Synthesis and characterization of a layered chlorozincophosphate templated by protonated 4-methylpiperidine

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  • Cryst. Res. Technol. 42, No. 4, 333 341 (2007) / DOI 10.1002/crat.200610824

    2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

    Synthesis and characterization of a layered chlorozincophosphate

    templated by protonated 4-methylpiperidine

    R. Kefi1, F. Lefebvre

    2, and C. Ben Nasr*

    1

    1 Laboratoire de Chimie des Matriaux, Facult des Sciences de Bizerte, 7021 Zarzouna, Tunisie 2 Laboratoire de Chimie Organomtallique de Surface (LCOMS), Ecole Suprieure de Chimie Physique

    Electronique, Villeurbanne Cedex, France

    Received 12 September 2006, revised 24 November 2006, accepted 31 November 2006 Published online 10 March 2007

    Key words X-ray diffraction, layered compounds, NMR spectroscopy, 4-methyl-piperidine, organic template.

    PACS 61.66.Hq

    A chlorozincophosphate with the composition Zn(HPO4)Cl.[C6H14N] has been synthesised under mild

    conditions in water medium in presence of 4-methylpiperidine as organic template. The structure was determinated by single crystal X-ray diffraction. The unit cell is orthorhombic (space group Pcab) with a = 8.743(9), b = 9.592(6), c = 26.573(6) , Z = 8 and V = 2228.91(12) 3. The structure involves a network of ZnO3Cl and PO3(OH) tetrahedra forming macroanionic inorganic layers with four and eight-membered rings. Charge balance is achieved by the protonated amine which is trapped in the interlayers space and interacts with the organic framework through hydrogen bonding. Solid state 31P and 13C MAS-NMR spectroscopies are in full agreement with the X-ray structure.

    2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

    1 Introduction

    Works on the synthesis and characterization of new microporous materials continue to grow owing to their interesting structural chemistry and potential applications as adsorbents, catalysts, and ion-exchange media, revealing an increasing variety of framework compositions topologies. A large number of these materials have been synthesized in the presence of organic amines as structure-directing agent [1-3]. They are also exploited in other areas such as electronic materials [4], photochemical, and photophysical processes [5]. Since the discovery of AlPO molecular sieves in 1982 [6], a large number of phosphate-based materials have been prepared under hydrothermal conditions. Between those metal phosphates, zincophosphates constitute a large family. So far, zincophosphates with monomeric phases, chains, layers and three-dimensional open-framework have been prepared in the presence of different amines, alkali metal cations or metal complexes as structure directing agent [7-15].

    In a continuing theme of research aiming at producing new materials, we investigated the formation of zincophosphates in the presence of a variety of organic amine molecules. During the course of this study, we isolated a new chlorozincophosphate Zn(HPO4)Cl.[C6H14N], with a layered structure in the presence of 4-methylpiperidine cations. The present compound, in which the chlorine is part of the framework, has been characterized by X-ray diffraction, NMR, infrared spectroscopy and TGA-DTA.

    2 Experimental

    2.1 Chemical preparation

    Crystals of the title compound Zn(HPO4)Cl.[C6H14N] have been obtained at room temperature according to the following procedure: a mixture of 1.8 g of 4-methylpiperidine (Acros) dissolved in water and 3.9 g of ____________________

    * Corresponding author: e-mail: cherif.bennasr@fsb.rnu.tn

  • 334 R. Kefi et al.: Synthesis and characterization of a layered chlorozincophosphate

    2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.crt-journal.org

    phosphoric acid ( Fluka 85 % weight H3PO4) has been firstly prepared. An aqueous solution containing 4.0 g of zinc chloride (Prolabo) was then added dropwise to this solution under continuous stirring. A white precipitate formed which was recrystallized in diluted phosphoric acid. Schematically the reaction can be written as follows:

    C6H13N + H3PO4 + ZnCl2 Zn(HPO4)Cl [C6H14N] + HCl

    2.2 Investigation techniques

    The title compound has been studied by various physico-chemical methods: X-ray diffraction, Solid state NMR, Infrared spectroscopy and Thermal analysis.

    X-ray diffraction The intensity data collection was performed using a MACH3 Enraf Nonius diffractometer. The experimental conditions of data collection, the strategy followed for the structure determination and the final results are given in table 1. The structure was solved by direct methods using the SIR92 [16] program and refined by full matrix least-squares techniques based on F2, using SHELXL97 [17]. The structure factors were obtained after Lorentz polarization corrections. The positions of the heavier atoms, including the Zn atom, were located by the direct method. The remaining atoms were found in a series of alternating difference Fourier maps and least-square refinements. The positions of the hydrogen atoms of this hybrid title compound were located directly from the difference Fourier maps. The drawings were made with Diamond [18].

    Table 1 Crystal data and experimental parameters used for the intensity data collection strategy and final results of the structure determination.

    I.Crystal data Formula : Zn(HPO4)Cl[C6H14N] Crystal system : orthorhombic a = 8.7439(9), b = 9. 592(6), c = 26.573(6) , = = = 90 , V = 2228.91(12) 3. Z = 8 Refinement of unit-cell parameters with cal. = 1.8 g.cm

    -3

    Linear absorption factor : (Mo K ) = 2.577 cm-1 Crystal size (mm) : 0.25 x 0.15 x 0.20 II. Intensity measurements Temperature : 293.2 K Diffractometer : Enraf-Nonius FR590 Monochromator : graphite plate Measurement area : (h. k. l) Nb of scanned reflections Nb of independent reflections Orientation and control reflections III. Structure determination Lorentz and polarization corrections Program used : SHELX-97 [36] All the hydrogen atoms were located from difference Fourier maps. They are not refined. Unique reflections included : (2011( I >2 )) Weighting scheme : Residual Fourier density : -0.90 3 < < 0.64 3 Drawings made with Diamond [37]

    Fw = 297 Space group : Pcab 25 reflections (7 < < 10) F(000) = 1256.00 Morphology : prism Color : transparent Wavelength : MoK

    (0.7107 ) Scan mode : _ 2 Theta range : 1.53 27.85 hmax.= 10; k max. = 12; lmax. = 33 2632 (Rint. = 0.071) 2011 0 3 2 and 0 0 -1 No absorption correction Determination : direct methods

    Refined parameters : 124 R = 0.042 ; Rw = 0.1125 Goodness-of-fit on F 2: 1.045 Largest shift/error = 0.000

    NMR Spectroscopy All NMR spectra were recorded on a Bruker DSX-300 spectrometer operating at 75.49 MHz for 13C and 121.51 MHz for 31P with a classical 4 mm probehead allowing spinning rates up to 10 kHz. 13C chemical shifts are given relative to tetramethylsilane and 31P ones relative to 85 % H3PO4 (external references, precision 0.5 ppm). Phosphorus spectrum was recorded under classical MAS conditions while the carbon one was recorded by use of cross-polarization from protons (contact time 5ms) and MAS. In

  • Cryst. Res. Technol. 42, No. 4 (2007) 335

    www.crt-journal.org 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

    all cases it was checked that there was a sufficient delay between the scans allowing a full relaxation of the nuclei.

    Thermal behavior Thermal analysis was performed using the multimodule 92 Setaram analyzer operating from room temperature up to 500C at an average heating rate of 5 K/min.

    IR Spectroscopy Spectra were recorded in the range 4000 - 400 cm-1 with a Perkin-Elmer FTIR spectrophotometer 1000 using a sample dispersed in spectroscopically pure KBr pellet.

    3 Results and discussion

    3.1 Structure description

    Final atomic coordinates and thermal parameters for Zn(HPO4)Cl.[C6H14N] are given in table 2. The main geometrical features entities are reported in table 3. All atoms are at general positions. An ORTEP drawing of the asymmetric unit of the chlorozincophosphate templated Zn(HPO4)Cl.[C6H14N] by organic cations is shown in figure 1.

    Fig. 1 ORTEP representation of the asymmetric unit of Zn(HPO4)Cl.[C6H14N].

    Table 2 Final atomic coordinates in Zn(HPO4)Cl[C6H14N]. Esd are given in parentheses. 1

    *3Ueq. = ( . )*ijaUi j a a ai ji j

    atomes x y z Ueq Zn(1) Cl(1) P(1) O(1) O(2) O(3) O(4) N(1) C(1) C(2) C(3) C(4) C(5) C(6) H(1) H(2) H(3) H(4) H(5) H(6) H(7)

    0.70164(4) 0.73807(15) 0.58279(9) 0.4645(3) 0.7119(2) 0.5037(3) 0.6394(3) 0.6929(5) 0.8494(7) 0.8674(6) 0.8340(5) 0.6748(6) 0.6538(6) 0.8527(9)

    0.4006 0.6806 0.6242 0.9594 0.8741 0.7972 0.9535

    0.96228(3) 1.04197(13) 1.20546(7) 1.2370(2) 1.1244(2) 1.1165(2) 1.3408(2) 0.9226(4) 0.9808(5) 1.1063(4) 1.0715(4) 1.0109(5) 0.8890(4) 1.1975(6)

    1.2891 0.8278 0.9884 0.9095 0.9975 1.1916 1.1399

    0.44262(2) 0.36480(4) 0.51406(3) 0.47075(9) 0.48835(10) 0.55377(8) 0.53530(11) 0.60902(17) 0.60353(19) 0.63701(16) 0.69132(15) 0.6948(2) 0.6621(2) 0.7260(2)

    0.4801 0.5990 0.5998 0.6178 0.5695 0.6287 0.6377

    0.0308(6) 0.0640(3) 0.0305(2) 0.0387(6) 0.0395(6) 0.0387(5) 0.0468(6)

    0.0747(13) 0.0699(13) 0.0570(10) 0.0513(9)

    0.0659(13) 0.0671(13) 0.095(2)

    0.051 0.13 0.079 0.14 0.093 0.048 0.060

  • 336 R. Kefi et al.: Synthesis and characterization of a layered chlorozincophosphate

    2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.crt-journal.org

    H(8) H(9) H(10) H(11) H(12) H(13) H(14) H(15)

    0.8934 0.6475 0.5972 0.7173 0.5494 0.9467 0.7855 0.8553

    0.9856 0.9781 1.0654 0.8091 0.8377 1.2552 1.2654 1.1946

    0.6989 0.7258 0.6829 0.6697 0.6656 0.7273 0.7117 0.7631

    0.084 0.064 0.073 0.087 0.071 0.13 0.09 0.16

    Table 3 Interatomic distances () and bond angles () in Zn(HPO4)Cl[C6H14N]. Esd are given in parentheses. Equivalent positions: (i): -0.5 + x,1.5 y, z ; (ii): 0.5 + x,1.5 y, z ; (iii): 1 - x,1 y, - z.

    The HPO42-

    P O(1)a O(2) O(3) O(4) O(1)-H(1) The ZnO3Cl tetrahedron Zn O(2) O(3) O(4) Cl Zn-O(2)-P = 129.83(14) Zn-O(4)-P = 152.32(17) The organic group N(1)-C(1) C(1)-C(2) C(2)-C(3) C(3)-C(4) C(4)-C(5) C(5)-N(1) C(3)-C(6) The hydrogen bonds O(N)-HO O(1)-H(1)O(2)i N(1)-H(2)...O(1)ii N(1)-H(3)...O(3)iii

    O(1)a 1.577(3) 104.81(14) 108.39(14) 108.96(14) O(2) 1.975(2) 108.46(10) 104.99(11) 107.12(8) 1.485(8) 1.505(6) 1.510(6) 1.511(7) 1.469(7) 1.485(8) 1.530(6) O(N)-H 0.79 0.95 0.91

    O(2) 2.463(3) 1.532(2) 111.04(14) 111.37(14) O(3) 3.185(0) 1.951(2) 114.79(10) 108.08(7) Zn-O(3)-P = 132.00(14) C(1)- N(1)-C(5) C(1)-C(2)-C(3) C(2)-C(3)-C(4) C(2)-C(3)-C(6) C(4)-C(3)-C(6) C(5)-C(4)-C(3) N(1)-C(1)-C(2) C(4)-C(5)-N(1) H...O 1.86 2.33 2.03

    O(3) 2.514(3) 2.518(3) 1.523(2) 111.95(15) H(1)-O(1)-P 110.8 O(4) 3.080(1) 3.249(7) 1.907(2) 113.02(9) 112.8(4) 111.6(4) 108.8(4) 112.4(4) 111.4(5) 112.6(4) 109.8(4) 111.1(4) O(N)O 2.620(3) 2.955(5) 2.890(5)

    O(4) 2.504(3) 2.504(3) 2.505(3) 1.500(2) Cl 3.385(2) 3.386(5) 3.453(3) 2.227(6) O(N)- HO 161(4) 123(9) 158(1)

    Each Zn atom is tetrahedrally coordinated by three phosphate groups and has one terminal Zn-Cl vertex. The Zn-O bond lengths are in the range of 1.907(2)-1.975(2) , Zn-Cl distance is 2.227(6) , and the O-Zn-O(Cl) angles are between 104.99(11) and 114.79(10). On the other hand, each phosphorus atom is linked to three Zn atoms through three oxygen atoms with the fourth coordination site being a terminal P-OH group. The P-O distance is in the range 1.500(2)-1.577(3) and O-P-O angles are in the range 111.95(15)-104.81(14).

    The structure consists of two-dimensional neutral sheets of Zn(HPO4)Cl.[C6H14N] parallel to the ab plane, situated at z = 0 and z = with an interplane of 13.3 (Fig. 2). Each sheet shows that the inorganic entities have a layered organization along the c-axis (Fig. 3), and are constructed from strictly alternating ZnO3Cl and HPO4 tetrahedra sharing vertices. The covalent connectivity in the layer produces four-membered {Zn2P2} rings (approximate dimensions 3.62 x 4.45 2) and eight-membered {Zn4P4} rings (approximate dimensions 4.33 x 9.27 2), which fuse to propagate the network structure.

    The terminal chlorine atoms, hanging from the zinc center, project in a direction perpendicular to the layer. As with many two-dimensional structures, the amine molecules occupy the inter-lamellar space and participate in hydrogen bond interactions with the oxygen atoms of the framework through N-HO hydrogen bonds (Fig. 2). Both inter- and intra-layer hydrogen bond interactions are observed. The most important observed hydrogen bond interactions are listed in table 3.

  • Cryst. Res. Technol. 42, No. 4 (2007) 337

    www.crt-journal.org 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

    Fig. 2 Projection of the Zn(HPO4)Cl.[C6H14N] structure in the plane (a, c) (hydrogen atoms and layer-diamine H-bonds not shown).

    Fig. 3 Polyhedral representation of the framework Zn(HPO4)Cl.[C6H14N], viewed down the c direction.

    Fig. 4 31P MAS-NMR spectrum of Zn(HPO4)Cl.[C6H14N].

    Fig. 5 13C CP-MAS-NMR spectrum of Zn(HPO4)Cl

    .[C6H14N].

    It can be pointed out that the structure of Zn(HPO4)Cl.[C6H14N] is closely related to those of the two zincophosphates Zn(HINT)(HPO4) and [C10N2H10][ZnCl(HPO4)]2 [19,20]. The former has a similar inorganic framework consisting on a two-dimensional network constructed from edge-sharing 4-rings and 8-rings, with a 4.82 topology, but in this case the Zn is tetrahedrally coordinated by three phosphate groups and one carboxylate group of an HINT unit in a monodendate fashion. The second, having also a 2D anionic network,

  • 338 R. Kefi et al.: Synthesis and characterization of a layered chlorozincophosphate

    2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.crt-journal.org

    consist of corrugated tetrahedral layers composed solely of 6-rings to give a 63 topology, while the compound described in this paper shows 4-rings and 8-rings; it can be pointed out that these two types of 4.82 patterns are commonly observed: one with elongated 8-rings in a herringbone pattern [21] and one with 8-rings that more closely approximate octagons [22]. It is evident that the 4.82 pattern of the synthesized compound has elongated 8-rings.

    Hydrogen bonding plays an important role in stabilizing the Zn(HPO4)Cl.[C6H14N] structure. The 4-methyl-

    piperidinium cations occupy the interlayer sites and interact with zincophosphate layers by way of NH---O

    hydrogen bonds as NH(2)O(1) [d HO = 2.33 ] and NH(3)O(3) [d HO = 2.03 ]. An interesting feature

    is the absence of hydrogen bonding between the chloride atom and the organic molecule. The POH groups

    participate in sheets Hbonds: O(1)H(1)O(2) [d HO = 1.86 ]. N-C and C-C distances and C-C-N, C-N-C, and C-C-C in the template molecule are comparable with those found in the literature [20].

    Fig. 6 DTA curve of Zn(HPO4)Cl.[C6H14N] during two heating and cooling runs.

    Fig. 7 X-ray powder patterns of Zn(HPO4)Cl.[C6H14N]: not heated (a); heated and then cooled to room temperature (b).

    3. 2 NMR spectroscopy

    The 31P MAS NMR spectrum of the crystalline chlorozincophosphate Zn(HPO4)Cl.[C6H14N] is shown in Figure 4 and is in good agreement with the X-ray structure. Indeed, it exhibits a single resonanc...

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