Heterobinuclear Complexes as Tectons in Designing Coordination

CRYSTAL GROWTH & DESIGN

Heterobinuclear Complexes as Tectons in Designing Coordination Polymers

2008 VOL. 8, NO. 3 941–949

Diana G. Branzea,† Annalisa Guerri,‡ Oscar Fabelo,§ Catalina Ruiz-Pérez,§ Lise-Marie Chamoreau,# Claudio Sangregorio,‡ Andrea Caneschi,‡ and Marius Andruh*,† Faculty of Chemistry, Inorganic Chemistry Laboratory, UniVersity of Bucharest, Street DumbraVa Rosie nr. 23, 020464 Bucharest, Romania, Laboratory of Molecular Magnetism, Dipartimento di Chimica e UdR INSTM di Firenze, UniVersità degli Studi di Firenze, Polo Scientifico, Via della Lastruccia 3, 50019 Sesto Fiorentino, Firenze, Italy, Laboratorio de Rayos X y Materiales Moleculares, Departamento de Física Fundamental II, AVda. Astrofísico Francisco Sánchez s/n, Facultad de Física, UniVersidad de La Laguna, 38204-La Laguna, Tenerife, Spain, and Laboratoire de Chimie Inorganique et Matériaux Moléculaires, Unité CNRS 7071, UniVersité Pierre et Marie Curie, 4 Place Jussieu, Case 42, 75252 Paris Cedex 05, France ReceiVed September 5, 2007; ReVised Manuscript ReceiVed NoVember 9, 2007

ABSTRACT: Four new 1D coordination polymers have been constructed from [LCuIIMII] nodes connected by various spacerssthe dianion of pyrazole-3,5-dicarboxylic acid (pzdc2-), the trianion of trimesic acid (trim3-), the tetracyanonickelate(II) anion ([Ni(CN)4]2-), and the dicyanamide anion (dca-) [MII ) MnII, CoII, and L2- is the dianion of the Schiff-base resulting from the 2:1 condensation of 3-methoxysalicylaldehyde with 1,3-propanediamine, L2- ) N,N′-propylene-bis-(3-methoxysalycilideneiminato)]: [LCuMn(pzdc)(CH3OH)(H2O)] · H2O (1), [LCuMn(trim)2/3(CH3OH)2/3(H2O)1/3] · 0.66(H2O) · 0.66(CH3OH) (2), [LCuCo(dca)2] (3), and [LCu(CH3OH)(H2O)Mn(NC)2Ni(CN)2] · (H2O)(CH3CN) (4). The fifth compound, [{CuL}K{LCu}{Ag(CN)2}] (5), was obtained by reacting [CuL] with K[Ag(CN)2]. The magnetic investigation of compounds 1, 2, and 4 reveals antiferromagnetic CuII-MnII intranode interactions (1, J ) -48.9 cm-1; 2, J ) -64.7 cm-1; and 4, J ) -60.4 cm-1; H ) -JSMnSCu), as well as weak internodes antiferromagnetic interactions (for compounds 1 and 4). In the case of 2, a weak ferromagnetic internode interaction occurs through the spin polarization mechanism. Introduction The node and spacer approach is widely employed in designing coordination polymers with various dimensionalities and network topologies.1 It relies upon the strong directionality of the coordination bonds established between the metal ions (nodes or connectors) and the exo-dentate ligands (spacers or linkers). The desired network topology can be achieved by choosing the appropriate metal ion (coordination number and geometry, charge, and hard-soft acid base (HSAB) behavior) and the suitable designed bridging ligand (denticity, shape, size, and HSAB behavior). Coordination polymers can be constructed from oligonuclear nodes as well.2 The metal ions interact with the divergent ligand through their easily accessible coordination sites. The presence of two or more metal ions confers to the node a higher geometrical flexibility. Moreover, the metal-metal intra- and internode interactions can lead to new redox, electric, or magnetic properties. The incorporation of the oligonuclear complexes into extended frameworks occurs through the following steps: (i) formation of the nodes in a preliminary step, followed by the reaction with the appropriate spacers,3 (ii) formation of the nodes as a result of the interaction of the metal ions with the spacers,4 and (iii) serendipitous assembly of the metal ions into clusters, which are then interconnected by spacer molecules. The formation of the nodes in the preliminary step can be achieved by employing compartmental ligands. A rich library of discrete heterometallic complexes, which can act as nodes, is available.5 The dissymmetric compartmental ligands are particularly suited * To whom correspondence should be addressed. E-mail: marius.andruh@ dnt.ro. † University of Bucharest. ‡ Università degli Studi di Firenze. § Universidad de La Laguna. # Université Pierre et Marie Curie.

Scheme 1

Scheme 2

for obtaining heterobimetallic complexes. These ligands are readily accessible and allow a good control over the number and the nature of the metal ions.

10.1021/cg700846x CCC: $40.75  2008 American Chemical Society Published on Web 01/11/2008

942 Crystal Growth & Design, Vol. 8, No. 3, 2008

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Table 1. Crystallographic Data, Details of Data Collection, and Structure Refinement Parameters for Compounds 1-5 compound chemical formula M (g mol-1) temperature (K) wavelength (Å) crystal system space group a (Å) b (Å) c (Å) R (°) β (°) γ (°) V (Å3) Z Dc (g cm-3) µ (mm-1) F(000) goodness-of-fit on F2 final R1, wR2[I > 2σ(I)] R1, wR2 (all data) largest diff. peak and hole (e Å-3)

1

2

3

4

5

C25H30CuMnN4O11 681.01 250(2) 0.71073 monoclinic P21/n(14) 11.997(4) 14.8880(19) 16.429(4) 90 102.35(2) 90 2866.5(12) 4 1.578 1.248 1400 1.021 0.0734, 0.1874 0.1660, 0.2237 0.755, -0.522

C79H88Cu3Mn3N6O31 1886.90 293(2) 0.71073 monoclinic P121/a1(14) 12.5763(12) 41.171(5) 16.873(3) 90 94.435(12) 90 8710(2) 4 1.407 1.219 3708 1.019 0.0888, 0.2155 0.2052, 0.2670 0.937, -0.508

C23H20CoCuN8O4 594.94 150 0.71069 monoclinic P121/n1(14) 8.5290(10) 15.5760(10) 18.3450(10) 90 95.3380(10) 90 2426.5(18) 4 1.629 1.608 1208 1.093 0.0526, 0.1462 0.0680, 0.1580 0.568, -0.765

C26H31CuMnNiN7O7 730.77 120 0.71069 triclinic P 1j(2) 9.179(5) 10.958(5) 15.453(5) 87.149(5) 82.558(5) 80.138(5) 1517.8(12) 2 1.599 1.773 748 1.147 0.0522, 0.1287 0.0619, 0.1377 1.698, -0.729

C40H40AgCu2KN6O8 1006.83 150 0.71069 monoclinic C12/m1(12) 13.813(5) 15.387(5) 9.766(5) 90 106.316(5) 90 1992.1(14) 2 1.679 1.710 1020 1.091 0.0341, 0.0912 0.0426, 0.0960 1.632, -0.483

The compartmental ligands derived from 3-methoxysalicylaldehyde (Scheme 1) and a diamine have been specially designed to obtain binuclear 3d-4f complexes.6 We have recently shown that such ligands can generate 3d-3d′ heterometallic systems as well.7 The reaction between the [CuL] mononuclear complex, cobalt(II) acetate, and potassium thiocyanate (KSCN) forms zigzag chains made up of alternating up and down dinuclear {LCuCo} units linked by thiocyanato bridges (L is the dianion of the Schiff-base resulting from the 2:1 condensation of 3-methoxysalicyladehyde with 1,3-propanediamine).7 This result prompted us

to further investigate the ability of such ligands to generate heterometallic complexes, with a special emphasis on the construction of new coordination polymers. In this paper, we report on coordination polymers that are obtained by employing [CuIIMnII] and [CuIICoII] nodes and various anionic spacers. Experimental Section Synthesis of [LCuMn(pzdc)(CH3OH)(H2O)] · H2O (1), [LCu Mn(trim)2/3(CH3OH)2/3(H2O)1/3] · 0.66(H2O) · 0.66(CH3OH) (2), [LCuCo(dca)2] (3), [LCu(CH3OH)(H2O)Mn(NC)2Ni(CN)2] · (H2O)(CH3-

Figure 1. (a) Perspective view of two nodes connected by the pzdc2- spacer in 1 along with the atom numbering scheme. (b) Perspective view of a chain in crystal 1.


Crystal Growth & Design, Vol. 8, No. 3, 2008 943

Figure 2. (a) Perspective view of the crystallographically independent nodes in crystal 2 along with the atom numbering scheme. (b) View of a ladder-like polymer in 2. CN) (4), and [{CuL}K{LCu}{Ag(CN)2}] (5). All starting materials were of reagent grade and were used without further purification. The [LCu] (L2- ) N,N′-propylene-bis-(3-methoxysalycilideneiminato)) precursor was prepared according to the literature.8 Compounds 1 and 2. A methanolic solution of [LCu] (0.02 mmol) was reacted with solid Mn(NO3)2 (0.02 mmol). Green crystals were obtained upon slow diffusion, in a test tube, through a CH3OH/H2O layer (1 mL), of the resulting mixture into an aqueous solution of the pyrazole-3,5-dicarboxylic acid (0.02 mmol) deprotonated by LiOH (0.04 mmol) or trimesic acid (0.04 mmol) deprotonated by LiOH (0.12 mmol). Elemental anal. for 1. Calcd for C25H28CuMnN4O10 ) [LCuMn (pzdc)(CH3OH)(H2O)]: C, 45.28; H, 4.22; N, 8.45. Found: C, 44.21; H, 4.42; N, 8.25. IR bands (KBr, cm-1): 3410, 2938, 1623, 1480, 1411, 1338, 1312, 1242, 1229, 1074, 1013, 955, 855, 790, 743, 637, and 464. Elemental anal. for 2. Calcd for C77H88Cu3Mn3N6O31: C, 48.08; H, 4.26; N, 4.48. Found: C, 46.96; H, 4.57; N, 4.14. IR bands (KBr, cm-1): 3407, 2935, 1616, 1557, 1476, 1436, 1366, 1306, 1247, 1228, 1073, 953, 854, 770, 743, 637, and 465.

Compound 3. A methanolic solution of [LCu] (0.03 mmol) was reacted with solid Co(NO3)2 · 6H2O (0.03 mmol). Dark blue crystals were obtained upon slow diffusion, in a test tube, through a CH3OH/ H2O layer (1 mL), of the resulting mixture into an aqueous solution of NaN(CN)2 (0.06 mmol). Elemental anal. for 3. Calcd for C23H20 CoCuN8O4: C, 46.42; H, 3.36; N, 18.83. Found: C, 46.90; H, 3.63; N, 18.72. IR bands (KBr, cm-1): 2937, 2844, 2295, 2234, 2174, 1622, 1477, 1413, 1299, 1252, 1229, 1075, 955, 856, 740, 645, and 436. Compound 4. A methanolic solution of [LCu] (0.01 mmol) was reacted with solid Mn(NO3)2 (0.01 mmol). Green crystals were obtained by slow diffusion, in an H-shaped tube, of the resulting mixture into an aqueous solution of K2[Ni(CN)4] (0.02 mmol). Elemental anal. for 4. Calcd for C24H26CuMnNiN6O6 ) [LCu(CH3OH)(H2O)Mn(NC)2Ni(CN)2]: C, 42.90; H, 3.87; N, 12.51. Found: C, 42.96; H, 3.85; N, 12.54. IR bands (KBr, cm-1): 3436, 2942, 2143, 1622, 1561, 1476, 1416, 1306, 1249, 1230, 1075, 954, 856, 742, 637, and 424. Compound 5. Dark green crystals were obtained, in a test tube kept in the dark, by slow diffusion of a methanolic solution of [LCu] (0.01


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Figure 3. (a) View of a node and of the coordinated dca ions in crystal 3 along with the atom labeling scheme. (b) Perspective view of a chain in 3.

Figure 4. (a) View of a node and of two spacers in 4 along with the atom labeling scheme. (b) Perspective view of a chain in crystal 4.



[C(37a) and C(37b)] were assigned with a population factor of 0.65 and 0.35, respectively. Geometrical calculations were performed with the PARST97 program.12 Crystallographic data and refinement parameters are collected in Table 1. CCDC reference numbers: 653726-653730.

Results and Discussion

Figure 5. (a) Perspective view of the asymmetric unit in crystal 5. (b) View of the heterotrimetallic chain in crystal 5. mmol) into an aqueous solution of K[Ag(CN)2] (0.02 mmol). Elemental anal. for 5. Calcd for C40H40AgCu2KN6O8 ) [{CuL}K{LCu}{Ag(CN)2}]: C, 47.67; H, 3.97; N, 8.34. Found: C, 48.06; H, 5.15; N, 7.22. IR bands (KBr, cm-1): 3438, 2944, 2160, 2134, 1621, 1561, 1476, 1415, 1308, 1247, 1229, 1074, 954, 856, 740, 637, and 423. Physical Measurements. IR spectra were recorded on a Bio-Rad FTS 135 instrument in the 400–4000 cm-1 range. Samples were run as KBr pellets. Magnetic data were obtained with a Cryogenic SQUID magnetometer. They were corrected for the diamagnetic contribution of the samples estimated using Pascal’s constants and the sample holders. X-ray Structure Determination. Intensity data for compounds 1 and 2 were collected with a Bruker-Nonius Kappa charge-coupled device (CCD) with graphite-monochromated MoKR radiation (λ ) 0.7173 Å). The unit-cell parameters determination, the data collection strategy, and the integration were carried out with the Nonius EVAL14 suite of programs.9 The structure was solved by direct methods using the SIR97 program10 and refined anisotropically for non-hydrogen atoms by full-matrix least-squares methods by using the SHELXL-97 software package.11 X-ray diffraction measurements of 3, 4, and 5 were carried out on an Oxford Diffraction Xcalibur3 diffractometer equipped with a CCD area detector and with MoKR radiation (λ ) 0.71069 Å). The data collection was performed with the CrysAlis CCD program (CrysAlis CCD, Oxford Diffraction Ltd., Version 1.171.31.2 (release 07-07-2006 CrysAlis171 .NET)), and the data reduction was performed with the CrysAlis RED program (CrysAlis RED, Oxford Diffraction Ltd., Version 1.171.31.2 (release 07-07-2006 CrysAlis171 .NET)). Absorption corrections were applied through the program ABSPACK (CrysAlis RED, Oxford Diffraction Ltd., Version 1.171.31.2 (release 07-07-2006 CrysAlis171 .NET)). The structures were solved by using the package SIR-9710 and subsequently refined on the F2 values by the full-matrix least-squares programs SHELXL-97.11All non-hydrogen atoms were refined anisotropically. The hydrogen atoms were set in calculated positions and refined isotropically. In compound 3, the carbon atom labeled C(37) was affected by disorder, and two different positions

Our synthetic approach toward heterometallic coordination polymers consists of self-assembly processes between preformed heterobinuclear cations and divergent ligands (Scheme 2). Two nodes are employed in the present work: [LCuMn]2+ and [LCuCo]2+. As spacers, we have chosen the dianion of the pzdc2-, the trianion of the trim3-, the tetracyanonickelate(II) anion ([Ni(CN)4]2-), and the dicyanamide anion (dca-). Four new coordination polymers have been obtained: [LCuMn(pzdc) (CH3OH)(H2O)] · H2O (1), [LCuMn(trim)2/3(CH3OH)2/3(H2O)1/3] · 0.66(H2O) · 0.66(CH3OH) (2), [LCuCo(dca)2] (3), and [LCu(CH3OH)(H2O)Mn(NC)2Ni(CN)2] · (H2O)(CH3CN) (4). The fifth compound, [{CuL}K{LCu}{Ag(CN)2}] (5), results from the reaction of [CuL] with K[Ag(CN)2]. Coordination Polymers with Polycarboxylato Bridges. Let us first discuss the crystal structures of the two coordination polymers constructed from the {LCuMn} tectons and the anions of the pzdc2- and trim3-. The structure of [LCuMn(pzdc) (CH3OH)(H2O)] · H2O (1) consists of chains with {LCuMn} nodes connected by the pyrazole-dicarboxylato spacers. The pzdc2- ion coordinates the manganese ion from a node through one nitrogen and one oxygen atom from the vicinal carboxylato group and the manganese ion from the neighboring node through an oxygen atom from the other carboxylato group (Figure 1a). The manganese ion is hosted in the external compartment of the ligand and exhibits a coordination number of seven: four oxygen atoms from the organic ligand, two oxygen atoms from two carboxylato groups arising from two pzdc2- bridges, and one nitrogen atom from the pyrazole ring of one bridge. The copper ion is hosted in the N2O2 compartment of the Schiffbase ligand and displays an elongated octahedral geometry: the equatorial plane is formed by two nitrogen and two oxygen atoms from the inner compartment of the ligand [Cu1-O1 ) 1.945(4), Cu1-O2 ) 1.960(4), Cu1-N2 ) 1.971(6), and Cu1-N1 ) 2.002(6) Å], whereas the apical positions are occupied by one aqua ligand [Cu1-O10 ) 2.864(12) Å] and one methanol molecule [Cu1-O3 ) 2.406(5) Å]. The Cu · · · Mn intranode distance is 3.317 Å. The pzdc2- ligands connect the bimetallic nodes by coordination to only manganese ions, resulting in chains (Figure 1b). Although the pzdc2- ion seems to be appropriate for generating extended structures, the number of polynuclear complexes it generates is limited to only a few examples.13 The trim3- anion is currently employed in crystal engineering. Numerous complexes, ranging from high-nuclearity clusters to

Table 2. Selected Bond Distances (Å) and Angles (°) for Compound 1 Cu1-O1 Cu1-O2 Cu1-N2 Cu1-N1 Cu1-O3 Mn1-O6 Mn1-O2 Mn1-O8 Mn1-O1 Mn1-N4 Mn1-O4 Mn1-O5 O1-Cu1-O2 O1-Cu1-N2 O2-Cu1-N2

1.945(4) 1.960(4) 1.971(6) 2.002(6) 2.4046(5) 2.102(4) 2.176(4) 2.195(4) 2.199(4) 2.270(5) 2.456(5) 2.463(5) 78.49(17) 166.3(2) 91.7(2)

O1-Cu1-N1 O2-Cu1-N1 N2-Cu1-N1 O1-Cu1-O3 O2-Cu1-O3 N2-Cu1-O3 N1-Cu1-O3 O6-Mn1-O2 O6-Mn1-O8 O2-Mn1-O8 O6-Mn1-O1 O2-Mn1-O1 O8-Mn1-O1 O6-Mn1-N4 O2-Mn1-N4

92.1(2) 170.0(2) 98.2(3) 95.77(18) 87.56(18) 93.3(2) 90.3(2) 107.79(18) 88.78(16) 140.44(17) 98.89(17) 68.76(15) 145.45(18) 161.08(18) 89.08(17)

O8-Mn1-N4 O1-Mn1-N4 O6-Mn1-O4 O2-Mn1-O4 O8-Mn1-O4 O1-Mn1-O4 N4-Mn1-O4 O6-Mn1-O5 O2-Mn1-O5 O8-Mn1-O5 O1-Mn1-O5 N4-Mn1-O5 O4-Mn1-O5

72.52(16) 95.17(17) 82.84(18) 135.60(16) 80.77(17) 67.02(15) 91.12(18) 89.59(17) 67.54(16) 77.22(17) 135.99(16) 89.05(18) 156.86(16)


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Table 3. Selected Bond Distances (Å) and Angles (°) for Compound 2 Cu1-O2 Cu1-O1 Cu1-N1 Cu1-N2 Cu1-O1MC Cu2-O6 Cu2-O5 Cu2-N4 Cu2-N3 Cu2-O22 Cu3-O9 Cu3-O10 Cu3-N6 Cu3-N5 Mn1-O1 Mn1-O2 Mn1-O15 Mn1-O20 Mn1-O19 Mn1-O4 Mn1-O3 Mn2-O1W Mn2-O6 Mn2-O5 Mn2-O14 Mn2-O13 Mn2-O8 Mn2-O7 Mn3-O23 Mn3-O9 Mn3-O10 Mn3-O18 Mn3-O17 Mn3-O11 Mn3-O12 O2-Cu1-O1 O2-Cu1-N1 O1-Cu1-N1 O2-Cu1-N2 O1-Cu1-N2 N1-Cu1-N2 O2-Cu1-O1MC

1.951(5) 1.956(5) 1.966(7) 1.985(7) 2.410(6) 1.936(6) 1.949(5) 1.970(9) 2.011(9) 2.319(6) 1.938(5) 1.943(5) 1.972(7) 1.978(7) 2.200(5) 2.210(5) 2.222(6) 2.262(5) 2.334(5) 2.413(6) 2.426(6) 2.102(6) 2.135(5) 2.167(5) 2.242(5) 2.256(5) 2.460(7) 2.470(6) 2.088(5) 2.178(5) 2.190(6) 2.235(6) 2.284(5) 2.385(6) 2.450(6) 79.2(2) 168.8(3) 91.2(3) 91.8(3) 170.9(3) 97.7(3) 89.5(2)

O1-Cu1-O1MC N1-Cu1-O1MC N2-Cu1-O1MC O6-Cu2-O5 O6-Cu2-N4 O5-Cu2-N4 O6-Cu2-N3 O5-Cu2-N3 N4-Cu2-N3 O6-Cu2-O22 O5-Cu2-O22 N4-Cu2-O22 N3-Cu2-O22 O9-Cu3-O10 O9-Cu3-N6 O10-Cu3-N6 O9-Cu3-N5 O10-Cu3-N5 N6-Cu3-N5 O1-Mn1-O2 O1-Mn1-O15 O2-Mn1-O15 O1-Mn1-O20 O2-Mn1-O20 O15-Mn1-O20 O1-Mn1-O19 O2-Mn1-O19 O15-Mn1-O19 O20-Mn1-O19 O1-Mn1-O4 O2-Mn1-O4 O15-Mn1-O4 O20-Mn1-O4 O19-Mn1-O4 O1-Mn1-O3 O2-Mn1-O3 O15-Mn1-O3 O20-Mn1-O3 O19-Mn1-O3 O4-Mn1-O3 O1W-Mn2-O6 O1W-Mn2-O5

Table 4. Selected Bond Distances (Å) and Angles (°) for Compound 3a Cu1-O4 Cu1-O3 Cu1-N3 Cu1-N5 Cu1-N8 Co1-N1 Co1-N21 Co1-O4 Co1-O3

1.955(3) 1.955(3) 1.977(4) 1.983(4) 2.247(4) 1.979(4) 1.995(4) 2.013(3) 2.016(3)

O4-Cu1-O3 O4-Cu1-N3 O3-Cu1-N3 O4-Cu1-N5 O3-Cu1-N5 N3-Cu1-N5 O4-Cu1-N8 O3-Cu1-N8 N3-Cu1-N8

77.35(12) 165.85(14) 91.66(14) 90.75(15) 163.07(15) 97.94(16) 92.05(14) 98.61(14) 98.47(16)

N5-Cu1-N8 N1-Co1-N2 N1-Co1-O4 N2-Co1-O4 N1-Co1-O3 N2-Co1-O3 O4-Co1-O3

93.83(16) 117.53(17) 120.31(14) 108.21(16) 113.79(14) 115.19(15) 74.65(11)

a Symmetry transformations used to generate equivalent atoms: (1) x + 1/2, -y + 1/2, z + 1/2.

high-dimensionality coordination polymers, have been described.14 The self-assembly process involving the mononuclear copper complex, [CuL], MnII ions, and the trim3- ion leads to [LCuMn(trim)2/3(CH3OH)2/3(H2O)1/3] · 0.66(H2O) · 0.66(CH3OH) 2, a 1D coordination polymer with a unique topology. As in the case of complex 1, the copper ion is hosted in the inner compartment of the ligand, and the manganese ion is hosted in the external one. There are three crystallographically independent copper ions and three independent manganese ions. Two of the copper ions, Cu1 and Cu3, do not interact with the spacer. They are both pentacoordinated, with a square pyramidal geometry: the basal plane is formed by the N2O2 compartment of the organic ligand, and their apical positions are occupied by methanol molecules. Cu2 displays a square pyramidal geometry as well, but the apical position is occupied by an oxygen atom arising from the trim3- ion. The three types of manganese ions are

91.6(2) 96.5(3) 89.4(2) 78.4(2) 169.5(3) 91.2(3) 90.0(4) 158.8(3) 99.3(4) 93.9(2) 98.9(2) 89.2(3) 99.6(3) 78.2(2) 91.7(3) 169.6(3) 168.2(2) 91.2(3) 98.7(3) 68.71(19) 125.4(2) 119.4(2) 127.3(2) 137.63(19) 84.9(2) 91.8(2) 87.1(2) 139.2(2) 56.8(2) 135.6(2) 67.2(2) 82.3(2) 84.2(2) 80.6(2) 67.6(2) 135.6(2) 81.4(2) 78.0(2) 101.4(2) 156.9(2) 102.3(2) 95.4(2)

O6-Mn2-O5 O1W-Mn2-O14 O6-Mn2-O14 O5-Mn2-O14 O1W-Mn2-O13 O6-Mn2-O13 O5-Mn2-O13 O14-Mn2-O13 O1W-Mn2-O8 O6-Mn2-O8 O5-Mn2-O8 O14-Mn2-O8 O13-Mn2-O8 O1W-Mn2-O7 O6-Mn2-O7 O5-Mn2-O7 O14-Mn2-O7 O13-Mn2-O7 O8-Mn2-O7 O23-Mn3-O9 O23-Mn3-O10 O9-Mn3-O10 O23-Mn3-O18 O9-Mn3-O18 O10-Mn3-O18 O23-Mn3-O17 O9-Mn3-O17 O10-Mn3-O17 O18-Mn3-O17 O23-Mn3-O11 O9-Mn3-O11 O10-Mn3-O11 O18-Mn3-O11 O17-Mn3-O11 O23-Mn3-O12 O9-Mn3-O12 O10-Mn3-O12 O18-Mn3-O12 O17-Mn3-O12 O1-Mn3-O12

69.6(2) 153.6(2) 96.8(2) 108.3(2) 95.5(2) 141.0(2) 143.0(2) 58.52(19) 86.1(2) 68.8(2) 137.7(2) 84.1(2) 78.3(2) 87.5(2) 136.8(2) 67.6(2) 90.9(2) 77.7(2) 154.4(2) 111.3(2) 104.2(2) 68.11(19) 94.4(2) 139.6(2) 136.3(2) 151.9(2) 93.95(19) 96.3(2) 57.64(19) 88.0(2) 69.1(2) 137.1(2) 81.7(2) 89.9(2) 79.6(2) 136.2(2) 68.1(2) 77.3(2) 90.8(2) 154.6(2)

coordinated as follows: Mn1 is surrounded by eight oxygen atoms (four from the external compartment of the ligand and four from two chelating carboxylato groups arising from two spacers). The Mn1-O distances vary between 2.200(5) and 2.426(6) Å. Mn2 is heptacoordinated (four oxygen atoms from the compartmental ligand, two oxygen atoms from a chelating carboxylato group, and one aqua ligand). The Mn2-O distances range from 2.102(6) to 2.470(6) Å. Finally, Mn3 is also heptacoordinated by seven oxygen atoms (four from the Schiffbase, two from a chelating carboxylate, and one from a monodentate carboxylate arising from another spacer). The seven Mn3-O distances are range from 2.088(5) to 2.450(6) Å. The high coordination numbers observed with the manganese ions in 2 are not surprising because for MnII, as a high-spin d5 ion, the crystal field stabilization energy is zero for any coordination geometry. The intranode distances between the metal ions are as follows: Mn1 · · · Cu1 ) 3.3243 Å, Mn2 · · · Cu2 ) 3.255 Å, and Mn3 · · · Cu3 ) 3.314 Å. The binuclear nodes are connected by trim3- ions, resulting in a ladder-like topology (Figure 2b). The coordination polymer is constructed from two types of trim3- spacers, A and B (Figure 2b). The parallel chains are formed by the [Cu1Mn1] and [Cu3Mn3] nodes, whereas the ladder steps are formed by the [Cu2Mn2] ones. The A trim3ions coordinate to only manganese ions (each carboxylato group acts as a chelate toward Mn1, Mn2, and Mn3). The three craboxylato groups of the B trim3- ions are involved in coordination as follows: one carboxylato group acts as a chelate



Table 5. Selected Bond Distances (Å) and Angles (°) for Compound 4 Cu1-O3 Cu1-O5 Cu1-N5 Cu1-N6 Cu1-O6 Mn1-O5 Mn1-N1 Mn1-O3 Mn1-N4 Mn1-O4 Mn1-O2 Mn1-O1 Ni1-C29 Ni1-C17 Ni2-C18 Ni2-C16 O3-Cu1-O5

1.940(3) 1.951(3) 1.982(4) 1.988(3) 2.435(4) 2.185(3) 2.195(4) 2.204(3) 2.208(3) 2.234(3) 2.386(3) 2.430(3) 1.867(4) 1.868(4) 1.868(4) 1.870(5) 77.99(11)

O3-Cu1-N5 O5-Cu1-N5 O3-Cu1-N6 O5-Cu1-N6 N5-Cu1-N6 O3-Cu1-O6 O5-Cu1-O6 N5-Cu1-O6 N6-Cu1-O6 C29-Ni1-C17 C18-Ni2-C16 O5-Mn1-N1 O5-Mn1-O3 N1-Mn1-O3 O5-Mn1-N4 N1-Mn1-N4 O3-Mn1-N4

91.03(13) 168.88(14) 167.84(13) 91.90(12) 98.77(15) 94.71(12) 88.65(12) 94.09(14) 91.85(14) 90.66(18) 90.03(18) 140.39(12) 67.81(10) 144.08(12) 98.95(11) 100.56(13) 93.13(12)

O5-Mn1-O4 N1-Mn1-O4 O3-Mn1-O4 N4-Mn1-O4 O5-Mn1-O2 N1-Mn1-O2 O3-Mn1-O2 N4-Mn1-O2 O4-Mn1-O2 O5-Mn1-O1 N1-Mn1-O1 O3-Mn1-O1 N4-Mn1-O1 O4-Mn1-O1 O2-Mn1-O1

84.00(11) 80.90(13) 80.85(12) 172.86(12) 136.38(10) 80.70(12) 68.62(10) 81.43(12) 91.95(11) 67.95(9) 80.72(11) 135.06(10) 86.16(11) 100.97(11) 154.10(10)

Table 6. Selected Bond Distances (Å) and Angles (°) for Compound 5a Ag1-C33 Cu1-O2 Cu1-N2 Cu1-N5 O2-K1ii O4-K1ii Cu1-K1

2.065(4) 1.938(2) 2.004(2) 2.386(3) 2.744(2) 2.836(2) 3.769(2)

O2i-Cu1-O2 O2i-Cu1-N2 O2-Cu1-N2 N2-Cu1-N2i O2-Cu1-N5 N2-Cu1-N5 O2iii-K1-O2v

79.34(11) 166.76(9) 90.74(9) 97.56(14) 99.34(5) 90.86(6) 53.64(8)

O2iii-K1-O2vi O2iii-K1-O4iv O2iv-K1-O4iv O2v -K1-O4iv O2vi -K1-O4iv O4iv-K1-O4vi O4iii-K1-O4vi

126.36(8) 124.28(5) 55.72(5) 79.87(6) 100.13(6) 110.01(9) 69.99(9)

a Symmetry transformations used to generate equivalent atoms: (i) -x, -y, -z; (ii) x, -y, z; (iii) x, y, -1 + z; (iv) -0.5 + x, 0.5 - y, z; (v) 0.5 + x, 0.5 - y, z; (vi) 1 - x, y, 1 - z; (vii) x, -y, 1 + z; (viii) 1 - x, -y, 1 - z; (ix) x, y, 1 + z.

toward Mn1, the second one is coordinated to Mn3 through one oxygen atom, and the third one interacts with Cu2 through one oxygen atom. Short and long distances between the rungs alternate along the ladder (for example, the alternate distances between the Cu2 ions belonging to adjacent steps are 6.573 and 15.377 Å). We recall here that this ladder motif has been observed with a system constructed from trim3- ions and two types of cationic nodes: {Co(bipy)(H2O)}2+ and {Co(H2O)4}2+.15 In this case, unlike in the case of 2, the rungs, containing the {Co(H2O)4}2+ nodes, are equidistant. A Coordination Polymer with Dicyanamido Bridges. The dicyanamido(dca)-bridged polymer, [LCuCo(dca)2] (3), crystallizes from a solution containing [CuL], cobalt nitrate, and sodium dicyanamide. Its crystal structure consists of linear chains, resulting from the connection of the [CuCo] nodes through single µ1,5-dca bridges (one end of the dca bridge is coordinated into the apical position of the copper ion from a node and the other one to the cobalt ion from the next node). Within each dinuclear {LCuCo} unit (Figure 3a), the copper and cobalt ions are bridged by two phenoxo oxygen atoms belonging to the ligand L, with a Cu-Co separation equal to 3.123 Å. The copper ion is pentacoordinated with a square pyramidal geometry: the basal plane is formed by the four atoms of the N2O2 chromophore, and the apical position is occupied by one nitrogen arising from the bridge, as shown in Figure 3b. It is more delicate to state precisely the cobalt coordination environment. At first sight, a tetrahedral environment comprising the two phenoxo oxygen atoms of the bridge and the two nitrogen atoms from the two coordinated dca- ions can be envisaged (one bridging, the other one terminal). However, the values of the Co-O (methoxy oxygen atoms) distances (Co1-O1 ) 2.452(3) Å and Co1-O2 ) 2.450(4) Å) are not large enough to discard the eventuality of Co-O bonds. In this case, the hexacoordinate cobalt ion is in a strongly distorted (4 + 2) octahedral geometry. Within the chain, the Cu · · · Co distance through the dca- bridge is equal to 8.246 Å. Heterotrimetallic Coordination Polymers. Anionic metal complexes with potentially bridging ligands can also be

employed as spacers. Among these, the most popular are the cyano-complexes, [M(CN)n]q-, which have an enormous synthetic potential in designing heterometal complexes.16 The tetracyanocomplexes, [M(CN)4]2-, can interact with a second metal ion and with one, two, three, or all of the four CN groups.17 Compound 4, [LCu(CH3OH)(H2O)Mn(NC)2Ni(CN)2] · (H2O)(CH3CN), consists of linear zigzag chains constructed from [CuMn] nodes connected by [Ni(CN)4]2- spacers (Figure 4). It has been obtained by reacting [CuL] with manganese(II) nitrate and K2[Ni(CN)4]. The [Ni(CN)4]2- spacers interact with the manganese(II) ions from two nodes through two trans-CN groups (Figure 4a). The manganese ions are heptacoordinated: four oxygen atoms arising from the O2O2′ compartment (Mn-O distances varying between 2.185(3) and 2.430(3) Å), one methanol molecule (Mn1-O4 ) 2.234(3) Å), and two nitrogen atoms from the cyano groups (Mn1-N1 ) 2.195(4) Å and Mn1-N4 ) 2.208(3) Å). The copper ion is pentacoordinated with a square pyramidal geometry: the basal plane is formed by the four atoms of the N2O2 compartment, and the apical position is occupied by one aqua ligand, as shown in Figure 4b. The intranode Cu · · · Mn distance is 3.320 Å. The distance between the manganese and nickel ions bridged by the cyano group is 5.077 Å (Mn1 · · · Ni1 ) 5.180 Å and Mn1 · · · Ni2 ) 5.078 Å). Heterotrimetallic coordination polymers can also be obtained by reacting the [CuL] complex with bimetallic ionic complexes; for example, K[Ag(CN)2], the “naked” (actually hydrated) potassium ion, can be coordinated by the second compartment of the organic ligand, and the [Ag(CN)]- ion acts as a spacer. Indeed, the reaction between [CuL] and K[Ag(CN)2] leads to a heterotrimetallic coordination polymer, [{CuL}K{LCu}{Ag (CN)2}] 5, which is constructed from centrosymmetric {(CuL)2K} nodes and [Ag(CN)2]- spacers. The trinuclear node results from the coordination of two [CuL] complexes, through their O2O2′ compartments, to one potassium cation. This leads to a coordination number of eight (Figure 5a). The K-O distances vary between 2.744(2) and 2.836(2) Å. The two cyano groups from the spacers are coordinated into the apical positions


Branzea et al.

Selected bond distances and angles for complexes 1-5 are collected in Tables 2, 3, 4, 5, and 6. Magnetic Properties. The main interest in heterometallic complexes arises from their magnetic properties. The combination of metal ions carrying different spins is an important chapter in modern molecular magnetism.18 The magnetic properties of complexes 1, 2, and 4 have been investigated between 1.8 and 300 K. The χMT vs T curves are displayed in Figure 6. They are quite similar for each compound. The room temperature values of the product (per CuIIMnII unit) for the three compounds are 1. 4.20, 2, 3.85, and 4, 3.93 cm3 · mol-1 · K. These values are lower than the expected one (4.75 cm3 · mol-1 · K) for one [CuMn] pair with uncoupled ions (assuming gCu ) gMn ) 2), suggesting that the intranode antiferromagnetic interaction is effective even at room temperature. When the temperature is lowered, χMT shows a similar variation for the three compounds, namely it decreases continuously down to 44 K for 1, 64 K for 2, and 54 K for 4, reaching a plateau. For compounds 1 and 4, χMT then decreases abruptly. This behavior can be interpreted as follows: upon cooling, the CuII and MnII ions within each node are antiferromagnetically coupled. Indeed, the plateau observed in the three χMT vs T curves corresponds to S ) 2. The further decrease of the temperature is due to the intrachain antiferromagnetic interactions of the S ) 2 spins and to zero field splitting effects. In the case of compound 2, a slow increase of χMT is observed below 14 K, followed by a drop at 4 K. The increase of χMT below 14 K is due to the ferromagnetic coupling among the S ) 2 spin units, promoted by the trim3- anion (inset of Figure 6b). Indeed, the trim3- anion in 2 fulfills the necessary conditions to mediate a ferromagnetic coupling through the spin polarization mechanism: the whole bridging molecule is planar, and the metallic centers are separated by an odd number of atoms.14h,19 The magnetic data can be fitted for temperatures higher than those corresponding to the plateau by considering only the binuclear nodes. For the CuII(S ) 1/2)-MnII(S ) 5/2) system, the energies of the low-lying spin states are obtained by using the isotropic spin Hamiltonian: H ) -JSMnSCu, which leads to the following equation describing the temperature dependence of the susceptibility, χM: χM ) [2Nβ2/(T - θ)]([5g22 + 14g32 exp(x)]/[5 + 7 exp(x)]) with x ) 3J/kT, g2 ) (7gMn - gCu)/6, and g3 ) (5gMn + gCu)/6

Figure 6. χMT vs T curves for (a) compound 1 (inset: magnetization vs field curves at 2 and 4 K; solid lines: calculated Brillouin curves for S ) 2), (b) compound 2 (inset: χMT vsT between 2 and 20 K), and (c) compound 4.

Scheme 3

The Weiss term, θ, was included in order to take into account the internodes and other intermolecular interactions. The leastsquares fit to the data leads to the following values: compound 1: J ) -48.9 cm-1, gCu ) 2.10, gMn ) 1.99, θ ) -0.41 K; compound 2: J ) -64.7 cm-1, gCu ) 2.08, gMn ) 1.95, θ ) -0.05 K (mean values for the three crystallographically nonequivalent nodes); compound 4: J ) -60.4 cm-1, gCu ) 2.09, gMn ) 1.98, θ ) -0.39 K. The ground S ) 2 state has been confirmed also by magnetization vs field measurements (see inset of Figure 6a for compound 1). Conclusions

of the copper ions (Figure 5b). The intranode K · · · Cu distance is 3.769 Å. The distance between the cyano-bridged Cu(II) and Ag(I) ions is 5.465 Å.

The examples presented herein illustrate the versatility of the heterobinuclear nodes in designing coordination polymers. The spacers can interact with only one type of metal ions from different nodes (Scheme 3A), or they can connect one type of metal ion from a node with another type from the next node (Scheme 3B). The network topology is also influenced by the number of connecting groups (COO, CN) and their spatial orientation.


Acknowledgment. D.G.B. is grateful to the European Community for a Marie Curie Fellowship for her stay at the MC Training Site MolMag in Florence and O.F. to the Ministerio Español de Educación y Ciencia for a predoctoral fellowship. Financial support from the EC “MAGMANet” NMP3-CT-2005515767 and the CEEX Program (Project D11-17) and the Ministerio Español de Educaci“n y Ciencia (Projects MAT200403112 and ”Factoria de Cristalizaci“n” Consolider-Ingenio200600015) is gratefully acknowledged.

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CG700846X

Heterobinuclear Complexes as Tectons in Designing Coordination

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