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Synthesis, crystal structures and magnetic properties of three pentanuclear cyanide-bridged heterometallic complexes
Inorganica Chimica Acta 377 (2011) 165–169
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Synthesis, crystal structures and magnetic properties of three pentanuclear cyanide-bridged heterometallic complexes Daopeng Zhang a, Lifang Zhang b, Zengdian Zhao a, Xia Chen a, Zhonghai Ni b,⇑ a b
College of Chemical Engineering, Shandong University of Technology, Zibo 255049, PR China School of Chemical Engineering and Technology, China University of Mining and Technology, Xuzhou 221116, PR China
a r t i c l e
i n f o
Article history: Received 4 March 2011 Received in revised form 31 July 2011 Accepted 1 August 2011 Available online 11 August 2011 Keywords: Cyanide-bridged heterometallic complex Crystal structure Magnetic property
a b s t r a c t Three dicyanide-containing building blocks and one manganese(III) compound based on bicompartimental Schiff base ligand have been employed to assemble cyanide-bridged heterometallic complexes, resulting in three cyanide-bridged MIII–MnIII (M = Fe, Cr, Co) complexes: K{{[Mn(L)(CH3OH)][Fe(bpb)]}2}ClO4H2O (1), K{{[Mn(L)(CH3OH)][Cr(bpb)]}2}ClO4CH3OH (2) and K{{[Mn(L)(CH3OH)][Co(bpb)]}2}ClO4H2O (3) (bpb2 = 1,2-bis(pyridine-2-carboxamido)benzenate, L = N,N-ethylene-bis(3-methoxysalicylideneiminate). Single X-ray diffraction analysis shows their very similar pentanuclear structures consisting of two same units {[Mn(L)(CH3OH)][Fe(bpb)]} linked by K+ complexed to eight phenolic oxygen atoms. The coordination geometry for both of the M(III) and Mn(III) ion in all the complexes is a slightly distorted octahedron. Investigation over magnetic properties of complexes 1 and 2 reveals the antiferromagnetic magnetic coupling between the neighboring Fe(Cr)(III) and Mn(III) ions through the bridging cyanide group. A best-fit to the magnetic susceptibilities of these two complexes leads to the magnetic coupling constants J = 1.65(2) (1) and 0.99(1) cm1 (2), respectively. Ó 2011 Elsevier B.V. All rights reserved.
1. Introduction As one of the most famous magnetic transferring groups, cyanide groups show some unique characteristics in the process of preparing heterometallic molecular magnetic materials for some well known reasons. During the past several decades, over 20 cyanide-containing precursors with or without peripheral organic ligands have been employed to synthesize cyanide-bridged magnetic compounds [1] with diversified molecular topological structures and interesting magnetic properties such as high-Tc magnets [2], spin crossover materials [3,4], and single-molecule magnets (SMMs) [5,6] as well as single-chain magnets (SCMs) [7,8]. Recently, polynuclear and low-dimensional cyanide-bridged complexes attracted much attention due to the necessity for the full and clear elucidation of magneto-structural correlation and the preparation of some interesting molecular materials such as SMMs and SCMs [9–16]. Very recently, we have reported a serials of polynuclear cyanidebridged heterometallic complexes based on polycyanidemetalates and bicompartimental Schiff Base Manganese(III) compounds, which showed interesting metamagnet behavior caused by intermolecular hydrogen bonds interactions [17], indicating that the manganese(III) compounds containing bicompartimental ⇑ Corresponding author. E-mail address: [email protected] (Z. Ni). 0020-1693/$ - see front matter Ó 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.ica.2011.08.002
Schiff-base ligands are good candidates for constructing heterometallic cyanide-bridged system with interesting magnetic properties. To throw further light on the reactions of bicompartimental Schiff Base Manganese(III) compounds with different types of cyanidecontaining precursors, we investigated the reactions of bicompartimental Schiff Base Manganese(III) compounds [Mn(L)(H2O)2]ClO4 (L = N,N-ethylene-bis(3-methoxysalicylideneiminate) with pyridinecarboxamide dicyanide-containing building blocks (Scheme 1), which have been successfully used to assemble low-dimensional cyanide-bridged complexes in our recent works [18,19]. In this paper, we present our recent work which concerns the synthesis, crystal structures, and magnetic properties of three tetranuclear heterometallic cyanide-bridged complexes K{{[Mn(L)(CH3OH)] [Fe(bpb)]}2}ClO4H2O (1), K{{[Mn(L) (CH3OH)][Cr(bpb)]}2}ClO4 CH3OH (2) K{{[Mn(L)(CH3OH)][Co(bpb)]}2}ClO4H2O (3). 2. Experimental Elemental analyses of carbon, hydrogen, and nitrogen were carried out with an Elementary Vario El. The infrared spectroscopy on KBr pellets was performed on a Magna-IR 750 spectrophotometer in the 4000–400 cm1 region. Variable-temperature magnetic susceptibility and field dependence magnetization measurements were performed on a Quantum Design MPMS SQUID magnetometer. The experimental susceptibilities were corrected for the diamagnetism of the constituent atoms (Pascal’s tables).
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51.23; H, 4.06; N, 12.39%. 2158, 2130 (s, mC„N), 1620, 1628 (versus mC@N), 1097 (versus mCl@O). O N
N
C
O N
Mn
O
N
N
O O
M N
N C N
trans-[MIII(bpb)(CN)2 ]- (M = Fe, Cr, Co)
2.3. X-ray data collection and structure refinement
O
[Mn(L)]+ (L = N,N-ethylene-bis (3-methoxysalicylideneiminate)
Scheme 1. The starting reactants used to synthesize the complexes 1–3.
2.1. General procedures and materials All the reactions were carried out under an air atmosphere and all chemicals and solvents used were reagent grade without further purification. K[FeIII(bpb)(CN)2] [bpb2 = 1,2-bis(pyridine-2-carboxamido)benzenate] was synthesized as described in literature [20], and the two analogous complexes K[CrIII(bpb)(CN)2] and K[CoIII(bpb)(CN)2] were similarly prepared. The [Mn(L)(H2O)2]ClO4 were available from our previous work [17].
Single crystals of all the complexes for X-ray diffraction analysis with suitable dimensions were mounted on the glass rod and the crystal data were collected on a Bruker SMART CCD diffractometer with a Mo Ka sealed tube (k = 0.71073 Å) at 293 K, using a x scan mode. The structures were solved by direct method and expanded using Fourier difference techniques with the SHELXTL-97 program package. The nonhydrogen atoms were refined anisotropically, while hydrogen atoms were introduced as fixed contributors. All the nonhydrogen atoms except the disordered ones were refined with anisotropic displacement coefficients. Hydrogen atoms were assigned isotropic displacement coefficients U(H) = 1.2U(C) or 1.5U(C) and their coordinates were allowed to ride on their respective carbons using SHELXL-97 except some of the H atoms of the solvent molecules. For these H atoms, they were refined isotropically with fixed U values and the DFIX command was used to rationalize the bond parameter. Details of the crystal parameters, data collection, and refinement are summarized in Table 1.
3. Results and discussion 3.1. Synthesis and general characterization
2.2. Preparation of complexes 1–3 All the three target complexes were prepared using one similar procedure, therefore only the synthesis of 1 was detailed as a typical representative. To a solution of [Mn(L)(H2O)2]ClO4 (48.1 mg, 0.10 mmol) in methanol (10 mL), K[Fe(bpb)(CN)2] (46.5 mg, 0.10 mmol) dissolved in methanol/water (4:1, v:v) (10 mL) was carefully added. The resulting mixture was filtered at once and the filtrate kept undisturbed at room temperature. After 1 week, brown-black block crystals were collected by filtration with the yield of 52.3 mg, 57.1%. Anal. Calcd. for C78H70ClFe2KMn2N16O19: C, 51.15; H, 3.85; N, 12.24. Found: C, 51.04; H, 3.91; N, 12.39%. Main IR bands (cm1): 2164, 2131 (s, mC„N), 1611, 1618 (versus mC@N), 1100 (versus mCl@O). Complex 2: Yield: 49.6 mg, 54%. Anal. Calcd. for C79H72ClCr2KMn2N16O19: C, 51.63; H, 3.95; N, 12.19. Found: C, 51.48; H, 4.01; N, 12.49%. 2162, 2127 (s, mC„N), 1619, 1625 (versus mC@N), 1095 (versus mCl@O). Complex 3: Yield: 58.3 mg, 63.4%. Anal. Calcd. for C78H70ClCo2KMn2N16O19: C, 50.98; H, 3.84; N, 12.20. Found: C,
In our recent work [17], Mn(III) compounds containing the bicompartimental Schiff base ligands, H2-3-MeO salen and H2-3EtO salen (salen = N,N-ethylene-bissalicylideneiminate) have been successfully employed to assembly cyanide-bridged heterometallic complexes with interesting magnetic properties. In addition, the O4 compartment of one ligand could form hydrogen bonds with the water molecule which is coordinated with the metal ion complexed by the N2O2 compartment of another ligand, therefore forming novel supramolecular topological structures [17,21,22]. Based on these results, we further investigated the reactions of the bicompartimental Schiff base manganese compound [Mn(L)(H2O)2]ClO4 with three pyridinecarboxamide dicyanide-containing building blocks, and obtained three tetranuclear heterometallic cyanide-bridged complexes. All the three cyanide-bridged heterometallic complexes have been characterized by IR spectroscopy. In the IR spectra of 1–3, two sharp peaks due to the cyanide-stretching vibration were observed at about 2130 and 2160 cm1, respectively, indicating the presence of bridging and nonbridging cyanide ligands in these
Table 1 Crystallographic data for complexes 1–3.
Chemical formula Formula weight Crystal system Space group a (Å) b (Å) c (Å) a (°) b (°) c (°) V (Å3) Z F(0 0 0) h (°) Goodness-of-fit (GOF) on F2 R1[I > 2r(I)] wR2 (all data)
1
2
3
C78H70ClFe2KMn2N16O19 1831.63 monoclinic C2/c 34.1334(6 15.1684(3) 16.5366(3) 90 98.4910(10) 90 8468.0(3) 4 3760 1.47–25.01 1.053 0.0462 0.1492
C79H72ClCr2KMn2N16O19 1837.96 monoclinic C2/c 34.218(5) 15.278(2) 16.801(3) 90 99.468(5) 90 8664(2) 4 3776 1.97–25.01 1.014 0.0542 0.1728
C78H70ClCo2KMn2N16O19 1837.79 monoclinic C2/c 34.3356(4) 15.0827(2) 16.5346(2) 90 98.3930(10) 90 8471.13(18) 4 3768 1.48–25.01 1.002 0.0550 0.1724
D. Zhang et al. / Inorganica Chimica Acta 377 (2011) 165–169
complexes. The strong broad peak centered at about 1100 cm1 for these three complexes is attributed to the free ClO4 anion [23].
3.2. Crystal structures of complexes 1–3 Some important structural parameters for complexes 1–3 are collected in Table 2. The representative cationic structure for complexes 1–3, there one-dimensional chain structure formed depending on intermolecular hydrogen bonding and representative cell packing diagram along a are shown in Figs. 1–3, respectively. As can be found, these three complexes are isostructural and possess very similar molecular structure composed of cationic {{[Mn(L)][Fe(bpb)]}2K}+ containing M2Mn2K (M = Fe, Cr, Co) core and the free ClO4 acting as balance anion. In all the complexes,
Table 2 Selected bond lengths (Å) and angles (°) for complexes 1–3.
Mn(1)–N(1) Mn(1)–N(7) Mn(3)–N(8) Mn(1)–O(3) Mn(1)–O(4) Mn(1)–O(7) M(1)–C(1) M(1)–C(2) M(1)–N(3) M(1)–N(4) M(1)–N(5) M(1)–N(6) C(1)–N(1)–Mn(1) N(1)–C(1)–M(1) N(2)–C(2)–M(1)
1(M = Fe)
2(M = Cr)
3(M = Co)
2.257(3) 1.975(3) 1.972(3) 1.877(2) 1.865(2) 2.348(3) 1.968(3) 1.959(3) 1.901(2) 1.880(3) 1.998(2) 2.006(3) 164.1(3) 176.0(3) 177.7(3)
2.274(4) 1.985(3) 1.977(4) 1.879(3) 1.874(3) 2.353(3) 2.089(4) 2.100(4) 1.986(3) 1.961(3) 2.075(3) 2.084(3) 164.8(4) 175.9(5) 174.1(4)
2.273(4) 1.968(4) 1.971(4) 1.864(3) 1.878(3) 2.345(3) 1.907(4) 1.929(4) 1.892(3) 1.887(3) 1.981(3) 1.975(3) 162.4(3) 176.7(4) 174.2(4)
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each cyanide-containing building block acts as a monodentate ligand through one of its two cyanide groups towards the central Mn(III) ion. The M(III) ion is coordinated by four N atoms of cyanide-containing precursor and two C atoms of cyanide groups in trans position, so that forming a distorted octahedral geometry, which can be proved by the bond parameters around the M(III) ion (Table 2). The bond angle of M–C„N in a very narrow range of 174.1(4)–177.7(3)° clearly indicates that the three atoms are in a good linear configuration. The coordination sphere for the Mn atom in these three complexes is also described as a distorted octahedral, in which four equatorial positions are occupied by two N atoms and two O atoms from the Schiff base ligand, and the other two axial ones come from the N atoms of the bridging cyanide group and the O atom of the coordinated methanol molecule. As shown in Table 2, the distance between the Mn atom and the N, O atoms of the Schiff-base ligand is obviously shorter than the Mn–Ncyanide and Mn–Omethanol bond length, which gives further information about the elongation octahedron surrounding the Mn(III) ion, typically accounting for the well known Jahn–Teller effect. For the angle of C(1)„N(1)–Mn(1) in these three complexes, there exists no conspicuous difference with the value close to about 164°, indicative of that these three atoms deviate slightly from a linear configuration. The intramolecular MIII–MnIII separation through bridging cyanide(s) in complexes 1–3 are 5.308, 5.454 and 5.258 Å, respectively, while the shortest intermolecular metal–metal distance is obviously longer than the above separation with the value of about 7.65 Å. For the K+, which is coordinated by eight O phenolic atoms coming from the two Schiff-base ligands, its coordination surroundings and the K–O bond lengths are very close to those found in the complex reported recently [17]. It is worth noting that, under the help of the intermolecular O–HO hydrogen bond interactions, the three target complexes are linked into one-dimensional chain structure (Fig. 2). 3.3. Magnetic properties of complexes 1 and 2
Fig. 1. The representative cationic structure for complexes 1–3. The balanced ClO4, the solvent molecule and all the H atoms are omitted for clarity.
The temperature dependences of magnetic susceptibilities measured in the temperature range of 2–300 K in the applied field of 2000 Oe for complexes 1 and 2 are given in Fig. 4. The room temperature vmT values of these two complexes are 6.42 and 9.83 emu K mol1, respectively, which are basically consistent with the spin only value of 6.75 and 9.75 emu K mol1 for two uncoupled Mn(III) (S = 5/2) and two low spin Fe(III) (S = 1/2) or Cr(III) (S = 3/2) based on g = 2.00. With the temperature decreasing, the vmT value decreases gradually and attains the value of 6.11 emu K mol1 for 1 and 9.04 emu K mol1 for 2 at about 50 K, then decreases sharply to their lowest value of 3.19 and 1.59 emu K mol1 at 2 K for 1 and 2, respectively. The magnetic susceptibilities for these two complexes conform well to Curie–Weiss law in the range of 2–300 K and give the negative Weiss constant h = 3.59 K and Curie constant
Fig. 2. The one-dimensional chain structure for these three complexes depending on intermolecular O–HO hydrogen bond interactions.
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Fig. 3. The representative cell packing diagram along a for complexes 1–3.
Fig. 4. Temperature dependences of vmT (the solid line represents the best fit based on the parameters discussed in the text) for complex 1 (left) and 2 (right). Inset: Temperature dependences vm1 (the solid line was calculated from the Curie–Weiss law).
C = 6.42 emu K mol1 for 1 and h = 7.42 K and C = 9.20 emu K mol1 for 2, respectively. The negative Weiss constant as well as the change tendency of the vmT–T give information that there exist overall antiferromagnetic interactions between the Fe/ Cr(III) and Mn(III) ions bridged by cyanide group in the two complexes. The fitting of the magnetic susceptibilities for the cyanidebridged binuclear FeIII(CrIII)–MnIII complexes have been detailed carried out in the very recent report [18e,24]. On the basis of the binuclear FeIII–MnIII (S = 1/2 and 2) and CrIII–MnIII (S = 3/2 and 2) model, the magnetic susceptibilities for these two complexes can be fitted with the zfs parameter (D) of Mn(III) considered by the reported method [18e,24] derived from the following isotropic exchange spin Hamiltonian:
^ ¼ 2J^SM ^SMn þ DMn ð^S2 SMn ðSMn þ 1Þ=3Þ þ gbH^S zJ 0 < ST H z z > ^STz ðM ¼ Fe; CrÞ The best-fit parameters obtained are J = 1.65(2) cm1, g = 1.99(6), DMn = 1.38(1) cm1, zJ0 = 0.032(4) cm1, R = 1.92 105 for complex 1 and J = 0.99(1) cm1, g = 2.00(9), DMn = 1.58(5) cm1, zJ0 = 0.052(1) cm1, R = 2.12 105 for complex 2, respectively, where J = coupling constant between the cyanide-bridged Fe(III)/Cr(III)–Mn(III); g = Lande factor; D = the zero field splitting (zfs) parameter of Mn(III) ion, zJ0 = the contributions except for the intramolecular magnetic coupling and R = the P P agreement factor defined as (vobsdT vcaldT)2/ (vobsdT)2. For
complex 1, the fitting values are comparable with those for the reported cyanide-bridged Fe–Mn complex [Mn3((R,R)-Salcy)3(H2O)2Fe(CN)62H2O]n, while these values for complex 2 are slightly smaller than those for the cyanide-bridge binuclear Cr– Mn complex [Mn(3-MeOsalen)(H2O)(l-NC)Cr(bipy)(CN)3]2H2O [25,24]. From the discussion above, we can see that the two cyanidebridged complexes exhibit overall antiferromagnetic coupling between the FeIII/CrIII ion and MnIII ion through cyanide-bridge. It has been improved that ferromagnetic or antiferromagnetic coupling could be found between low-spin Fe(III) and high-spin Mn(III) in cyanide-bridged complexes because of the strict orthogonality of the magnetic orbitals ([dxy/dxz/dyz]1 in FeIII versus dz21 in MnIII) and the orbital overlap between dxz, dyz, dxy orbitals of FeIII and MnIII, while for cyanide-bridged Cr(III)–Mn(III) complexes there usually exhibit antiferromagnetic coupling. Although the orbital orthogonality effect, which can result in ferromagnetic coupling, usually overwhelms the orbital overlap effect, the frequent bending of the Mn–N„C–Fe linkages and the rotation of the x and z axes for Mn(III) should enlarge the overlap, therefore weaken the ferromagnetic contribution and sometime giving rising to antiferromagnetic coupling. The recent study [18e] revealed that compounds with C„N–Mn bond angles below 162° most probably exhibit ferromagnetic interaction with few exceptions [18e,26], and above 162° both ferromagnetic and antiferromagnetic properties are possible, which can be further confirmed by the present complex with the C„N–Mn bond angle about 164°.
D. Zhang et al. / Inorganica Chimica Acta 377 (2011) 165–169
4. Conclusion In summary, three heterometallic pentanuclear cyanide-bridged complexes have been designed and successfully synthesized based on bicompartimental Schiff Base Manganese(III) segments using trans-dicyanide-containing building blocks K[M(bpb)(CN)2] (M = Fe, Cr, Co). Investigation over their magnetic properties reveals an overall antiferromagnetic interaction between the cyanide-bridged metal centers in Fe–Mn and Cr–Mn complexes. The results here and those reported recently by our group [17,24] indicated that the bicompartimental Schiff Base Manganese(III) compounds were good candidates for assembling cyanide-bridged heterometallic complexes with various structure types. Acknowledgement This work was supported by the Fundamental Research Funds for the Central Universities, the Natural Science Foundation of Shandong Province (ZR2011BM008) and the Science and Technology Project of High Education, Shandong Province (No.J11LB09). Appendix A. Supplementary material CCDC 799057, 799058, 799059; contains the supplementary crystallographic data for this paper. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif. Supplementary data associated with this article can be found, in the online version, at doi:10.1016/j.ica.2011.08.002. References [1] (a) K.R. Dunbar, R.A. Heintz, Progr. Inorg. Chem. 45 (1997) 283; (b) M. Verdaguer, A. Bleuzen, V. Marvaud, J. Vaissermann, M. Seuleiman, C. Desplanches, A. Scuiller, C. Train, R. Garde, G. Gelly, C. Lomenech, I. Rosenman, P. Veillet, C. Cartie, F. Villain, Coord. Chem. Rev. 190–192 (1999) 1023; (c) M. Ohba, H. Okawa, Coord. Chem. Rev. 198 (2000) 313; (d) J. Cernák, M. Orendác, I. Potocnák, J. Chomic, A. Orendácová, J. Skorsepa, A. Feher, Coord. Chem. Rev. 224 (2002) 51; (e) O. Kahn, J. Larionova, L. Ouahab, Chem. Commun. (1999) 945; (f) M. Shatruk, C. Avendano, K.R. Dunbar, Progr. Inorg. Chem. 56 (2009) 155. [2] O. Sato, T. Iyoda, A. Fujishima, K. Hashimoto, Science 271 (1996) 49. [3] V. Niel, A.L. Thompson, M.C. Muñoz, A. Galet, A.E. Goeta, J.A. Real, Angew. Chem., Int. Ed. 42 (2003) 3760.
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Synthesis, crystal structures and magnetic properties of three pentanuclear cyanide-bridged heterometallic complexes Daopeng Zhang a, Lifang Zhang b, Zengdian Zhao a, Xia Chen a, Zhonghai Ni b,⇑ a b
College of Chemical Engineering, Shandong University of Technology, Zibo 255049, PR China School of Chemical Engineering and Technology, China University of Mining and Technology, Xuzhou 221116, PR China
a r t i c l e
i n f o
Article history: Received 4 March 2011 Received in revised form 31 July 2011 Accepted 1 August 2011 Available online 11 August 2011 Keywords: Cyanide-bridged heterometallic complex Crystal structure Magnetic property
a b s t r a c t Three dicyanide-containing building blocks and one manganese(III) compound based on bicompartimental Schiff base ligand have been employed to assemble cyanide-bridged heterometallic complexes, resulting in three cyanide-bridged MIII–MnIII (M = Fe, Cr, Co) complexes: K{{[Mn(L)(CH3OH)][Fe(bpb)]}2}ClO4H2O (1), K{{[Mn(L)(CH3OH)][Cr(bpb)]}2}ClO4CH3OH (2) and K{{[Mn(L)(CH3OH)][Co(bpb)]}2}ClO4H2O (3) (bpb2 = 1,2-bis(pyridine-2-carboxamido)benzenate, L = N,N-ethylene-bis(3-methoxysalicylideneiminate). Single X-ray diffraction analysis shows their very similar pentanuclear structures consisting of two same units {[Mn(L)(CH3OH)][Fe(bpb)]} linked by K+ complexed to eight phenolic oxygen atoms. The coordination geometry for both of the M(III) and Mn(III) ion in all the complexes is a slightly distorted octahedron. Investigation over magnetic properties of complexes 1 and 2 reveals the antiferromagnetic magnetic coupling between the neighboring Fe(Cr)(III) and Mn(III) ions through the bridging cyanide group. A best-fit to the magnetic susceptibilities of these two complexes leads to the magnetic coupling constants J = 1.65(2) (1) and 0.99(1) cm1 (2), respectively. Ó 2011 Elsevier B.V. All rights reserved.
1. Introduction As one of the most famous magnetic transferring groups, cyanide groups show some unique characteristics in the process of preparing heterometallic molecular magnetic materials for some well known reasons. During the past several decades, over 20 cyanide-containing precursors with or without peripheral organic ligands have been employed to synthesize cyanide-bridged magnetic compounds [1] with diversified molecular topological structures and interesting magnetic properties such as high-Tc magnets [2], spin crossover materials [3,4], and single-molecule magnets (SMMs) [5,6] as well as single-chain magnets (SCMs) [7,8]. Recently, polynuclear and low-dimensional cyanide-bridged complexes attracted much attention due to the necessity for the full and clear elucidation of magneto-structural correlation and the preparation of some interesting molecular materials such as SMMs and SCMs [9–16]. Very recently, we have reported a serials of polynuclear cyanidebridged heterometallic complexes based on polycyanidemetalates and bicompartimental Schiff Base Manganese(III) compounds, which showed interesting metamagnet behavior caused by intermolecular hydrogen bonds interactions [17], indicating that the manganese(III) compounds containing bicompartimental ⇑ Corresponding author. E-mail address: [email protected] (Z. Ni). 0020-1693/$ - see front matter Ó 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.ica.2011.08.002
Schiff-base ligands are good candidates for constructing heterometallic cyanide-bridged system with interesting magnetic properties. To throw further light on the reactions of bicompartimental Schiff Base Manganese(III) compounds with different types of cyanidecontaining precursors, we investigated the reactions of bicompartimental Schiff Base Manganese(III) compounds [Mn(L)(H2O)2]ClO4 (L = N,N-ethylene-bis(3-methoxysalicylideneiminate) with pyridinecarboxamide dicyanide-containing building blocks (Scheme 1), which have been successfully used to assemble low-dimensional cyanide-bridged complexes in our recent works [18,19]. In this paper, we present our recent work which concerns the synthesis, crystal structures, and magnetic properties of three tetranuclear heterometallic cyanide-bridged complexes K{{[Mn(L)(CH3OH)] [Fe(bpb)]}2}ClO4H2O (1), K{{[Mn(L) (CH3OH)][Cr(bpb)]}2}ClO4 CH3OH (2) K{{[Mn(L)(CH3OH)][Co(bpb)]}2}ClO4H2O (3). 2. Experimental Elemental analyses of carbon, hydrogen, and nitrogen were carried out with an Elementary Vario El. The infrared spectroscopy on KBr pellets was performed on a Magna-IR 750 spectrophotometer in the 4000–400 cm1 region. Variable-temperature magnetic susceptibility and field dependence magnetization measurements were performed on a Quantum Design MPMS SQUID magnetometer. The experimental susceptibilities were corrected for the diamagnetism of the constituent atoms (Pascal’s tables).
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51.23; H, 4.06; N, 12.39%. 2158, 2130 (s, mC„N), 1620, 1628 (versus mC@N), 1097 (versus mCl@O). O N
N
C
O N
Mn
O
N
N
O O
M N
N C N
trans-[MIII(bpb)(CN)2 ]- (M = Fe, Cr, Co)
2.3. X-ray data collection and structure refinement
O
[Mn(L)]+ (L = N,N-ethylene-bis (3-methoxysalicylideneiminate)
Scheme 1. The starting reactants used to synthesize the complexes 1–3.
2.1. General procedures and materials All the reactions were carried out under an air atmosphere and all chemicals and solvents used were reagent grade without further purification. K[FeIII(bpb)(CN)2] [bpb2 = 1,2-bis(pyridine-2-carboxamido)benzenate] was synthesized as described in literature [20], and the two analogous complexes K[CrIII(bpb)(CN)2] and K[CoIII(bpb)(CN)2] were similarly prepared. The [Mn(L)(H2O)2]ClO4 were available from our previous work [17].
Single crystals of all the complexes for X-ray diffraction analysis with suitable dimensions were mounted on the glass rod and the crystal data were collected on a Bruker SMART CCD diffractometer with a Mo Ka sealed tube (k = 0.71073 Å) at 293 K, using a x scan mode. The structures were solved by direct method and expanded using Fourier difference techniques with the SHELXTL-97 program package. The nonhydrogen atoms were refined anisotropically, while hydrogen atoms were introduced as fixed contributors. All the nonhydrogen atoms except the disordered ones were refined with anisotropic displacement coefficients. Hydrogen atoms were assigned isotropic displacement coefficients U(H) = 1.2U(C) or 1.5U(C) and their coordinates were allowed to ride on their respective carbons using SHELXL-97 except some of the H atoms of the solvent molecules. For these H atoms, they were refined isotropically with fixed U values and the DFIX command was used to rationalize the bond parameter. Details of the crystal parameters, data collection, and refinement are summarized in Table 1.
3. Results and discussion 3.1. Synthesis and general characterization
2.2. Preparation of complexes 1–3 All the three target complexes were prepared using one similar procedure, therefore only the synthesis of 1 was detailed as a typical representative. To a solution of [Mn(L)(H2O)2]ClO4 (48.1 mg, 0.10 mmol) in methanol (10 mL), K[Fe(bpb)(CN)2] (46.5 mg, 0.10 mmol) dissolved in methanol/water (4:1, v:v) (10 mL) was carefully added. The resulting mixture was filtered at once and the filtrate kept undisturbed at room temperature. After 1 week, brown-black block crystals were collected by filtration with the yield of 52.3 mg, 57.1%. Anal. Calcd. for C78H70ClFe2KMn2N16O19: C, 51.15; H, 3.85; N, 12.24. Found: C, 51.04; H, 3.91; N, 12.39%. Main IR bands (cm1): 2164, 2131 (s, mC„N), 1611, 1618 (versus mC@N), 1100 (versus mCl@O). Complex 2: Yield: 49.6 mg, 54%. Anal. Calcd. for C79H72ClCr2KMn2N16O19: C, 51.63; H, 3.95; N, 12.19. Found: C, 51.48; H, 4.01; N, 12.49%. 2162, 2127 (s, mC„N), 1619, 1625 (versus mC@N), 1095 (versus mCl@O). Complex 3: Yield: 58.3 mg, 63.4%. Anal. Calcd. for C78H70ClCo2KMn2N16O19: C, 50.98; H, 3.84; N, 12.20. Found: C,
In our recent work [17], Mn(III) compounds containing the bicompartimental Schiff base ligands, H2-3-MeO salen and H2-3EtO salen (salen = N,N-ethylene-bissalicylideneiminate) have been successfully employed to assembly cyanide-bridged heterometallic complexes with interesting magnetic properties. In addition, the O4 compartment of one ligand could form hydrogen bonds with the water molecule which is coordinated with the metal ion complexed by the N2O2 compartment of another ligand, therefore forming novel supramolecular topological structures [17,21,22]. Based on these results, we further investigated the reactions of the bicompartimental Schiff base manganese compound [Mn(L)(H2O)2]ClO4 with three pyridinecarboxamide dicyanide-containing building blocks, and obtained three tetranuclear heterometallic cyanide-bridged complexes. All the three cyanide-bridged heterometallic complexes have been characterized by IR spectroscopy. In the IR spectra of 1–3, two sharp peaks due to the cyanide-stretching vibration were observed at about 2130 and 2160 cm1, respectively, indicating the presence of bridging and nonbridging cyanide ligands in these
Table 1 Crystallographic data for complexes 1–3.
Chemical formula Formula weight Crystal system Space group a (Å) b (Å) c (Å) a (°) b (°) c (°) V (Å3) Z F(0 0 0) h (°) Goodness-of-fit (GOF) on F2 R1[I > 2r(I)] wR2 (all data)
1
2
3
C78H70ClFe2KMn2N16O19 1831.63 monoclinic C2/c 34.1334(6 15.1684(3) 16.5366(3) 90 98.4910(10) 90 8468.0(3) 4 3760 1.47–25.01 1.053 0.0462 0.1492
C79H72ClCr2KMn2N16O19 1837.96 monoclinic C2/c 34.218(5) 15.278(2) 16.801(3) 90 99.468(5) 90 8664(2) 4 3776 1.97–25.01 1.014 0.0542 0.1728
C78H70ClCo2KMn2N16O19 1837.79 monoclinic C2/c 34.3356(4) 15.0827(2) 16.5346(2) 90 98.3930(10) 90 8471.13(18) 4 3768 1.48–25.01 1.002 0.0550 0.1724
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complexes. The strong broad peak centered at about 1100 cm1 for these three complexes is attributed to the free ClO4 anion [23].
3.2. Crystal structures of complexes 1–3 Some important structural parameters for complexes 1–3 are collected in Table 2. The representative cationic structure for complexes 1–3, there one-dimensional chain structure formed depending on intermolecular hydrogen bonding and representative cell packing diagram along a are shown in Figs. 1–3, respectively. As can be found, these three complexes are isostructural and possess very similar molecular structure composed of cationic {{[Mn(L)][Fe(bpb)]}2K}+ containing M2Mn2K (M = Fe, Cr, Co) core and the free ClO4 acting as balance anion. In all the complexes,
Table 2 Selected bond lengths (Å) and angles (°) for complexes 1–3.
Mn(1)–N(1) Mn(1)–N(7) Mn(3)–N(8) Mn(1)–O(3) Mn(1)–O(4) Mn(1)–O(7) M(1)–C(1) M(1)–C(2) M(1)–N(3) M(1)–N(4) M(1)–N(5) M(1)–N(6) C(1)–N(1)–Mn(1) N(1)–C(1)–M(1) N(2)–C(2)–M(1)
1(M = Fe)
2(M = Cr)
3(M = Co)
2.257(3) 1.975(3) 1.972(3) 1.877(2) 1.865(2) 2.348(3) 1.968(3) 1.959(3) 1.901(2) 1.880(3) 1.998(2) 2.006(3) 164.1(3) 176.0(3) 177.7(3)
2.274(4) 1.985(3) 1.977(4) 1.879(3) 1.874(3) 2.353(3) 2.089(4) 2.100(4) 1.986(3) 1.961(3) 2.075(3) 2.084(3) 164.8(4) 175.9(5) 174.1(4)
2.273(4) 1.968(4) 1.971(4) 1.864(3) 1.878(3) 2.345(3) 1.907(4) 1.929(4) 1.892(3) 1.887(3) 1.981(3) 1.975(3) 162.4(3) 176.7(4) 174.2(4)
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each cyanide-containing building block acts as a monodentate ligand through one of its two cyanide groups towards the central Mn(III) ion. The M(III) ion is coordinated by four N atoms of cyanide-containing precursor and two C atoms of cyanide groups in trans position, so that forming a distorted octahedral geometry, which can be proved by the bond parameters around the M(III) ion (Table 2). The bond angle of M–C„N in a very narrow range of 174.1(4)–177.7(3)° clearly indicates that the three atoms are in a good linear configuration. The coordination sphere for the Mn atom in these three complexes is also described as a distorted octahedral, in which four equatorial positions are occupied by two N atoms and two O atoms from the Schiff base ligand, and the other two axial ones come from the N atoms of the bridging cyanide group and the O atom of the coordinated methanol molecule. As shown in Table 2, the distance between the Mn atom and the N, O atoms of the Schiff-base ligand is obviously shorter than the Mn–Ncyanide and Mn–Omethanol bond length, which gives further information about the elongation octahedron surrounding the Mn(III) ion, typically accounting for the well known Jahn–Teller effect. For the angle of C(1)„N(1)–Mn(1) in these three complexes, there exists no conspicuous difference with the value close to about 164°, indicative of that these three atoms deviate slightly from a linear configuration. The intramolecular MIII–MnIII separation through bridging cyanide(s) in complexes 1–3 are 5.308, 5.454 and 5.258 Å, respectively, while the shortest intermolecular metal–metal distance is obviously longer than the above separation with the value of about 7.65 Å. For the K+, which is coordinated by eight O phenolic atoms coming from the two Schiff-base ligands, its coordination surroundings and the K–O bond lengths are very close to those found in the complex reported recently [17]. It is worth noting that, under the help of the intermolecular O–HO hydrogen bond interactions, the three target complexes are linked into one-dimensional chain structure (Fig. 2). 3.3. Magnetic properties of complexes 1 and 2
Fig. 1. The representative cationic structure for complexes 1–3. The balanced ClO4, the solvent molecule and all the H atoms are omitted for clarity.
The temperature dependences of magnetic susceptibilities measured in the temperature range of 2–300 K in the applied field of 2000 Oe for complexes 1 and 2 are given in Fig. 4. The room temperature vmT values of these two complexes are 6.42 and 9.83 emu K mol1, respectively, which are basically consistent with the spin only value of 6.75 and 9.75 emu K mol1 for two uncoupled Mn(III) (S = 5/2) and two low spin Fe(III) (S = 1/2) or Cr(III) (S = 3/2) based on g = 2.00. With the temperature decreasing, the vmT value decreases gradually and attains the value of 6.11 emu K mol1 for 1 and 9.04 emu K mol1 for 2 at about 50 K, then decreases sharply to their lowest value of 3.19 and 1.59 emu K mol1 at 2 K for 1 and 2, respectively. The magnetic susceptibilities for these two complexes conform well to Curie–Weiss law in the range of 2–300 K and give the negative Weiss constant h = 3.59 K and Curie constant
Fig. 2. The one-dimensional chain structure for these three complexes depending on intermolecular O–HO hydrogen bond interactions.
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Fig. 3. The representative cell packing diagram along a for complexes 1–3.
Fig. 4. Temperature dependences of vmT (the solid line represents the best fit based on the parameters discussed in the text) for complex 1 (left) and 2 (right). Inset: Temperature dependences vm1 (the solid line was calculated from the Curie–Weiss law).
C = 6.42 emu K mol1 for 1 and h = 7.42 K and C = 9.20 emu K mol1 for 2, respectively. The negative Weiss constant as well as the change tendency of the vmT–T give information that there exist overall antiferromagnetic interactions between the Fe/ Cr(III) and Mn(III) ions bridged by cyanide group in the two complexes. The fitting of the magnetic susceptibilities for the cyanidebridged binuclear FeIII(CrIII)–MnIII complexes have been detailed carried out in the very recent report [18e,24]. On the basis of the binuclear FeIII–MnIII (S = 1/2 and 2) and CrIII–MnIII (S = 3/2 and 2) model, the magnetic susceptibilities for these two complexes can be fitted with the zfs parameter (D) of Mn(III) considered by the reported method [18e,24] derived from the following isotropic exchange spin Hamiltonian:
^ ¼ 2J^SM ^SMn þ DMn ð^S2 SMn ðSMn þ 1Þ=3Þ þ gbH^S zJ 0 < ST H z z > ^STz ðM ¼ Fe; CrÞ The best-fit parameters obtained are J = 1.65(2) cm1, g = 1.99(6), DMn = 1.38(1) cm1, zJ0 = 0.032(4) cm1, R = 1.92 105 for complex 1 and J = 0.99(1) cm1, g = 2.00(9), DMn = 1.58(5) cm1, zJ0 = 0.052(1) cm1, R = 2.12 105 for complex 2, respectively, where J = coupling constant between the cyanide-bridged Fe(III)/Cr(III)–Mn(III); g = Lande factor; D = the zero field splitting (zfs) parameter of Mn(III) ion, zJ0 = the contributions except for the intramolecular magnetic coupling and R = the P P agreement factor defined as (vobsdT vcaldT)2/ (vobsdT)2. For
complex 1, the fitting values are comparable with those for the reported cyanide-bridged Fe–Mn complex [Mn3((R,R)-Salcy)3(H2O)2Fe(CN)62H2O]n, while these values for complex 2 are slightly smaller than those for the cyanide-bridge binuclear Cr– Mn complex [Mn(3-MeOsalen)(H2O)(l-NC)Cr(bipy)(CN)3]2H2O [25,24]. From the discussion above, we can see that the two cyanidebridged complexes exhibit overall antiferromagnetic coupling between the FeIII/CrIII ion and MnIII ion through cyanide-bridge. It has been improved that ferromagnetic or antiferromagnetic coupling could be found between low-spin Fe(III) and high-spin Mn(III) in cyanide-bridged complexes because of the strict orthogonality of the magnetic orbitals ([dxy/dxz/dyz]1 in FeIII versus dz21 in MnIII) and the orbital overlap between dxz, dyz, dxy orbitals of FeIII and MnIII, while for cyanide-bridged Cr(III)–Mn(III) complexes there usually exhibit antiferromagnetic coupling. Although the orbital orthogonality effect, which can result in ferromagnetic coupling, usually overwhelms the orbital overlap effect, the frequent bending of the Mn–N„C–Fe linkages and the rotation of the x and z axes for Mn(III) should enlarge the overlap, therefore weaken the ferromagnetic contribution and sometime giving rising to antiferromagnetic coupling. The recent study [18e] revealed that compounds with C„N–Mn bond angles below 162° most probably exhibit ferromagnetic interaction with few exceptions [18e,26], and above 162° both ferromagnetic and antiferromagnetic properties are possible, which can be further confirmed by the present complex with the C„N–Mn bond angle about 164°.
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4. Conclusion In summary, three heterometallic pentanuclear cyanide-bridged complexes have been designed and successfully synthesized based on bicompartimental Schiff Base Manganese(III) segments using trans-dicyanide-containing building blocks K[M(bpb)(CN)2] (M = Fe, Cr, Co). Investigation over their magnetic properties reveals an overall antiferromagnetic interaction between the cyanide-bridged metal centers in Fe–Mn and Cr–Mn complexes. The results here and those reported recently by our group [17,24] indicated that the bicompartimental Schiff Base Manganese(III) compounds were good candidates for assembling cyanide-bridged heterometallic complexes with various structure types. Acknowledgement This work was supported by the Fundamental Research Funds for the Central Universities, the Natural Science Foundation of Shandong Province (ZR2011BM008) and the Science and Technology Project of High Education, Shandong Province (No.J11LB09). Appendix A. Supplementary material CCDC 799057, 799058, 799059; contains the supplementary crystallographic data for this paper. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif. Supplementary data associated with this article can be found, in the online version, at doi:10.1016/j.ica.2011.08.002. References [1] (a) K.R. Dunbar, R.A. Heintz, Progr. Inorg. Chem. 45 (1997) 283; (b) M. Verdaguer, A. Bleuzen, V. Marvaud, J. Vaissermann, M. Seuleiman, C. Desplanches, A. Scuiller, C. Train, R. Garde, G. Gelly, C. Lomenech, I. Rosenman, P. Veillet, C. Cartie, F. Villain, Coord. Chem. Rev. 190–192 (1999) 1023; (c) M. Ohba, H. Okawa, Coord. Chem. Rev. 198 (2000) 313; (d) J. Cernák, M. Orendác, I. Potocnák, J. Chomic, A. Orendácová, J. Skorsepa, A. Feher, Coord. Chem. Rev. 224 (2002) 51; (e) O. Kahn, J. Larionova, L. Ouahab, Chem. Commun. (1999) 945; (f) M. Shatruk, C. Avendano, K.R. Dunbar, Progr. Inorg. Chem. 56 (2009) 155. [2] O. Sato, T. Iyoda, A. Fujishima, K. Hashimoto, Science 271 (1996) 49. [3] V. Niel, A.L. Thompson, M.C. Muñoz, A. Galet, A.E. Goeta, J.A. Real, Angew. Chem., Int. Ed. 42 (2003) 3760.
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