3d-4f Coordination Polymers Containing Alternating EE/EO Azido Chain Synthesized by Synergistic Coordination of Lanthanide and Transition Metal Ions Xin Hu,† Yong-Fei Zeng,† Zhuo Chen,† E. C. San˜udo,‡ Fu-Chen Liu,† J. Ribas,‡ and Xian-He Bu*,†
CRYSTAL GROWTH & DESIGN 2009 VOL. 9, NO. 1 421–426
Department of Chemistry, Nankai UniVersity, Tianjin 300071, China, and Departament de Quı´mica Inorga`nica UniVersitat de Barcelona, Diagonal, 6487, 08028-barcelona, Spain ReceiVed June 19, 2008; ReVised Manuscript ReceiVed September 1, 2008
ABSTRACT: A series of MII-LnIII azido-containing complexes: [LnNi2(IN)5(N3)2(H2O)3] · 2H2O (Ln ) NdIII (2), EuIII (3), SmIII (4), LaIII (5)) and [GdCu2(IN)5(N3)2(H2O)3] · 2H2O (6) have been prepared hydrothermally by using isonicotinate (IN) and azide as bridging ligands with the strategy of synergistic coordination. Their structures have been determined by single-crystal X-ray diffraction analyses and their magnetic properties have been probed by changing the LnIII metal ions and the 3d ions. All of them crystallize in the monoclinic space group P2(1)/n. The structural analyses revealed that alternating EE/EO azido-M chain and RCOO-/Ln chain are presented in these compounds due to coordination synergy. The variable temperature magnetic susceptibility studies demonstrate that the magnetic properties of the complexes are dominated by the 3d metal ions. Introduction The design and construction of 3d-4f coordination polymers have stimulated researchers’ considerable interests, not only for their fascinating architectures,1 but also for their possible applications as multifunctional materials.2-5 Frequently, a wellknown principle is employed to synthesize such materials: the 4f ions act as hard acids, thus they prefer oxygen to nitrogen donors and possess high coordination numbers and variable coordination geometries,6,7 while 3d metal ions (borderline acids) have strong capability to coordinate to N-donors and O-donors.7 Therefore, the interesting so-called “synergistic coordination” may happen after introduction of ligands containing N-donor and O-donor into a 3d-4f system. Three good examples of this phenomenon are the compounds [Ln14(µ6O)(µ3-OH)20(IN)22Cu6X4(H2O)8] · 6H2O, [Er7(µ3-O)(µ3-OH)6(bdc)3](IN)9[Cu3X4], and [Ln6(µ3-O)2](IN)18[Cu8(µ4-I)2(µ2-I)3] · H3O.8,9 The azido ligand is well-known as an effective ligand to provide strong superexchange pathway between metal ions. Due to this and its various possible binding modes, the azido anion is exhaustively used in constructing magnetic materials whose structures range from 0D (discrete),10 1D (chain),11 2D (sheet)12 to 3D (network).13 The magnetic exchange provided by the azido ligand in its common bridging modes of EE (µ2-1,3) and EO (µ2-1,1) are well studied and usually afford antiferromagnetic and ferromagnetic couplings, respectively.14 Among these structures, various 1D azido-bridged chains, such as uniform single or double EO and EE chain, alternating EE/EO, EE/EE/ EO, EE/EE/EE/EO, EE-/EE/EE/EE/EO, etc., have been reported.15 Careful investigation on the references indicate that such 1D system are mostly based on neutral ligands with monodentate or bidentate (bridging or chelating) donors, especially ligands containing pyridyl groups.16 Previously, a compound [GdNi2(IN)5(N3)2(H2O)3] · 2H2O (1) (IN ) isonicotinate) with alternating EE and EO azido chains has been reported.17 However, further investigation on this * To whom correspondence should be addressed. E-mail:
[email protected]. Fax: +86-22-23502458. Telephone: +86-22-23502809. † Nankai University. ‡ Universitat de Barcelona.
synthesis revealed that coordination synergy between 3d-4f metal ions and ligands of IN and azido anions would occur in this system, which is overlooked in our previous work. This strategy has now been used to extend our studies of 3d-4f materials. Herein we report a family of complexes related to [GdNi2(IN)5(N3)2(H2O)3] · 2H2O (1) in which both the LnIII and the 3d metal ions have been varied systematically: [LnNi2(IN)5(N3)2(H2O)3] · 2H2O (Ln ) NdIII (2), EuIII (3), SmIII (4), LaIII (5)) and [GdCu2(IN)5(N3)2(H2O)3] · 2H2O (6), which show the same overall topology with alternating EE and EO azido chains. Notably, to our knowledge, complexes 1-6 are the first heterometallic 3d-4f in azido-derivatives synthesized by synergistic coordination; moreover, complex 6 is the first heterometallic Cu-4f azido-derivative. Experimental Section Materials and Physical Measurements. The lanthanide nitrate Ln(NO3)3 · 6H2O (Ln ) NdIII, SmIII, LaIII, GdIII) were prepared by dissolving Ln2O3 (99.9%) in nitric acid, followed by drying and crystallization. The EuCl3 · 6H2O salt were prepared in the same way as Ln(NO3)3 · 6H2O, using hydrochloric acid to replace nitric acid. Other chemicals were commercially available and used as received. IR spectra were measured on a TENSOR 27 (Bruker) FT-IR spectrometer with KBr pellets in the range 4000-400 cm-1. Elemental analyses of C, H, N were performed on a Perkin-Elmer 240C analyzer. Magnetic measurements were carried out in the “Servei de Magnetoquı´mica (Universitat de Barcelona)” on polycrystalline samples with a Quantum Design SQUID MPMS-XL magnetometer working in 2-300 K range. The magnetic field was 0.1 T. The diamagnetic corrections were evaluated from Pascal’s constants. Syntheses of Compounds. Complexes 2-5 were prepared by a similar method used for complex 117 as follows. [NdNi2(IN)5(N3)2(H2O)3] · 2H2O (2). A mixture of Nd(NO3)3 · 6H2O (0.5 mmol), Ni(NO3)2 · 6H2O (1 mmol), NaN3 (1 mmol), isonicotinic acid (2.5 mmol) and H2O (13.5 mL) at the ratio of 1:2:2:5:1500 was sealed in a Teflon-lined autoclave and heated at a rate of 3 °C/h to 160 °C under autogenous pressure. After maintained for 48 h, the reaction vessel was cooled 6 h to room temperature. The green crystals in ca. 20% yield based on nickel were obtained and washed by water (the crystals were carefully picked one by one). Anal. Calcd for C30H30NdNi2N11O15 (2): C, 34.44; H, 2.89; N, 14.73. Found: C, 34.73; H, 3.23; N, 14.42%. IR (KBr pellet, cm-1): ν ) 2095, 2056, 1651, 1583, 1542, 1412, 857, 779, 687.
10.1021/cg8006475 CCC: $40.75 2009 American Chemical Society Published on Web 11/24/2008
422 Crystal Growth & Design, Vol. 9, No. 1, 2009
Hu et al.
Table 1. Crystallographic Data for Complexes 2-6
formula fw T [K] cryst system space group a [Å] b [Å] c [Å] β [deg] V [Å3] Z Dcaled [g cm-3] µ [mm-1] 2θmax [deg] index range no. of reflns collected/unique no. of data/restraints/parameters GOF on F2 R1/wR2 [I > 2σ(I)] R1/wR2 (all data) largest diff. peak/hole [e Å-3]
2
3
4
5
6
C30H30NdNi2N11O15 1046.32 294(2) monoclinic P2(1)/n 8.2193(9) 26.890(3) 16.9816(18) 95.751(2) 3734.4(7) 4 1.861 2.454 52.72 -10 e h e 9 -33 e k e 28 -21 e l e 18 20965/7608 7608/0/532 1.068 0.0343/0.0789 0.0538/ 0.0863 0.773/-0.756
C30H30EuNi2N11O15 1053.98 293(2) monoclinic P2(1)/n 8.1978(8) 26.866(3) 16.9079(16) 95.508(2) 3706.7(6) 4 1.871 2.763 52.80 -10 e h e 5 -32 e k e 33 -20 e l e 21 20817/7591 7591/0/612 1.041 0.0296/0.0658 0.0430/ 0.0701 0.826/-0.643
C30H30SmNi2N11O15 1052.37 294(2) monoclinic P2(1)/n 8.2071(11) 26.893(4) 16.931(2) 95.538(2) 3719.4(8) 4 1.861 2.646 52.76 -9 e h e 10 -33 e k e 27 -21 e l e 20 20867/7575 7575/0/532 1.034 0.0327/0.0717 0.0530/0.0789 0.855/-0.803
C30H30LaNi2N11O15 1040.98 293(2) monoclinic P2(1)/n 8.2521(9) 26.966(3) 17.0838(18) 96.254(2) 3779.0(7) 4 1.830 2.181 52.73 -9 e h e 9 -30 e k e 32 -9 e l e 20 19845/7003 7003/0/612 1.092 0.0291/0.0704 0.0355/0.0730 0.835/-0.547
C30H30GdCu2N11O15 1068.98 293(2) monoclinic P2(1)/n 8.1982(8) 27.328(3) 16.4634(17) 93.154(2) 3682.9(6) 4 1.928 3.011 51.00 -9 e h e 9 -30 e k e 33 -19 e l e 16 19399/6846 6846/0/532 1.050 0.0319/0.0763 0.0500/0.0817 1.245/-0.855
[EuNi2(IN)5(N3)2(H2O)3] · 2H2O (3). Complex 3 was prepared in the same way as 2, using EuCl3 · 6H2O instead of Nd(NO3)3 · 6H2O, as green crystals in ca. 20% yield based on nickel. Anal. Calcd for C30H30EuNi2N11O15 (3): C, 34.19, H, 2.87, N, 14.62. Found: C, 34.51; H, 3.08; N, 14.72%. IR (KBr pellet, cm-1): ν ) 2097, 2056, 1655, 1586, 1543, 1412, 858, 779, 695. [SmNi2(IN)5(N3)2(H2O)3] · 2H2O (4). Complex 4 was prepared in the same way as 2, using Sm(NO3)3 · 6H2O instead of Nd(NO3)3 · 6H2O. Green crystals yielded in ca. 20% based on nickel. Anal. Calcd for C30H30SmNi2N11O15 (4): C, 34.24, H, 2.87, N, 14.64. Found: C, 34.73; H, 2.82; N, 14.70%. IR (KBr, cm-1): ν ) 2097, 2056, 1654, 1585, 1543, 1413, 859, 779, 696. [LaNi2(IN)5(N3)2(H2O)3] · 2H2O (5). Complex 5 was prepared in the same way as 2, using La(NO3)3 · 6H2O instead of Nd(NO3)3 · 6H2O. Green crystals yielded in ca. 30% based on nickel. Anal. Calcd for C30H30LaNi2N11O15 (5): C, 34.62; H, 2.91; N, 14.80. Found: C, 33.47; H, 2.71; N, 14.93%. IR (KBr, cm-1): ν ) 2094, 2056, 1650, 1582, 1541, 1411, 856, 779, 686. [GdCu2(IN)5(N3)2(H2O)3] · 2H2O (6). Complex 6 was prepared in the similar procedure as 2, but some modifications were made. A mixture of Gd(NO3)3 · 6H2O (0.25 mmol), Cu(NO3)2 · 6H2O (0.5 mmol), NaN3 (0.5 mmol), isonicotinic acid (1.25 mmol) and H2O (13.5 mL) at the ratio of 1:2:2:5:3000 was sealed in a Teflon-lined autoclave and heated at a rate of 3 °C/h to 120 °C under autogenous pressure. After maintained for 48 h, the reaction vessel was cooled 6 h to room temperature. The black crystals in ca. 20% yield based on copper were obtained and washed by water. Anal. Calcd. for C30H30GdCu2N11O15 (6): C, 33.71, H, 2.83, N 14.41. Found: C, 34.01; H, 2.91; N, 14.32%. IR (KBr, cm-1): ν ) 2098, 2053, 1652, 1583, 1542, 1412, 857, 779, 692. Caution! Although we have not experienced any problems in this work, azide and its complexes are potentially explosive. Only a small amount of the materials should be prepared and handled with care. All the experiments were carried out in an isolated room. All the experimenters should be equipped with safety protection. Crystal Structure Determinations. The chosen crystals were mounted on a glass fiber. All diffraction data were collected on a Bruker Smart 1000 CCD diffractometer at 293(2) K with Mo KR radiation (λ ) 0.71073 Å) by ω scan mode. The program SAINT was used for integration of the diffraction profiles.18 The structures were solved by direct methods using the SHELXS program of the SHELXTL package and refined by full-matrix least-squares methods with SHELXL (semiempirical absorption corrections were applied using SADABS program).19 The positions of metal atoms were located from E-map by direct-method, and other non-hydrogen atoms were located in difference Fourier syntheses and least-squares refinement cycles, and finally refined anisotropically. The hydrogen atoms of the ligands were placed theoretically onto the specific atoms and refined isotropically
as riding atoms. Details of the crystal data collection and refinement parameters for 2-6 are given in Table 1.
Results and Discussion Syntheses. For 2-5, large block green crystals with jadegreen powder were obtained at 160 °C in hydrothermal conditions. The crystals can be separated from the powder by washing with methanol or water and picked one by one. For 6, the reaction temperature determined its crystallization, if the temperature was over 140 °C, black powder deposited due to the instability and decomposition of azido-copper complexes. At lower temperatures (
