Construction of Planar Clusters Using Planar Aromatic Polyoxime

Oct 5, 2010 - 12-MC-4 metallacrowns as versatile tools for SMM research. Peter Happ , Christian Plenk , Eva Rentschler. Coordination Chemistry Reviews...
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DOI: 10.1021/cg100694w

Construction of Planar Clusters Using Planar Aromatic Polyoxime Ligands: Synthesis, Structure, and Magnetic Properties

2010, Vol. 10 4806–4814

Zilu Chen,* Maomao Jia, Zhong Zhang, and Fupei Liang* Key Laboratory for the Chemistry and Molecular Engineering of Medicinal Resources (Ministry of Education of China), School of Chemistry & Chemical Engineering of Guangxi Normal University, Guilin 541004, People’s Republic of China Received May 24, 2010; Revised Manuscript Received September 17, 2010

ABSTRACT: The reactions of NiSO4 3 6H2O or Mn(CH3COO)2 3 4H2O with the planar ligands of indane-1,2,3-trione trioxime (H3Itto) or indane-1,2,3-trione-1,2-dioxime (H2Itdo) gave two planar pentanuclear clusters [Et3NH]2[Ni5(HItto)4(MeOH)2(H2O)6(SO4)2] 3 2H2O (1) and [Ni5(HItdo)2(Itdo)2(DMF)4(MeOH)(H2O)(SO4)2] 3 CH3OH 3 6H2O (2), one planar trinuclear cluster, [MnIII3(μ3-O)(Itdo)3(CH3COO)(DMF)2(H2O)2] 3 H2O (3), and one planar platelike trinuclear cluster, [MnIII3(μ3-O)(Itdo)3(CH3COO)(DMF)2(MeOH)(H2O)] 3 H2O (4). Five Ni(II) ions of 1 and 2 are consolidated by four indane-1,2,3-trione trioxime ligands and four indane-1,2,3-trione-1,2-dioxime ligands, respectively, to form square topological planar pentanuclear clusters with five Ni(II) ions and all atoms of the four oxime ligands nearly in one plane. However, 1 and 2 show some differences in the bridging of the central metal ion with the metal ions on the square corners. Both 3 and 4 feature a planar isosceles triangular [Mn3(μ3-O)]7þ core. Each edge of the triangular [Mn3(μ3-O)]7þ core in 3 and 4 is bridged by a μ2,η3-bridging indane-1,2,3-trione1,2-dioxime ligand to construct a planar skeleton for 3 with the central oxygen atom, three Mn(III) ions, and all atoms of the indane-1,2,3-trione-1,2-dioxime ligands nearly in one plane, and a planar platelike skeleton for 4 with the ligand planes deviating from the triangular metal plane. Magnetic studies of 1-4 reveal the presence of antiferromagnetic interactions between the metal ions in 1-4.

Introduction The construction of planar discrete polynuclear compounds is drawing increasing interest in these years due to their interesting structural topologies, such as planar triangular,1 square,2 planar diamond,3,4 planar disklike,5,6 wheel,7 rodlike,8 and starlike topologies,7,9 as well as their appealing magnetic properties, such as spin-frustration,6 ferric properties,7 magnetocaloric effects,10 and single molecule magnets.4,5,8,11 In most of the reported planar clusters, only the metal ions are located in nearly one plane, with the atoms of the ligands deviating from the cluster plane. However, the planar clusters with all metal ions and all atoms of the main ligands in one plane are much less reported. As reported, planar topological clusters may possibly lead to the emergence of aromaticity, involving the d orbitals of transition metals in the cluster plane,12 which may contribute significantly to the magnetic properties of the clusters. Based on this consideration, we take the challenge to prepare a series of planar clusters with all metal ions and all atoms of the main ligands in one plane and to make a systematic investigation on the structure-magnetic correlation with the goal in mind of developing a new kind of magnetic materials. To fulfill the goal of obtaining clusters with planar topologies, we managed to introduce noncoordinating groups onto the ligands to block the growth of dimensionalities and to fuse the oxime group onto the planar aromatic groups to control the coplanarity. Thus, we prepared two planar aromatic polyoxime ligands of indane-1,2,3-trione trioxime (H3Itto) and indane1,2,3-trione-1,2-dioxime (H2Itdo), as shown in Scheme 1. With the help of two planar aromatic polyoxime ligands, we succeeded in separation of two planar pentanuclear clusters and *To whom correspondence should be addressed. E-mail: chenziluczl@ yahoo.co.uk. pubs.acs.org/crystal

Published on Web 10/05/2010

one trinuclear cluster, with all metal ions and all atoms of the polyoxime ligands nearly in one plane and another trinuclear cluster with a platelike skeleton formed by three metal ions and three oxime ligands. The magnetic properties of 1-4 were investigated. Experimental Section Materials and General Methods. All chemicals were used as obtained without further purification. Infrared spectra were recorded as KBr pellets using a Nicolet 360 FT-IR spectrometer. Elemental analyses (C, H, and N) were performed on a Vario EL analyzer. Thermogravimetric analyses were recorded with a Perkin-Elmer Pyris Diamond TG/DTA analyzer at a rate of 10 °C/min from room temperature to 900 °C under a nitrogen atmosphere. All magnetic measurements were carried out on a Quantum Design MPMS-XL SQUID magnetometer. Data were corrected for the diamagnetic contribution calculated from Pascal constants, and the diamagnetism of the sample and sample holder were taken into account. Synthesis of Indane-1,2,3-trione Trioxime (H3Itto). An ethanol solution (8 mL) of hydroxylamine hydrochloride (4 mmol, 0.2780 g) was added dropwise under stirring to an ethanol solution (5 mL) of indane-1,2,3-trione hydrate (1 mmol, 0.1781 g). Subsequently, a water solution (5 mL) of CH3COONa 3 3H2O (4 mmol, 0.5443 g) was added dropwise, resulting in a red color and finally a purple color of the solution. Then the reaction mixture was heated at 75 °C and the reaction was monitored by TLC techniques, giving a white precipitate and a yellow solution. Twenty-four hours later, it was allowed to cool down to ambient temperature. The white precipitate was separated in a yield of 75% by filtration, washed with ice water (10 mL  3), and dried in vacuo. mp 210-212 °C. Anal. Calcd (%) for C9H7O3N3: C, 52.69; H, 3.44; N, 20.48. Found (%): C, 52.97; H, 3.10; N, 20.17. IR (cm-1): 3216 s, 2884 s, 1664 w, 1594 m, 1393 s, 1336 m, 1235 w, 1174 m, 1099 m, 1088 m, 1016 s, 967 s, 922 m, 889 w, 859 s, 796 m, 772 m, 719 m, 703 m, 635 w, 563 w, 519 w. 1H NMR δ (ppm): 8.54 (m, 2H), 7.59 (m, 2H). 13C NMR δ (ppm): 147.1, 146.6, 144.3, 133.2, 132.8, 131.7, 131.6, 129.2, 128.8. MS: m/z 205. r 2010 American Chemical Society

Article Scheme 1. Synthesis of Indane-1,2,3-trione Trioxime (H3Itto) and Indane-1,2,3-trione 1,2-Dioxime (H2Itdo)

Synthesis of Indane-1,2,3-trione-1,2-dioxime (H2Itdo). Indane1,2,3-trione (1 mmol, 0.1781 g) was dissolved in hot water (9 mL). To this solution were added 0.25 mL of acetic acid and an ethanol solution (10 mL) of hydroxylamine hydrochloride (2 mmol, 0.1390 g) dropwise under stirring. The resulting mixture was refluxed at 80 °C, and the reaction was complete in 10 h, monitored by a TLC technique. Upon cooling the mixture in a refrigerator, a light yellow precipitate was given, which was collected via filtration, washed with cold water, and dried in vacuo, giving H2Itdo in a yield of 64%. mp 172-173 °C. Anal. Calcd (%) for C9H6O3N2: C, 56.84; H, 3.18; N, 14.73. Found (%): C, 57.02; H, 3.08; N, 14.56. IR (cm-1): 3220 s, 2879 m, 1720 s, 1624 m, 1596 m, 1472 m, 1404 m, 1342 w, 1318 w, 1296 w, 1236 m, 1199 w, 1160 w, 1096 m, 1085 m, 1025 s, 1011 s, 963 s, 881 s, 856 m, 793 w, 767 m, 722 m, 690 m, 636 w, 516 w. 1H NMR δ (ppm): 8.58 (d, 1H, 3J = 8 Hz, 5-H), 7.90 (d, 1H, 3J = 7.5 Hz, 8-H), 7.85 (dt, 1H, 3J = 7.5 Hz, 4J = 1 Hz, 6-H), 7.71 (dt, 1H, 3J = 7.5 Hz, 4 J = 0.5 Hz, 7-H). 13C NMR δ (ppm): 147.6, 145.0, 144.3, 138.2, 136.5, 131.9, 129.8, 128.3, 123.9. MS: m/z 190. Synthesis of [Et3NH]2[Ni5(HItto)4(MeOH)2(H2O)6(SO4)2] 3 2H2O (1). NiSO4 3 7H2O (0.2 mmol, 0.0562 g) was added slowly to a methanol solution (15 mL) of indane-1,2,3-trione trioxime (0.2 mmol, 0.0410 g) and 0.25 mL of NEt3. The resulting mixture was stirred at 40 °C for 10 h and then cooled to room temperature over a period of 1 day and filtered, giving a crude powdery product in a yield of 80%, which is difficult to purify because of its low solubility. Pure products in brown crystalline form suitable for all kinds of measurements could be isolated in a low yield of 15% by slow evaporation of the filtrate at room temperature for 2 weeks or by diffusing Et2O into the filtrate. Anal. Calcd (%) for C50H76N14Ni5O30S2 (1): C, 35.10; H, 4.48; N, 11.46. Found (%): C, 35.38; H, 4.80; N, 11.71. IR (cm-1): 3391 s, 1602 m, 1542 w, 1473 w, 1443 w, 1386 wm, 1385 w, 1257 w, 1180 m, 1151 m, 1112 s, 1055 s, 1011 m, 884 m, 778 w, 699 w, 619 w. Synthesis of [Ni5(HItdo)2(Itdo)2(DMF)4(MeOH)(H2O)(SO4)2] 3 CH3OH 3 6H2O (2). NiSO4 3 7H2O (0.1 mmol, 0.0281 g) was added to a DMF (2 mL) and newly distilled methanol (10 mL) solution of indane1,2,3-trione-1,2-dioxime (0.1 mmol, 0.0190 g). The resulting mixture was stirred at ambient temperature for 20 h and subsequently filtered to give a crude powdery product in a yield of 75%, which is difficult to purify because of its low solubility. The filtrate was left at ambient temperature to evaporate, giving pure product as brown crystals in a yield of 10%. Anal. Calcd (%) for C49H52N12Ni5O26S2: C, 37.19; H, 3.31; N, 10.62. Found (%): C, 37.53; H, 3.11; N, 10.79. IR (cm-1): 3426 s, 2972 w, 1659 s, 1599 m, 1556 m, 1470 w, 1390 w, 1317 w, 1236 w, 1180 m, 1128 m, 1104 m, 1086 m, 1050 m, 910 w, 875 w, 699 w, 519 w. Synthesis of [MnIII3(μ3-O)(Itdo)3(CH3COO)(DMF)2(H2O)2] 3 H2O (3). Mn(CH3COO)2 3 4H2O (0.2 mmol, 0.0490 g) was added to a DMF (2 mL) and methanol (10 mL) solution of indane-1,2,3-trione dioxime (0.2 mmol, 0.0380 g). The resulting mixture was stirred at ambient temperature for 20 h or transferred into a 25 mL Teflon-lined autoclave and heated at 60 °C for 4 days, and subsequently filtered after being cooled to ambient temperature to give a crude powdery product for the former method and just a clear solution for the latter method. The filtrate obtained from the two methods mentioned above was left at ambient temperature to evaporate, giving brown crystals in a yield of

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12% for the former method and about 45% for the latter method. Anal. Calcd (%) for C35H35Mn3N8O17: C, 41.85; H, 3.51; N, 11.16. Found (%): C, 41.52; H, 3.65; N, 11.34. IR (cm-1): 3426 s, 2365 w, 1718 s, 1651 s, 1603 m, 1535 s, 1467 w, 1413 m, 1385 m, 1306 w, 1244 m, 1181 w, 1119 m, 1098 m, 1070 s, 1026 m, 995 m, 888 s, 774 w, 722 m, 694 m, 620 m, 528 w. Synthesis of [MnIII3(μ3-O)(Itdo)3(CH3COO)(DMF)2(MeOH)(H2O)] 3 H2O (4). Mn(CH3COO)2 3 4H2O (0.2 mmol, 0.0490 g) was added to a DMF (2 mL) and methanol (10 mL) solution of indane1,2,3-trione-1,2-dioxime (0.2 mmol, 0.0380 g). Imidazole (0.2 mml, 0.0136 g) was added dropwise after the resulting mixture was stirred at 50 °C for 1 h. Then it was further stirred at 50 °C for 12 h and filtered. The filtrate was left at ambient temperature to evaporate, giving brown crystals in a yield of 25%. Anal. Calcd (%) for C36H37Mn3N8O17: C, 42.45; H, 3.66; N, 11.00. Found (%): C, 42.33; H, 3.47; N, 11.26. IR (cm-1): 3228 s, 2345 m, 1721 s, 1613 m, 1596 m, 1534 w, 1470 w, 1247 w, 1169 w, 1098 w, 1081 w, 1021 m, 1011 m, 963 s, 880 m, 858 m, 762 w, 721 w. Single Crystal X-ray Diffraction Determination. The selected single crystals of 1-4 were put in a sealed tube, and the measurement was performed on a Bruker Smart Apex-II CCD diffractometer using graphite-monochromated Mo KR radiation (λ = 0.71073 A˚). Absorption correction was applied by using the multiscan program SADABS.13 The structures were solved by direct methods using SHELXS-9714 and refined by full-matrix leastsquares against F2 using the SHELXL-97 program15 or the corresponding programs in the SHELXTL package.16 H atoms on C and N atoms were placed in calculated positions. One ethyl group of Et3NHþ, one oxime group of NO in every indane-1,2,3-trione trioxime ligand, and the sulfate ligand in 1 are disordered. The experimental details for the structural analysis of 1-4 are given in Table 1. The selected bond distances and angles for 1-4 are listed in Tables S1-S4, respectively.

Results and Discussion Synthesis and Characterization. Elemental analysis results of compounds 1-4 are in agreement with the composition derived from the single crystal X-ray diffraction analysis. Single crystals of 1 suitable for X-ray diffraction analysis were obtained only from the reaction with the addition of NEt3 to tune the pH value of the reaction mixture. For preparation of 1, all attempts using KOH or NaOH instead of NEt3 provide also some crystals, but not suitable for single crystal X-ray diffraction analysis. For the preparation of 2, the selection of solvents is of importance. Solitary solvent of methanol or DMF could not give the product of 2. However, the reaction carried out in a mixed solvent of methanol and DMF produced 2. Further attempts to use other anions such as ClO4- and NO3- instead of SO42- for the preparation of 1 and 2 did not gave any targeted products. The infrared spectrum displays several vibration bands for sulfate ion in the range 1011-1180 cm-1 (ν1 and ν3) for 1 and 1050-1180 cm-1 (ν1 and ν3) for 2, which indicates a low symmetry of the sulfate ion in the title compounds,17 as revealed by the crystal structure. The IR band at 1659 cm-1 assigned for the CdO group of 2 has a shift in contrast to that (1721 cm-1) for the free indane-1,2,3-trione1,2-dioxime, indicating the coordination of the CdO group of 2 to metal ions. The TGA curve of 1 (Figure S1) reveals the first weight loss of 14.06% upon heating from 26 to 110 °C, which corresponds to the removal of two lattice water molecules and two triethylamine molecules per formula unit (calcd: 13.93%). The second weight loss (10.17%) is found in the temperature range of 208-273 °C, which corresponds to the loss of six coordinated water molecules and two coordinated methanol molecules (calcd: 10.07%). Subsequently, combustion of the organic components in the residual planar framework of 1 was observed upon further heating, and the weight loss did not stop

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Table 1. Crystallographic Data and Structure Refinement Parameters for 1-4 1

2

3

4

C35H35Mn3N8O17 1004.53 223(2) 0.71073 monoclinic C2/c 35.293(7) 17.769(4) 13.601(3) 90 92.72(3) 90 8520(3) 8 1.566 0.957 3.00-25.00 4096 0.45  0.35  0.15 18191 7111 0.0663 1.033 0.0997 0.2511 0.1368 0.2857

C36H37Mn3N8O17 1018.56 296(2) 0.71073 monoclinic P21/c 16.3831(10) 17.8693(11) 13.7435(9) 90 95.6490(10) 90 4003.9(4) 4 1.690 1.020 1.25-26.06 2080 0.50  0.28  0.20 22036 7909 0.0389 1.060 0.0440 0.1174 0.0647 0.1348

)

)

C50H68N12Ni5O33S2 formula C50H76N14Ni5O30S2 fw 1710.92 1722.83 temperature/K 296(2) 296(2) wavelength/A˚ 0.71073 0.71073 crystal system triclinic monoclinic P21/n space group Pi a/A˚ 11.578(4) 21.2288(15) b/A˚ 12.193(4) 15.8791(12) c/A˚ 13.787(4) 22.8186(17) R/deg 66.907(4) 90 β/deg 86.720(5) 112.8130(10) γ/deg 80.131(5) 90 1763.7(10) 7090.3(9) V/A˚3 Z 1 4 -3 1.611 1.614 Dc/(g cm ) 1.462 1.458 μ/mm-1 θ/deg 2.41-25.01 1.67-25.01 F(000) 886 3240 crystal size/mm 0.20  0.10  0.10 0.45  0.30  0.20 reflections collected 9107 34820 reflections unique 6069 12240 0.0357 0.0758 Rint 2 1.011 1.027 GOF on F 0.0627 0.0702 R1a (I > 2σ(I )) 0.1437 0.1768 wR2b (I > 2σ(I )) 0.1104 0.1316 R1a (all data) b 0.1739 0.2169 wR2 (all data) P P P a b 2 2 2 P R1 = Fo| - |Fc / |Fo|. wR2 = [ w(Fo - Fc ) / w(Fo2)2]1/2.

even when the temperature reached 896 °C. The TGA curve of 2 (Figure S1) reveals the first weight loss of 8.14% below 164 °C for six uncoordinated water molecules and one uncoordinated methanol molecule (calcd: 8.13%) and the second weight loss of 19.56% (calcd: 19.88%) in the temperature range 164-365.5 °C, owing to the loss of all coordinated solvent molecules (one MeOH, one H2O, and four DMF molecules). At last, the combustion of HItdo- and Itdo2- occurred in the temperature range 365.5-750 °C. Single crystals of 3 suitable for X-ray diffraction analysis were separated from the reaction in a mixed solvent of DMF and methanol. The addition of DMF is of importance for the formation of crystals of 3 suitable for single crystal X-ray diffraction analysis. 3 could also be obtained from the reaction in a solitary solvent of methanol, however giving crystals not suitable for single crystal X-ray diffraction analysis. Imidazole plays an important role in the formation of 4, although it does not appear in 4. It is just the addition of imidazole that led to the formation of the skeleton of 4, which is different from that of 3. The IR bands at 1718 and 1721 cm-1 for the CdO groups in indane-1,2,3-trione-1,2dioxime ligands of 3 and 4, respectively, are close to that (1721 cm-1) of free indane-1,2,3-trione-1,2-dioxime, indicating the CdO groups in indane-1,2,3-trione-1,2-dioxime ligands of 3 and 4 are free from coordination to metal ions. In the TG curve of 3 (Figure S1), a weight loss of 12.23% (calcd: 12.66%) was found below 196.8 °C, which corresponds to the loss of one uncoordinated water molecule, two coordinated water molecules, and one DMF molecule. As the temperature rises, another weight loss of 13.56% (calcd: 13.15%) in 3 occurred in the temperature range 196.8-251.5 °C, which is presumably ascribe to the loss of one coordinated DMF and one CH3COO- ion. The further heating of 3 led to the combustion of Itdo2-, but the weight loss did not stop even when the temperature reached 965 °C. In the TG curve of 4 (Figure S1), the first weight loss of 12.14% below 132 °C corresponds to the loss of one uncoordinated water molecule, one coordinated

water molecule, and one coordinated DMF molecule (calcd: 12.09%). The following weight loss of 14.01% in the temperature range 132-262 °C is assigned to the loss of one CH3COOion, one coordinated water molecule, and another coordinated DMF molecule (calcd: 14.74%). The further weight loss did not stop even when the temperature reached 948 °C, which was assigned to the combustion of Itdo2-. Crystal Structure of Complexes 1-4. The X-ray diffraction analysis reveals two uncoordinated water molecules, two [Et3NH]þ cations, and one [Ni5(HItto)4(MeOH)2(H2O)6(SO4)2]2- with three chemically different Ni(II) ions in 1 (Figure 1a). The Ni1 center of 1 is coordinated in distorted octahedral geometries completed by four oxime oxygen atoms in the equatorial positions and another two oxygen atoms from two different sulfate ions in axial positions. The Ni2 and Ni2A centers of 1 are coordinated by three oxime nitrogen atoms and one oxime oxygen atom from two indane-1,2,3-trione trioxime ligands in the equatorial positions and two water molecules in the axial positions, forming a distorted octahedral geometry. Similar to Ni2 and Ni2A, the equatorial positions of Ni3 and Ni3A of 1 are also occupied by two oxime nitrogen atoms from one indane1,2,3-trione trioxime ligand and one oxime oxygen atom and one oxime nitrogen atom from another indane-1,2,3-trione trioxime ligand. The difference of Ni3 and Ni3A from Ni2 and Ni2A in 1 is that the axial positions of Ni3 and Ni3A are occupied by one water molecule and one methanol molecule. Five Ni(II) ions of 1 are consolidated by four indane-1,2,3trione trioxime ligands to form a planar pentanuclear cluster with five Ni(II) ions and all atoms of the four indane-1,2,3trione trioxime ligands nearly in one plane, as shown in Figure 1b. Ni2, Ni2A, Ni3, and Ni3A form a square, and the adjacent Ni(II) ions on the corners of the square are linked by one oxime NO group with the Ni 3 3 3 Ni separations of 4.9424(10) and 4.9020(10) A˚ for Ni2 3 3 3 Ni3 and Ni2 3 3 3 Ni3A, respectively. Ni1 is located on the center of the square and is linked to each Ni(II) ion around it by one oxime

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Figure 1. Side views of ORTEP diagrams of 1 (a) and 2 (c) with H atoms and uncoordinated solvent molecules omitted for clarity, emphasizing the planarity of five metal ions and four oxime ligands and perspective views of the planar pentanuclear square skeleton of 1 (b) and 2 (d) with axial molecules omitted for clarity. The displacement ellipsoids are drawn at the 30% probability level. The disordered atoms in 1 are also omitted for clarity. Symmetry codes for 1: (A) 1 - x, 1 - y, 1 - z.

Scheme 2. Coordination Modes of HItto2- (a) and Itdo2- (b and c) in Compounds 1-4

oxygen atom and one oxime NO group with the Ni 3 3 3 Ni separations of 3.477(1) and 3.485(1) A˚ for Ni1 3 3 3 Ni2 and Ni1 3 3 3 Ni3, respectively. Each indane-1,2,3-trione trioxime ligand acts as a μ3,η5-bridging ligand (Scheme 2a) to connect three Ni(II) ions using three oxime nitrogen atoms and one oxime oxygen atom. The formation of intramolecular hydrogen bonds O2-H 3 3 3 O5 and O6-H 3 3 3 O3A (Table S6) further stabilizes the planar pentanuclear cluster. Similar to compound 1, compound 2 presents also a planar pentanuclear skeleton formed by the consolidation of five Ni(II) ions via four μ3,η5-bridging indane-1,2,3-trione-1,2dioxime ligands (Scheme 2b) with the five Ni(II) ions and all atoms of the four indane-1,2,3-trione-1,2-dioxime ligands in one plane shown in Figure 1c and d. All Ni(II) ions are sixcoordinated in distorted octahedral geometry. Ni1 was coordinated by four oxime oxygen atoms from four indane1,2,3-trione-1,2-dioxime ligands in the equatorial positions and another two oxygen atoms from two sulfate ions in the axial positions. The equatorial positions of the other Ni(II)

ions are occupied by two nitrogen atoms and two oxygen atoms from two indane-1,2,3-trione-1,2-dioxime ligands. The axial sites of the other Ni(II) ions are occupied by two oxygen atoms from one DMF and one sulfate ion for Ni2 and Ni4 ions, two oxygen atoms from one DMF and one water molecule for Ni3, and two oxygen atoms from one DMF and one methanol for Ni5, respectively. Ni2, Ni3, Ni4, and Ni5 are connected by four oxime groups from four indane-1,2,3-trione-1,2-dioxime ligands to form a square with Ni 3 3 3 Ni separations of 4.9899(2), 4.9826(3), 4.9805(2), and 4.9651(3) A˚ for Ni2 3 3 3 Ni3, Ni3 3 3 3 Ni4, Ni4 3 3 3 Ni5, and Ni5 3 3 3 Ni2, respectively, as depicted in Figure 1d. The Ni1 ion is located on the center of the square. Different from that of 1, Ni1 of complex 2 was connected to Ni2 and Ni4 by double oxime oxygen atoms with Ni 3 3 3 Ni separations of 3.1518(2) and 3.1541(2) A˚ for Ni1 3 3 3 Ni2 and Ni1 3 3 3 Ni4, respectively, and connected to Ni3 and Ni5 by double oxime groups with Ni 3 3 3 Ni separations of 3.8572(3) and 3.8507(3) A˚ for Ni1 3 3 3 Ni3 and Ni1 3 3 3 Ni5, respectively. Another difference of 2 from 1 is that the two sulfate ions in 2 act as μ2-bridges to connect Ni1 and Ni2 or Ni1 and Ni4. 1 and 2 present similar 2D π-bonded supramolecular topologies (Figure 2). The planar pentanuclear unit in 1 and 2 behaves as a four-connected node to link another four planar pentanuclear units by two kinds of π 3 3 3 π interactions, as indicated in Table S5, forming a two-dimensional supramolecular structure in the bc plane for 1 and in the ab plane for 2, as shown in Figure 2. The π-bonded supramolecular 2D sheets in 1 and 2 are further consolidated by hydrogen bonds (Table S6 and S7) to construct a 3D supramolecular structure, as shown in Figure S2 and S3

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Figure 2. Two-dimensional supramolecular sheets of 1 (a) and 2 (b) formed from the pentanuclear units via π 3 3 3 π interactions. Hydrogen atoms are omitted for clarity. Purple dashed lines represent π 3 3 3 π interactions.

Figure 3. ORTEP diagrams of 3 (a) and 4 (c) and side views of 3 (b) and 4 (d) emphasizing the planar skeleton for 3 and the planar platelike skeleton for 4 constructed by three metal ions and three oxime ligands. The H atoms and uncoordinated water molecules are omitted for clarity, and the displacement ellipsoids are drawn at the 30% probability level.

for 1 and 2, respectively. The [Et3NH]þ cations in 1 are located between the π-bonded supramolecular 2D sheets and stabilize the 3D supramolecular structure of 1. Single crystal X-ray analysis reveals in the asymmetric unit of 3 and 4 an uncoordinated water molecule and a neutral trinuclear cluster with three crystallographically independent

manganese atoms, as shown in Figure 3a and c. Both 3 and 4 feature a planar isosceles triangular [Mn3(μ3-O)]7þ core with bond angles of 114.9(2), 121.4(3), and 122.2(3)° for Mn1-O1Mn3, Mn1-O1-Mn2, and Mn3-O1-Mn2 in compound 3 and 119.236(4), 120.538(4), and 115.108(3)° for Mn1-O1Mn3, Mn1-O1-Mn2, and Mn3-O1-Mn2 in compound 4,

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Figure 4. Plots of χm and χmT vs T for 1. Solid lines show the best fit of the data according to the proposed model.

respectively. Each edge of the triangular [Mn3(μ3-O)]7þ core in 3 and 4 is further bridged by one μ2,η3-bridging indane-1,2,3trione-1,2-dioxime ligand (Scheme 2c) with Mn 3 3 3 Mn separations of 3.2752(6), 3.2901(6), and 3.1646(5) A˚ for Mn1 3 3 3 Mn2, Mn2 3 3 3 Mn3, and Mn3 3 3 3 Mn1 in 3 and Mn 3 3 3 Mn separations of 3.2606(2), 3.1809(2), and 3.2440(1) A˚ for Mn1 3 3 3 Mn2, Mn2 3 3 3 Mn3, and Mn3 3 3 3 Mn1 in 4, respectively. This leads to the construction of a planar skeleton for 3 with the central oxygen atom, the three Mn(III) ions, and all atoms of the three indane-1,2,3-trione-1,2-dioxime ligands nearly in one plane (Figure 3b), and a platelike skeleton for 4 with dihedral angles of 23.315, 11.230, and 20.085° between the Mn3 plane and the molecular planes of three indane-1,2,3-trione-1,2-dioxime ligands (Figure 3d). The edges of Mn1 3 3 3 Mn3 for 3 and Mn2 3 3 3 Mn3 for 4 in the triangular [Mn3(μ3-O)]7þ cores are further bridged by a syn-syn carboxylato group in the axial positions. All Mn(III) ions in compounds 3 and 4 show a distorted octahedral geometry. The equatorial sites of the three Mn(III) ions in both 3 and 4 are occupied by one nitrogen atom and two oxygen atoms from two indane-1,2,3-trione-1,2-dioxime ligands and the central oxygen atom. The two coordinated DMF molecules in the axial positions in 3 are located on two sides of the Mn3 plane and coordinated to the same Mn(III) ion (Mn2). However, the two coordinated DMF molecules in the axial positions in 4 are located on the same side of the Mn3 plane and coordinated to different Mn(III) ions (Mn1 and Mn2). The steric hindrance imposed by the two DMF molecules located on the same side helps to expel the indane-1,2,3-trione-1,2-dioxime ligands to form a platelike skeleton in 4, different from the planar skeleton in 3. The axial Mn-O bond distances in both 3 and 4 are apparently longer than the equatorial Mn-O and Mn-N bond distances, as shown in Table S3 and S4. This might be attributed to the presence of MnIII Jahn-Teller elongation axes and thus reveals an oxidation state of þ3 for all manganese atoms in both 3 and 4. The oxidation states (þ3) of the three Mn atoms and the central O2- protonation level in compounds 3 and 4 were further established by bond valence sum (BVS) calculations18 and charge balance considerations. BVS calculations gave values of 3.360-3.480 and 3.455-3.462 for the Mn atoms and 2.367 and 2.348 for the central O atoms in 3 and 4, respectively. As mentioned above, the manganese oxidation states established by charge balance considerations, bond-valence sum (BVS) calculations, and the observed Mn(III) Jahn-Teller distortion agree well with each other and were further confirmed by the magnetic properties to be discussed hereinafter. 3 and 4 show different supramolecular structures. The neighboring planar trinuclear units of 3 are connected by two kinds of intralayer π 3 3 3 π interactions, as shown in Table S5,

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Figure 5. Plots of χm and χmT vs T for 2.

to form two-dimensional supramolecular sheets of 3 in the bc plane, as depicted in Figure S4. The phenyl rings from the adjacent planar trinuclear units overlap partly each other by the formation of another two kinds of interlayer π 3 3 3 π interactions, as shown in Table S5, to construct a threedimensional structure of 3 (Figure S5), which is further stabilized by uncoordinated water molecules via hydrogen bonds, as listed in Table S8. Platelike trinuclear units of 4 are linked alternatively by two π 3 3 3 π interactions and one π 3 3 3 π interaction (Table S5) to build a one-dimensional chain (Figure S6), which interacts with another four ones around it by π 3 3 3 π interactions (Table S5) to construct a three-dimensional structure (Figure S7). The uncoordinated water molecules in 4 also contribute significantly in stabilizing the three-dimensional supramolecular structure via hydrogen bonds (Table S9). Magnetic Properties of Complexes 1-4. The magnetic properties of 1-4 were investigated by solid state magnetic susceptibility (χm) measurements in the 2.0-300 K range in a dc field of 1000 Oe. The magnetic properties of complexes 1-4 in the form of both χMT and χM versus T plots are shown in Figures 4-7, respectively. As shown in Figures 4 and 5, the values of χMT at 300 K for 1 and 2 are 4.35 and 4.29 cm3 K mol-1, respectively, which are lower than that expected (5.00 cm3 K mol-1) for five magnetically isolated high-spin Ni(II) ions. The χmT values of 1 and 2 decrease continuously with decreasing temperature, reaching 0.13 and 0.60 cm3 K mol-1 at 2.0 K for 1 and 2, respectively. These features are typical of a significant antiferromagnetic coupling in 1 and 2. Fitting of the χm-1-T above 100 K using the Curie-Weiss law χm = C/(T - θ) gives the Curie constant C = 8.42 cm3 K mol-1 and the Weiss constant θ = -282.84 K for 1 and the Curie constant C = 8.77 cm3 K mol-1 and the Weiss constant θ = -316.69 K for 2, respectively. The largely negative θ values of 1 and 2 support the presence of overall antiferromagnetic interactions in the two complexes and suggest that the antiferromagnetic interactions between adjacent Ni(II) ions in the two compounds are relatively strong. As discussed in the structural analysis, compounds 1 and 2 present square topologies with four Ni(II) ions on the four corners of the square and the fifth Ni(II) ion on the center of the square. They show some similarities in magnetic interaction (J2) between the Ni(II) ions on the edges of the square, which are transmitted by one oxime NO group. However, there is a big difference for the two compounds in magnetic interactions between the central Ni(II) ion and the Ni(II) ion on the corner of the square, as shown in Figure 1 and Scheme 3. The magnetic interaction (J1) between the central Ni(II) ion and the Ni(II) ion on the corner of the square in 1 is

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Chen et al.

where ST = SR þ S1, SR = S24 þ S35, S35 = S3 þ S5, and S24 = S2 þ S4. After the energy levels are applied, the Van Vleck formula can be deduced and expressed theoretically by the following equation with x = J1/kT and y = J2/kT: P χNi5

2 2

Ng β ¼ 3kT

ST

ST ðST þ 1Þð2ST þ 1Þe - EðST Þ=kT P ð2ST þ 1Þe - EðST Þ=kT ST

¼ Figure 6. Plots of χm and χmT vs T for 3. Solid lines show the best fit of the data according to the proposed model.

Ng2 β2 A 3kT B

ð2Þ

A ¼ 6 þ 6e - 2x þ 30e2x þ 6e - 6x þ 30e - 2x þ 84e4x þ 6e - 2x þ 30e2x þ 6e - 4y þ 6e - ð2xþ2yÞ þ 30e - ð - 2xþ2yÞ þ 6e - ð6x - 2yÞ þ 30e - ð2x - 2yÞ þ 84e - ð - 4x - 2yÞ þ 6e - ð2xþ6yÞ þ 30e - ð - 2xþ6yÞ þ 6e - ð6xþ2yÞ þ 30e - ð2xþ2yÞ þ 84e - ð - 4xþ2yÞ þ 30e - ð8x - 4yÞ þ 84e - ð2x - 4yÞ þ 180e - ð - 6x - 4yÞ þ 6e - 6x þ 30e - 2x þ 84e4x þ 6e - ð2xþ6yÞ þ 30e - ð - 2xþ6yÞ þ 6e - ð6xþ2yÞ þ 30e - ð2xþ2yÞ þ 84e - ð - 4xþ2yÞ þ 30e - ð8x - 4yÞ þ 84e - ð2x - 4yÞ þ 180e - ð - 6x - 4yÞ þ 6e - 12y þ 6e - ð2xþ10yÞ

Figure 7. Plots of χm and χmT vs T for 4. Solid lines show the best fit of the data according to the proposed model.

þ 30e - ð - 2xþ10yÞ þ 6e - ð6xþ6yÞ þ 30e - ð2xþ6yÞ

Scheme 3. Schematic for the Magnetic Model of 1 and 2

þ 84e - ð - 4xþ6yÞ þ 30e - 8x þ 84e - 2x þ 180e6x þ 84e - ð10x - 8yÞ þ 180e - ð2x - 8yÞ þ 330e - ð - 8x - 8yÞ B ¼ 3 þ e - 4x þ 3e - 2x þ 5e2x þ 3e - 6x þ 5e - 2x þ 7e4x þ e - 4x þ 3e - 2x þ 5e2x þ 3e - 4y þ e - ð4xþ2yÞ þ 3e - ð2xþ2yÞ þ 5e - ð - 2xþ2yÞ þ 3e - ð6x - 2yÞ þ 5e - ð2x - 2yÞ þ 7e - ð - 4x - 2yÞ þ e - ð4xþ6yÞ þ 3e - ð2xþ6yÞ þ 5e - ð - 2xþ6yÞ þ 3e - ð6xþ2yÞ þ 5e - ð2xþ2yÞ þ 7e - ð - 4xþ2yÞ þ 5e - ð8x - 4yÞ

conveyed by one oxime NO group and one oxime oxygen atom. For 2, there are two kinds of magnetic interactions between the central Ni(II) ion and the Ni(II) ion on the corner of the square: magnetic interaction mediated by two oxime oxygen atoms between Ni1 and Ni2 or Ni4 (J1) and magnetic interaction mediated by two oxime NO groups between Ni1 and Ni3 or Ni5 (J3). Given the pentanuclear square-planar topology of 2 and the resulting number of inequivalent magnetic exchange constants, it is not possible to derive an appropriate equation to estimate these magnetic coupling constants in 2. Therefore, only the fitting of magnetic couplings in 1 was discussed here in detail. Assuming isotropic magnetic exchange, the spin Hamiltonian for compound 1 is given in eq 119 with J12 = J13 = J14 = J15 = J1, J23 = J34 = J45 = J52 = J2, and S1 = S2 = S3 = S4 = S5 = 2/2. The susceptibility per pentanuclear complex (χNi5) of 1 is given in eq 2. H ¼ - 2J1 ðS1 S2 þ S1 S3 þ S1 S4 þ S1 S5 Þ - 2J2 ðS2 S3 þ S3 S4 þ S4 S5 þ S5 S2 Þ

ð1Þ

The eigenvalues E(S) are written as EðST , SR , S35 , S24 Þ ¼ - J1 ST ðST þ 1Þ þ J1 S1 ðS1 þ 1Þ þ ðJ1 - J2 ÞSR ðSR þ 1Þ þ J2 ½S35 ðS35 þ 1Þ þ S24 ðS24 þ 1Þ

þ 7e - ð2x - 4yÞ þ 9e - ð - 6x - 4yÞ þ 3e - 6x þ 5e - 2x þ 7e4x þ e - ð4xþ6yÞ þ 3e - ð2xþ6yÞ þ 5e - ð - 2xþ6yÞ þ 3e - ð6xþ2yÞ þ 5e - ð2xþ2yÞ þ 7e - ð - 4xþ2yÞ þ 5e - ð8x - 4yÞ þ 7e - ð2x - 4yÞ þ 9e - ð - 6x - 4yÞ þ 3e - 12y þ e - ð4xþ10yÞ þ 3e - ð2xþ10yÞ þ 5e - ð - 2xþ10yÞ þ 3e - ð6xþ6yÞ þ 5e - ð2xþ6yÞ þ 7e - ð - 4xþ6yÞ þ 5e - 8x þ 7e - 2x þ 9e6x þ 7e - ð10x - 8yÞ þ 9e - ð2x - 8yÞ þ 11e - ð - 8x - 8yÞ χM ¼

χNi5 0 1 - ð2zJ =Ng2 β2 ÞχNi5

ð3Þ

where N, g, β, and k have their usual meanings and zJ 0 accounts for the intermolecular interactions. The best least-squares fit of the theoretical equation (eq 3) to experimental data above 12 K leads to J1 = -14.12 cm-1, J2 = -20.32 cm-1, 2zJ 0 = -0.24 cm-1, and g = 2.15 with an agreement factor R = 8.28  10-4. The negative values of J1 (-14.12 cm-1) and J2 (-20.32 cm-1) confirm the presence of antiferromagnetic interactions between the central metal ion and the metal ions on the corners of the square, as well as between the neighboring metal ions on

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Crystal Growth & Design, Vol. 10, No. 11, 2010

the corners of the square. This is also justified by the large Ni-O-Ni angles of 117.3(5)-119.4(6)° in 1. The magnetostructural correlations in the documents revealed a Ni( μ2-O)-Ni borderline angle of 93.5° for the magnetic transition from antiferromagnetic into ferromagnetic with the decreasing Ni-(μ2-O)-Ni bond angle.20 The χMT values at 300 K are 8.19 and 8.81 cm3 K mol-1 for 3 and 4, respectively, which are lower than the spin-only value for three noninteracting Mn(III) ions (9.00 cm3 K mol-1).21-23 When the temperature is lowered, the χmT values of 3 and 4 decrease gradually, reaching 1.61 and 1.93 cm3 K mol-1 at 2.0 K for 3 and 4, respectively, as shown in Figures 6 and 7. These features are typical of a significant antiferromagnetic coupling in 3 and 4. Fitting of the χm-1-T above 50 K using the Curie-Weiss law χm = C/(T - θ) gives a Curie constant C = 9.61 cm3 K mol-1 and a negative Weiss constant θ = -55.18 K for 3 and a Curie constant C = 9.89 cm3 K mol-1 and a negative Weiss constant θ = -31.63 K for 4, respectively. The negative θ values also support the presence of an overall antiferromagnetic interaction in 3 and 4. Structurally, the three Mn(III) ions in the asymmetric unit of compounds 3 and 4 are consolidated by a μ3-oxido bridge and every adjacent two Mn(III) ion is further connected by a NO moiety. Furthermore, two of the three Mn(III) ions are additionally bridged by a syn-syn carboxylato group. This structural information confirms that the [Mn3O]7þ core in 3 and 4 features a planar isosceles triangle. Magnetically, it shows two kinds of magnetic couplings (J1 and J2) between the Mn(III) ions, as demonstrated in Scheme 4. On the basis of the nonequivalent exchange paths in the molecular structure, the magnetic data of 3 and 4 can thus be fitted to the susceptibility (eq 4) calculated from the magnetic energy level spectrum for three spins S = 2 coupled by isotropic Heisenberg interactions on the isosceles triangle model (H = -2[J1(S1S2 þ S2S3) þ J2S1S3]),21-24 as shown in Scheme 4. P ST ðST þ 1Þð2ST þ 1Þe - EðST Þ=kT Ng2 β2 ST P χM ¼ 3kT ð2ST þ 1Þe - EðST Þ=kT ST

¼

Ng2 β2 A 3kT B

ð4Þ

A ¼ 30e6x þ 6e2y þ 30e - ð - 4x - 2yÞ þ 84e - ð - 10x - 2yÞ þ 6e - ð4x - 6yÞ þ 30e6y þ 84e - ð - 6x - 6yÞ þ 180e - ð - 14x - 6yÞ þ 6e - ð10x - 12yÞ þ 30e - ð6x - 12yÞ þ 84e - ð - 12yÞ þ 180e - ð - 8x - 12yÞ þ 330e - ð - 18x - 12yÞ þ 30e - ð14x - 20yÞ þ 84e - ð8x - 20yÞ þ 180e - ð - 20yÞ þ 330e - ð - 10x - 20yÞ þ 546e - ð - 22x - 20yÞ B ¼ 5e6x þ 3e2y þ 5e - ð - 4x - 2yÞ þ 7e - ð - 10x - 2yÞ þ e - ð6x - 6yÞ þ 3e - ð4x - 6yÞ þ 5e6y þ 7e - ð - 6x - 6yÞ þ 9e - ð - 14x - 6yÞ þ 3e - ð10x - 12yÞ þ 5e - ð6x - 12yÞ þ 7e - ð - 12yÞ þ 9e - ð - 8x - 12yÞ þ 11e - ð - 18x - 12yÞ þ 5e - ð14x - 20yÞ þ 7e - ð8x - 20yÞ þ 9e - ð - 20yÞ þ 11e - ð - 10x - 20yÞ þ 13e - ð - 22x - 20yÞ where x = J1/kT and y = J2/kT.

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Scheme 4. Schematic of the Magnetic Model of 3 and 4

The magnetic susceptibility data were least-squares fit to eq 4 to give the best fitting parameters J1 = -2.40 cm-1, J2 = -5.44 cm-1, and g = 2.01 with an agreement factor R = 8.95  10-5 for 3 and J1 = -1.85 cm-1, J2 = -4.64 cm-1, and g = 2.18 with an agreement factor R = 8.81  10-4 for 4, respectively. These results indicate that antiferromagnetic couplings occur between the Mn(III) ions on the three edges of the triangular trinuclear Mn(III) cluster. It was shown in previous studies that the net superexchange interaction around the value of 120° for the Mn-O-Mn angle in related compounds can be expected to change from antiferromagnetic to ferromagnetic.21,23 However, this kind of correlation between the Mn-O-Mn angle and the magnetic interaction was not detected in 3 and 4. But 3 and 4 seem to present some possible correlation between the magnetic exchange and the Mn-NO-Mn torsion angle. The Mn1-N-O-Mn3, Mn2-N-OMn1, and Mn3-N-O-Mn2 torsion angles are -10.2(6), 5.3(6), and 3.9(7)° for 3 and -10.3(3), -20.4(3), and -16.6(3)° for 4, respectively, which are small just for antiferromagnetic interactions, as indicated in the reported papers.23,25 Conclusion In this paper we succeeded in preparing two planar pentanuclear clusters 1 and 2 and two planar trinuclear clusters 3 and 4 using planar indane-1,2,3-trione trioxime (H3Itto) or indane-1,2,3-trione-1,2-dioxime (H2Itdo) ligands. Complexes 1 and 2 present planar square topologies with the five metal ions and all atoms of the four polyoxime ligands nearly in one plane. However, 1 and 2 show some differences in the bridging of the central metal ion with the metal ions in the square corners. Both trinuclear clusters 3 and 4 show planar triangular topologies. For 3, the three metal ions and all atoms of the three indane-1,2,3-trione-1,2-dioxime ligands are located nearly in one plane. However, all planes of the three indane1,2,3-trione-1,2-dioxime ligands of 4 deviate from the plane of the three metal ions, constructing a planar platelike skeleton of 4. Magnetic studies of 1-4 were conducted. They revealed the presence of antiferromagnetic interactions between the adjacent metal ions in these compounds. Acknowledgment. The authors acknowledge the financial support by the National Natural Foundation of China (Grant No. 20962003), Guangxi Natural Science Foundation of China (Grant No. 0991008 and 2010GXNSFF013001), and the Scientific Research Foundation for the Returned Overseas Chinese Scholars (No. [2006]331), State Education Ministry, China. Supporting Information Available: X-ray crystallographic files in CIF format, additional figures, selected bond distances and angles, and weak interaction information of compounds 1-4. This information is available free of charge via the Internet at http:// pubs.acs.org.

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