Tuning magnetic exchange using the versatile azide ligand

Inorganica Chimica Acta 361 (2008) 3847–3855

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Tuning magnetic exchange using the versatile azide ligand Guillaume Chastanet a,b,*, Boris Le Guennic b, Christophe Aronica a,b, Guillaume Pilet a, Dominique Luneau a, Marie-Laure Bonnet b, Vincent Robert b a b

Laboratoire des Multimatériaux et Interfaces (UMR 5615) CNRS, Université Claude Bernard Lyon 1, Campus de la Doua, 69622 Villeurbanne Cedex, France Laboratoire de Chimie (UMR 5182), Ecole Normale Supérieure de Lyon, 46 Allée d’Italie, 69364 Lyon Cedex 07, France

a r t i c l e

i n f o

Article history: Received 13 February 2008 Accepted 27 February 2008 Available online 4 March 2008 This paper is dedicated to Dante Gatteschi for his great contribution to science and the wonderful time spent in his laboratory. Keywords: Coordination chains 3D metal ions Azide Magnetic properties X-ray structures Ab initio calculations

a b s t r a c t The ability of the azido ligand to generate various chemical architectures and magnetic couplings is surveyed, using Cu(II) and Ni(II) derivatives. Depending on the ratio between the azide salt, the metal salt and the tridentate Schiff base LH (L:1,1,1-trifluoro-7-(dimethylamino)-4-methyl-5-aza-3-hepten-2onato), molecular bimetallic [CuL(l1,3-N3)]2 (1) and monometallic [NiL(l1-N3)] (2) as well as extended {[CuL(l1,1-N3)]}n (3) and {[Ni2(l1,1-N3)(l1,3-N3)(L)2(MeOH)2]}n (4) chains were obtained. These systems were fully characterized by X-ray diffraction and magnetic susceptibility measurements. In 1, the asymmetrical double l1,3-N3 bridge mediates a ferromagnetic exchange whereas 3 and 4 exhibit unusual symmetric and asymmetric single l1,1-N3 coordination modes that transmit weak ferromagnetic interactions. Ab initio calculations were systematically performed to clarify the origin of the observed magnetic exchanges and to study the role of the asymmetric coordination modes on the magnetic coupling. Ó 2008 Elsevier B.V. All rights reserved.

1. Introduction The development of new functional molecular-based materials associated with the miniaturization of electronic devices has led to tremendous progresses in low-dimensional systems, in both chemistry and physics communities [1,2]. One of the main challenges in the synthesis of such systems is to prevent the local magnetic moments from cancelling out. Obviously, this condition is fulfilled as soon as ferromagnetic interactions dominate. However, in the presence of most frequent antiferromagnetic interactions, different strategies have been developed. Especially in the case of 1D systems, pioneer approaches were devoted to regular heterospin ferrimagnetic chains [2] holding alternating spin carriers, coupled through a unique exchange interaction. Another strategy has consisted in varying the magnetic exchange constants between homospin carriers [3]. Finally, the use of strong anisotropic metal ions has generated the promising field of the single-chain magnets (SCMs) [4]. Pseudo-halide anions are known to be excellent ligands to obtain materials with several structures’ dimensionalities. Among

* Corresponding author. Address: Laboratoire des Multimatériaux et Interfaces (UMR 5615) CNRS, Université Claude Bernard Lyon 1, Campus de la Doua, 69622 Villeurbanne Cedex, France. Tel.: +33 (0)4 72 72 88 55. E-mail address: [email protected] (G. Chastanet). 0020-1693/$ - see front matter Ó 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.ica.2008.02.045

these, the azido ligand turned out to be extremely versatile in linking metals and a remarkable magnetic coupler for propagating interactions between paramagnetic ions [5,6]. The structural variety of the azido-complexes ranges from molecular clusters [6] to extended 1D [5,7], 2D [8] and 3D [9] materials. The versatility of the N3  ligand arises from the different coordination modes it can offer. The most encountered are the end-to-end (l1,3-N3, EE) and end-on (l1,1-N3, EO) modes (Scheme 1)[5] whereas triply l1,1,1 [10], l1,1,3 [11], or quadruply l1,1,1,1 [12], l1,1,3,3 [13] modes remain relatively rare. An additional interesting feature stands in the number of azide ions involved in the coordination of the metal centres. One, two or three azides can be encountered, both for the EE and EO modes, two bridges being the most common coordination [5]. Furthermore, different bridging modes of the azide ions may simultaneously exist in the same species, leading to original alternating topologies and magnetic behaviours exemplified by the widespread {EO-EE}n sequence [5,7] and the less common, {EO-EE-EE}n, {EO-EO-EO-EE}n, {EO-EO-EO-EO-EE}n chain assemblies [14]. Concerning the magnetism, the sign and amplitude of the magnetic exchange may be tuned by differences in the bonding and symmetry modes of the azido-bridge. Several magnetostructural and theoretical studies have evidenced general trends: the EE mode favours antiferromagnetic interaction whereas the EO one leads to ferromagnetic behaviour [5,15,16]. These studies have also

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N

N

N

N

N

2.1. Syntheses

Cu

Cu N

2. Experimental

N

Cu

D

N

N

Cu

D

d

N

d

N N Scheme 1. EE (left) and EO (right) coordination modes of the azide bridge. c = D  d measures the asymmetry of the coordination mode (‘‘shearing-like” distortion).

shown that structural parameters, such as the M–N(azide)–M angle, greatly affect the nature and magnitude of the magnetic exchange in these systems. Apart from the tremendously abundant Cu(II) 1-D compounds, Ni(II), Mn(II), Fe(II) and Co(II) azido-bridged chains have been reported and some of them show promising SCM behaviour [17]. While the azide has the ability to link metal centres, it should be associated to other ligands to complete the coordination sphere of the metal ions. Among those, Schiff base molecules built on the condensation of diketone with amines offer a broad panel of ligands widely used in coordination chemistry. Depending on the amine involved in the synthesis, the multidentate character of the ligand as well as the nuclearity of the resulting complexes can be tuned as illustrated by numerous examples in the literature. As part of this work, we recently studied the coordination ability of tridentate Schiff base ligands holding fluorinated group in order to facilitated the crystallizations of the compounds [18–20]. We report here the association of the LH ligand (1,1,1-trifluoro7-(dimethylamino)-4-methyl-5-aza-3-hepten-2-onate) shown in Scheme 2, with azido and metal ions in different ratio. It has led to the synthesis of binuclear [CuL(l1,3-N3)]2 (1) [19] and chain {[CuL(l1,1-N3)]}n (3) systems based on Cu(II) cation and of mononuclear [NiL(l1-N3)] (2) and chain {[Ni2(l1,1-N3)(l1,3-N3)(L)2(MeOH)2]}n (4) [20] architectures with Ni(II). All of these compounds were structurally characterized and turned out to be a perfect illustration of the versatility of the azide ligand. Indeed, double EE bridges are encountered in 1 whereas only the single EO coordination mode is present along the copper chain 3. Finally, an alternation of single EE and EO modes appeared in the nickel chain 4. This variety of architectures induces different magnetic behaviours that have been experimentally and theoretically studied. Magnetostructural correlations are discussed on the basis of these studies.

Caution! Although we did not experience any problem, azide complexes and perchlorate are potentially explosive. Small amount of material should be prepared and handled with care. The syntheses of the ligand LH, complex 1 [CuL(l1,3-N3)]2 and complex 4 {[Ni2(l1,1-N3)(l1,3-N3)(L)2(MeOH)2]}n have been previously reported [19–21]. 2.1.1. Complex [NiL(l1-N3)] (2) A solution of 0.238 g (1 mmol) of NiCl2  6H2O with 0.224 g (1 mmol) of the ligand (LH) in 20 mL of methanol was added to a 10 mL methanolic solution of 0.065 g (1 mmol) of the NaN3. 0.2 mL of triethylamine (1.4 mmol) was added to the resulting solution. After filtration, the solvent was removed by slow evaporation to get red crystals isolated upon filtration and suitable for single-crystal X-ray diffraction. Yield: 52%; Elemental Anal. Calc. (%) for NiC9H14N5OF3 (M = 323.9 g mol1): Ni, 18.1; C, 33.4; H, 4.36; N, 21.6; Found: Ni, 18.4; C, 32.9; H, 4.32; N, 20.7%. 2.1.2. Complex {[CuL(l1,1-N3)]}n (3) A solution of Cu(ClO4)2  6H2O (0.37 g, 1 mmol) in methanol (20 mL) was added to a 20 mL methanolic solution of the ligand (LH; 0.217 g, 1 mmol) followed by the addition of a solution of NaN3 (120 mg, 2 mmol) in methanol (10 mL). 0.2 mL of triethylamine (1.4 mmol) has been added and the solvent of the resulting solution was slowly evaporated in a week to give crystals isolated upon filtration. Yield: 48%; Elemental Anal. Calc. (%) for CuC9H14N5OF3 (M = 328.8 g mol1): Cu, 19.3; C, 32.9; H, 4.29; N, 21.3. Found: Cu, 19.4; C, 32.6; H, 4.32; N, 19.7. 2.2. Crystallographic data collection and refinement Diffraction data were collected at room temperature using a Nonius KappaCCD and the related analysis softwares [22]: Lorentz-polarization correction, peak integration and background determination were carried out with the DENZO program; frame scaling and unit-cell parameters refinement were made through the SCALEPACK program. The lattice constants were refined by leastsquare refinement. No absorption correction was applied to the data sets. The structure was solved by direct methods using the SIR97 program [23] combined to Fourier difference synthesis and refined against F using reflections with [I/r(I) > 2] and [I/r(I) > 3] for 3 and 4, respectively, via the CRYSTALS program [24]. All the thermal atomic displacements for non-hydrogen atoms have been refined with anisotropic terms. Hydrogen atoms have been located either theoretically or by Fourier difference. Crystal structures of 1 and 4 are already published [19,20]. 2.3. Magnetic measurements

F3C

O

LH

HN

N

Scheme 2. LH ligand.

Magnetic measurements were performed on polycrystalline samples using a Quantum Design SQUID magnetometer MPMSXL that works between 1.8 and 300 K for DC applied fields ranging from 5 to 5 T. The magnetic data were corrected for the sample holder and diamagnetic contributions. All our magnetic data were b ¼ fitted using the Heisenberg spin Hamiltonian written as H P 2 hi;ji J ij Si Sj . 2.4. Computational details All our calculations were performed using the crystal data and no geometry optimizations were undertaken. Since the systems

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3.1. Compound 1: [CuL(l1,3-N3)]2 The crystal structure of 1 consists of discrete neutral and centrosymmetric binuclear units with two azido groups bridging in a EE fashion (l1,3) two Cu(II) ions (Fig. 1) [19]. As generally observed,

1.0

0.9

-1

The syntheses of systems 1–4 are based on the one-pot method using the LH ligand (Scheme 2) with metal and azide salts in the presence of a base to deprotonate the ligand. Such syntheses were conducted with Cu(II) salts in the Cu(II):L:N3 1:1:1 ratio and has led to the [CuL(l1,3-N3)]2 binuclear complex (1) [19]. The same procedure with Ni(II) has led to the crystallization of the [NiL(l1-N3)] monomer (2). Nevertheless, in the presence of an excess of azide, extended architectures were obtained such as {[CuL(l1,1-N3)]}n (3) and {[Ni2(l1,1-N3)(l1,3-N3)(L)2(MeOH)2]}n (4) [20]. Even if the ratio between ligand, azide and metal ion during the reaction strongly affects the nuclearity of the systems, the resulting complexes possess the same stoichiometry: one metal associated to one ligand L and one azido-bridge. However, the coordination modes of the azide ligand are completely different. Indeed, double EE bridges are encountered in 1 whereas only the single EO coordination mode is present in the copper chain 3. Finally, the nickel chain 4 presents an alternation of single EE and EO modes. Surprisingly, despite the large excess of azide salt during the synthesis of 3 and 4, only one azido-bridge is observed. The coordination ability of the LH ligand combined with the versatility of the azide magnetic coupler gives rise to significantly different magnetic behaviours.

Cu(II) ions are five-coordinated in a slightly distorted square pyramid (Addison parameter s of 0.18) [35], with the apical position being occupied by the terminal nitrogen atom (N3) of an azidobridge with a long Cu–N bond length (Cu–N3 = 2.356(2) Å) and a basal position occupied by the second azide ligand (N5) and a short Cu–N bond length (Cu–N5 = 2.000(2) Å). The presence of a long and a short Cu–N(azide) distance induces an asymmetric EE coordination mode of the double azido-bridge, with a Cu—Cu distance of 5.105(1) Å. The eight-membered ring formed by the two Cu(II) ions and the two azido groups displays a chair-type conformation. The dihedral angle (d) between the plane formed by the two azides {N3N5N3iN5i} and the {CuN3N5i} plane is 29.0° and the torsion angle, D [36], Cu1–N3  N5–Cu1i is 47.4°. The magnetic behaviour has been recorded for 1 (Fig. 2). At room temperature, the vT value of 0.85 cm3 K mol1 corresponds to the expected value for two uncoupled copper(II) ions (0.75 cm3 K mol1) with a slight anisotropy of the g factor (2.13). On cooling, vT increases continuously to 8 K, where it reaches a maximum of 1.05 cm3 K mol1 indicating ferromagnetic interactions. The further decrease observed at lower temperatures could be ascribed to weak inter-binuclear antiferromagnetic interactions. The magnetic susceptibility data were successfully fitted and suggested a ferromagnetic exchange parameter J = +7.96 cm1 with g = 2.096 and a small inter-dimer interaction h = 0.6 K. Such ferromagnetic interaction is rather unexpected since the general trend is that the EE mode affords antiferromagnetic inter-

0.8

3

3. Results and discussion

Fig. 1. Crystal structure of 1, with heteroatom and metal labels (H atoms have been omitted for clarity).

χT (cm mol K)

we are interested in consist of open d-shell ions (d9 and d8 for Cu(II) and Ni(II), respectively) we favoured explicitly correlated ab initio calculations. Besides, the evaluation of magnetic coupling constants calls for accurate low energy spectrum description (10 cm1). Thus, rigorous multireference calculations were carried out to take advantage of the relevant information conveyed by the wavefunction. Firstly, complete active space self-consistent field (CASSCF) [25] calculations, including n electrons in m MOs, were performed using the MOLCAS package [26] to generate a reference space (CAS(n, m)) which consists in the configurations that qualitatively describe the problem. The dynamical correlation effects were then incorporated using the dedicated difference configuration interaction (DDCI) [27] method implemented in the CASDI code [28]. With this approach, one concentrates on the differential effects rather than on the evaluation of the absolute energies. The number of degrees of freedom (i.e. holes and particles) on top of the reference CASSCF wavefunction defines the successive DDCI1, DDCI-2 and DDCI-3 levels of calculation. The physical contributions of the corresponding determinants have been debated in the literature [29]. Such strategy has been successfully used to study the magnetic properties of various molecular and extended materials [30]. More details about the computational strategy used for compounds 1 and 4 are given in Refs. [19,20], respectively. For complex 3, two different active spaces (CAS) have been used. The CAS(2,2) includes one orbital on each Cu(II) centre. One doubly occupied and one vacant azido orbitals are added in the enlarged CAS(4,4). The dynamic correlation contributions are included on top of the triplet CASSCF wavefunction using the DDCI procedure. In order to reduce the multireference expansion in the demanding DDCI-2 and DDCI-3 calculations, only the most relevant determinants were selected according to spatial proximity considerations through a threshold on the exchange integral values [31]. Basis sets and pseudo-potentials on the Cu atoms (9s6p6d)/[3s3p4d] [32] as well as (4s4p)/[2s2p] for C and N, and (4s5p)/[2s3p] for O [33] were used whereas the H atoms were described with (3s)/[1s] [34].

0.7

0.6

0.5 0

50

100

150

200

250

300

T (K) Fig. 2. vMT thermal evolution of compound 1. Solid line shows the best fit.

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actions. Therefore, to clarify this situation, theoretical ab initio calculations have been performed [19a] whose main conclusions are reported here. Since Cu(II) ion is formally a d9 ion, a zeroth-order description lies in CAS(2,2)SCF calculations, allowing the occupations of the two dx2 y2 atomic orbitals by two electrons. At the DDCI-2 level of calculation, the energy difference between the singlet and the triplet has been estimated at 15.2 cm1 which leads to a magnetic exchange constant J of 7.6 cm1, in very good agreement with the experimental fit.

6.348(1) Å distance separates two parallel molecules and 6.615(1) Å the twisted molecules. Tetra- and penta-coordinated mononuclear Ni(II) complexes are promising building blocks to generate high magneto-anisotropy in clusters or chains as they exhibit large anisotropy [39]. However, it was only observed for tetrahedral and square pyramid geometries and the square planar coordination in 2 that induces a diamagnetic ground state due to the electronic configuration is not favourable to this observation [40].

3.2. Compound 2: [NiLN3]

3.3. Compound 3: [CuLN3]n

Complex 2 crystallizes in the monoclinic Cc space group [37]. Its structure consists in Ni(II) cations surrounded by one deprotonated ligand (L) and one mono-coordinated l1-azido ligand (Fig. 3). The Ni(II) cation is located in the square plane defined by {O1N4N5N1} with an almost negligible out-of-plane displacement (0.012 Å) and Ni1–N1 = 1.895(5) Å, Ni1–N4 = 1.874(4) Å, Ni1–N5 = 1.949(4) Å and Ni1–O1 = 1.831(4) Å bond lengths. The red colour of the crystals is characteristic of such square planar Ni(II) complexes [38]. The azido ligand is mono-coordinated to the Ni(II) and is almost linear (N1N2N3 angle = 174.7(7)°). In the unit-cell, two orientations of the mononuclear molecules are encountered, with a dihedral angle of 79.56° between two {O1N4N5N1} square planes. A

Complex 3 crystallizes in the P21/a space group [41]. The asymmetric unit of this structure is built from two independent Cu(II) ions (Cu1 and Cu2). They both have a similar environment composed by one deprotonated ligand (L) and one azide. Therefore, this molecular structure can be viewed as {CuL} sub-units linked together via single EO azido ligands, growing neutral infinite chains running along the b-axis of the unit-cell (Fig. 4). These two chains, one built from Cu1 and the other from Cu2, are parallel but tilted by an angle of 49° in the (a,c) plane and separated by 10.2 Å. The Cu(II) ions are located in a distorted CuON4 polyhedron. Two nitrogen and the oxygen atoms come from the L ligand with bond lengths Cu1–O1 = 1.917(1) Å, Cu1–N1 = 1.97(2) Å and Cu1– N2 = 2.059(2) Å and Cu2–O2 = 1.929(1) Å, Cu2–N6 = 1.922(1) Å and Cu2–N7 = 2.067(1) Å. The two other nitrogen atoms surrounding the metal ions belong to azide ligands with a short and a long Cu–N distances (Cu1–N3 = 1.96(2) Å, Cu1–N3i = 2.44(3) Å, Cu2– N8 = 2.00(1) Å and Cu2–N8i = 2.61(1) Å). The CuON4 polyhedrons are close to square pyramids (Addison parameters of 0.34 for Cu1 and 0.18 for Cu2) with the Cu(II) ions lying 0.12 Å and 0.20 Å above the {O2N6N7N8} and {O1N1N2N3} square bases, respectively. The apical positions are occupied by the N3i and N8i atoms for Cu1 and Cu2, respectively, leading to asymmetric coordination modes of the azide ligands.

Fig. 3. Crystal structure of 2, with heteroatom and metal labels (H atoms have been omitted for clarity).

Fig. 4. (a) View of one {Cu(l1,1-N3)L} unit of 3, with atomic labels; (b) view of one chain along the b-axis without the ligands (H atoms have been omitted for clarity).

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2.0

1.0 M (µB)

1.5

-1

χT (cm K mol )

1.0

0.5

3

The presence of a single EO bridging mode between two metal ions is original as it is rarely encountered [42]. In the EO unit, the Cu1–N3–Cu1i and Cu2–N8–Cu2i bond angle values are 145.1° and 131.0°, respectively. They are in the range of the rare examples of single EO azido-bridges reported (97–137° in Table 1) [42] except the notably large Cu2–N8–Cu2i value. Interestingly, a decrease in the reported Cu–N–Cu bond angles is observed from 120° to 103° and 86° [5,16], for single, double and triple bridges, respectively. The angle between three consecutive Cu1 ions is 107.6° and 107.7° for Cu2. The chain can therefore be viewed as {Cu2(N3)(L)2}+ dimeric units linked to each other in a zig-zag way by the other azides (Fig. 4). Due to this configuration, the distances between nearest neighbours are equal to 4.20 Å and between second nearest neighbours 6.78 Å, in both chains. The magnetic behaviour has been recorded for 3 (Fig. 5). At room temperature, the vT value of 0.825 cm3 K mol1 corresponds to the expected value for two uncoupled copper(II) ions (0.75 cm3 K mol1) with a slight anisotropy of the g factor (2.08). On cooling, vT increases continuously to 2 K, where it reaches a value of 1.02 cm3 K mol1. This behaviour indicated a ferromagnetic coupling between the two copper(II) ions. This was confirmed by the magnetic field dependence of the magnetization at 2 K that saturates at 1.83 lB and follows the Brillouin function for a triplet ground state (Fig. 5, inset). The magnetic susceptibility data were fitted using several chain models already reported [43]. Despite the low agreement with the experiment at low temperature, all models gave the same results, namely J  +2.5 cm1 and g = 2.08 (Fig. 5). The introduction of ferromagnetic interactions between a copper(II) ion and its second nearest neighbour did not improve the quality of the fit. One may think that the presence of two different chains tilted by 49° leads to a more complicated magnetic behaviour. Therefore, the fitting procedure has included the description of two chains either ferro- or antiferromagnetic. The ferromagnetic character of one chain has been confirmed with a J value around 4 cm1. However, the sign of the exchange constant in the second chain turned out to be difficult to extract and always associated with very weak amplitudes. Ab initio theoretical calculations were performed on two binuclear entities {Cu2L2(N3)3} extracted from both chains (see Section 2.4). The energy separation DE between the calculated singlet and triplet states is equal to 2|J|. At the highest level of calculations (DDCI-3), a small ferromagnetic exchange constant was calculated in both chains, i.e. DE  9 cm1 and 3 cm1 within the chains built from Cu1 and Cu2, respectively. Even if these results lie within the limits of accuracy of such a method, the global ferromagnetic

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1

2

3

4

5

H (T)

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50

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T (K) Fig. 5. vMT thermal evolution of compound 3. The insert reports the magnetization curve recorded at 2 K. Solid lines show the fits obtained from the models discussed in the text.

behaviour of compound 3 was confirmed. Surprisingly, the strongest ferromagnetic interaction calculated may be attributed to the highest Cu–N–Cu angle. 3.4. Compound 4: [NiLN3MeOH]n The crystal structure of complex 4 consists in Ni(II) cations surrounded by one coordinated solvent molecule (MeOH) and one deprotonated ligand (L) with the resulting {Ni(L)(MeOH)} units linked to each other by single azido ligands that give a neutral mono-dimensional compound running along the c-axis of the unit-cell (Fig. 6) [20]. Two azide coordination modes are present in an alternating fashion along the chain. Each Ni(II) cation has one EO bridge mode with one of the neighbouring Ni(II) ion whereas the second is bridged by a single EE azido-linkage. The chain can therefore also be viewed as {Ni2(N3)(L)2(MeOH)2}+ binuclear units linked to each other in a zig-zag way by the other azide (Fig. 6) with a centre of symmetry lying in the middle of this EE azido-bridge. Here again, the presence of a single EO mode is original as it has been rarely reported and always associated with copper(II) compounds [42]. In the EO unit, the Ni1–N3–Ni1i bond angle (133.3(2)°) is higher than the ones encountered in double (103°) and triple (85°) azidobridged Ni(II) complexes [5,16]. The EE azido-bridge unit involves

Table 1 Structural and magnetic parameters for single EO bridges Formulaa 1

1D-{[CuL (N3)2]}n 2D-{[Cu3(L2)2(N3)6]}n [{Cu(acac)(phen)(ClO4)}2{Cu(phen)(N3)2}2] 1D-{[Cu2(L3)2(H2O)(N3)4]}n [Cu2(L4)2(N3)3]  NO3  (H2O)2 1D-{[CuL5(N3)2]}n 1D-{[Cu(Me–L5)(N3)4]}n 2D-{[Cu4(L6)2(N3)3]}n(ClO4)n  2n(H2O) 1D-{[CuL(N3)]}n (3)

cb (Å)

hc (°)

dd (Å)

se

Jf (cm1)

Magnetic modelg

Ref.

0.27 0.43/ 0.45 0.66 0.81 0.31 0.35 0.33 0.00/0.46 0.48 0.61

129.9 132.6/ 137.1 115.6 136.1 117.4 116.6 100.9 111.8/97.3 145.1 131.0

3.88 4.11/ 4.17 3.98 4.50 3.67 3.69 3.52 3.28/3.37 4.20 4.20

0.02/ 0.10 0.07 0.26 0.07/ 0.22 0.09/ 0.18 0.21/ 0.10 0.21/0.28 0.19/0.05 0.34 0.18

7.75 +1.34 +0.18 2.50 +2.89 +7.05 F AF/F +4/ +4.5 /+ 1

Alternated chain zJ0 inter-chains J intra-tetramer zJ0 inter-dimers J intra-dimer J intra-dimer — — Chain models Ab initio calc.

[42a] [42b] [42c] [42d] [42e] [42f] [42g] This work

a acac = acetylacetonate; phen = 1,10-phenanthroline; L1 = homopiperazine; L2 = 1-phenylethylamine; L3 = 5-methylpyrimidin-2-amine; L4 = 5,500 -dimethyl-2,20 :60 ,200 -terpyridine; L5 = 2-(pyrazol-1-ylmethyl)pyridine; Me–L5 = 2-(3-methylpyrazol-1-ylmethyl)pyridine; L6H2 = N,N0 -bis(2-aminoethyl)oxamide. b Difference between the long and the short Cu–N distances. c The Cu–N–Cu valence angle. d The Cu—Cu distance spanned by the EO bridge. e Addison parameter [35]. f Magnetic exchange constant. g b ¼ 2P J Si Sj ; F and AF stand for ferromagnetic and antiferromagnetic interactions, respectively. Model used for the determination of J, based on the Hamiltonian H i;j ij

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Fig. 6. (a) View of the dimeric {Ni2(l1,1-N3)(l1,3-N3)(L)2(MeOH)2} unit of 4, with heteroatom and metal labels; (b) view of the chain along the b-axis without the ligands (H atoms have been omitted for clarity).

a symmetric coordination mode of the azide and displays an expected Ni1–N6–N7 bond angle of 124.1(2)°, which falls within the usual bond angles values [5]. Due to the alternation of EE and EO bridging modes, two different Ni—Ni distances are observed, a short one at 3.839(1) Å and a long one at 5.868(2) Å along the EO and EE linkage, respectively. The magnetic behaviour of 4 is shown in Fig. 7. At 300 K, the vMT product is 1.90 cm3 K mol1, slightly lower than the expected value for two Ni(II) metal ions (2.0 cm3 K mol1 with g = 2). Decreasing the temperature, the vMT product continuously decreases to reach 0.008 cm3 K mol1 at 1.8 K indicating dominant antiferromagnetic interactions between the Ni(II) ions and the presence of a diamagnetic ground state. Magnetization curve recorded at 2 K reveals the presence of a small paramagnetic residual contribution (impurity or chain defects). From data simulations using different models, it turned out that the magnetic behaviour of the chain 4 tends to be equivalent to that of binuclear {Ni2} isolated entities with

2.0

10.0

1.5

7.5

J = 37 cm1 (Fig. 7). However, these simulations did not indicate to which coordination mode of the azide the antiferromagnetic interaction should be ascribed. Ab initio calculations were therefore performed on the two binuclear moieties extracted from the crystal structure {Ni2(l1,3N3)(L)2(MeOH)2}+ and {Ni2(l1,1-N3)(L)2(MeOH)2}+ of 4 [20]. Since the Ni(II) ion is formally d8, one expects exchange interactions between S = 1 ions giving rise to three spin-states in the Ni2 units, namely singlet (S), triplet (T) and quintet (Q) states. Our CASSCF calculations were based on an enlarged CAS(6,5) space that includes two orbitals on each Ni(II) centre and one doubly occupied ligand orbital. The energy separations are 6|J| and 4|J| between the quintet and singlet, quintet and triplet states, respectively. Within the EE unit, a relatively large antiferromagnetic exchange constant (JEE = 53 cm1) is calculated in relatively good agreement with the extracted value from experiment. This is to be contrasted with the EO Ni2 unit, which exhibits a negligibly small magnetic interaction (a = JEO/|JEE| ratio 0.02). Our ab initio calculations not only confirmed the isolated dimers picture, but also associated the leading antiferromagnetic exchange pathway to the EE bridging mode, as expected.

-1 3

-3

χM (10 cm mol )

χMT (cm K mol )

3.5. Discussion

5.0

0.5

2.5

3

1.0

-1

0.0 0

50

100

150

200

250

0.0 300

T (K) Fig. 7. vMT and vM thermal evolution of compound 4. Solid lines show the best fit obtained from the dimeric model with the refined parameters g = 2.15, J = 37.1 cm1, vTIP = 6.3  104 cm3 mol1 and 0.7% of paramagnetic impurity.

Complexes 1–4 illustrate the versatility of the coordination modes of the azido ligand. Starting from the same Schiff base ligand LH, mononuclear (2) binuclear (1) and chains (3 and 4) have been obtained with the same resulting stoichiometry: one ligand for one metal and one azide, with the exception of 4 that presents an additional solvent molecule in the coordination sphere of the metal. However, the coordination modes strongly differ from one compound to the other. Indeed, binuclear 1 exhibits an asymmetric double EE bridge. An asymmetry is observed as soon as the Cu–N3– Cu coordination presents an alternation of a long and a short Cu–N distance (Scheme 1). This situation, that follows from the involvement of one apical and one basal positions of the coordination spheres of the two connected Cu(II) ions, is scarcely reported in the literature and the magnetic exchanges range from slightly ferromagnetic to strongly antiferromagnetic [15g,15h,34,44]. The

G. Chastanet et al. / Inorganica Chimica Acta 361 (2008) 3847–3855

magnetostructural correlations reported to date were mainly oriented to symmetric EE and EO modes, and reproduced undoubtedly the experimental data. However, the situation with double asymmetric EE and EO modes is less clear. Concerning chains 3 and 4, they contribute to enrich the rare examples of architectures with single EO bridging mode of the azide [42]. Whereas the single EE mode encountered in 4 is often observed, the single EO form is much less reported. Generally, single EO azides are associated to additional ligands such as oxygen, carboxylate, and other traditional bridges used in coordination chemistry, to connect metal ions [6]. Let us note that such association is common in the azide chemistry of clusters but very rare in extended structures. The presence in 3 of only single EO coordination mode is therefore noticeable whereas 4 represent the first example of an alternating Ni(II) chain with only single azido-bridges in symmetric EE and EO fashions. To date, no theoretical investigations have been devoted to the study of such systems. Compounds 1, 3 and 4 are then original examples of the versatility of the azido-bridge. Due to the differences in coordination modes between these three complexes, any magnetostructural correlation seems to be illusive. However, one can compare each of these systems to the already reported ones and try to extract some trends. We first concentrated on binuclear 1 and the effect on the asymmetric double EE coordination mode on the magnetic exchange. Some attempts have already been done to draw general trends and have pointed out that the deviation of the Cu(II) coordination sphere from the square pyramid (Addison parameter) could weaken the magnetic exchange whereas large Cu–N  N–Cu torsion angles D enhance its ferromagnetic character [15g,15h,36]. As part of this work of understanding, we theoretically investigated the role of the ‘‘shearing-like” distortion (Scheme 1), and then of the asymmetry, on the magnetic exchange. The structural parameter we studied to evaluate this distortion is the difference between the long and the short Cu–N distances, c. Therefore, starting from the description of the EE mode in 1, the Cu–N distances were modified to evaluate the sensitivity of the singlet–triplet gap with respect to this distortion. We evidenced that an increase of c (i.e. increase of the asymmetry) favours ferromagnetic exchange whereas its decrease switches the exchange from ferromagnetic to antiferromagnetic [19b]. This study has been extended to several similar copper binuclear and turned out to be predictive, underlining the crucial role played by the symmetry of the azidobridge coordination mode on the propagation of the magnetic exchange. Let us concentrate on complex 3, which is an original example of chain exhibiting only single EO bridging modes. The originality also lies in the presence of two chains in the structure, exhibiting pronounced differences as reported in Table 1. The more asymmetric chain (c = 0.61) is associated with the lower Cu–N–Cu angle (131°) and the lower deviation from the square pyramid environment of the Cu(II) ion (s = 0.18). From previous magnetostructural correlations on double symmetric [16] and asymmetric [15g,15h] EO bridges, it has been stated that the interaction is ferromagnetic for low Cu–N–Cu valence angles and antiferromagnetic for higher angles (the critical angle being around 104–108°). However, if we collect all the structural and magnetic data from the reported examples (Table 1), we clearly see that these conclusions are not applicable in the case of single bridges. For example, Most of the angles reported in Table 1 are above this critical angle and related to ferro- and antiferromagnetic interactions. This is further illustrated by 3 that exhibits two different chains associated with two ferromagnetic exchanges amplitudes as evidenced by ab initio theoretical investigations: the most symmetric chain exhibit a stronger exchange (J1 = +4.5 cm1) than the most asymmetric chain (J2 = +1 cm1). These values are in the range 8 to +8 cm1 of the previously reported magnetic interactions in such systems

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(Table 1). Let us note that the way the exchange parameter is extracted strongly differs from one study to the other. Indeed, it could be determined from direct interaction between two ions or from an intermolecular parameter zJ0 . It is therefore difficult to compare these values and no general trend seems to be drawn between the structural parameters and the magnetic exchange values. Finally, the study of chain 4 has revealed symmetric EE and EO bridges with magnetic exchanges strongly antiferromagnetic through the EE bridge and almost null through the EO linker. As this chain is the first example of a Ni(II) compound exhibiting single EO bridge, we cannot compare with other results. However, single EE bridges are more common and a look at magnetostructural correlations performed on these systems reveals that the amplitude of the exchange interaction is smaller in single bridges than in double and triple ones[5]. The value of the dihedral angle Ni1–N6–N7 (124.1°) associated to JAF = 37 cm1 in 4 is consistent with the values found in the literature [5] .Concerning the EO coordination mode, previous DFT calculations performed on double and triple EO bridges have shown that the interaction is always ferromagnetic for Ni– N–Ni angles ranging from 80° to 110° [16]. Whereas calculations and experimental data agree well for double-bridged Ni(II) complexes, they notably differ for triple bridge systems as the nature of the magnetic interaction (ferromagnetic [45] versus antiferromagnetic [46]) is very sensitive to small Ni–N–Ni angle variations. In 4, the Ni1–N3–Ni1i angle is 133°, much greater than the one usually encountered in other EO bridges, and is associated with an almost null ferromagnetic coupling constant. One may therefore wonder whether a variation of this particular structural parameter may induce ferromagnetic character enhancement and then if an alternated chain picture can be recovered. Therefore, ab initio calculations were performed to investigate the variation of the magnetic exchange constant JEO with respect to the Ni1–N3–Ni1i valence angle, h, in the EO unit. The h value was artificially modified from 120° to 140° by displacing the N3 moieties perpendicularly to the Ni–Ni direction while the rest of the dimer was not altered. Let us mention that the Ni1–N3 and Ni1i–N3 distances are then modified by less than 9% as h is varied whereas the symmetry of the bridge was conserved. From this magnetostructural inspection, the magnetic exchange constant variations are smaller than 1 cm1. Such value is not relevant from a computational point of view. However, this variation must be compared with the variation observed in 3 between the two chains, even if the metal ions are different. Indeed in 4, the variation of the angle does not seem to affect the magnetic exchange, whereas in 3, the 15° difference between the two chains strongly affects the nature of the interaction. One may therefore think on the pertinence of such structural parameter on magnetostructural correlations when it is not associated to other parameters like c and/or h. There is no doubt that a single parameter cannot fully account for the nature and values of the magnetic exchanges [19b]. It appears clearly that the lack of experimental of theoretical studies on single, symmetrical or asymmetrical, EO coordination mode of the azido-bridge has to be filled. The role of the asymmetry has been underlined in copper(II) binuclear complexes and should be extended to the other modes. One of the questions that could be stressed by such studies is the link between the asymmetry of the binuclear units and antisymmetric magnetic exchange able to generate spin canting [2].

4. Concluding remarks Starting from the same Schiff base ligand LH, and only by controlling the initial stoichiometry of the reaction, mononuclear (2) binuclear (1) and chains (3 and 4) have been obtained with Cu(II) and Ni(II) and the same resulting stoichiometry: one ligand for

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one metal and one azide. However, the coordination modes strongly differ from one compound to the other and systems 1–4 illustrate the versatility of the coordination modes of the azido ligand. This versatility is also expressed through the variety of magnetic exchanges mediated. In 1, the asymmetrical double l1,3-N3 bridge conducts a ferromagnetic exchange whereas 3 and 4 exhibit unusual symmetric and asymmetric single l1,1-N3 coordination modes that transmit weak ferromagnetic interactions. Acknowledgements We thank the ‘‘Région Rhône-Alpes”, Lyon 1 University and the CNRS for financial support. Single-crystal X-diffraction studies were performed at the ‘‘Centre de Diffractometrie Henri Longchambon” at Université Claude Bernard Lyon 1. Magnetic measurements were provided by the ‘‘Commissariat à l’Energie Atomique” (CEA) through a ‘‘Laboratoire de Recherche Conventioné” (LRC No. DSM-03-31) and by Drs Rodolphe Clérac and Corine Mathonière that are friendly thank. B.L.G. and V.R. thank Dr. Daniel Maynau for kindly providing the CASDI code, and the ‘‘Institut de Développement et de Ressources en Informatique” (IDRIS) for computing facilities. Finally, C.G. is very grateful to Pr. Andrea Dei for his very kind invitation to contribute to this special issue. Appendix A. Supplementary material CCDC 675812 and 675813 contain 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.2008.02.045.

[8]

[9]

[10]

[11] [12] [13]

[14]

References [15] [1] D. Gatteschi, R. Sessoli, J. Villain, Molecular Nanomagnets, Oxford University Press, 2006. [2] (a) O. Kahn, Molecular Magnetism, VCH, Cambridge, UK, 1993; (b) J.S. Miller, M. Drillon (Eds.), Magnetism: Molecules to Materials II: Molecule-Based Materials, Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim, 2002. [3] (a) M. Julve, F. Lloret, J. Faus, G. De Munno, M. Verdaguer, A. Caneschi, Angew. Chem., Int. Ed. Engl. 32 (1993) 1046; (b) R. Vicente, A. Escuer, J. Ribas, X. Solans, Inorg. Chem. 31 (1992) 1726. [4] (a) A. Caneschi, D. Gatteschi, N. Lalioti, C. Sangregorio, R. Sessoli, G. Venturi, A. Vindigni, A. Rettori, M.G. Pini, M.A. Novak, Angew. Chem., Int. Ed. Engl. 40 (2001) 1760; (b) C. Coulon, H. Miyasaka, R. Clérac, Struct. Bond. 122 (2006) 163; (c) R. Lescouezec, L.M. Toma, J. Vaissermann, M. Verdaguer, F.S. Delgado, C. Ruiz-Perez, F. Lloret, M. Julve, Coord. Chem. Rev. 249 (2005) 2691; (d) R. Clérac, H. Miyasaka, M. Yamashita, C. Coulon, J. Am. Chem. Soc. 43 (2002) 12837. [5] (a) J. Ribas, A. Escuer, M. Monfort, R. Vicente, R. Cortes, L. Lezama, T. Rojo, M.A.S. Goher, in: J.S. Miller, M. Drillon (Eds.), Magnetism: Molecules to Materials II: Molecule-Based Materials, Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim, 2002; (b) J. Ribas, A. Escuer, M. Monfort, R. Vicente, R. Cortes, L. Lezama, T. Rojo, Coord. Chem. Rev. 193 (1999) 1027. [6] A. Escuer, G. Aromi, Eur. J. Inorg. Chem. (2006) 4721 and references cited therein. [7] For examples: (a) E.-Q. Gao, S.-Q. Bai, Y.-F. Yue, Z.-M. Wang, C.-H. Yan, Inorg. Chem. 42 (2003) 3642; (b) A. Escuer, R. Vicente, J. Ribas, M.S. El Fallah, X. Solans, M. Font-Bardia, Inorg. Chem. 32 (1993) 3727; (c) G. Viau, M.G. Lombardi, G.D. Munno, M. Julve, F. Lloret, J. Faus, A. Caneschi, G.M. Clemente-Juan, Chem. Commun. (1997) 1195; (d) F. Meyer, H. Pritzkow, Inorg. Chem. Commun. 4 (2001) 305; (e) T.-F. Liu, D. Fu, S. Gao, Y.-Z. Zhang, H.-L. Sun, G. Su, Y.-J. Liu, J. Am. Chem. Soc. 125 (2003) 13976; (f) Z. Shen, J.-L. Zuo, Z. Yu, Y. Zhong, J.-F. Bai, C.-M. Che, H.-K. Fun, J.J. Vittal, X.-Z. You, J. Chem. Soc., Dalton Trans. (1999) 3393; (g) A. Escuer, R. Vicente, F.A. Mautner, M.A.S. Goher, Inorg. Chem. 36 (1997) 1233; (h) A. Escuer, R. Vicente, M.S. El Fallah, S.B. Kumar, F.A. Mautner, D. Gatteschi, J. Chem. Soc., Dalton Trans. (1998) 3905;

[16]

[17]

[18]

[19]

[20] [21] [22]

(i) U. Ray, S. Jasimuddin, B.K. Ghosh, M. Monfort, J. Ribas, G. Mostafa, T.-H. Lu, C. Sinha, Eur. J. Inorg. Chem. (2004) 250. (a) J.L. Manson, A.M. Arif, J.S. Miller, Chem. Commun. (1999) 1479; (b) M. Monfort, I. Resino, J. Ribas, H. Stoeckli-Evans, Angew. Chem., Int. Ed. Engl. 39 (2000) 191; (c) Z. Shen, J.-L. Zuo, S. Gao, Y. Song, C.-M. Che, H.-K. Fun, X.-Z. You, Angew. Chem., Int. Ed. Engl. 39 (2000) 3633; (d) M. Monfort, J. Ribas, X. Solans, J. Chem. Soc., Chem. Commun. (1993) 350; (e) J. Ribas, M. Monfort, X. Solans, M. Drillon, Inorg. Chem. 33 (1994) 742; (f) R. Cortès, L. Lezama, T. Rojo, J.L. Pizarro, I. Arriortua, Angew. Chem., Int. Ed. Engl. 35 (1996) 1810. (a) F.A. Mautner, R. Cortes, L. Lezema, T. Rojo, Angew. Chem., Int. Ed. Engl. 35 (1996) 78; (b) F.-C. Liu, Y.-F. Zeng, J. Jiao, X.-H. Bu, J. Ribas, S.R. Batten, Inorg. Chem. 45 (2006) 2776; (c) F.-C. Liu, Y.-F. Zeng, J.-R. Li, H.-J. Zhang, X.-H. Bu, Inorg. Chem. 44 (2005) 7298. (a) M.A. Halcrow, J.C. Huffman, G. Christou, Angew. Chem., Int. Ed. Engl. 34 (1995) 889; (b) M.A. Halcrow, J.-S. Sun, J.C. Huffman, G. Christou, Inorg. Chem. 34 (1995) 4167; (c) M.W. Wemple, D.M. Adams, K.S. Hagen, K. Folting, D.N. Hendrickson, G. Christou, Chem. Commun. (1995) 1591; (d) D. Ma, S. Hikichi, M. Akita, Y. Morooka, J. Chem. Soc., Dalton Trans. (2000) 1123; (e) M.A.S. Goher, J. Cano, Y. Journaux, M.A.M. Abu-Yussef, F.A. Mautner, A. Escuer, R. Vicente, Chem. Eur. J. 6 (2000) 778. F. Meyer, S. Demeshko, G. Leibeling, B. Kersting, E. Kaifer, Chem. Eur. J. 11 (2005) 1518. G.S. Papaefstathiou, S.P. Perlepes, A. Escuer, R. Vicente, M. Font-Bardia, Angew. Chem., Int. Ed. Engl. 40 (2001) 884. (a) F. Meyer, P. Kircher, H. Pritzkow, Chem. Commun. (2003) 774; (b) S. Demeshko, G. Leibeling, W. Maringgele, F. Meyer, C. Mennerich, H.-H. Klauss, H. Pritzkow, Inorg. Chem. 44 (2005) 519; (c) C. Golze, A. Alfonsov, R. Klingeler, B. Büchner, V. Kataev, C. Mennerich, H.-H. Klauss, M. Goiran, J.-M. Broto, H. Rakoto, S. Demeshko, G. Leibeling, F. Meyer, Phys. Rev. B 73 (2006) 2244031. For recent examples: (a) M.A.M. Abu-Youssef, M. Drillon, A. Escuer, M.A.S. Goher, F.A. Mautner, R. Vicente, Inorg. Chem. 39 (2000) 5022; (b) F.-C. Liu, Y.-F. Zeng, J.-P. Zhao, B.-W. Hu, X.-H. Bu, J. Ribas, J. Cano, Inorg. Chem. 46 (2007) 1520; (c) M.A.M. Abu-Youssef, A. Escuer, M.A.S. Goher, F.A. Mautner, G.J. Reiss, R. Vicente, Angew. Chem., Int. Ed. Engl. 39 (2000) 1624; (d) F.-C. Liu, Y.-F. Zeng, J.-P. Zhao, B.-W. Hu, X.-H. Bu, J. Ribas, J. Cano, Inorg. Chem. 46 (2007) 1520. (a) J. Ribas, M. Monfort, C. Diaz, C. Bastos, X. Solans, Inorg. Chem. 32 (1993) 3557; (b) R. Vicente, A. Escuer, Polyhedron 14 (1995) 2133; (c) A. Escuer, R. Vicente, M.A.S. Goher, F.A. Mautner, Inorg. Chem. 37 (1998) 782; (d) R.J. Butcher, C.J. O’Connor, E. Sinn, Inorg. Chem. 20 (1981) 3486; (e) S.S. Tandon, L.K. Thompson, M.E. Manuel, J.N. Bridson, Inorg. Chem. 33 (1994) 5555; (f) T.K. Karmakar, B.K. Ghosh, A. Usman, H.K. Fun, E. Riviere, T. Mallah, G. Aromí, S.K. Chandra, Inorg. Chem. 44 (2005) 2391; (g) S. Triki, C.J. Gomez-Garcia, E. Ruiz, J. Sala-Pala, Inorg. Chem. 44 (2005) 5501; (h) A. Escuer, M. Font-Bardia, S.S. Massoud, F.A. Mautner, E. Penalba, X. Solans, R. Vicente, New. J. Chem. 28 (2004) 681. (a) E. Ruiz, J. Cano, S. Alvarez, P. Alemany, J. Am. Chem. Soc. 120 (1998) 11122; (b) F. Fabrizi di Biani, E. Ruiz, J. Cano, J.J. Novoa, S. Alvarez, Inorg. Chem. 39 (2000) 3221; (c) O. Castell, R. Caballol, V.M. Garcia, K. Handrick, Inorg. Chem. 35 (1996) 1609; (d) J. Cabrero, C. de Graaf, E. Bordas, R. Caballol, J.-P. Malrieu, Chem. Eur. J. 9 (2003) 2307. (a) T.-F. Liu, D. Fu, S. Gao, Y.-Z. Zhang, H.-L. Sun, G. Su, Y.-J. Liu, J. Am. Chem. Soc. 125 (2003) 13976; (b) X.-T. Liu, X.-Y. Wang, W.X. Zhang, P. Cui, S. Gao, Adv. Mater. 18 (2006) 2852. (a) C. Aronica, G. Pilet, G. Chastanet, W. Wernsdorfer, J.-F. Jacquot, D. Luneau, Angew. Chem., Int. Ed. Engl. 45 (2006) 4659; (b) C. Aronica, G. Chastanet, G. Pilet, B. Le Guennic, V. Robert, W. Wernsdorfer, D. Luneau, Inorg. Chem. 46 (2007) 6108; (c) B. Le Guennic, S. Petit, G. Chastanet, G. Pilet, D. Luneau, N. Ben Amor, V. Robert, Inorg. Chem. 47 (2008) 572. (a) C. Aronica, E. Jeanneau, H. El Moll, D. Luneau, B. Gillon, A. Goujon, A. Cousson, M.A. Carvajal, V. Robert, Chem. Eur. J. 13 (2007) 3666; (b) M.A. Carvajal, C. Aronica, D. Luneau, V. Robert, Eur. J. Inorg. Chem. 28 (2007) 4434. M.-L. Bonnet, C. Aronica, G. Chastanet, G. Pilet, D. Luneau, C. Mathonière, R. Clérac, V. Robert, Inorg. Chem. 47 (2008) 1127. S. Shit, P. Talukdar, J. Chakraborty, G. Pilet, M.S. El Fallah, J. Ribas, S. Mitra, Polyhedron 26 (2007) 1357. NONIUS, Kappa CCD Program Package: COLLECT, DENZO, SCALEPACK, SORTAV, Nonius B.V., Delft, The Netherlands, 1999.

G. Chastanet et al. / Inorganica Chimica Acta 361 (2008) 3847–3855 [23] G. Cascarano, A. Altomare, C. Giacovazzo, A. Guagliardi, A.G.G. Moliterni, D. Siliqi, M.C. Burla, G. Polidori, M. Camalli, Acta. Crystallogr., Sect. A 52 (1996) C79. [24] D.J. Watkin, C.K. Prout, J.R. Carruthers, P.W. Betteridge, CRYSTALS Issue 11, Chemical Crystallography Laboratory, Oxford, UK, 1999. [25] B.O. Roos, Adv. Chem. Phys. LXIX (1987) 399. [26] K. Anderson, M.P. Fülscher, G. Karlström, R. Lindh, P.A. Malqvist, J. Olsen, B. Roos, A.J. Sadlej, M.R.A. Blomberg, P.E.M. Siegbahn, V. Kello, J. Noga, M. Urban, P.O. Widmark, MOLCAS, Version 5.4, University of Lund, Lund, Sweden, 1998. [27] J. Miralles, O. Castell, R. Caballol, J.P. Malrieu, Chem. Phys. 172 (1993) 33. [28] N. Ben Amor, D. Maynau, Chem. Phys. Lett. 286 (1998) 211. [29] (a) C.J. Calzado, J. Cabredo, J.P. Malrieu, R. Caballol, J. Chem. Phys. 116 (2002) 2728; (b) C.J. Calzado, J. Cabredo, J.P. Malrieu, R. Caballol, J. Chem. Phys. 116 (2002) 3985. [30] For instance: (a) I.P.R. Moreira, N. Suaud, N. Guihéry, J.-P. Malrieu, R. Caballol, J.M. Bofill, F. Illas, Phys. Rev. B 66 (2002) 134430; (b) J. Cabrero, C. de Graaf, E. Bordas, R. Caballol, J.-P. Malrieu, Chem. Eur. J. 9 (2003) 2307. [31] B. Bories, D. Maynau, M.-L. Bonnet, J. Comput. Chem. 28 (2007) 632. [32] Z. Barandiaran, L. Seijo, Can. J. Chem. 70 (1992) 409. [33] A. Bergner, M. Dolg, W. Kuechle, H. Stoll, H. Preuss, Mol. Phys. 80 (1993) 1431. [34] W.J. Hehre, R.F. Stewart, J.A. Pople, J. Chem. Phys. (1969) 2657. [35] A.W. Addison, T.N. Rao, J. Reedijk, G.C. Verschoor, J. Chem. Soc., Dalton Trans. (1984) 1349. [36] Y. Xie, Q. Liu, H. Jiang, C. Du, X. Xu, M. Yu, Y. Zhu, New J. Chem. (2002) 176. [37] C9H14F3N5Ni1O1, FW = 323.9 g mol1, Z = 4; a = 20.545(5) Å, b = 6.615(5) Å, c = 11.789(5) Å, b = 124.204(5)°, V = 1325(1) Å3; kMo (Ka) = 0.71073 Å (Nonius KappaCCD, graphite monochromator); data collection performed at 293 K, no absorption correction was applied to the data set, 2254 reflections were collected (2.40° < h < 27.89°), 2130 independent reflections (R = 0.040); monoclinic system, Cc (No. 9); crystal characteristics: 0.04  0.05  0.12 mm3, dark red needle, l = 1.624 cm1, density = 1.5 g cm3; R = 0.0405, Rw = 0.0459 for I/r(I) > 3, S = 1.10, Dqmax = 0.51 e Å3, Dqmin = 0.36 e Å3, 1864 reflections used to refine 215 parameters. [38] F.A. Cotton, G. Wilkinson, Basic Inorganic Chemistry, Wiley, London, 1984. [39] (a) P.J. Desrochers, J. Telser, S.A. Zvyagin, A. Ozarowski, J. Krzystek, D.A. Vicic, Inorg. Chem. 45 (2006) 8930; (b) J.-N. Rebilly, G. Charron, E. Rivière, R. Guillot, A.-L. Barra, M. Durán Serrano, J. van Slageren, T. Mallah, Chem. Eur. J. 14 (2008) 1169.

3855

[40] R.L. Carlin, Magnetochemistry, Springer-Verlag, 1986. [41] {C9H14Cu1F3N5O1}n, FW = 328.78 g mol1, Z = 8; a = 20.7053(8) Å, b = 6.7855(4) Å, c = 21.397(1) Å, b = 118.930(2)°, V = 2631.1(2) Å3; kMo (Ka) = 0.71073 Å (Nonius KappaCCD, graphite monochromator); data collection performed at 293 K, no absorption correction was applied to the data set, 4022 reflections were collected (1.09° < h < 24.01°), 4022 independent reflections (R = 0.065); monoclinic system, P21/a (No. 14); crystal characteristics: 0.04  0.04  0.09 mm3, dark green needle, l = 1.696 cm1, density = 1.660 g cm3; R = 0.0598, Rw = 0.0707 for I/r(I) > 2, S = 1.03, Dqmax = 0.56 e Å3, Dqmin = 0.40 e Å3, 2122 reflections used to refine 343 parameters. [42] (a) P.S. Mukherjee, T.K. Maji, G. Mostafa, T. Mallah, N.R. Chaudhuri, Inorg. Chem. 39 (2000) 5147; (b) Z.-G. Gu, Y. Song, J.-L. Zuo, X.-Z. You, Inorg. Chem. 46 (2007) 9522; (c) A.M. Madalan, M. Noltemeyer, M. Neculai, H.W. Roesky, M. Schmidtmann, A. Müller, Y. Journaux, M. Andruh, Inorg. Chim. Acta 359 (2006) 459; (d) X.-Y. Song, W. Li, L.-C. Li, D.-Z. Liao, Z.-H. Jiang, Inorg. Chem. Commun. 10 (2007) 567; (e) X.-J. Lin, Z. Shen, Y. Song, H.-J. Xu, Y.-Z. Li, X.-Z. You, Inorg. Chim. Acta 358 (2005) 1963; (f) E.-Q. Gao, S.-Q. Bai, C.-H. Wang, Y.-F. Yue, C.-H. Yan, Inorg. Chem. 42 (2003) 8456; (g) Z.N. Chen, J. Qiu, Z.K. Wu, D.G. Fu, K.B. Yu, W.X. Tang, J. Chem. Soc., Dalton Trans. (1994) 1923. [43] (a) G.A. Baker Jr., G.S. Rushbrooke, H.E. Gilbert, Phys. Rev. 135 (1964) A1272; (b) J. Souletie, P. Rabu, M. Drillon, Phys. Rev. B 72 (2005) 214427. [44] (a) M.A. Aebersold, B. Gillon, O. Plantevin, L. Pardi, O. Kahn, P. Bergerat, I. von Seggern, F. Tuczek, L. Örström, A. Grand, E. Lelièvre-Berna, J. Am. Chem. Soc. 120 (1998) 5238; (b) I. Bkouche-Waksman, S. Sikorav, O. Kahn, J. Crystallogr. Spectrosc. Res. 13 (1983) 303; (c) A. Escuer, M. Font-Bardia, E. Peñalba, X. Solans, R. Vicente, Inorg. Chim. Acta 298 (2000) 195; (d) T.R. Felthouse, D.N. Hendrickson, Inorg. Chem. 17 (1978) 444; (e) L. Li, D. Liao, Z. Jiang, J.M. Mouesca, P. Rey, Inorg. Chem. 45 (2006) 7665. [45] P.D. Beer, M.G.B. Drew, P.B. Leeson, K. Lyssenko, M.I. Ogden, J. Chem. Soc., Chem. Commun. (1995) 929. [46] J. Ribas, M. Montfort, B. Kumar Gosh, X. Solans, Angew. Chem., Int. Ed. Engl. 33 (1994) 2087.