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Synthesis and crystal structure of [2-NH2-5-CH3C5H4N]4P4O12·6H2O
Materials Research Bulletin 40 (2005) 2130–2138 www.elsevier.com/locate/matresbu
Synthesis and crystal structure of [2-NH2-5-CH3C5H4N]4P4O126H2O H. Hemissi *, S. Abid, M. Rzaigui Laboratoire de Chimie des Mate´riaux, Faculte´ des Sciences, 7021 Zarzouna, Bizerte, Tunisia Received 1 December 2004; received in revised form 13 May 2005; accepted 5 July 2005 Available online 31 August 2005
Abstract Chemical preparation, crystal structure, IR absorption and thermal analysis of a new cyclotetraphosphate [2-NH2-5-CH3C5H4N]4P4O126H2O are reported. This compound is triclinic P-1 with unit-cell parameters: ˚ , a = 110.40(6), b = 117.74(6), g = 86.41(3)8, V = 989.1(8) A ˚ 3, a = 10.206(5), b = 11.778(1), c = 9.991(4) A 3 Z = 1, Dx = 1.445 g cm . The structure has been determined and refined to R = 0.034 and Rw = 0.044, using 3663 independent reflections. The P4 O4 12 ring anions and water molecules form layers spreading around (a, b + c) planes via O–H O hydrogen bonds. Between them are anchored 2-amino-5-methylpyridium cations, which establish H-bonds to interconnect the different adjacent layers and so contribute to the cohesion of the threedimensional network. Tautomerization of (C6H9N2)+ groups was evidenced in the present structure. # 2005 Elsevier Ltd. All rights reserved. Keywords: B. Chemical synthesis; C. X-ray diffraction; C. Infrared spectroscopy; D. Crystal structure
1. Introduction Phosphates have received considerable attention for several decades due to their many practical and potential uses in various fields, such as catalysts, protonic conductors, linear optics, . . . [1–3]. As a contribution to the elaboration of this kind of material, we report in the present work, a part of a new hybrid compound, which associates the cyclotetraphosphate anion to the 2-amino-5-methylpyridinium cation. Its chemical preparation, crystal structure and characterization by IR spectroscopy and thermal analysis are reported. * Corresponding author. E-mail address: [email protected] (H. Hemissi). 0025-5408/$ – see front matter # 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.materresbull.2005.07.042
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2. Experimental Crystals of the title compound were prepared by slowly adding a stoichiometric amount of diphosphorus pentoxide to an aqueous solution of 2-amino-5-methylpyridine kept at temperature close to 273 K. The reaction is: 4½2-NH2 -CH3 C5 H3 N þ P4 O10 þ 8H2 O ! 4½2-NH2 -CH3 C5 H3 NH4 P4 O12 6H2 O The obtained solution is slowly evaporated at room temperature until crystallization occurs, a colourless crystal were obtained in this way. For data collection, a prismatic single crystal, with 0.30 mm 0.15 mm 0.10 mm was selected and mounted on an Enraf–Nonius Mach 3 four-circle diffractometer operating with Ag Ka radiation. The intensities were corrected for Lorentz and polarization factors and absorption. The structure was solved by direct method using the SIR92 [4] program and refined by full-matrix least-squares techniques on F, using teXsan [5]. All non-hydrogen atoms were refined anisotropically. The hydrogen atoms involved in methyl groups CH3 were fixed and refined as a riding model, while the remaining hydrogen atoms were deduced from different Fourier maps and are not refined. Infrared spectrum was recorded on a ‘‘spectrum 1000 Perkin-Elmer’’ spectrometer using samples dispersed in spectroscopically pure KBr pellet in 3000–400 cm1 region. Thermal analysis was carried out from room temperature up to 723 K using ‘‘multimodule 92 Setaram analyser’’ at an average heating rate of 5 K/min. Table 1 Crystal and experimental data, measurement conditions and refinement results of [2-NH2-5-CH3C5H4N]4P4O126H2O (I) Crystal data Formula: [2-NH2-5-CH3C5H4N]4P4O126H2O Crystal system: triclinic ˚ , b = 11.778(1) A ˚ , c = 9.991(4) A ˚, a = 10.206(5) A a = 110.40(6)8, b = 117.74(6)8, g = 86.41(3)8 Refinement of unit-cell parameters with rcal. = 1.445 g cm3 Linear absorption factor Color
Fw = 860.58 Space group P1¯ Z=1 ˚3 V = 989.1(8) A 25 reflections (8 < u < 108) F(0 0 0) = 452 mAg Ka = 1.471 cm1 Colorless
(II) Intensity measurements Temperature = 296 K Diffractometer: Enraf–Nonius Mach 3 Monochromator: graphite plate Measurement area: h, k, l Absorption correction type Nb of measured reflections Nb of collected unique reflections Two intensity and orientation control reflections
˚) Wavelength: Ag Ka (0.5608 A Scan mode: v/2u Theta range: 2–258 hmax = 15, kmax = 9, lmax = 14 Empirical (DIFABS) 5279 4983 (Rint = 0.01) 5 2 4 and 5 3 5
(III) Structure determination Unique reflections included: 3663 with I > 3s(I) Weighting scheme: s2 ˚ 3 Residual Fourier density: 0.20 < r < 0.21 e A Largest shift/error = 0.01
Refined parameters: 244 R = 0.034, Rw = 0.044 Esd = 1.93
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Table 2 ˚ 2) for the non-hydrogen atoms in [2-NH2-5-CH3C5H4N]4P4O126H2O Final atomic coordinates and Beq. (A Atoms
x
P(1) P(2) O(W1) O(W2) O(W3) O(E11) O(E12) O(L12) O(L21) O(E21) O(E22) N(1) N(2) N(3) N(4) C(1) C(2) C(3) C(4) C(5) C(6) C(7) C(8) C(9) C(10) C(11) C(12)
0.78395(3) 1.00536(3) 0.53257(10) 0.77651(13) 1.21860(11) 0.75957(9) 0.65771(8) 0.92446(8) 1.16249(7) 0.92553(9) 1.03143(10) 0.90087(12) 1.0765(2) 0.63509(10) 0.45537(13) 0.9652(1) 0.9104(2) 0.7950(2) 0.7279(2) 0.7852(2) 0.5957(2) 0.52980(12) 0.5037(2) 0.5868(2) 0.7000(2) 0.71995(13) 0.7922(2)
y
-0.05742(3) 0.15826(3) 0.19606(9) 0.38336(11) 0.36741(10) 0.15357(8) 0.01037(8) 0.03505(8) 0.11365(8) 0.18710(8) 0.24941(8) 0.35324(11) 0.2959(1) 0.11072(10) 0.22296(13) 0.36150(13) 0.4402(2) 0.5013(2) 0.4903(1) 0.4150(1) 0.5544(2) 0.18397(12) 0.2178(1) 0.1788(2) 0.1050(1) 0.07254(13) 0.0630(2) P P Estimated standard deviations are given in parentheses. Beq. = 4/3 i j aiaj bij.
z
Beq.
0.97074(3) 1.14646(3) 1.03513(13) 1.2632(2) 0.62121(12) 1.02241(11) 0.90231(9) 1.12244(8) 1.16477(9) 0.99748(10) 1.30346(10) 0.87236(13) 0.7847(2) 0.68196(11) 0.7252(2) 0.7857(2) 0.6990(2) 0.7017(2) 0.7915(2) 0.8756(2) 0.7897(3) 0.64092(13) 0.5097(2) 0.4330(2) 0.4809(2) 0.6065(2) 0.3965(2)
2.379(6) 2.385(6) 4.17(2) 7.32(3) 4.66(2) 3.27(2) 3.06(2) 2.72(2) 2.85(2) 3.24(2) 3.73(2) 3.56(2) 4.79(3) 3.11(2) 4.38(3) 3.59(3) 4.69(4) 5.09(4) 4.53(3) 4.21(3) 6.62(5) 3.22(2) 3.82(3) 4.13(3) 3.95(3) 3.62(3) 6.43(5)
3. Results and discussion 3.1. Structural description All data concerning the experimental parameters used for the structure determination as well as their final results are gathered in Table 1. Final atomic coordinates of non-hydrogen atoms of [2-NH2-5CH3C5H4N]4P4O126H2O and their Beq. are reported in Table 2. Those of hydrogen atoms have been determined too but not given to shorten the table. The asymmetric unit of the crystal structure, depicted in an ORTEP drawing (Fig. 1), consists of two PO4 tetrahedra, two organic cations and three water molecules. The main feature of the atomic arrangement in the 2-amino-5-methylpyridinium cyclotetraphosphate hexahydrate is the existence of infinite layers spreading around (a, b + c) planes. In such layer, adjacent anionic (P4O12)4 rings are interconnected by H-bonds from OW1 water molecules forming so an infinite ribbon ½P4 O12 ðH2 OÞ2 4n n running along the ~ a-direction. The remaining water molecules OW2 and OW3 link these ribbons along (Fig. 2). The organic [0 1 1] direction generating a two-dimensional network of ½P4 O12 ðH2 OÞ6 4n n
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Fig. 1. ORTEP drawing of the asymmetric unit of the title compound, representing heaving atoms as 30% probability ellipsoids and H atoms as spheres of arbitrary radius.
Fig. 2. Projection along the a-axis of [2-NH2-5-CH3C5H4N]4P4O126H2O structure. The phosphoric anions are given in tetrahedral representation. The other atoms are labelled in figure. Hydrogen bonds are denoted by dotted lines.
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Fig. 3. Projection along the [0 1 1] direction of the [P4O12(H2O)6]n layer. The phosphoric anions are given in tetrahedral representation. The other atoms are labelled in figure. Hydrogen bonds are denoted by dotted lines.
cations are anchored to anionic layers through hydrogen bonds as shown in Fig. 3. Each cation links these layers through –NH2 groups performing so a three-dimensional network. 3.1.1. The P4O12 ring The anion ring (P4O12)4 involved in the inorganic layers, is located around the inversion centre (0, 0, 0); so, it is built up by only two independent tetrahedra P(1)O4 and P(2)O4. This type of internal symmetry leads to a large deviation of P–P–P angle from the ideal value (908) [6,7]. Indeed, the P–P–P angle is 98.09(6)8. The P–O–P angles values are 129.80(8) and 131.95(9), while the P–O distances range ˚ with an average of 1.539 A ˚ (Table 3). In spite of these differences in P–O bond from 1.469 to 1.609 A lengths, which can be explained by different environments of the O atoms, the PO4 tetrahedron is ˚ described by regular oxygen atoms arrangement with phosphorus atom shifted of 0.1154 and 0.1497 A from the gravity centre.
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Table 3 ˚ ) and bond angles (8) in P4 O4 anion of [2-NH2-5-CH3C5H4N]4P4O126H2O Main interatomic distances (A 12 Tetrahedron P(1)O4 P(1) O(E11) O(E12) O(L12) O(L21)
O(E11) 1.474(1) 118.44(8) 107.09(8) 110.14(8)
Tetrahedron P(2)O4 P(2) O(E21) O(E22) O(L12) O(L21) P(1)–P(2) P(2)–P(1)–P(2) P(1)–O(L12)–P(2) Estimated standard deviations are
O(E12) 2.540(2) 1.482(2) 110.41(8) 105.72(7)
O(L12) 2.474(3) 2.532(2) 1.600(2) 104.15(8)
O(L21) 2.529(2) 2.465(2) 2.447(2) 1.609(1)
O(E21) 1.478(1) 120.01(9) 109.60(9) 110.00(7)
O(E22) O(L12) O(L21) 2.552(2) 2.518(2) 2.525(2) 1.469(2) 2.482(3) 2.486(2) 107.76(9) 1.603(2) 2.532(3) 107.97(8) 99.54(8) 1.603(1) 2.909(2) P(2)–P(1) 2.925(3) 81.91(6) P(1)–P(2)–P(1) 98.09(6) 129.80(8) P(2)–O(L21)–P(1) 131.95(9) given in parentheses.The underlined digits in the table are the bond lengths P-O.
3.1.2. The organic groups Two crystallographically independent cationic groups of [2-NH2-5-CH3C5H4N]+ coexist in this atomic arrangement. These entities are planar, with mean plane deviations of atoms forming each ˚ . The two independent pyridine rings form between them a dihedral angle of 12.728 cation of 0.0176 A ˚ , indicating so the existence of p–p interactions [8]. Main and are separated with a distance of 3.55 A bond lengths and angles are presented in Table 4. In the two 2-amino-5-methylpyridinium groups, both ˚ , respectively, justifying the bond lengths C1–N2 and C7–N4 have a length of 1.334(3) and 1.334(2) A Table 4 ˚ ) and bond angles (8) in the organic groups of the [2-NH2-5-CH3C5H4N]4P4O126H2O Selected bond lengths (A [2-NH2-5-CH3C5H4N(1)]+ N1–C1 1.337(3) N1–C5 1.355(3) N2–C1 1.334(3) N1–C1–N2 119.6(2) N1–C1–C2 117.2(2) N1–C5–C4 121.8(2) N2–C1–C2 123.2(2) [2-NH2-5-CH3C5H4N(2)]+ N3–C7 1.337(2) N3–C11 1.358(2) N4–C7 1.334(2) N3–C7–N4 N3–C7–C8 N4–C7–C8 N3–C11–C10
119.7(2) 122.6(2) 117.6(2) 121.4(2)
C1–C2 C2–C3 C3–C4 C1–N1–C5 C1–C2–C3 C2–C3–C4
1.402(3) 1.348(3) 1.398(3) 122.7(2) 120.2(2) 121.8(2)
C7–C8 C8–C9 C9–C10 C7–N3–C11 C7–C8–C9 C8–C9–C10
Estimated standard deviations are given in parentheses.
C4–C5 C4–C6
1.354(4) 1.500(3)
C3–C4–C5 C3–C4–C6 C5–C4–C6
116.4(2) 121.9(2) 121.7(2)
1.405(3) 1.353(3) 1.404(3)
C10–C11 C10–C12
1.359(3) 1.494(3)
122.7(2) 119.8(2) 121.8(2)
C9–C10–C11 C9–C10–C12 C11–C10–C12
116.6(2) 121.5(2) 121.9(2)
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Scheme 1. Tautomerization of the organic molecule [2-NH2-5-CH3C5H4N]+.
existence of an electronic resonance between the pyridine ring and the amine group, similar to that observed in other 2-aminomethylpyridinium compounds [9,10]. This tautomerization is shown in Scheme 1. The hydrogen atoms H(1N) and H(3N) are involved in H-bonding to link the organic ˚. molecules to the phosphoric rings via N–H OE hydrogen bonds with dN O = 2.609(2) and 2.757(2) A Whereas, among the four hydrogen of the two independent –NH2 groups, only one establishes H-bond with external oxygen of P4O12 ring N–H OE, the remaining hydrogen atoms are connected to the oxygen atoms of the water molecules OW. This network of hydrogen bonds participate to the cohesion of ˚ (Table 5). the three-dimensional network with distances N O ranging from 2.862(3) to 2.966(3) A 3.1.3. The water molecules Inside the unit-cell coexist also three crystallographically independent water molecules. As evidenced from Fig. 2, water molecules are assembled as triplet and labelled (OW1, OW2 and OW3). Each triplet is connected by hydrogen bonds to three P4O12 groups and so contributes to the intralayer cohesion. The ˚ and from 168.3 to O H distances and O–H O angles spread in the range from 2.696(3) to 2.894(3) A 173.68, respectively (Table 5). 3.2. IR spectroscopic study The IR spectrum (Fig. 4) of the title compound is characterized by the presence of strong bands in the regions 1350–1220, 1150–1100, 1080–980 and 750–680 cm1. These bands can be assigned to Table 5 Main geometrical features of the hydrogen-bond scheme in [2-NH2-5-CH3C5H4N]4P4O126H2O D–H A
˚) D–H (A
O(W1)–H(1W) O(E12) O(W1)–H(1W2) O(E11) O(W2)–H(1W2) O(E22) O(W2)–H(2W2) O(W1) O(W3)–H(1W3) O(W2) O(W3)–H(2W3) O(E22) N(1)–H(1N1) O(E21) N(2)–H(2N2) O(E11) N(2)–H(2N2) O(W3) N(3)–H(1N3) O(E12) N(4)–H(1N4) O(W1) N(4)–H(2N4) O(W3)
0.92 0.97 0.88 0.93 0.96 0.93 0.93 0.96 0.96 0.95 0.87 0.95
˚) H A (A
1.84 1.85 2.03 1.95 1.79 1.77 1.71 1.93 2.02 1.82 2.11 1.92 H(1W1)–O(W1)–H(2W1) 109.8 H(1W2)–O(W2)–H(2W2) 113.2 H(1W3)–O(W3)–H(2W3) 108.6
˚) D A (A
˚) D–H A (A
2.717(2) 2.804(2) 2.894(3) 2.856(4) 2.749(3) 2.696(3) 2.609(2) 2.868(3) 2.966(3) 2.757(2) 2.948(2) 2.862(3)
158.6 166.7 168.3 165.5 173.3 173.6 161.5 166.7 166.2 168.5 161.2 178.0
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Fig. 4. IR spectra of [2-NH2-5-CH3C5H4N]4P4O126H2O: (a) not heated and (b) heated at 423K.
stretching vibrations nas(OPO), ns(OPO), nas(POP) and ns(POP), respectively [11]. Nevertheless, special caution must be paid in attribution of these bands because of their possible overlapping with n(C– N) stretching vibration and d(C–H) bending vibration bands. The two vibration bands observed at 757 and 703 cm1 are the most striking feature of cyclotetraphosphate spectra and can be considered as a signature of the local symmetry Ci of the P4O12 ring as confirmed by X-rays results. Frequencies below 660 cm1 can be assigned to bending vibrations of P4O12 ring, and those in the range of 4000–1350 cm1 are attributed to O(N,C)–H stretching and bending modes [12]. 3.3. Thermal behaviour The two thermograms corresponding to DTA and TGA carried out in an argon atmosphere are given in Fig. 5. The DTA thermogram shows an endothermic peak in a wide temperature range [330, 383 K] with
Fig. 5. DTA and TGA thermograms of the title compound at rising temperature.
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a maximum at 350 K, which corresponds to the departure of the six water molecules well-confirmed by the weight loss observed in TGA thermogram (% water experimental 12.20, calculated 12.54). This total dehydration leads to the anhydrous phosphate [2-NH2-5-CH3C5H4N]4P4O12, since its IR spectrum (Fig. 4) exhibits the characteristic bands of the P4O12 ring and the organic molecule. An other series of peaks beginning at 481 K and accompanied by an important weight loss in a wide temperature range [433, 723 K] correspond to a degradation of the obtained anhydrous compound leading to a polyphosphoric acid and a black deposit of carbon.
References [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12]
V. Tananaev, H. Gru¨nze, N.N. Chudinova, Izv. Akad. Nauk. SSSR Neorg. Mater. 20 (1984) 887. G. Le Flem, Eur. J. Solid State Inorg. Chem. 28 (1991) 3. J. Pe´caut, R. Masse, Acta Crystallogr. B49 (1993) 277. A. Altomare, M. Cascarano, C. Giacovazzo, A. Guagliardi, J. Appl. Crystallogr. 26 (1993) 343. teXsan for Windows Version 1.03, Single Crystal, Structure Analysis Software, Version 1.03, Molecular Structure Corporation, MSC, 3200 Research Forest Drive, The Woodlands, TX 77381, USA, 1997. E.H. Soumhi, I. Saadoune, A. Driss, J. Solid State Chem. 156 (2001) 364. Z. Aloui, S. abid, M. Rzaigui, Mater. Res. Bull. 1936 (2002) 697. C.A. Hunter, J.K.M. Sanders, J. Am. Chem. Soc. 112 (1990) 5525. Z. Jin, Y. Pan, M.L. Hu, S. Liang, J. Chem. Crystallogr. 31 (2002) 191. Z. Jin, Y. Pan, J. Liu, D. Xu, J. Chem. Crystallogr. 30 (2000) 195. G. Foumakoye, R. Cahay, P. Tarte, Spectrochim. Acta A46 (1990) 1245. R.M. Silverstein, G.C. Bassler, T.C. Morrill, Spectrometric Identification of Organic Compounds, 3rd ed., John Wiley and Sons, Inc., New York, 1974.
Synthesis and crystal structure of [2-NH2-5-CH3C5H4N]4P4O126H2O H. Hemissi *, S. Abid, M. Rzaigui Laboratoire de Chimie des Mate´riaux, Faculte´ des Sciences, 7021 Zarzouna, Bizerte, Tunisia Received 1 December 2004; received in revised form 13 May 2005; accepted 5 July 2005 Available online 31 August 2005
Abstract Chemical preparation, crystal structure, IR absorption and thermal analysis of a new cyclotetraphosphate [2-NH2-5-CH3C5H4N]4P4O126H2O are reported. This compound is triclinic P-1 with unit-cell parameters: ˚ , a = 110.40(6), b = 117.74(6), g = 86.41(3)8, V = 989.1(8) A ˚ 3, a = 10.206(5), b = 11.778(1), c = 9.991(4) A 3 Z = 1, Dx = 1.445 g cm . The structure has been determined and refined to R = 0.034 and Rw = 0.044, using 3663 independent reflections. The P4 O4 12 ring anions and water molecules form layers spreading around (a, b + c) planes via O–H O hydrogen bonds. Between them are anchored 2-amino-5-methylpyridium cations, which establish H-bonds to interconnect the different adjacent layers and so contribute to the cohesion of the threedimensional network. Tautomerization of (C6H9N2)+ groups was evidenced in the present structure. # 2005 Elsevier Ltd. All rights reserved. Keywords: B. Chemical synthesis; C. X-ray diffraction; C. Infrared spectroscopy; D. Crystal structure
1. Introduction Phosphates have received considerable attention for several decades due to their many practical and potential uses in various fields, such as catalysts, protonic conductors, linear optics, . . . [1–3]. As a contribution to the elaboration of this kind of material, we report in the present work, a part of a new hybrid compound, which associates the cyclotetraphosphate anion to the 2-amino-5-methylpyridinium cation. Its chemical preparation, crystal structure and characterization by IR spectroscopy and thermal analysis are reported. * Corresponding author. E-mail address: [email protected] (H. Hemissi). 0025-5408/$ – see front matter # 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.materresbull.2005.07.042
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2. Experimental Crystals of the title compound were prepared by slowly adding a stoichiometric amount of diphosphorus pentoxide to an aqueous solution of 2-amino-5-methylpyridine kept at temperature close to 273 K. The reaction is: 4½2-NH2 -CH3 C5 H3 N þ P4 O10 þ 8H2 O ! 4½2-NH2 -CH3 C5 H3 NH4 P4 O12 6H2 O The obtained solution is slowly evaporated at room temperature until crystallization occurs, a colourless crystal were obtained in this way. For data collection, a prismatic single crystal, with 0.30 mm 0.15 mm 0.10 mm was selected and mounted on an Enraf–Nonius Mach 3 four-circle diffractometer operating with Ag Ka radiation. The intensities were corrected for Lorentz and polarization factors and absorption. The structure was solved by direct method using the SIR92 [4] program and refined by full-matrix least-squares techniques on F, using teXsan [5]. All non-hydrogen atoms were refined anisotropically. The hydrogen atoms involved in methyl groups CH3 were fixed and refined as a riding model, while the remaining hydrogen atoms were deduced from different Fourier maps and are not refined. Infrared spectrum was recorded on a ‘‘spectrum 1000 Perkin-Elmer’’ spectrometer using samples dispersed in spectroscopically pure KBr pellet in 3000–400 cm1 region. Thermal analysis was carried out from room temperature up to 723 K using ‘‘multimodule 92 Setaram analyser’’ at an average heating rate of 5 K/min. Table 1 Crystal and experimental data, measurement conditions and refinement results of [2-NH2-5-CH3C5H4N]4P4O126H2O (I) Crystal data Formula: [2-NH2-5-CH3C5H4N]4P4O126H2O Crystal system: triclinic ˚ , b = 11.778(1) A ˚ , c = 9.991(4) A ˚, a = 10.206(5) A a = 110.40(6)8, b = 117.74(6)8, g = 86.41(3)8 Refinement of unit-cell parameters with rcal. = 1.445 g cm3 Linear absorption factor Color
Fw = 860.58 Space group P1¯ Z=1 ˚3 V = 989.1(8) A 25 reflections (8 < u < 108) F(0 0 0) = 452 mAg Ka = 1.471 cm1 Colorless
(II) Intensity measurements Temperature = 296 K Diffractometer: Enraf–Nonius Mach 3 Monochromator: graphite plate Measurement area: h, k, l Absorption correction type Nb of measured reflections Nb of collected unique reflections Two intensity and orientation control reflections
˚) Wavelength: Ag Ka (0.5608 A Scan mode: v/2u Theta range: 2–258 hmax = 15, kmax = 9, lmax = 14 Empirical (DIFABS) 5279 4983 (Rint = 0.01) 5 2 4 and 5 3 5
(III) Structure determination Unique reflections included: 3663 with I > 3s(I) Weighting scheme: s2 ˚ 3 Residual Fourier density: 0.20 < r < 0.21 e A Largest shift/error = 0.01
Refined parameters: 244 R = 0.034, Rw = 0.044 Esd = 1.93
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Table 2 ˚ 2) for the non-hydrogen atoms in [2-NH2-5-CH3C5H4N]4P4O126H2O Final atomic coordinates and Beq. (A Atoms
x
P(1) P(2) O(W1) O(W2) O(W3) O(E11) O(E12) O(L12) O(L21) O(E21) O(E22) N(1) N(2) N(3) N(4) C(1) C(2) C(3) C(4) C(5) C(6) C(7) C(8) C(9) C(10) C(11) C(12)
0.78395(3) 1.00536(3) 0.53257(10) 0.77651(13) 1.21860(11) 0.75957(9) 0.65771(8) 0.92446(8) 1.16249(7) 0.92553(9) 1.03143(10) 0.90087(12) 1.0765(2) 0.63509(10) 0.45537(13) 0.9652(1) 0.9104(2) 0.7950(2) 0.7279(2) 0.7852(2) 0.5957(2) 0.52980(12) 0.5037(2) 0.5868(2) 0.7000(2) 0.71995(13) 0.7922(2)
y
-0.05742(3) 0.15826(3) 0.19606(9) 0.38336(11) 0.36741(10) 0.15357(8) 0.01037(8) 0.03505(8) 0.11365(8) 0.18710(8) 0.24941(8) 0.35324(11) 0.2959(1) 0.11072(10) 0.22296(13) 0.36150(13) 0.4402(2) 0.5013(2) 0.4903(1) 0.4150(1) 0.5544(2) 0.18397(12) 0.2178(1) 0.1788(2) 0.1050(1) 0.07254(13) 0.0630(2) P P Estimated standard deviations are given in parentheses. Beq. = 4/3 i j aiaj bij.
z
Beq.
0.97074(3) 1.14646(3) 1.03513(13) 1.2632(2) 0.62121(12) 1.02241(11) 0.90231(9) 1.12244(8) 1.16477(9) 0.99748(10) 1.30346(10) 0.87236(13) 0.7847(2) 0.68196(11) 0.7252(2) 0.7857(2) 0.6990(2) 0.7017(2) 0.7915(2) 0.8756(2) 0.7897(3) 0.64092(13) 0.5097(2) 0.4330(2) 0.4809(2) 0.6065(2) 0.3965(2)
2.379(6) 2.385(6) 4.17(2) 7.32(3) 4.66(2) 3.27(2) 3.06(2) 2.72(2) 2.85(2) 3.24(2) 3.73(2) 3.56(2) 4.79(3) 3.11(2) 4.38(3) 3.59(3) 4.69(4) 5.09(4) 4.53(3) 4.21(3) 6.62(5) 3.22(2) 3.82(3) 4.13(3) 3.95(3) 3.62(3) 6.43(5)
3. Results and discussion 3.1. Structural description All data concerning the experimental parameters used for the structure determination as well as their final results are gathered in Table 1. Final atomic coordinates of non-hydrogen atoms of [2-NH2-5CH3C5H4N]4P4O126H2O and their Beq. are reported in Table 2. Those of hydrogen atoms have been determined too but not given to shorten the table. The asymmetric unit of the crystal structure, depicted in an ORTEP drawing (Fig. 1), consists of two PO4 tetrahedra, two organic cations and three water molecules. The main feature of the atomic arrangement in the 2-amino-5-methylpyridinium cyclotetraphosphate hexahydrate is the existence of infinite layers spreading around (a, b + c) planes. In such layer, adjacent anionic (P4O12)4 rings are interconnected by H-bonds from OW1 water molecules forming so an infinite ribbon ½P4 O12 ðH2 OÞ2 4n n running along the ~ a-direction. The remaining water molecules OW2 and OW3 link these ribbons along (Fig. 2). The organic [0 1 1] direction generating a two-dimensional network of ½P4 O12 ðH2 OÞ6 4n n
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Fig. 1. ORTEP drawing of the asymmetric unit of the title compound, representing heaving atoms as 30% probability ellipsoids and H atoms as spheres of arbitrary radius.
Fig. 2. Projection along the a-axis of [2-NH2-5-CH3C5H4N]4P4O126H2O structure. The phosphoric anions are given in tetrahedral representation. The other atoms are labelled in figure. Hydrogen bonds are denoted by dotted lines.
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Fig. 3. Projection along the [0 1 1] direction of the [P4O12(H2O)6]n layer. The phosphoric anions are given in tetrahedral representation. The other atoms are labelled in figure. Hydrogen bonds are denoted by dotted lines.
cations are anchored to anionic layers through hydrogen bonds as shown in Fig. 3. Each cation links these layers through –NH2 groups performing so a three-dimensional network. 3.1.1. The P4O12 ring The anion ring (P4O12)4 involved in the inorganic layers, is located around the inversion centre (0, 0, 0); so, it is built up by only two independent tetrahedra P(1)O4 and P(2)O4. This type of internal symmetry leads to a large deviation of P–P–P angle from the ideal value (908) [6,7]. Indeed, the P–P–P angle is 98.09(6)8. The P–O–P angles values are 129.80(8) and 131.95(9), while the P–O distances range ˚ with an average of 1.539 A ˚ (Table 3). In spite of these differences in P–O bond from 1.469 to 1.609 A lengths, which can be explained by different environments of the O atoms, the PO4 tetrahedron is ˚ described by regular oxygen atoms arrangement with phosphorus atom shifted of 0.1154 and 0.1497 A from the gravity centre.
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Table 3 ˚ ) and bond angles (8) in P4 O4 anion of [2-NH2-5-CH3C5H4N]4P4O126H2O Main interatomic distances (A 12 Tetrahedron P(1)O4 P(1) O(E11) O(E12) O(L12) O(L21)
O(E11) 1.474(1) 118.44(8) 107.09(8) 110.14(8)
Tetrahedron P(2)O4 P(2) O(E21) O(E22) O(L12) O(L21) P(1)–P(2) P(2)–P(1)–P(2) P(1)–O(L12)–P(2) Estimated standard deviations are
O(E12) 2.540(2) 1.482(2) 110.41(8) 105.72(7)
O(L12) 2.474(3) 2.532(2) 1.600(2) 104.15(8)
O(L21) 2.529(2) 2.465(2) 2.447(2) 1.609(1)
O(E21) 1.478(1) 120.01(9) 109.60(9) 110.00(7)
O(E22) O(L12) O(L21) 2.552(2) 2.518(2) 2.525(2) 1.469(2) 2.482(3) 2.486(2) 107.76(9) 1.603(2) 2.532(3) 107.97(8) 99.54(8) 1.603(1) 2.909(2) P(2)–P(1) 2.925(3) 81.91(6) P(1)–P(2)–P(1) 98.09(6) 129.80(8) P(2)–O(L21)–P(1) 131.95(9) given in parentheses.The underlined digits in the table are the bond lengths P-O.
3.1.2. The organic groups Two crystallographically independent cationic groups of [2-NH2-5-CH3C5H4N]+ coexist in this atomic arrangement. These entities are planar, with mean plane deviations of atoms forming each ˚ . The two independent pyridine rings form between them a dihedral angle of 12.728 cation of 0.0176 A ˚ , indicating so the existence of p–p interactions [8]. Main and are separated with a distance of 3.55 A bond lengths and angles are presented in Table 4. In the two 2-amino-5-methylpyridinium groups, both ˚ , respectively, justifying the bond lengths C1–N2 and C7–N4 have a length of 1.334(3) and 1.334(2) A Table 4 ˚ ) and bond angles (8) in the organic groups of the [2-NH2-5-CH3C5H4N]4P4O126H2O Selected bond lengths (A [2-NH2-5-CH3C5H4N(1)]+ N1–C1 1.337(3) N1–C5 1.355(3) N2–C1 1.334(3) N1–C1–N2 119.6(2) N1–C1–C2 117.2(2) N1–C5–C4 121.8(2) N2–C1–C2 123.2(2) [2-NH2-5-CH3C5H4N(2)]+ N3–C7 1.337(2) N3–C11 1.358(2) N4–C7 1.334(2) N3–C7–N4 N3–C7–C8 N4–C7–C8 N3–C11–C10
119.7(2) 122.6(2) 117.6(2) 121.4(2)
C1–C2 C2–C3 C3–C4 C1–N1–C5 C1–C2–C3 C2–C3–C4
1.402(3) 1.348(3) 1.398(3) 122.7(2) 120.2(2) 121.8(2)
C7–C8 C8–C9 C9–C10 C7–N3–C11 C7–C8–C9 C8–C9–C10
Estimated standard deviations are given in parentheses.
C4–C5 C4–C6
1.354(4) 1.500(3)
C3–C4–C5 C3–C4–C6 C5–C4–C6
116.4(2) 121.9(2) 121.7(2)
1.405(3) 1.353(3) 1.404(3)
C10–C11 C10–C12
1.359(3) 1.494(3)
122.7(2) 119.8(2) 121.8(2)
C9–C10–C11 C9–C10–C12 C11–C10–C12
116.6(2) 121.5(2) 121.9(2)
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Scheme 1. Tautomerization of the organic molecule [2-NH2-5-CH3C5H4N]+.
existence of an electronic resonance between the pyridine ring and the amine group, similar to that observed in other 2-aminomethylpyridinium compounds [9,10]. This tautomerization is shown in Scheme 1. The hydrogen atoms H(1N) and H(3N) are involved in H-bonding to link the organic ˚. molecules to the phosphoric rings via N–H OE hydrogen bonds with dN O = 2.609(2) and 2.757(2) A Whereas, among the four hydrogen of the two independent –NH2 groups, only one establishes H-bond with external oxygen of P4O12 ring N–H OE, the remaining hydrogen atoms are connected to the oxygen atoms of the water molecules OW. This network of hydrogen bonds participate to the cohesion of ˚ (Table 5). the three-dimensional network with distances N O ranging from 2.862(3) to 2.966(3) A 3.1.3. The water molecules Inside the unit-cell coexist also three crystallographically independent water molecules. As evidenced from Fig. 2, water molecules are assembled as triplet and labelled (OW1, OW2 and OW3). Each triplet is connected by hydrogen bonds to three P4O12 groups and so contributes to the intralayer cohesion. The ˚ and from 168.3 to O H distances and O–H O angles spread in the range from 2.696(3) to 2.894(3) A 173.68, respectively (Table 5). 3.2. IR spectroscopic study The IR spectrum (Fig. 4) of the title compound is characterized by the presence of strong bands in the regions 1350–1220, 1150–1100, 1080–980 and 750–680 cm1. These bands can be assigned to Table 5 Main geometrical features of the hydrogen-bond scheme in [2-NH2-5-CH3C5H4N]4P4O126H2O D–H A
˚) D–H (A
O(W1)–H(1W) O(E12) O(W1)–H(1W2) O(E11) O(W2)–H(1W2) O(E22) O(W2)–H(2W2) O(W1) O(W3)–H(1W3) O(W2) O(W3)–H(2W3) O(E22) N(1)–H(1N1) O(E21) N(2)–H(2N2) O(E11) N(2)–H(2N2) O(W3) N(3)–H(1N3) O(E12) N(4)–H(1N4) O(W1) N(4)–H(2N4) O(W3)
0.92 0.97 0.88 0.93 0.96 0.93 0.93 0.96 0.96 0.95 0.87 0.95
˚) H A (A
1.84 1.85 2.03 1.95 1.79 1.77 1.71 1.93 2.02 1.82 2.11 1.92 H(1W1)–O(W1)–H(2W1) 109.8 H(1W2)–O(W2)–H(2W2) 113.2 H(1W3)–O(W3)–H(2W3) 108.6
˚) D A (A
˚) D–H A (A
2.717(2) 2.804(2) 2.894(3) 2.856(4) 2.749(3) 2.696(3) 2.609(2) 2.868(3) 2.966(3) 2.757(2) 2.948(2) 2.862(3)
158.6 166.7 168.3 165.5 173.3 173.6 161.5 166.7 166.2 168.5 161.2 178.0
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Fig. 4. IR spectra of [2-NH2-5-CH3C5H4N]4P4O126H2O: (a) not heated and (b) heated at 423K.
stretching vibrations nas(OPO), ns(OPO), nas(POP) and ns(POP), respectively [11]. Nevertheless, special caution must be paid in attribution of these bands because of their possible overlapping with n(C– N) stretching vibration and d(C–H) bending vibration bands. The two vibration bands observed at 757 and 703 cm1 are the most striking feature of cyclotetraphosphate spectra and can be considered as a signature of the local symmetry Ci of the P4O12 ring as confirmed by X-rays results. Frequencies below 660 cm1 can be assigned to bending vibrations of P4O12 ring, and those in the range of 4000–1350 cm1 are attributed to O(N,C)–H stretching and bending modes [12]. 3.3. Thermal behaviour The two thermograms corresponding to DTA and TGA carried out in an argon atmosphere are given in Fig. 5. The DTA thermogram shows an endothermic peak in a wide temperature range [330, 383 K] with
Fig. 5. DTA and TGA thermograms of the title compound at rising temperature.
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a maximum at 350 K, which corresponds to the departure of the six water molecules well-confirmed by the weight loss observed in TGA thermogram (% water experimental 12.20, calculated 12.54). This total dehydration leads to the anhydrous phosphate [2-NH2-5-CH3C5H4N]4P4O12, since its IR spectrum (Fig. 4) exhibits the characteristic bands of the P4O12 ring and the organic molecule. An other series of peaks beginning at 481 K and accompanied by an important weight loss in a wide temperature range [433, 723 K] correspond to a degradation of the obtained anhydrous compound leading to a polyphosphoric acid and a black deposit of carbon.
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