Polyhedron 66 (2013) 212–217

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Polyhedron

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Synthesis, structures and magnetic properties of cyano-bridged 3d–4frectangular tetranuclear [FeIII

2LnIII2] (Ln = Y, Tb, Dy) compounds containing

[FeIII(bpy)(CN)4]� unit

Xiao-Jiao Song, Jing-Jing Xu, Ying Chen, Mohd. Muddassir, Fan Cao, Rong-Min Wei, You Song ⇑,Xiao-Zeng YouState Key Lab of Coordination Chemistry, Nanjing National Laboratory of Microstructures and School of Chemistry and Chemical Engineering, Nanjing University, Hankou Road22, Nanjing 210093, PR China

a r t i c l e i n f o a b s t r a c t

Article history:Received 3 January 2013Accepted 19 April 2013Available online 28 April 2013

Keywords:Cyano-bridgedIron ionRare-earth ionRectangular tetranuclearMagnetic properties

0277-5387/$ - see front matter � 2013 Elsevier Ltd. Ahttp://dx.doi.org/10.1016/j.poly.2013.04.037

⇑ Corresponding author. Tel.: +86 25 83593739; faxE-mail address: yousong@nju.edu.cn (Y. Song).

Three cyano-bridged 3d–4f bimetallic rectangular tetranuclear compounds, [FeIII(bpy)(CN)2(l-CN)2]2

[LnIII(NO3)2(H2O)3]2�2H2O�2CH3CN (Ln = Y (1), Tb (2), Dy (3); bpy = 2,20-bipyridine), have been preparedby diffusion and characterized by single crystal X-ray diffraction, IR spectra, elemental analysis and mag-netic measurement. Single-crystal structural analysis shows that 1–3 are isomorphous and made of aneutral tetranuclear unit [FeIII

2LnIII2] with two free water and two acetonitrile molecules. Furthermore,

the tetranuclear unit [FeIII2LnIII

2] is connected into supermolecular three-dimensional framework throughhydrogen bonds. Magnetic susceptibility measurements for compounds 1–3 were performed on poly-crystalline samples. For compounds 2 and 3, there is weak ferromagnetic interaction between Fe(III)and Ln(III) ions.

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1. Introduction

Design and synthesis of 3d–4f compounds have receivedsignificant attention due to their special properties and potentialapplications in molecular adsorption [1,2], light conversion devices[3–6], bimetallic catalysis [7,8], and molecular magnetism [9–13].Since the first report of cyano-bridged 3d–4f compounds(Ln[M(CN)6]�nH2O; M = Cr(III), Fe(III)) in 1976 [14], much efforthas been devoted to the synthesis of new molecules that combinethe large magnetic anisotropic rare-earth cation and cyanometal-late anion. To date, a large number of cyano-bridged rare-earth-transition metal compounds with different dimensionality havebeen synthesized and investigated for understanding the magneticbehavior of this system [15–20]. Some of these compounds revealfascinating magnetic properties such as long-range magneticordering [14,21–24], slow relaxation of magnetization [25], photo-induced magnetization [26,27]. Furthermore, Tb(III) and Dy(III)ions are highly promising to get enticing magnetic properties be-cause they possess strong single-ion magnetic anisotropy and sev-eral unpaired electrons, and isomorphic compound withdiamagnetic Y(III) serves to take into account the anisotropy ofthe Fe(III) ion. To obtain more information of magneto-structuralcorrelation, researchers chose specifically tailored cyano-bearing

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units with formula [MIII(L)(CN)x](x+l�m)� (M = Fe, Cr or Ru; L = poly-dentate ligand; l = charge of L) as building blocks to control thedimensionality of the cyano-bridged 3d–4f system [28–31]. Tothe best of our knowledge, the 3d–4f compounds containing [MIII

(L)(CN)x](x+l�m)� units are very few, and only three examples werereported until now although both rare-earth ions and [MIII

(L)(CN)x](x+l�m)� unit are very potential candidates for the designof low-dimensional magnets [32–34].

In this work, we attempt to construct new molecules throughreacting PPh4[Fe(bpy)(CN)4]�H2O precursor with trivalent rare-earth cations by inter-layer diffusing in test tube. Three isomorphiccyano-bridged 3d–4f rectangular tetranuclear compounds, [FeIII

(bpy)(CN)2(l-CN)2]2[LnIII(NO3)2(H2O)3]2�2H2O�2CH3CN (Ln = Y (1),Tb (2), Dy (3)), were afforded. So far, compounds 1–3 are the sec-ond 3d–4f example based on [FeIII(bpy)(CN)4]� building block.Herein, the synthesis, crystal structures and magnetic propertiesof all compounds are reported in details.

2. Experimental

2.1. Materials and physical measurements

All manipulations were carried out under aerobic conditions.Chemicals and solvents were purchased from commercial sourcesas analytical reagents and used without further purification.

Table 1Crystal structural data and refinement parameters for 1–3 at 173 K.

Compounds 1 2 3

Formula C32H38N18O20

Fe2Y2

C32H38N18O20

Fe2Tb2

C32H38N18O20

Fe2Dy2

FW (g/mol) 1284.32 1424.36 1431.50Crystal system triclinic triclinic triclinicSpace group P�1 P�1 P�1a (Å) 9.875(8) 9.8883(8) 9.8785(11)b (Å) 10.175(8) 10.1485(8) 10.1233(11)c (Å) 13.968(14) 14.0045(12) 13.9577(15)a (�) 104.754(16) 105.164(1) 105.084(10)b (�) 109.724(11) 109.808(1) 109.712(10)c (�) 90.321(12) 90.121(1) 90.137(10)V (Å3) 1271.1(19) 1269.79(18) 1262.5(2)Z 1 1 1qcalc (g cm�3) 1.678 1.863 1.883F(000) 646 698 700h (�) 2.202–27.293 2.879–27.521 2.201–27.478Index ranges �12 6 h 6 12 �12 6 h 6 12 �12 6 h 6 12

�12 6 k 6 12 �12 6 k 6 12 �12 6 k 6 12�17 6 l 6 17 �17 6 l 6 17 �16 6 l 6 17

Reflections collected 10029 10232 10123Independent

reflections4926 4923 4900

Data/restraints/parameters

4926/0/335 4923/6/335 4900/0/335

Goodness-of-fit(GOF) on F2

1.039 1.024 1.038

R1 [I > 2r(I)] 0.0317 0.0334 0.0295wR2 (all data) 0.0985 0.1177 0.1134

X.-J. Song et al. / Polyhedron 66 (2013) 212–217 213

PPh4[FeIII(bpy)(CN)4]�H2O was prepared according to the literaturemethod [35].

Caution! Cyanides are hyper-toxic and hazardous, which shouldbe handled in small quantities and with great caution!

The IR spectra were recorded with a VECTOR 22 spectrometerusing KBr pellets in the 400–4000 cm�1 region. Elemental analysesof C, H and N were carried out on a PerkinElmer 240C elementalanalyzer.

The data of magnetic properties for crystalline samples wereperformed on a Quantum Design MPMP-XL 7 superconductingquantum interference device (SQUID) magnetometer. The correc-tions of magnetic susceptibilities were carried out consideringboth the sample holder as the background and the diamagnetismof the constituent atoms estimated from Pascal’s constant [36].

Single crystals with suitable dimensions for X-ray diffractionanalyses were coated with Paratone-N and mounted on a glassrod. The crystal data were collected with a Siemens (Bruker)SMART CCD diffractometer using monochromated Mo Ka radiation(k = 0.71073 Å) at 173 K. The method used to solve the structurewas direct method and the structure was further expanded usingFourier difference techniques with the SHELXTL-97 program package[37]. Absorption corrections were carried out using the SADABS pro-gram supplied by Bruker [38]. The anisotropic refinement was ap-plied for all non-hydrogen atoms while the hydrogen atoms wereadded geometrically and refined isotropically with fixed U valuesusing a riding model. Details of the crystallographic data collection,structural determination and refinement are summarized in Ta-ble 1. Crystallographic data for 1–3 have been deposited at theCambridge Crystallographic Data Centre as CCDC 931407, 914007and 914006, respectively.

2.2. Synthesis

2.2.1. [FeIII(bpy)(CN)2(l-CN)2]2[YIII(NO3)2(H2O)3]2�2H2O�2CH3CN (1)Compound 1 was synthesized by the method of slow inter-layer

diffusion in a test tube. Solution of PPh4[FeIII(bpy)(CN)4]�H2O(6.7 mg, 0.01 mmol) dissolved in 1 mL mixture of acetonitrile andchloroform (1:1 (v/v)) was added to the bottom of a tube, and amixture of acetonitrile and chloroform (3.0 mL, 2:1 (v/v)) wasadded carefully along the tube wall as the inter layer, and thensolution of Y(NO3)3�6H2O (3.8 mg, 0.01 mmol) in 1.0 mL acetoni-trile was gently added as the top layer. The tube was sealed witha pinhole and left in dark for two weeks, the X-ray quality crystalsas orange prisms of 1 were afforded with the high yield.

Elemental analysis: Calc. for C32H38N18O20Fe2Y2: C, 29.93; H,2.98; N, 19.63. Found: C, 29.89; H, 2.93; N, 19.35%. Main IR peaks(KBr)/cm�1: 3429.8 (m), 2157.8 (m), 2147.2 (w), 2075.8 (w),1606.1 (m), 1503.0 (s), 1475.0 (m), 1384.3 (s), 1293.7 (s), 1162.5(w), 1032.8 (m), 774.4 (m).

2.2.2. [FeIII(bpy)(CN)2(l-CN)2]2[TbIII(NO3)2(H2O)3]2�2H2O�2CH3CN (2)Compound 2 was also synthesized by diffusion in test tube, but

the solvent is different. Solution of PPh4[FeIII(bpy)(CN)4]�H2O(6.7 mg, 0.01 mmol) dissolved in 1 mL dichloromethane was addedto the bottom of a tube, and a mixture of acetonitrile and dichloro-methane (3.5 mL, 10 : 7 (v/v)) was added as the inter layer, andthen solution of Tb(NO3)3�6H2O (4.5 mg, 0.01 mmol) in 1.5 mL ace-tonitrile was gently added as the top layer. The tube was sealedand left in dark for three weeks, the X-ray quality crystals as or-ange prisms of 2 were afforded with the high yield.

Elemental analysis: Calc. for C32H38N18O20Fe2Tb2: C, 26.98; H,2.69; N, 17.70. Found: C, 27.09; H, 2.76; N, 17.79%. Main IR peaks(KBr)/cm�1: 3421.1 (m), 2158.0 (m), 2144.5 (m), 2067.3 (w),1608.3 (m), 1500.3 (m), 1471.1 (m), 1384.6 (s), 1299.8 (m),1162.9 (w), 1033.7 (w), 775.2(m).

2.2.3. [FeIII(bpy)(CN)2(l-CN)2]2[DyIII(NO3)2(H2O)3]2�2H2O�2CH3CN (3)Compound 3 was prepared as described for 2, except

that Dy(NO3)3�6H2O (4.6 mg, 0.01 mmol) was used instead ofTb(NO3)3

-�6H2O. The X-ray quality crystals as orange prisms of 3were afforded with high yield for three weeks.

Elemental analysis: Calc. for C32H38N18O20Fe2Dy2: C, 26.85; H,2.68; N, 17.61. Found: C, 26.97; H, 2.78; N, 17.77%. Main IR peaks(KBr)/cm�1: 3421.1 (s), 2160.0 (m), 2146.4 (m), 2061.5 (w),1629.6 (m), 1608.3 (m), 1500.3 (s), 1473.3 (s), 1384.6 (w), 1292.1(s), 1160.9 (w), 1033.7 (m), 775.2 (m).

3. Results and discussion

3.1. Structural description

All compounds crystallize in the triclinic space group P�1 andtheir main bond lengths and angles are listed in Table 2. Theyare isomorphous compounds, and their structure is made up of aneutral tetranuclear unit ([FeIII

2LnIII2], Ln = Y (1), Tb (2), Dy (3)),

two free water and two uncoordinated acetonitrile molecules(Fig. 1(a)). The tetranuclear unit is linked into supermolecularthree-dimentional framework by hydrogen bonds involving termi-nal cyanide groups, nitrate ions, and coordinated and free watermolecules.

The rare-earth ions (III) are nine-coordinated, being surroundedby two nitrogen atoms of the cyano-bridge and seven oxygenatoms from three coordinated water molecules and two bidentatenitrate ions for all compounds. The coordination geometry of therare-earth ions (III) can be best approximated as a distorted mono-capped square antiprism, in which O1N3AO4O8 and O2O3O5N2construct the two square basic planes and O7 as the capping atom(Fig. 1(b)), symmetry codes: A = �x, 1 � y, �z. The highly asymmet-ric bidentate coordination of the nitrate is the main source of thedistortion of the nine-coordinated environment of each trivalentrare-earth cation. The Ln–N bond lengths in the square antiprism

Table 2Selected bond lengths (Å) and angles (�) for 1–3.

1 2 3

Ln1–O1 2.308(3) 2.318(4) 2.302(4)Ln1–O2 2.362(3) 2.395(4) 2.385(3)Ln1–O3 2.401(3) 2.431(4) 2.400(3)Ln1–O4 2.466(3) 2.497(4) 2.471(4)Ln1–O5 2.452(3) 2.476(4) 2.456(3)Ln1–O7 2.505(3) 2.512(4) 2.501(4)Ln1–O8 2.401(3) 2.422(4) 2.424(4)Ln1–N2 2.455(3) 2.482(4) 2.465(4)Ln1–N3A 2.434(3) 2.467(4) 2.452(4)Fe1–C1 1.945(4) 1.947(6) 1.946(5)Fe1–C2 1.921(3) 1.922(5) 1.930(4)Fe1–C3 1.921(3) 1.908(5) 1.910(5)Fe1–C4 1.961(4) 1.948(5) 1.962(5)Fe1–N5 1.986(3) 1.983(4) 1.978(4)Fe1–N6 1.996(3) 1.979(4) 1.984(4)C1–N1 1.148(4) 1.148(8) 1.153(7)C2–N2 1.155(4) 1.149(6) 1.144(6)C3–N3 1.149(4) 1.153(6) 1.149(6)C4–N4 1.144(5) 1.159(7) 1.129(7)N1–C1–Fe1 178.7(3) 178.7(5) 178.9(4)N2–C2–Fe1 178.5(3) 178.8(5) 178.7(4)N3–C3–Fe1 176.7(3) 177.8(4) 177.3(4)N4–C4–Fe1 176.6(3) 176.1(5) 175.6(5)N5–Fe1–N6 81.27(10) 81.05(17) 81.19(16)N3A–Ln1–N2 78.69(9) 78.57(14) 78.70(13)C2–N2–Ln1 176.2(2) 175.4(4) 176.2(4)C3-N3-Ln1-A 165.0(2) 163.4(4) 164.1(3)

A = �x, 1 � y, �z.

214 X.-J. Song et al. / Polyhedron 66 (2013) 212–217

are 2.434(3)–2.455(3) Å (1), 2.467(4)–2.482(4) Å (2) and 2.452(4)–2.465(4) Å (3), and the Ln–O bond lengths are 2.308(3)–2.466(3) Å(1), 2.318(4)–2.497(4) Å (2) and 2.302(4)–2.471(4) Å (3), while thecapping bond lengths are 2.505(3) Å (1), 2.512(4) Å (2) and2.501(4) Å (3). One of the N„C–Ln link deviates significantly fromlinearity with the value of 165.0(2)� (1), 163.4(4)� (2) and 164.1(3)�(3), but the other one is close to linearity with the value of176.2(2)� (1), 175.4(4)� (2) and 176.2(4)� (3).

The [FeIII(bpy)(CN)4]� entity acts as a bis-monodentate bridgingligand towards two rare-earth ions through two of its four cyanidegroups in cis positions affording rectangular tetranuclear. The iron(III) ions adopt six-coordinated distorted octahedral geometries,where each FeIII centre surrounded by two nitrogen atoms from2,20-bipyridine and four cyanide-carbon atoms. The value of bondlengths around iron (III) ion of 1–3 are 1.986(3)–1.996(3),

Fig. 1. (a) Perspective view of the neutral tetranuclear (FeIII2LnIII

2) unit in 1–3, with theSymmetry code: A = �x, 1 � y, �z.

1.979(4)–1.983(4), 1.978(4)–1.984(4) Å for Fe–N, and 1.921(3)–1.961(4), 1.908(5)–1.948(5), 1.910(5)–1.962(5) Å for Fe–C, respec-tively. The values of N5–Fe1–N6 angle are 81.27(10)� (1),81.05(17)� (2) and 81.19 (16)� (3), which are consistent with thereported compounds [32]. The Fe–C„N links are deviated slightlyfrom the strict linearity (176.6(3)–178.7(3), 176.1(5)–178.8(4) and175.6(5)–178.9(4)� for 1–3, respectively). The values of C„N bondare 1.144(5)–1.155(4) Å (1), 1.148(8)–1.159(7) Å (2) and 1.129(7)–1.153(7) Å (3). The occurrence of cyanide groups was proved by thepresence of C„N stretching vibration peaks at 2061–2160 cm�1 inthe IR spectrum. The FeIII� � �LnIII distances mediated by single cya-no-bridges of 1–3 are 5.442(3)–5.526(8), 5.460(7)–5.547(8) and5.447(2)–5.534(2) Å, respectively.

The [FeIII2LnIII

2] (Ln = Y (1), Tb (2), Dy (3)) units are connected toeach other through O1–H1Y� � �N1B hydrogen bonds, giving rise toan infinite one-dimension chain which runs along a axis(Fig. 2(a)). These chains are linked to the adjacent ones throughO3–H3Y� � �N4D and O3–H3X� � �O5D hydrogen bonds, building alayer which extends in ab plane (Fig. 2(b) and Fig. S1 in Supple-mentary material). Finally, the layers are linked through O1–H1X� � �O10B, O10–H10X� � �O9E and O10–H10X� � �N4F hydrogenbonds, stacking along the c axis and forming a supramolecularthree-dimensional framework (Fig. 2(c), Figs. S2 and S3 in Supple-mentary material). The uncoordinated acetonitrile molecules arecontributing to the stabilization of the high-dimensional frame-works through O2–H2X� � �N7 and O2–H2Y� � �N7C hydrogen bonds.The distances of O� � �O are 2.694(4)–2.780(5) Å (1), 2.703(6)–2.768(6) Å (2) and 2.700(6)–2.796(7) Å (3), while the distances ofN� � �O are 2.760(4)–3.252(5) Å (1), 2.754(6)–3.223(7) Å (2) and2.741(6)–3.226(7) Å (3). The details of parameters of the hydrogenbonds are listed in Table 3 (symmetry codes: B = �x + 1, �y + 1, �z;C = �x + 1, �y + 2, �z; D = �x, �y + 2, �z; E = x + 1, y, z + 1; F = x + 1,y, z).

3.2. Magnetic properties

Magnetic susceptibility measurements for 1–3 were performedon polycrystalline samples in the range of 1.8–300 K under an ap-plied magnetic field of 100 Oe by using a SQUID magnetometer. Inall cases, the magnetic susceptibility, vM, corresponds to one[FeIII

2LnIII2] unit. Compound 1 with diamagnetic Y(III) ion serves

to determine the magnetic behavior of the low-spin Fe(III) ion.Plot of vMT for 1–3 is shown in Fig.3, together with

atom labeling scheme. (b) The coordination environment around the rare-earth ion.

Fig. 2. (a) A view of the chain for 1–3 running along a axis via O1� � �N1 hydrogen bonds. (b) A view of the chain for 1–3 running along b axis via O3� � �N4 and O3� � �O5hydrogen bonds. (c) A view of the chain for 1–3 running along c axis via O1� � �O10� � �O9 and O10� � �N4 hydrogen bonds.

X.-J. Song et al. / Polyhedron 66 (2013) 212–217 215

DvMT = v½Fe2Ln2 �M T � v½Fe2Y2 �

M T (Ln = Tb (2), Dy (3)). For compound 1,the vMT value at 300 K is 1.47 cm3 mol�1 K, which is consist withthe expected value of two diamagnetic Y(III) and two magneticnon-interacting low-spin Fe(III) ions (S = 1/2, g = 2.1) with an orbi-

tal contribution [39]. Upon cooling, the vMT value continuously de-creases and reaches a minimum of 0.74 cm3 mol�1 K at 1.8 K. Forcompounds 2 and 3, the corresponding vMT values at 300 K are24.80 and 28.66 cm3 mol�1 K, respectively. These values are closed

Table 3Hydrogen bonds for compounds 1–3.

1 2 3

O1–H1X� � �O10B 2.694(4) 2.703(6) 2.700(6)O1–H1Y� � �N1B 2.760(4) 2.754(6) 2.741(6)O2–H2X� � �N7 2.802(5) 2.812(7) 2.794(6)O2–H2Y� � �N7C 3.252(5) 3.223(7) 3.226(7)O3–H3X� � �O5D 2.774(4) 2.768(6) 2.768(4)O3–H3Y� � �N4D 2.845(5) 2.814(7) 2.843(5)O10–H10X� � �O9E 2.780(5) 2.762(8) 2.796(7)O10–H10Y� � �N4F 3.141(5) 3.121(8) 3.122(7)

Symmetry code: B = �x + 1, �y + 1, �z; C = �x + 1, �y + 2, �z; D = �x, �y + 2, �z;E = x + 1, y, z + 1; F = x + 1, y, z.

Fig. 4. Plot of M vs. H at 1.8 K for compounds 1–3.

216 X.-J. Song et al. / Polyhedron 66 (2013) 212–217

to the theoretical ones (25.11 cm3 mol�1 K (2) and 29.75 cm3 -mol�1 K (3)) of magnetically isolated two low-spin Fe(III) ionsand two Ln(III) ions (Tb and Dy with the ground state 7F6 (g6 =3/2) and 6H15/2 (g15/2 = 4/3), respectively). As the system cooling,the values of vMT decrease smoothly in the high temperature rangeand then exhibit an abrupt decrease at T < 75 K, reaching the min-ima of 18.94 cm3 mol�1 K (2) and 22.54 cm3 mol�1 K (3) at 3.5 K.The decrease of vMT are mainly attributed to the strong depopula-tion of the Stark sublevels of rare-earth ions and/or orbital contri-bution of 3d and 4f spin carriers because the coupling interaction isusually very weak in lanthanide compounds. A continued decreasein the temperature leads to a sharp increase of vMT with19.46 cm3 mol�1 K (2) and 23.57 cm3 mol�1 K (3) at 1.8 K, indicat-ing that the contribution of net spins in the compounds alongexternal field overcomes the thermal depopulation effect of Starklevels due to the magnetic coupling interaction between Ln andFe ions. For lanthanide-based compounds, the significant orbitalcontribution leads to the interaction analysis between metal ionsin difficulty. However, we can compare the magnetic propertiesof 2 and 3 with those of 1, further qualitatively determine the mag-netic interaction type. The minimum values of DvMT are18.12 cm3 mol�1 K (2) at 3 K and 21.77 cm3 mol�1 K (3) at 3.5 K,which are larger than two times of vMT value for single Ln(III)ion at the same temperatures [40–42], indicating that there isweak ferromagnetic interaction between the spin carrier.

The field dependence of the magnetization for 1–3 was mea-sured at 1.8 K up to 7 T as shown in Fig. 4. In the case of compound1, the magnetization value increases monotonously with the

Fig. 3. Plot of vMT vs. T in the range of 1.8–300 K in 100 Oe for compounds 1–3, andplot of DvMT vs. T with DvMT = v½Fe2 Ln2 �

M T � v½Fe2 Y2 �M T (Ln = Tb (2), Dy (3)).

increasing field and reaches the expected value of 2.16 NlB. Forcompounds 2 and 3, the M values increase gradually with theincreasing H and reach the maximum values of 12.09 NlB (2) and13.74 NlB (3) at 7 T. The maximum M value of 2 is in good agree-ment with the theoretical non-interacting value (12.16 NlB, withMTb = 5.0 NlB [24,43–45]), while the maximum M value of 3 isslight higher than non-interacting value (12.62 NlB, withMDy = 5.23 NlB [46,47]). Both plots of reduced magnetization Mvs. H/T for 2 and 3 show that the isofield lines do not superimpose,indicating significant magnetic anisotropy (zero-field splitting) inthe ground state (Fig. 5 and Fig. S4 in Supplementary material).

To investigate the dynamics of magnetization, the alternatingcurrent (AC) magnetic measurements on 2 and 3 have been per-formed in zero applied dc field and 5 Oe oscillating field in the fre-quency range of 1–1488 Hz (Figs. S5 and S6 in Supplementarymaterial). Unfortunately, no out-of-phase susceptibility signalswere detected above 1.8 K, though both compounds contain highanisotropic spin carries. This may be explained that the slow mag-netization relaxation was completely quenched by the mixing ofthe d and f orbits in this system [11].

Fig. 5. Plot of M vs. H/T between 1.8 and 10 K for compound 3.

X.-J. Song et al. / Polyhedron 66 (2013) 212–217 217

4. Conclusions

Three isomorphic cyano-bridged 3d–4f compounds have beenprepared by inter-layer diffusion in test tube. The single crystalstructure shows that the basic unit is rectangular tetranuclear([FeIII

2LnIII2], Ln = Y (1), Tb (2), Dy (3)), which can be connected into

supermolecular three-dimensional framework by the intermolecu-lar hydrogen bonds. To our knowledge, 1–3 are the second exam-ple of 3d–4f compounds based on [FeIII(bpy)(CN)4]� buildingblock. The investigation of the magnetic properties reveals weakferromagnetic interaction in compounds 2 and 3. Although thepresence of significant magnetic anisotropy for the rare-earth ionsin compounds 2 and 3, no single-molecule magnetic propertieswere observed. The continuing work is going on the preparationand investigation of 3d–4f systems with [FeIII(bpy)(CN)4]� buildingblock by removal of the coordinated and free solvent molecules.

Acknowledgments

We are thankful for financial support from the Major State BasicResearch Development Program (2011CB808704 and2013CB922102) and the National Nature Science Foundation ofChina (21171089, 21021062 and 91022031).

Appendix A. Supplementary data

CCDC 931407, 914007 and 914006 contain the supplementarycrystallographic data for compound 1. These data can be obtainedfree of charge via http://www.ccdc.cam.ac.uk/conts/retriev-ing.html, or from the Cambridge Crystallographic Data Centre, 12Union Road, Cambridge CB2 1EZ, UK; fax: (+44) 1223-336-033;or e-mail: deposit@ccdc.cam.ac.uk. Supplementary data associatedwith this article can be found, in the online version, at http://dx.doi.org/10.1016/j.poly.2013.04.037.

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