Abstract
Nine metal compounds of Mn(II), Zn(II) and Cd(II) derived from dinitropyridone ligands (3,5-dinitro-pyrid-2-one, 2HDNP; 3,5-dinitropyrid-4-one, 4HDNP and 3,5-dinitropyrid-4-one-N- hydroxide, 4HDNPO) were characterized by elemental analysis, FT-IR and partly by TG-DSC. Three of which were further structurally characterized by X-ray single-crystal diffraction analysis. The structures of the three compounds, Mn(4DNP)2(H2O)4, 4, Zn(4DNPO)2(H2O)4, 8, and Cd(4DNPO)2(H2O)4, 9, crystallize in the monoclinic space group P2(1)/n and Z = 2, with a = 8.9281(9), b = 9.1053(9), c = 10.6881(11) Å, β = 97.9840(10)° for 4; a = 8.4154(7), b = 9.9806(8), c = 10.5695(8) Å, β = 97.3500(10)° for 8; a = 8.5072(7), b = 10.2254(8), c = 10.5075(8) Å, β 96.6500(10)° for 9. All three complexes are octahedral consisting of four equatorial water molecules, and two nitrogen or oxygen donor ligands (DNP or DNPO). The abundant hydrogen-bonding and π-π stacking interactions seem to contribute to stabilization of the crystal structures of the compounds. The TG-DTG results revealed that the complexes showed a weight loss sequence corresponding to all coordinated water molecules, nitro groups, the breaking of the pyridine rings and finally the formation of metal oxides.
Keywords: Dinitropyridone, Transition-metal compound, Structural characterization, Thermoanalysis
Introduction
The reactivity and structure of transition metal complexes has been the focus of much research owing to their supposed catalytic property. The knowledge of their structure is of importance for an understanding of their reactivity. In last decades, much attention has been focused on the research of energetic catalysts, which usually contain nitro groups on the molecule, in order to adjust trajectory properties of solid propellants. In the case of energetic catalysts in two-base propellants, metal salts, particularly copper and lead salts, of polynitrophenols [1], picric acids [2-6] and 3-nitro-1,2,4-triazole-5-one (NTO) [7-13] have been extensively studied. In contrast, few metal salts of polynitropyridone derivatives are investigated and no crystal structures have been reported until we begin to study their molecular structures and thermodecomposition behaviors [14, 15], while polynitropyridone derivatives are found themselves in many other applications [16-18]. To date, crystal structures of a number of alkali and alkaline-earth metals as well as a few transition-metal salts derived from three kinds of dinitropyridone ligands, i.e., 2(4)-hydroxyl-3,5-dinitropyridine(-N-oxide) (2HDNP, 4HDNP and 4HDNPO), have been determined and their thermodecomposition behaviors have also been investigated and explained by our group [19-22]. As an extension of our work on the study of the transition-metal compounds derived from polynitropyridone, herein we report the syntheses, crystal structures and thermal behaviors of compounds of Mn(II), Zn(II) and Cd(II) with 3,5-dinitropyridone.
Experimental
Reagents and Physical measurements
The three ligands, 2-hydroxyl-3,5-dinitropyridine (2HDNP), 4-hydroxyl-3,5-dinitro- pyridine (4HDNP) and 4-hydroxyl-3,5-dinitropyridine-N-oxide (4HDNPO) were synthesized following the methods previously described with slight modification [14]. MnCO3, ZnCO3 and CdCO3 were of analytical reagent grade and used directly without further purification. All experiments were carried out in twice distilled water.
IR spectra of the complexes were recorded on a Perkin Elmer FT-IR spectrophotometer in the 4,000–400 cm−1 region using KBr pellets method. Elemental contents of carbon, hydrogen and nitrogen were determined by a German Vario EL III analyzer. The DSC and TG-DTG measurements were done with a Thermoanalyzer Systems Q1000DSC + LNCS + FACS Q600SDT of TA company.
Synthesis
The procedure to synthesize the nine complexes is the same and, therefore, we only describe the synthesis of one complex as an example.
Manganese 3,5-dinitropyrid-2-onate tetrahydrate (1 Mn(2DNP)2(H2O)4)
To a solution of 2-hydroxyl-3,5-di-nitropyridine (1.85 g, 10 mmol) in 60 mL distilled water at 60 °C was added manganese carbonate (0.575 g, 5 mmol) under stirring until the bubbling of CO2 ceased. The reaction was maintained for at least 30 min until completion and the pH of this solution was approx. 7.0. The water was evaporated completely after filtration and the residue was recrystallized in ethanol and air dried to afford the pale yellow powder. Yield: 1.80 g (72.7%). Fw = 495.17 g mol−1. IR (KBr, cm−1): 3568, vs, ν(O–H); 3421, br, ν(O–H); 1610, s, ν(C=O); 1580, s, ν(C=C); 1540, s, vasym(N–O); 1329, s, vsym(N–O); 1260, s, ν(C–N). Elemental analysis Calcd for Mn(2DNP)2(H2O)4 (C10H12O14N6Mn): C 24.26, H 2.44, N 16.97; Found: C 24.35, H 2.02, N 16.62%.
Zinc 3,5-dinitropyrid-2-onate tetrahydrate (2 Zn(2DNP)2 (H2O)4)
Deep yellow powder. Yield: 1.65 g (65.3%). Fw = 505.62 g mol−1. IR (KBr, cm−1): 3552, s, ν(O–H), 3412, br, ν(O–H), 1630, s, ν(C=O); 1565, s, ν(C=C); 1542, s, vasym(N–O); 1363, s, vsym(N–O); 1263, s, ν(C–N). Elemental analysis Calcd for Zn(2DNP)2(H2O)4 (C10H12O14N6Zn): C 23.75, H 2.39, N 16.62; Found: C 23.87, H 2.25, N 16.34%.
Cadmium 3,5-dinitropyrid-2-onate tetrahydrate (3 Cd (2DNP)2(H2O)4)
Deep yellow powder. Yield: 1.90 g (68.8%). Fw = 552.65 g mol−1. IR (KBr, cm−1): 3532, s, ν(O–H), 3365, br, ν(O–H), 1613, s, ν(C=O); 1575, s, ν(C=C); 1543, s, vasym(N–O); 1326, s, vsym(N–O); 1260, s, ν(C–N). Elemental analysis Calcd for Cd(2DNP)2(H2O)4 (C10H12O14N6Cd): C 21.73, H 2.19, N 15.21; Found: C 21.45, H 2.26, N 15.02%.
Manganese 3,5-dinitropyrid-4-onate tetrahydrate (4 Mn(4DNP)2(H2O)4)
Pale yellow powder. Yield: 1.74 g (70.3%). Fw = 495.17 g mol−1. IR (KBr, cm−1): 3521, vs, ν(O–H), 3434, br, ν(O–H), 1657, s, ν(C=O); 1598, s, ν(C=C); 1505, s, vasym(N–O); 1350, s, vsym(N–O); 1277, s, ν(C–N). Elemental analysis Calcd for Mn(2DNP)2(H2O)4 (C10H12O14N6Mn): C 24.26, H 2.44, N 16.97; Found: C 24.05, H 2.12, N 16.75%. Single crystals suitable for X-ray diffraction analysis are grown up by solvent evaporation of its aqueous solution.
Zinc 3,5-dinitropyrid-4-onate tetrahydrate (5 Zn(4DNP)2 (H2O)4)
Deep yellow powder. Yield: 1.82 g (72.0%). Fw = 505.62 g mol−1. IR (KBr, cm−1): 3526, vs, ν(O–H), 3382, vs, ν(O–H), 1656, s, ν(C=O); 1585, s, ν(C=C); 1512, s, vasym(N–O); 1349, s, vsym(N–O); 1276, s, ν(C–N). Elemental analysis Calcd for Zn(4DNP)2(H2O)4 (C10H12O14N6Zn): C 23.75, H 2.39, N 16.62; Found: C 23.62, H 2.46, N 16.51%.
Cadmium 3,5-dinitropyrid-4-onate tetrahydrate (6 Cd(4DNP)2(H2O)4)
Deep yellow powder. Yield: 1.69 g (61.2%). Fw = 552.65 g mol−1. IR (KBr, cm−1): 3543, vs, ν(O–H), 3352, vs, ν(O–H), 1661, s, ν(C=O); 1579, s, ν(C=C); 1507, s, vasym(N–O); 1319, s, vsym(N–O); 1283, s, ν(C–N). Elemental analysis Calcd for Cd(4DNP)2(H2O)4 (C10H12O14N6Cd): C 21.73, H 2.19, N 15.21; Found: C 21.61, H 2.32, N 15.07%.
Manganese 3,5-dinitropyrid-4-pyridone-N-hydroxylate tetrahydrate (7Mn(4DNPO)2(H2O)4)
black powder. Yield: 1.93 g (73.2%). Fw = 526.17 g-mol−1. IR (KBr, cm−1): 3559, vs, ν(O–H), 3362, vs, ν(O–H), 1666, s, ν(C=O); 1561, s, ν(C=C); 1489, s, vasym(N–O); 1344, s, vsym(N–O); 1239, s, ν(Npy–O). Elemental analysis Calcd for Mn(4DNPO)2(H2O)4 (C10H12O14N6Mn): C 22.78, H 2.29, N 15.94; Found: C 23.02, H 2.11, N 15.68%.
Zinc 3,5-dinitropyrid-4-pyridone-N-hydroxylate tetrahydrate (8Zn(4DNPO)2(H2O)4)
red crystallline powder. Yield: 1.80 g (70.0%). Fw = 537.62 g mol−1. IR (KBr, cm−1): 3548, s, ν(O–H), 3382, br, ν(O–H), 1663, s, ν(C=O); 1542, s, ν(C=C); 1491, s, vasym(N–O); 1346, s, vsym(N–O); 1233, s, ν(Npy–O). Elemental analysis Calcd for Zn(4DNPO)2(H2O)4 (C10H12O14N6Zn): C 22.34, H 2.25, N 15.63; Found: C 21.72, H 2.16, N 16.06%. Single crystals suitable for X-ray diffraction analysis are grown up by solvent evaporation of its aqueous solution.
Cadmium 3,5-dinitropyrid-4-pyridone-N-hydroxylate tetrahydrate (9Cd(4DNPO)2(H2O)4)
Red crystalline powder. Yield: 2.12 g (72.5%). Fw = 584.64 g mol−1. IR (KBr, cm−1): 3576, s, ν(O–H); 3442, br, ν(O–H), 1665, s, ν(C=O); 1555, s, ν(C=C); 1526, s, vasym(N–O); 1360, s, vsym(N–O); 1256, s, ν(Npy–O). Elemental analysis Calcd for Cd(4DNPO)2(H2O)4 (C10H12O14N6Cd): C 20.54, H 2.07, N 14.37; Found: C 20.80, H 1.85, N 14.75%. Single crystals suitable for X-ray diffraction analysis are grown up by solvent evaporation of its aqueous solution.
X-Ray Diffraction Analysis
The determination of the unit cell and the data collection for the complexes 4, 8 and 9 were performed on a Bruker Smart-1000 CCD diffractionmeter with graphite mono-chromated Mo Kα radiation (λ = 0.71073 Å) using phi and omega scan technique. The structures were solved by direct methods and refined on F2 by full matrix least-squares with the Bruker's SHELXL-97 program [23, 24]. All non-hydrogen atoms were refined with anisotropic displacement parameters. All hydrogen atoms were treated using a riding model. Data collection details and structure determination results are summarized in Table 1. Selected bond lengths and angles are presented in Table 2.
Table 1.
Crystal data and structure refinements for compounds 4, 8 and 9
| 4 | 8 | 9 | |
|---|---|---|---|
| Empirical formula | C10H12MnN6O14 | C10H12ZnN6O16 | C10H12CdN6O16 |
| Crystal size (mm) | 0.29 × 0.18 × 0.12 | 0.39 × 0.24 × 0.06 | 0.28 × 0.20 × 0.15 |
| Molecular mass | 495.20 | 537.63 | 584.66 |
| Crystal system | Monoclinic | Monoclinic | Monoclinic |
| Space group | P2(1)/n | P2(1)/n | P2(1)/n |
| a (Å) | 8.9281(9) | 8.4154(7) | 8.5072(7) |
| b (Å) | 9.1053(9) | 9.9806(8) | 10.2254(8) |
| c (Å) | 10.6881(11) | 10.5695(8) | 10.5075(8) |
| β (°) | 97.9840(10) | 97.3500(10) | 96.6500(10) |
| V (Å 3) | 860.45(15) | 880.45(12) | 907.89(12) |
| Z | 2 | 2 | 2 |
| Temperature (K) | 293(2) | 293(2) | 293(2) |
| DCalc (g cm−3) | 1.911 | 2.208 | 2.139 |
| F(000) | 534 | 544 | 580 |
| Reflections collected | 7099 | 6687 | 7587 |
| Independent reflections | 1689 | 1824 | 1819 |
| Data/restraints/parameters | 1966/6/155 | 1995/6/167 | 2085/6/167 |
| Goodness-of-fit on F2 | 1.061 | 1.034 | 1.013 |
| Final R indices [I > 2σ(I)] | R1 = 0.0501, wR2 = 0.1558 | R1 = 0.0243, wR2 = 0.0696 | R1 = 0.0217, wR2 = 0.0604 |
| R indices (all data) | R1 = 0.0574, wR2 = 0.1641 | R1 = 0.0271, wR2 = 0.0722 | R1 = 0.0259, wR2 = 0.0642 |
Table 2.
Selected bond lengths (Å) and bond angles (°) for compound 4, 8 and 9
| 4 | 8 | 9 | |||
|---|---|---|---|---|---|
| Mn(1)–O(1w) | 2.1722(19) | Zn(1)–O(1) | 2.0576(11) | Cd(1)–O(1) | 2.2241(14) |
| Mn(1)–O(2w) | 2.1775(19) | Zn(1)–O(1w) | 2.1221(12) | Cd(1)–O(1)w | 2.3008(15) |
| Mn(1)–N(2) | 2.277(2) | Zn(1)–O(2w) | 2.1148(12) | Cd(1)–O(2)w | 2.2880(15) |
| O(3)–C(3) | 1.243(3) | O(1)–C(3) | 1.2433(17) | O(2)–C(3) | 1.243(2) |
| O(2w)–Mn(1)–O(1w) | 92.41(9) | O(1)–Zn(1)–O(1w) | 91.52(5) | O(1)–Cd(1)–O(2w) | 89.03(6) |
| O(2w)–Mn(1)–O(1w)A | 87.59(9) | O(1)–Zn(1)–O(1w)A | 88.48(5) | O(1)–Cd(1)–O(2w) A | 90.97(6) |
| O(2w)–Mn(1)–N(1) | 92.64(8) | O(1)–Zn(1)–O(2w) | 88.06(5) | O(1)–Cd(1)–O(1w) | 89.29(6) |
| O(1w)–Mn(1)–N(1) | 88.67(8) | O(1)–Zn(1)–O(2w)A | 91.94(5) | O(1)–Cd(1)–O(1w) A | 90.71(6) |
| O(2w)–Mn(1)–N(1)A | 87.36(8) | O(2w)–Zn(1)–O(1w) | 92.07(5) | O(2w) –Cd(1)–O(1w) | 83.68(6) |
| O(1w)–Mn(1)–N(1)A | 91.33(8) | O(2w)–Zn(1)–O(1w)A | 87.82(5) | O(2w)–Cd(1)–O(1w) A | 96.34(6) |
| O(1w)–Mn(1)–O(1w)A | 180.000(1) | N(1)–O(1)–Zn(1) | 117.24(9) | N(1)–O(1)–Cd(1) | 115.96(11) |
| N(1)–Mn(1)–N(1)A | 180.000(1) | O(1)–Zn(1)–O(1)A | 180.0 | O(1)–Cd(1)–O(1)A | 180.00 |
| O(1w)–Zn(1)–O(1w)A | 180.0 | O(1w) –Cd(1)–O(1w) A | 180.00 |
Symmetry transformations (A) in 4: −x + 1, −y + 1, −z + 1; (A) in 8: −x + 1, −y + 1, −z + 1; (A) in 9: −x + 1, −y + 1, −z + 1
Results and Discussion
IR Spectra
The strong and/or broad adsorptions in the ranges of 3,600–3,350~ cm−1 for the complexes are indicative of the presence of hydrogen-bonded water molecules in these complexes [25]. The peaks at 1,610, 1,630 and 1,613 cm−1 for complexes 1–3, respectively, could be attributed to stretching vibration of the coordinated CO group of the 2-pyridone ligand, which shift 60–78 cm−1 wavenumber upon coordination with metal atoms, indicating strong coordination of the 2-pyridone ligand by carbonyl groups with metal atoms. And the peaks at 1,657, 1,656, 1,661, 1,666, 1,663 and 1,665 cm−1 for complexes 4–9, respectively, could be attributed to stretching vibration of uncoordinated C=O group of the 4-pyridone ring (in the free ligands the corresponding C=O stretching mode is at 1,656 and 1,664 cm−1 for ligands 4HDNP and 4HDNPO, respectively). The N–O stretching vibration of the pyridine- N-oxide ring in complexes 7–9 (1,239, 1,233 and 1,256 cm−1, respectively) shift to low wavenumber compared with that in the free ligand (1,288 cm−1). The IR attribution is consistent with the single crystal structural analysis.
Crystal Structures
The molecular structures of compounds Mn(4DNP)2(H2O)4, 4, and Zn(4DNPO)2(H2O)4, 8, are displayed in Figs. 1 and 2, respectively. Selected bond distances and angles are listed in Table 2. It is clear that all three compounds are essentially isomorphous in structure, exhibiting slightly distorted octahedral coordination geometry with an inversion center located on each central metal. The principal difference between the Mn compound and the Zn/Cd complex is the presence of an oxygen “spacer” between the ligands and the central metal of the Zn/Cd complex. This difference has two effects: it changes the angle between the ligand plane and the equatorial plane, and the relative positions of the ligands when the complex packs to form chains.
Fig. 1.
The structure of the compound Mn(4DNP)2(H2O)4, 4, showing 30% probability displacement ellipsoids
Fig. 2.
The structure of the compound Zn(4DNPO)2(H2O)4, 8, showing 30% probability displacement ellipsoids
The bond distances of Mn-Ow at the equatorial positions are slightly different, with average distance of 2.1749(19) Å. The distance of axial Mn–Npy bond (2.277(2) Å) is longer than those of Mn–Ow bonds. Thus the coordination geometry around the Mn(II) is of an elongated octahedron, in contrast with our reported copper (II) analogs earlier, which displays a compressed octahedral geometry [22].
Since the structures between the compounds 8 and 9 are almost similar only the structure of the Zinc(II) compound is discussed. The Zn(II) centre in compound 8 is defined by six oxygen donors from four water molecules and two 3,5-dinitro-4-pyridone-N-hydroxyl (DNPO) anions to finish the octahedral geometry. The Zn–Ow bond distances are 2.1221(12) Å (Zn(1)–O(1w)) and 2.1148(12) Å (Zn(1)–O(2w)), with average distance of 2.1184(12) Å. The Zn–O bond distance at the axial positions is 2.0576(11) Å, slightly shorter by ~0.06 Å than those of average Zn(1)–O(w) bond distance, indicating that the Zn(II) complex displays compressed octahedral geometry as in the case of Co(4DNPO)2(H2O)4 [22] and Cu(4DNPO)2(H2O)4 [20]. The angles between the DNPO ligand planes and the equatorial planes are 27.14° for compound 8 and 24.18° for compound 9, which are significantly smaller than that of compound 4 (71.14°), due to the presence of the oxygen “spacer”.
There exist abundant intermolecular hydrogen bonds between the carbonyl and nitro groups of the ligands and water molecules in all three compounds, and intramolecular hydrogen bonds within the structures of the Zn/Cd complexes (Fig. 3; Table 3). In the crystal of Mn(II) compound the Mn(4DNP)2(H2O)4 units are connected via the O(1w)–H(11)⋯O(1)B and O(2w)–H(21)⋯O(1)B hydrogen bonds to form one-dimensional chain and extends further to two-dimensional plane via O(1w)–H(12)⋯O(4)C and O(2w)–H(22)–O(3)D hydrogen bonds. There have also 3.694 Å offset face-to-face π-π stacking interactions between pyridine rings of ligands of adjacent 1D chains, constructing thus a 3D molecular network. These weak interactions seem to contribute to the stabilization of the crystal structure.
Fig. 3.
View of a hydrogen-bonded pairs and b other weak interactions between chains in the compound Cd(4DNPO)2(H2O)4, 9
Table 3.
Hydrogen bond lengths (Å) and angles (°) in compounds 4, 8 and 9
| D–H⋯A | d(D–H) | d(H⋯A) | d(D ⋯A) | D–H⋯A |
|---|---|---|---|---|
| 4 | ||||
| O(1w)–(H11)⋯O(1)B | 0.846(10) | 1.999(19) | 2.745(3) | 146(3) |
| O(1w)–(H12)⋯O(4)C | 0.844(10) | 2.73(2) | 3.492(3) | 152(3) |
| O(2w)–(H21)⋯O(1)B | 0.846(10) | 2.04(2) | 2.777(3) | 145(3) |
| O(2w)–(H22)⋯O(3)D | 0.841(10) | 2.60(3) | 3.317(3) | 144(4) |
| 8 | ||||
| O(1w)–(H11)⋯O(2)B | 0.847(9) | 2.005(13) | 2.7719(17) | 150(2) |
| O(1w)–(H12)⋯O(5)C | 0.836(9) | 2.256(13) | 3.0629(19) | 162(2) |
| O(2w)–(H21)⋯O(2)B | 0.842(9) | 2.018(12) | 2.7976(16) | 154(2) |
| O(2w)–(H22)⋯O(4)D | 0.834(9) | 2.366(17) | 3.1083(18) | 149(2) |
| 9 | ||||
| O(1w)–(H11)⋯O(2)B | 0.834(9) | 2.014(13) | 2.775(2) | 152(2)) |
| O(1w)–(H12)⋯O(5)C | 0.839(10) | 2.148(10) | 2.986(2) | 175(3) |
| O(2w)–(H21)⋯O(2)B | 0.841(10) | 2.021(14) | 2.800(2) | 154(3) |
| O(2w)–(H22)⋯O(4)D | 0.834(10) | 2.231(14) | 3.026(2) | 159(3) |
Symmetry transformations in all three compounds are similar: B: −x + 1/2, y + 1/2, −z + 1/2; C: −x, −y, −z; D: x − 1/2, −y − 1/2, −z − 1/2
In Zn/Cd compounds, Each Zn/Cd(4DNPO)2(H2O)4 unit connects other two units through its four coordinated water molecules by oxygen atoms donating protons to the adjacent molecule to form tri-centered hydrogen bonds, which link the molecules into an infinite one-dimensional chain. The adjacent one-dimensional chains are further extended into two-dimensional nets by weak π-π stacking interactions between pyridine rings of ligands of adjacent 1D chains and the hydrogen bonding between the molecular layers and the coordinated water molecules form a 3D molecular network.
Thermal Analysis
In order to evaluate the thermal stability of the synthesized compounds, TG-DTG and DSC experiments were employed under N2 atmosphere. Typical TG-DTG curve for cadmium compound 9 are shown in Fig. 4. There are five main peaks (142.45, 240.32, 290.55, 337.21 and 556.74 °C) on the DTG curve, indicating that the decomposition process of Cd(4DNPO)2·4H2O can be divided into five stages. The first stage completes at 176.46 °C accompanying with 12.54% mass loss. It is in agreement with the theoretical value of the mass loss of 12.34%, corresponding to the loss of 4H2O. The second and third stages can't be distinguished clearly. These two stages ceased at 306.85 °C accompanied with 19.93% weight loss, which corresponding to the leaving of 2.5 nitryl. The fourth stage ends at 400 °C accompanied with 27.27% mass loss, indicating the decomposition of other nitro groups and the breaking of the pyridine rings, as with the thermal behavior of its analog Cu(4DNPO)2·4H2O we reported earlier [19]. After the fifth stage the mass of the residue is 20.54% according with the mass summation (20.68%) of CdO. During the three exothermic decomposition processes, the reaction heat reaches 2644 J/g, indicating that the cadmium compound 9 is thermal stable than those reported lead (II) and copper (II) salts of 3,5-dini-tropyridone [19], although less thermal stable on comparison with our reported nickel compound Ni(2DNP)2(H2O)4 [22]. Similarly, the studies on the thermal decomposition behaviors of other compounds (1, 4 and 8) showed that the decomposition processes are similar, that is, the first stage is the dehydration course and the finial residue is the corresponding metal oxides.
Fig. 4.
The TG-DTG curves for Cd(4DNPO)2(H2O)4, 9, at a heating rate of 10 °C min−1
On the basis of the TG-DTG and DSC experiments and the calculated results, the pyrolysis mechanism for Cd(4DNPO)2·4H2O could be shown as follows:
Conclusions
We have successfully synthesized and determined the molecular structures of Mn(4DNP)2(H2O)4 (4) Zn(4DNPO)2(H2O)4 (8) and Cd(4DNPO)2(H2O)4 (9). The crystal structures showed that each metal center is six-coordinate in octahedral geometry, with the equatorial positions being occupied by four water molecules and the axial positions by two ligand molecules. The thermoanalyses showed that the first weight loss is the dehydration step and the finial residue is the corresponding metal oxides. The investigations of their catalytic properties are currently underway in our laboratory.
Supplementary Material
Acknowledgments
The authors thank the National Defense Key Laboratory of Propellant and Explosive Combustion of China, Sha-anxi Normal University and University of Malaya for financial support.
Footnotes
Supplementary Materials
CCDC-687764 (4), CCDC-659745 (8) and CCDC-658379 (9) contain the supplementary crystallographic data for this paper. These data can be obtained free of charge at www.ccdc.cam.ac.uk/conts/retrieving.html [or from the Cambridge Crystallographic Data Centre (CCDC), 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44(0)1223-336033; deposit@ccdc.cam.ac.uk].
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