1H} NMR spectra were recorded in DMSO-d6 for 1 and 2 and in CDCl3 for 3 on a JEOL JNM LAMBDA 400 model spectrometer operating at 400.0, 161.7, and 100.4 MHz, respectively. Chemical shifts are reported in ppm with respect to internal tetramethylsilane (1H and 13C) and external 85% H3PO4 (31P). X-ray Crystallography. Crystal data for compounds 1-3 are given in Table 1. Single crystals suitable for X-ray crystallographic analyses were obtained from a slow evaporation of the methanol solutions. The crystal data of compounds 1 and 3 were collected on Stoe IPDS machine, and data for 2 was collected on Bruker SMART APEX CCD diffractometer. Structures 1 and 3 were solved by direct methods using the programs SHELXS-97 and refined by full matrix least-squares methods against F2 with SHELXL-97.11 Hydrogen atoms were fixed at calculated positions, and the position of hydrogen atoms were refined by a riding model. All non-hydrogen atoms were refined with anisotropic displacement parameters. Hydrogen atoms on oxygen were refined after location on a difference map. In the case of 2, the SMART
10.1021/cg050426v CCC: $33.50 © 2006 American Chemical Society Published on Web 03/01/2006
Supramolecular Architectures of Hydrazones
Crystal Growth & Design, Vol. 6, No. 4, 2006 911
Table 1. Crystal Data for the Compounds 1-3
formula formula weight T/K λ/Å crystal system space group a/Å b/Å c/Å R/° β/° γ/° V/Å 3 Z µ (Mo KR)/mm-1 F(000) density cm3/g θ range/° reflns collected unique reflns data/restraints/ params GOF on F2 final R indices [II > 2σ(I)] largest diff peak and hole/e Å-3
Table 2. Selected Bond Lengths (Å) and Angles (°) in 1-3
1
2
3
C22H23N4O3P 422.41 213(2) 0.71073 monoclinic P21/n 8.7339(11) 12.202(2) 20.083(3) 90 90.886(15) 90 2140.0(5) 4 0.159 888 1.311 1.95-24.13 13274 3265 3265/0/281
C22H23N4O3P 422.41 100(2) 0.71073 monoclinic P21/c 13.361(5) 13.967(6) 12.022(5) 90 102.75(8) 90 2188.3(15) 4 0.156 888 1.282 2.14-28.35 14454 5406 5406/0/275
C22H23N4O3P 422.41 213(2) 0.71073 orthorhombic Pna21 7.0504(8) 35.688(5) 8.7657(12) 90 90 90 2205.6(5) 4 0.155 888 1.272 2.39-22.39 10842 2787 2787/1/281
1.019 R1 ) 0.0415 wR2 ) 0.0914 0.163 and -0.279
1.011 R1 ) 0.0706 wR2 ) 0.1516 0.356 and -0.227
1.114 R1 ) 0.0388 wR2 ) 0.0996 0.132 and -0.162
(version 5.628) program was used for collecting data frames, and SAINT (version 6.45) was used for integration of the intensity of reflections and scaling. SADABS was used for absorption correction. The structure was solved and refined by full matrix least-squares methods against F2 with SHELXTL (version 6.14).12 All non-hydrogen atoms were refined with anisotropic thermal parameters. Hydrogen atoms were fixed at calculated positions, and the positions of hydrogen atoms were refined isotropically. Synthesis. Preparation of the Dihydrazones 1-3. To a stirred solution of C6H5P(O)[N(CH3)NH2]2 (0.20 g, 0.93 mmol) in methanol (30 mL) was added dropwise a solution of the substituted benzaldehyde (0.23 g, 1.88 mmol) also in methanol (30 mL) at room temperature. After the addition was over, the reaction mixture was allowed to stir for 6 h. The removal of solvent from the reaction mixture in vacuo affords the corresponding dihydrazones as white solids. These products were further washed with diethyl ether to remove traces of unreacted benzaldehydes. Finally, recrystallization from acetonitrile afforded the dihydrazones (1-3) in a pure state. Characterization data for these compounds are given below. C6H5P(O)[N(CH3)NdCHC6H4-p-OH]2 (1). Yield: 0.32 g, 81.2%. mp. 184 °C. FT-IR νO-H/cm-1: 3246; νCdN/cm-1: 1593. 1H NMR: 3.19 (b, 6H, -N(CH3)), 6.67-6.94 (multiplets due to aromatic protons), 7.41 (a broad signal due to aromatic protons), 7.88 (s, 2H, imino), 8.80
P-O P-N C-P-O N-P-O
1
2
3
1.4913(12) 1.6541(14) 1.6594(14) 110.66(8) 110.31(7) 113.03(7)
1.4814(18) 1.651(2) 1.664(2) 111.02(12) 108.47(12) 115.31(12)
1.465(2) 1.680(3) 1.668(3) 111.60(14) 111.36(13) 117.27(15)
(s, 2H, hydroxyl). 13C NMR: 29.9 (N-CH3), 114.9, 126.4, 127.0, 127.2, 131.1, 132.4, 136.3, 136.5 (aromatic carbon atoms), 157.4 (NdCH). 31 P NMR: 24.28(s). Anal. calcd. for C22H23PO3N4: C, 62.55; H, 5.49; N, 13.26. Found: C, 61.90; H, 5.4; N, 13.1. C6H5P(O)[N(CH3)NdCHC6H4-m-OH]2 (2). Yield: 0.34 g, 86.2%. mp. 179 °C. FT-IR νO-H/cm-1: 3251; νCdN/cm-1: 1590. 1H NMR: 3.11(b, 6H, -N(CH3)), 6.72 (a broad signal due to aromatic protons), 7.30 (a broad signal due to aromatic protons), 7.46-7.55 (multiplets due to aromatic protons), 7.94 (s, 2H, imino), 9.15 (s, 2H, hydroxyl). 13 C NMR: 30.3 (N-CH3), 112.4, 115.6, 117.5, 127.4, 128.9, 131.4, 132.6, 136.1, 136.8, 136.9 (aromatic carbon atoms), 156.9 (NdCH). 31 P NMR: 24.94(s). Anal. calcd. for C22H23PO3N4: C, 62.55; H, 5.49; N, 13.26. Found: C, 62.20; H, 5.30; N, 13.1. C6H5P(O)[N(CH3)NdCHC6H4-o-OH]2 (3). Yield: 0.32 g, 81.2%. mp. 171 °C. FT-IR νO-H/cm-1: 3056; νCdN/cm-1: 1593. 1H NMR: 3.22 (d, 6H, -N(CH3); 3J(1H-31P) ) 7.1 Hz), 6.73-6.81 (multiplets due to aromatic protons), 7.09-7.20 (multiplets due to aromatic protons), 7.46-7.51 (multiplets due to aromatic protons), 7.57-7.61 (multiplets due to aromatic protons), 7.72 (s, 2H, imino), 7.79-7.84 (multiplets due to aromatic protons), 10.02 (s, 2H, hydroxyl). 13C NMR: 30.2 (N-CH3), 116.7, 118.3, 119.2, 126.3, 127.9, 129.1, 130.4, 132.2, 133.2, 142.2 (aromatic carbon atoms), 157.1 (NdCH). 31P NMR: 25.05(s). Anal. calcd. for C22H23PO3N4: C, 62.55; H, 5.49; N, 13.26. Found: C, 62.15; H, 5.45; N, 13.25.
Results and Discussion All three phosphorus-based hydrazones 1-3 were obtained in excellent yields by the condensation of the hydrazide, C6H5P(O)[N(Me)NH2]2, with the corresponding hydroxy benzaldehyde (Scheme 1). The 31P NMR spectra of compounds 1-3 show single resonances and are upfield shifted (24.28 ppm for 1, 24.94 ppm for 2, and 25.05 ppm for 3) with respect to the parent hydrazide {C6H5P(O)[N(CH3)NH2]2} (31.0 ppm). Compounds 1 and 2 crystallized in the space groups P21/n and P21/c, while 3 crystallized in Pna21. The bond parameters for the compounds 1-3 are summarized in Table 2. The central phosphorus atom is tetracoordinate (1C,1O,2N) with an approximate tetrahedral geometry. It is interesting to note that the P-O bond distance in 1 (1.4913(12) Å) and 2 (1.4814(18) Å) is considerably lengthened in comparison to trimethylphosphine oxide13a (1.44
Scheme 1
912 Crystal Growth & Design, Vol. 6, No. 4, 2006
Chandrasekhar et al. Scheme 2. Schematic Representation of the Alternate Right- (P) and Left-Handed (M) Fused Helical Chains Formed in 1 as a Result of Intermolecular O-H‚‚‚OdP Interactions
Figure 1. (a) A view of the alternate right- and left-handed fused helical chains of structure 1. The phenyl group attached to phosphorus atom, the methyl group attached to the nitrogen atom, and hydrogen atoms that are not involved in hydrogen bonding are removed for clarity. (b, c) Two different models and views of a fused helical chain formed by O-H‚‚‚OdP bonds in 1. The right- and left-handed fused helical chains are represented in two different colors.
Å), phosphorus pentoxide6a (1.43 Å), PhP(O)(NButS-SSNBut)13b (1.460 Å). The PdO elongation in 1 and 2 is clearly due to the influence of strong O-H‚‚‚OdP hydrogen bonding. In the case of 3, where such an interaction is absent but a weaker C-H‚‚‚OdP interaction is present, the P-O bond distance is slightly shorter (1.465(2) Å). The analysis of the crystal structures of 1-3 reveals a subtle, yet decisive, influence of the orientation of the phenolic OH unit on the final supramolecular assembly. In the crystal structure
of 1, the PdO group of one hydrazone molecule interacts intermolecularly with two phenolic O-H groups in a bifurcated manner through O-H‚‚‚OdP hydrogen bonding [O(2)‚‚‚O(1) 2.738 Å (symmetry: 0.5 + x, 0.5 - y, 0.5 + z) and 2.757 Å (symmetry: -0.5 + x, 0.5 - y, 0.5 + z)]. The two phenolic O-H groups involved in hydrogen bonding are derived from two different hydrazone molecules. This leads to the formation of alternate right- (P) and left- (M) handed fused helical chains (Scheme 2, Figure 1). The pitch distance of these O-H‚‚‚OdP hydrogen-bond mediated helical chains is 8.734 Å. In addition to the induction of a helical chain in 1, the PdO group acts as a bridge by linking the P and M helical chains. Among synthetic compounds, hydrogen-bonding mediated helical chains are quite rare.14 The most common way of achieving helicity is through the metal-ligand interactions in coordination polymers. Further analysis of the crystal structure of 1 reveals intermolecular C-H‚‚‚π interactions15 leading to a polymeric chain (See Supporting Information). The crystal structure of 2 also shows a bifurcated hydrogen bonding involving the O-H‚‚‚OdP interactions. This is a result of the PdO group of one molecule of hydrazone interacting with two phenolic O-H groups of two other molecules [O‚‚‚O, 2.766 Å (symmetry: 1 - x, -y, 2 - z) and 2.622 Å (symmetry: x, y, -1 + z)]. However, in contrast to 1, these interactions led to the formation of the ladder structure (Figure 2). In addition to this hydrogen bond, the phenolic oxygen interacts with the para hydrogen atom of the phenyl group to form a C-H‚‚‚O mediated helical chain (Supporting Information).16 We made a Cambridge Structural Database (CSD version 5.26, November 2004 release) search for the bifurcated O‚‚‚OdP hydrogen bonds. The scatter plot of O‚‚‚OdP vs O‚‚‚OdP bond distances in these bifurcated O‚‚‚OdP hydrogen bonds is presented in Figure 3. Only good quality structures containing ordered, error-free, nonpolymeric compounds, no ions, and no powder structures were chosen for analysis]. 276 crystal structures possessing bifurcated O‚‚‚OdP hydrogen bonds reveal that the O‚‚‚OdP average distance is 2.7205 Å.
Figure 2. View of the ladder structure of compound 2. The phenyl group attached to the phosphorus atom, methyl group attached to the nitrogen atom, and hydrogen atom, which are not involved in hydrogen bonding, are removed for clarity.
Supramolecular Architectures of Hydrazones
Crystal Growth & Design, Vol. 6, No. 4, 2006 913 Table 3. Hydrogen Bond Parameter for 3 D-H‚‚‚A
D‚‚‚A/Å H‚‚‚A/Å D-H‚‚‚A/°
C(8)-H(8)‚‚‚O(1) C(14)-H(14)‚‚‚O(1) C(15)-H(15A)‚‚‚O(2) C(12)-H(12)‚‚‚O(2)
3.244(4) 3.286(4) 3.302(5) 3.502(4)
2.423(2) 2.451(2) 2.474(3) 2.673(3)
145.96(21) 147.93(21) 143.17(27) 147.44(22)
C(3)-H(3A)‚‚‚O(3)
3.430(5)
2.546(3)
156.83(27)
symmetry operators 1 + x, y, z 1 + x, y, z x, y, -1 + z 2 - x, 1 - y, 0.5 + z 0.5 + x, 0.5 - y, z
prevent intermolecular O-H‚‚‚OdP hydrogen bonding. However, the presence of five distinct intermolecular C-H‚‚‚O contacts led to the generation of a 3-D supramolecular architecture (Figure 5).16 A summary of these weak interactions is presented in Table 3. Conclusion
Figure 3. CSD distribution of bifurcated O‚‚‚OdP hydrogen bonds in related systems.
In summary, we have shown the formation of new supramolecular assemblies, including alternating right- and left-handed fused helical structures in phosphorus-based hydrazones that are mediated primarily through O-H‚‚‚OdP interactions. A clear influence of the geometrical disposition of the phenolic OH units on the final supramolecular assembly is seen. Acknowledgment. We thank Council of Scientific and Industrial Research, New Delhi, India, and Department of Science and Technology, New Delhi, India, for financial support. R.A. thanks IIT Kanpur for financial assistance. A.S. thanks EPSRC (Engineering and Physical Sciences Research Council), U.K. for financial support. Supporting Information Available: Ortep diagram of 1 and 2. Figure of C-H‚‚‚π interaction in 1 and C-H‚‚‚O interaction in 2. X-ray crystallographic information files (CIF) for 1-3. This material is available free of charge via the Internet at http://pubs.acs.org.
Figure 4. ORTEP diagram of compound 3 showing intramolecular O-H‚‚‚N hydrogen bonds.
Figure 5. The 3-D network structure of the compound 3 mediated by the C-H‚‚‚O interactions. Hydrogen atoms which are not involved in the interactions are removed for clarity.
The molecular structure of 3 reveals strong intramolecular O-H‚‚‚N hydrogen bonds9 involving phenolic OH groups and imino nitrogen atoms to form six-membered rings (Figure 4) (O‚‚‚N, 2.596, 2.632 Å). These intramolecular interactions
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CG050426V
