Polyhedron 56 (2013) 90–95

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A novel coordination polymer with an unusual [3 � 2] oblique copper(II) grid:[Cu2(HBIMAM)2(C4O4)3(H2O)2]n�2nH2O [BIMAM = bis(imidazol-2-yl)methylaminomethane]. X-ray structure and magnetic characterization

Emilio Escrivá a,⇑, Lucía Soto a, Juan Server-Carrió a, Carlos J. Gómez-García b,⇑, Guillermo MínguezEspallargas b, Nailette Ruiz c, Amparo Sancho a, Julia García-Lozano a, Carmen Ramírez de Arellano d

a Departament de Química Inorgànica, Universitat de València, c/Vicent Andrés Estellés, s/n, 46100 Burjassot, València, Spainb Instituto de Ciencia Molecular (ICMol), Parque Científico, Universidad de Valencia, C/Catedrático José Beltrán, 2, 46980 Paterna, Valencia, Spainc Departamento de Química, Universidad de Oriente Patricio Lumumba s/n, Santiago de Cuba, Cubad Departament de Química Orgànica, Universitat de València, c/Vicent Andrés Estellés, s/n, 46100 Burjassot, València, Spain

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

Article history:Received 26 September 2012Accepted 5 March 2013Available online 20 March 2013

Dedicated to the memory of Juan Server-Carrio deceased on March 19, 2013 and tothe memory of Prof. Purificación Escribano.

Keywords:2-D coordination polymer[3 � 2] Oblique gridBis(imidazolyl) ligandsSquarate bridgeMagnetic properties

0277-5387/$ - see front matter � 2013 Elsevier Ltd. Ahttp://dx.doi.org/10.1016/j.poly.2013.03.016

⇑ Corresponding authors.E-mail addresses: emilio.escriva@uv.es (E. Escriv

Gómez-García).

This paper reports the synthesis, X-ray structure and magnetic characterization of [Cu2(HBIMAM)2

(C4O4)3(H2O)2]n�2nH2O [BIMAM = bis(imidazol-2-yl)methylamino methane]. This compound is made ofinfinite chains – running along the [110] direction – with copper ions bridged by l1,3-squarato ligands.Furthermore, these chains are further cross-linked through additional squarate anions (with the samel1,3-bis(monodentate) bridging mode) to generate two-dimensional sheets parallel to the ab plane. Thereare inter-chains links every two copper atoms in a chain, forming an unusual (3 � 2) oblique copper(II)grid. Magnetic susceptibility measurements in the range 2–300 K show weak antiferromagnetic exchangeinteractions. A detailed analysis of the structure shows that the more appropriate model to be used toreproduce the magnetic properties is a regular S = 1/2 antiferromagnetic chain model including aninter-chain interaction (j0). Finally, the observed magnetic behavior (Jchain = �0.97(1) cm�1 andj0 = �0.03(1) cm�1) is compared with that observed in related hexacoordinated copper(II) compoundscontaining l1,3-squarato bridges.

� 2013 Elsevier Ltd. All rights reserved.

1. Introduction

In the last decade there has been a growing interest in the de-sign, syntheses and characterization of coordination polymers(CPs) and metal–organic frameworks (MOFs) due to the variety oftheir framework topologies and their potential technological appli-cations [1]. In general, the crystalline network of CPs is substan-tially controlled by the stereo-electronic preferences of the metalion and the spatial disposition of the binding sites on the ligands[2]. However, non covalent interactions (in particular H-bondingand aromatic-aromatic interactions) can also play a determinantrole in the modulation of the final extended network [3].

Among the extensive group of polyfunctional ligands with N/Odonors groups considered for the design of CPs, the interest forthose that possess one or more heterocyclic groups has grown ina notable way in the last years [4]. In this context, a considerablenumber of the described systems have been built up from flexibleligands based on the bis(imidazolyl) moiety, which offers a great

ll rights reserved.

á), carlos.gomez@uv.es (C.J.

capacity to act as suitable building blocks for the synthesis of MOFs[5].

We have previously shown that the flexible bis(imidazolyl)-based ligands HBIP (3,3-di(2-1H-2-imidazolyl)propanoic acid) [6]and DIMMAL (2-di1H-2-imidazolylmethylmalonate) [7] show aremarkable capability for the formation of interesting oligomericand polymeric systems. In addition to the metal–ligand covalentinteractions, these scorpionate-like ligands are involved in noncovalent interactions, through their hydrogen-bonding functional-ities as well as aromatic interactions between the imidazole rings.These interactions are driving forces involved in the formation ofhigh-dimensional systems and the modulation of the crystallineframework.

The inclusion of –NH groups in the side chain provides addi-tional hydrogen bonding capabilities. BIMAM (bis(imidazol-2-yl)methylaminomethane) ligand, with two imidazole groups and–NH amine functionalities in the side chain, is a flexible ligand thatuses two N-donor atoms to bind to the copper atom (see Scheme 1).In addition, it possesses a NH group which can be protonated undersuitable conditions.

Recently we have described several dinuclear and polymericBIMAM-containing copper(II) compounds with multiatomic

Scheme 1. The HBIMAM ligand.

Table 1Crystallographic data for compound 1.

Empirical formula C14H16CuN5O8

a (Å) 13.464(1)b (Å) 8.224(1c (Å) 15.153(1)a (�) 90b (�) 97.418(1)c (�) 90V (Å3) 1663.9(2)Crystal system monoclinicSpace group P21/nZ 4No. reflections collected 16376No. independent reflections 3075R(int) 0.0326No. observed rflns. [I > 2R(I)] 3438Data completeness [2h = 50�] 0.998R1

a 0.0438wR2

b 0.1039No. of parameters/restraints 336/16

a R1 = R||Fo| � |Fc||/R|Fo| for reflections with I > 2RI.b wR2 =

p(R[w(Fo

2 � Fc2)2]/R[w(Fo

2)2]) for all reflections.

E. Escrivá et al. / Polyhedron 56 (2013) 90–95 91

bridged ligands as oxalato or squarato [8]. In these systems, as wellas in other previously described in the literature [9], protonatedHBIBAM behaves as a bidentate k2-N,N0 ligand with the aminenitrogen not coordinated to the metal center. The high versatilityof this ligand is proven by the formation of different relatedcompounds, [Cu(HBIMAM)(C2O4)]2[Cu(C2O4)2(H2O)2] and {[Cu(HBIMAM) (H2O)(OClO3)]2(l-C2O4)}(ClO4)2 [9], with the use of dif-ferent synthetic conditions. Both compounds possess quite differ-ent 3D architectures in spite of being formed the same startingmaterials. The replacement of the oxalato ones by squarato onesresults in the formation of a 1-D polymeric [Cu(HBIMAM)Cl(C4-

O4)]n�nH2O compound [9], which consists of infinite chains builtfrom [Cu(HBIMAM)Cl]+ moieties bridged together by squarate an-ions acting in a l1,3-bis(monodentate) fashion.

We report herein the syntheses, X-ray structure and magneticcharacterization of a new 2-D coordination polymer based on theBIMAM ligand with an unusual [3 � 2] oblique copper(II) grid,where the metal atoms are organized in a bidimensional structurethrough l1,3-squarato bridges. In addition, the layers are held to-gether by a combination of H-bonding and aromatic-aromaticinteractions provided by the convenient structural features of BI-MAM and squarato.

2. Experimental

2.1. Synthesis

All reagents (except the HBIBAM) were purchased from com-mercial sources and used as received.

2.1.1. Bis(imidazol-2-yl)methylaminomethane (BIMAM)The synthesis of HBIMAM was carried out according to the

method described by Joseph et al. [10], and characterized by 1HNMR, 13C NMR and IR spectroscopy.

2.1.2. [Cu2(HBIMAM)2(C4O4)3(H2O)2]n�2nH2O (1)Aqueous solutions of HBIMAM (0.25 mmol, 15 mL) and Cu(BF4)2

�6H2O (0.25 mmol, 5 mL) were mixed together, resulting in a bluesolution. Upon addition of an aqueous solution of squaric acid(0.5 mmol, 5 mL) the color changed to intense green. Slow evapo-ration at room temperature yields a brown greenish precipitate,which was removed by filtration. The filtrate (pH 2.1) was allowedto stand at 20 �C. After several days, crystals appeared which wereseparated by filtration and washed with a 1:1 mixture of water–ethanol. Anal. Calc. for C14H16CuN5O8: C, 37.71; H, 3.62; Cu,14.25; N, 15.71. Found: C, 37.41; H, 3.58; Cu, 14.33; N, 15.41%.

2.2. X-ray structure

X-ray data were collected on a Bruker Smart Apex CCD diffrac-tometer, using graphite monochromated Mo Ka radiation. Thecrystal structure was solved and refined against all F2 values usingthe SHELXTL suite of programs [11a]. A summary of the data collec-tion, and structure refinement information is provided in Table 1.Data were corrected for absorption using empirical methods (SAD-

ABS) based upon symmetry-equivalent reflections combined withmeasurements at different azimuthal angles [11b]. Non-hydrogen

atoms were refined anisotropically. Hydrogen atoms (except thoseof water) were placed in calculated positions, refined using ideal-ized geometries (riding model) and assigned fixed isotropic dis-placement parameters.

2.3. Magnetic properties

Variable temperature susceptibility measurements were carriedout in the temperature range 2–300 K with an applied magneticfield of 0.1 T on a ground polycrystalline sample (42.72 mg) witha SQUID magnetometer (Quantum Design MPMS-XL-5). The iso-thermal magnetization of the sample was measured in the sameSQUID magnetometer at 2 K with magnetic fields up to 5 T. Thesusceptibility data were corrected for the sample holder, measuredin the same conditions, and for the diamagnetic contributions ofthe sample as deduced by using Pascals constant tables (vdia = -�383.54x10�6 emu.mol�1) [12].

3. Results and discussion

3.1. Synthesis of [Cu2(HBIMAM)2(C4O4)3(H2O)2]n�2nH2O (1)

Simple modifications of the reaction conditions (pH, molarratios, and source of CuII) for the synthesis of the Cu(II)–BIMAM–squarato system results in the formation of two differentcoordination polymers. The use of a 1:1:1 molar ratio of CuCl2�2H2

O:BIMAM:H2C4O4 yields the 1D coordination polymer [Cu(HBIMAM)Cl(C4O4)]n�(H2O)n [8a], which is composed of [CuCl(HBIMAM)]+ units bridged by l1,3-bis(monodentate) squarateanions. However, the use of a 1:1:2 molar ratio of Cu(BF4)2�6H2

O:BIMAM:H2C4O4, yields the coordination polymer [Cu2

(HBIMAM)2(C4O4)3(H2O)2]n�2nH2O (1) which is described below.

3.2. Crystal structure of [Cu2(HBIMAM)2(C4O4)3(H2O)2]n�2nH2O

Single-crystal X-ray analysis of compound 1 reveals that it iscomposed of a two-dimensional network that crystallizes in themonoclinic P21/n space group. The asymmetric unit contains twohalf Cu(II) ions, one HBIMAM ligand and one and a half squaratoligands, in addition to one coordinated and one non-coordinatedwater molecules.

The geometry (interatomic distances and angles) of the HBI-MAM molecule is similar to those previously reported for othercopper(II)–HBIMAM complexes [8]. The imidazole rings are planar,

Fig. 1. Coordination environments of the Cu(II) ions in 1.

Table 2Selected bond lengths (Å) and angles (�) in 1.

Cu(1) Cu(2)

Atoms distance atoms distance

Cu1–N2 2.015(3) Cu2–O1 2.036(2)Cu1–N3 1.993(3) Cu2–O5 2.328(2)Cu1–O3 2.473(3) Cu2–O7 1.983(2)

Atoms angle atoms angle

N2–Cu1–N3 92.9(1) O1–Cu2–O7 94.2(1)N2i–Cu1–N3 87.1(1) O1–Cu2–O7i 85.6(1)O3–Cu1–N3 88.4(1) O5–Cu2–O1 89.2(1)

Squarate anion

Atoms distance atoms distance

C11–O1 1.264(4) C11–C12 1.453(5)C12–O2 1.255(4) C12–C13 1.452(5)C13–O3 1.253(4) C13–C14 1.452(5)C14–O4 1.237(4) C14–C11 1.471(5)C1–O6 1.248(4) C1–C2 1.458(5)C2–O5 1.256(4) C1–C2i 1.472(5)

Symmetry code: (i) �x, �y, �z.

92 E. Escrivá et al. / Polyhedron 56 (2013) 90–95

with deviations from the mean planes not greater than 0.005 Å.The dihedral angle between the two imidazole rings of theHBIMAM ligand is 43.6(2)�. On the other hand, the dihedral anglesbetween the imidazole rings and the basal plane of the Cu1coordination polyhedron are 31.8(2)� and 31.1(2)� for [N1–N2]and [N3–N4], respectively.

The squarate dianions are essentially planar, the largest devia-tion from the mean plane being 0.044(2) Å. All the carboxylateoxygen atoms (except O1) are involved in hydrogen bonding. A dparameter has been previously introduced by us [7], as a measureof the asymmetry in the C4O4 group, defined as d = R|d(C–C)i -� d(C–C)mean| + R|d(C–O)i � d(C–O)mean|. Thus, d = 0 indicates anideal D4h symmetry and d = 0.221 Å (observed in the acid molecule)[13], indicates a C2v symmetry and substantial conjugation. The dvalues of compound 1 are 0.060 and 0.064 for the two crystallo-graphically independent squarato ligands, thus indicating a lowasymmetry in both C4O4 groups.

The crystal structure can be described as consisting in zig-zagchains, running along the [110] direction, built from copper ionsbridged by squarato ligands (see Fig. 1). A relevant structural fea-ture of these chains is that they contain two crystallographicallyindependent copper atoms, hereinafter referred to as Cu1 and Cu2.

The squarate anion within the Cu1–sq–Cu2 chains acts as l1,3-bis(monodentate) bridging ligand with an intra-chain copper–cop-per distance of 7.90 Å. Additional squarato ligands complete thecoordination sphere of Cu2 whereas HBIMAM ligands completethe coordination sphere of Cu1. The octahedral geometries aroundeach of the crystallographycally independent Cu(II) ions show thetypical Jahn–Teller distortion with an elongated octahedral coordi-nation (see Fig. 1 and Table 2).

The equatorial plane around Cu1 is made up of four nitrogenatoms from four imidazole rings, with Cu-N bond distances of1.989(2) and 1.987(2) Å (Table 2). The axial sites are occupiedby oxygen atoms from two squarato bridging ligands, (O3 andO3i, i = �x,�y,�z) with a Cu-O distance of 2.473(3) Å, indicatinga weak axial interaction. The tetragonality parameter (T = 0.81)is similar to those observed in several trans-CuN4O2 chromoph-ores of imidazole-containing hexacoordinated copper(II) com-plexes with four imidazole rings as strong donor ligands in theequatorial plane and weaker oxygen donor ligands in the apicalpositions [6,7,14].

The coordination environment of Cu2 is an octahedral CuO4O02,with the equatorial plane around Cu2 made up of two oxygenatoms from two squarato groups and two water molecules, withCu–O bond distances of 2.036(2) Å for Cu–Osq and 1.983(2) Å forCu–Ow (Table 2). The axial sites around Cu2 are occupied by O5and O5i oxygen atoms from two different squarato groups with alonger Cu–O5 bond length of 2.328(2) Å, as a consequence of theJahn–Teller ellongation. The calculated tetragonality parameter(T = 0.86) is close to those observed in related CuO4O02 copper(II)complexes [8b,15].

These zig-zag chains are further cross-linked through additionalsquarate anions to generate two-dimensional sheets parallel to theab plane. In addition, these layers are subsequently interconnectedinto a 3-D network by multiple H-bonds and aromatic-aromaticinteractions.

As described above, the zigzag Cu1–sq–Cu2 chains are furthercross-linked by additional squarate anions through O5 and O5i

(i = �x,�y,�z) acting in a l1,3-bis(monodentate) bridging modeand connecting Cu2 atoms of neighboring chains to generate a2D array (the Cu2–Cu2 distance is 8.22 Å). These layers are parallelto the ab plane (see Fig. 2). Importantly, these inter-chain bridgesconnect solely one type of crystallographycally independent Cu(II)atom (Cu2). Thus, since the main chain alternates both Cu1 andCu2 atoms, the squarato ligands link alternating metal centersforming a (3 � 2) oblique copper(II) grid (see Fig. 2).

It is in this sense that the net topology showed by the title com-pound can be considered unusual. Most two-dimensional coordi-nation polymers are built from simple geometrical units such astriangles (Schäfli symbol for this topological arrangement is 63),squares or rectangles (44), and hexagons (36) [16]. In general, allmetal nodes in 2-D frameworks have one single connectivity mode.However, the 3 � 2 oblique grid herein described contains twotypes of nodes, namely 4-connected Cu2 nodes and 2-connectedCu1 nodes within the same basic ring. This topological arrange-ment may be described by the symbol (64

2) [16] (see Fig. 3). Notethat a similar (3 � 2) copper(II) grid has been described in the 2Dcompound [Cu2(C2O4)2(pyrazine)3]n [17].

The three-dimensional crystal packing is driven primarily bythe H-bonds listed in Table 3. A relevant intra-chain interaction(N5� � �O3) is established between the NH2

+ groups (protonated sec-ondary amine) as the H-donors and the squarato coordinated O3atoms. In addition, the squarato ligands are also involved in hydro-gen bonds with both the coordinated and non-coordinated watermolecules, which play a relevant role in the crystal packing. Theyact as bifurcated H-donor towards two non-coordinated oxygenatoms, O2 and O6, from two different [C4O4]2� groups, thereforecontributing to the stabilization of the 2D framework. Both interac-tions are relatively strong since the O� � �O separations are not farfrom the range (2.4–2.7 Å) of the strong hydrogen-bonded O� � �Odistances [18].

Fig. 2. Two-dimensional rectangular network of compound 1 in the ab plane. H atoms have been omitted for clarity.

Fig. 3. Schematic representation of the (642) topological arrangement of the 2D

framework in 1.

Table 3Hydrogen bonds in compound 1.

X–H� � �Y X� � �Y (Å) \X–H� � �Y (�)

O7–H71� � �O6iv 2.621(4) 149.1O7–H72� � �O2 2.601(3) 173.7O8–H81� � �O6 3.029(4) 161.4O8–H82� � �O2 2.624(4) 164.0N1–H1� � �O5v 2.871(4) 170.7N4–H4� � �O4vi 2.794(4) 171.3N5–H5A� � �O7v 2.992(4) 145.9N5H–5B� � �O3i 2.670(4) 169.0

Symmetry codes: (i) –x, –y, –z; (iv) x, y + 1, z; (v) x–1/2, –y + 1/2, z + 1/2; (vi) –x + 1/2, –y + 1/2, z + 1/2.

0.30

0.32

0.34

0.36

0.38

0.40

0.42

0.44

0 50 100 150 200 250 300

χ mT

(em

u.K

.mol

-1)

T (K)

0.38

0.39

0.40

0.41

0.42

5 10 15 20 25 30

Fig. 5. Thermal variation of the vmT product for the title compound. Inset showsthe low temperature region. Solid and dotted lines are the best fit to the models (seetext).

E. Escrivá et al. / Polyhedron 56 (2013) 90–95 93

Finally, the protonated nitrogen atoms of the imidazole groupsparticipate in moderate hydrogen bonds as H-donors towardscarboxylate groups of neighboring building blocks. These set ofH-bond contacts, in combination with the p�p interaction be-tween imidazole rings (see below), connect the above describedab layers into an infinite three-dimensional array (see Fig. 4).

Fig. 4. Stacking of the ab layers along the crystallographic c a

As it was found in related bis(imidazolyl)-copper(II) systems[7,8] the butterfly configuration of the bis(imidazolyl) fragmentsplays a determinant role in the topological configuration of the3-D network. In 1 these heterocycles fill the gap between thesheets making up intercalated aromatic layers between them. Thistopology is similar (but not identical) to that described in severalDIMMAL derivatives [8].

3.3. Magnetic properties

The product of the molar magnetic susceptibility per Cu(II) iontimes the temperature (vmT) for compound 1 shows a room tem-

xis. Dashed lines represent the H-bonds listed in Table 3.

Table 4Relevant structural and magnetic data for hexacoordinated copper(II) compounds containing l1,3-squarato bridges.

Compounda C4O4coord. site Chromophore T Cu–Osq (Å) d (Å) d(Cu-Cu)b (Å) C–O–Cu (�) J (cm�1) Refs.

VAVLEJ axial CuN2O4 0.81 2.475 0.058 7.31 118.4 �0.8c [22]VUBNIP axial CuO4O02 0.79 2.469 0.081 7.86 119.8 �2.8c [23]QITSAN axial CuN3O3 0.90 2.242 0.061 7.47 129.4 �0 [24]FIZHOM equatorial CuN3O3 0.78 1.934 0.060 7.65 134.1 +1.3 [25]COHNOD equatorial CuN3O3 0.83 1.960 0.020 7.47 140.1 �1.2 [26]QAGZOP axial CuN4O2 0.83 2.241 0.082 7.83 121.1 �0 [27]1 axial-equatoriald CuN4O2 0.81 2.473 0.060 7.93 125.7f �0.97 This work

equatoriale CuO4O02 0.86 2.036 0.064 8.24 125.4 �0.03

a VAVLEJ = Cu(C4O4)(im)2�2H2O; VUBNIP = Cu(C4O4)�4H2O; QITSAN = [Cu4(pap)4(H2O)4(C4O4)2]n[C4O4]n[NO3]2n�12nH2O; FIZHOM = [Cu2(bpcam)2(C4O4)(H2O)4]�10H2O;COHNOD = [Cu2(MeDPA)2(l1,3-C4O4)(H2O)4](ClO4)2; QAGZOP = [Cu(C4O4)2(amp)2]�nH2O; im = imidazole, pap = pyrazine[2,3-f][4,7]phenanthroline, bpcam = bis(2-pyrim-idyl)amidate, MeDPA = N-methylbis(2-pyridylmethyl)amine, amp = 2-aminomethylpyridine.

b Copper–copper separation across the squarato bridge.c Weiss temperature, h, obtained from the Curie–Weiss fit.d For Cu1� � �[C4O4]� � �Cu2 bridges.e For Cu2� � �[C4O4]� � �Cu2 bridges.f Mean value.

94 E. Escrivá et al. / Polyhedron 56 (2013) 90–95

perature value of ca. 0.42 emu K mol�1, which is the expected va-lue for an isolated S = 1/2 Cu(II) ion with g � 2.12. When the tem-perature is decreased the vmT value remains constant down to ca.50 K and shows a progressive decrease below this temperature toreach a value of ca. 0.32 emu K mol�1 at 2 K (Fig. 5). This behaviorsuggests the presence of predominant Cu(II)-Cu(II) weak antiferro-magnetic interactions. As described above, the structure of com-pound 1 shows the presence of � � �Cu1–sq–Cu2� � � chainspropagating along the [110] direction which are further connectedthrough additional squarato ligands bridging the Cu2 atoms ofadjacent chains in a 2D array. Accordingly, we have used two dif-ferent models to reproduce the magnetic properties of compound1 which are consistent with the crystallographic description ofthe compound: (i) the S = 1/2 quadratic layer antiferromagneticmodel (QLAF) proposed by Lines [19] and (ii) the simple regularS = 1/2 antiferromagnetic chain model proposed by Hatfield andco-workers [20], including an inter-chain interaction (j0) by usingthe molecular field approximation [21]. Both models reproducevery satisfactorily the magnetic properties of compound 1 in thewhole temperature range with the following parameters:g = 2.138 and J = �0.44 cm�1 for the QLAF model (solid line inFig. 5) and g = 2.139, Jchain = �0.97(1) cm�1 and j0 = �0.03(1) cm�1

for the chain model with inter-chain interactions (dotted line inFig. 5). In both models the hamiltonian used is of the typeH = �JSiSi+1.

A detailed analysis of the structure shows that the more appro-priate model to be used is the second one (interacting antiferro-mangetic chains) since the intra- and inter-chain interactions arenot identical and the connections between the chains are not tak-ing place every Cu(II) ion but only every two Cu ions. Although thedifference is very small, these considerations agree with theslightly better fit produced by the second model (interacting anti-ferromagnetic chains). Finally, it is worth to mention that the veryweak antiferromagnetic coupling through the two different squa-rato bridges found in the title compound is not surprising since itis well known that the squarato bridge provides very weak mag-netic coupling (Table 4).

Furthermore, although the differences are small, the weakercoupling found in the inter-chain interaction agrees with the factthat this interaction implies a squarato bridge connecting two axialpositions with long Cu–O bond lengths whereas the intra-chaininteraction involves an axial and an equatorial position.

4. Conclusions

In summary, we have successfully obtained a novel 2-D coordi-nation polymer in the Cu(II)–BIMAM–squarato system with a two-

dimensional framework that exhibits an unusual (3 � 2) obliquegrid containing two types of nodes, a 4-connected and a 2-con-nected nodes, within the same basic ring.

Variable-temperature magnetic susceptibility results show theexistence of weak antiferromagnetic interactions between thecopper(II) ions through l1,3-squarato bridges. A detailed analysisof the structure allows us to consider, from a magnetic point ofview, that compound [Cu2(HBIMAM)2(C4O4)3(H2O)2]n�2nH2O isbuild up by a set of interacting chains (Jchain = �0.97(1) cm�1 andj0 = �0.03(1) cm�1).

Acknowledgements

We thank the Spanish Ministerio de Economía y Competitividad(Projects CONSOLIDER-INGENIO CSD 2010-00065 and CTQ-2011-26507) and the Generalitat Valenciana (Prometeo project 2009/095)for financial support.

Appendix A. Supplementary data

CCDC 860497 contains the supplementary crystallographic datafor this paper. These data can be obtained free of charge via http://www.ccdc.cam.ac.uk/conts/retrieving.html, or from the CambridgeCrystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ,UK; fax: +44 1223-336-033; or e-mail: deposit@ccdc.cam.ac.uk.

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