Highly Rare Ferromagnetic Interaction with theCu(tetrahedron)-Cu(square)-Cu(tetrahedron) Mode Observed in A2-Fold Interpenetrating Moganite Net

Feng Luo, Yun-xia Che, and Ji-min Zheng*

Department of Chemistry, Nankai UniVersity, Tianjin, China

ReceiVed October 28, 2008; ReVised Manuscript ReceiVed March 15, 2009

ABSTRACT: Polymer 1, Cu3(µ2-OH)2(nic)4 (Hnic) isonic otinic acid), was prepared by the hydrothermal self-assembly of CuCl andHnic in the presence of HClO4. The outstanding feature of it is the moganite matrix with 2-fold interpenetration built on two distinct coppernodes and ferromagnetic coupling pathway in the Cu(tetrahedron)-Cu(square)-Cu(tetrahedron) fashion.

The study of the magnetic interactions in polynuclear metalcomplexes is playing a key role in the development of magne-tochemistry. In the literature, extensive efforts have been devotedto magnetostructural research of d9 copper(II)-based complexes.1

Usually, the d9 copper(II) ion holds square, 4 + 1 pyramidal, 4 +2 octahedral, and tetrahedral geometry, and these geometriescooperating with different inorganic or organic mediums generatevarious structures and succedent magnetic phenomena. The firstmagnetostructural correlation about one planar hydroxo-bridgedcopper(II) dimers was theoretically interpreted by active-electronapproach reported by Hatfield and Hodgson, and succedent ab initiocalculation reported by Daudey.2 In light of these theoreticalinterpretations and numerous experimental results, they deduced alinear correlation of J (cm-1) ) -74R(degrees of Cu-O-Cu) +7270 between J and R to determine ferromagnetic or antiferro-magnetic interaction and evaluate the interaction strength.2 Andthe crucial R value is 97.5° with the below rule: if R > 97.5°, thenJ > 0, ferromagnetic interaction; if R < 97.5°, then J < 0,antiferromagnetic interaction. At the same time, such Hatfield andHodgson’s correlation can be also obtained via the natural andorthogonalized magnetic orbital approaches: for this hydroxo-bridged copper(II) dimers, each Cu(II) ions show the squaregeometry, thus their single magnetic orbital is b1 and the finalmagnetic interactions of J ) Jb1b1 depends on the R value. J ispositive for R close to 90°, and becomes negative for R far from90°.3 Thereby, it is believed that the Cu(II)-based magneticchemistry can be easily forecasted through the above theory andexperiential approximate.

On the basis of the copper(II) geometry, the possible magneticinteractions of hydroxo-bridged copper compounds between Cu(II)ions are (a) Cu(square)-Cu(square), (b) Cu(square)-Cu(pyramid),(c) Cu(square)-Cu(octahedron), (d) Cu(square)-Cu(tetrahedron), (e)Cu(pyramid)-Cu(pyramid), (f) Cu(pyramid)-Cu(octahedron), (g)Cu(pyramid)-Cu(tetrahedron), (h) Cu(octahedron)-Cu(octahedron),(i) Cu(octahedron)-Cu(tetrahedron), (j) Cu(tetrahedron)-Cu(tetra-hedron). On the basis of the natural and orthogonalized magneticorbital approaches, the a, b, c, e, f, and h magnetic correlation isdetermined by J ) Jb1b1

that depends on the R values as discussedabove; for the d, g, i, and j magnetic correlation, their singlemagnetic orbital is a1(dxy), a2(dyz), or b2(dzx) and the final magneticinteractions are J ) Ja1b1

, Ja2b1, and Jb2b1

, where all the Ja1b1, Ja2b1

,and Jb2b1

terms are strictly positive, then ferromagnetic interactionsare expected. In other words, these magnetic correlations areundependent on R values; the j magnetic correlation holds the singlemagnetic orbital of a1(dxy), a2(dyz), or b2(dzx) and correspondingmagnetic interactions of Ja1a1, Ja1a2, Ja1b2, Ja2a2, Ja2b2, Jb2b2, whereJa1a1, Ja2a2, Jb2b2 is expected to be antiferromagnetic, whereas Ja1b2,

Ja1a2, and Ja2b2 is viewed to be ferromagnetic, then the macroscopicalmagnetic behavior is determined by the final magnetic interactions.In the literature, the a, b, c, e f, h, and j magnetic correlations arecommon.3,4 By contrast, to the best of our knowledge, we are notaware of a precedent featuring the d, g, i, and j magnetic correlation.Herein, we report a new hydroxo-bridged copper polymer, Cu3(µ2-OH)2(nic)4, that displays the first d, viz. Cu(square)-Cu(tetrahedron),magnetic correlation.

In the presence of HClO4, polymer 1 was synthesized by thehydrothermal self-assembly of CuCl and Hnic in a 1:1 ratio.5

Additional experiments are also explored to confirm the relationshipbetween produces of 1 and reaction conditions. Either replacementof the copper source from CuCl2, CuSO4, or Cu(NO3)2 or theabsence of HClO4 will generate another compound.6 Thus, thecopper source from CuCl and the presence of HClO4 is crucial forthe formation of 1. Moreover, the phase purity of the bulk samplesof 1 is confirmed by powder X-ray diffraction studies, see theSupporting Information.

The single-crystal X-ray diffraction analysis suggests the P21/Cspace group for 1.7 As shown in Figure 1, Cu1 atoms located onthe inversion center holds the position occupation of 0.5 andCuN2O2 square geometry, completed by two µ2-OH oxygens andtwo nic nitrogens; Cu2 corresponds to the CuO3N tetrahedralgeometry, finished by one µ2-OH oxygen, two nic oxygens, andone nic nitrogen. The Cu-O bond lengths of 1.910(2)-1.989(2)Åare slightly shorter than the Cu-N bond lengths in the range of2.012(3)-2.054(3)Å, because of the different atom radius of N, Oatoms. The nic ligands adopt the linear coordinated mode with oneN and one carboxylate O donor to ligate copper atoms.

* To whom correspondence should be addressed. Fax: 86-22-23502458. Tel:86-22-23507950. E-mail: jmzheng@nankai.edu.cn.

Figure 1. View of the Cu3(µ2-OH)2(CO2)4 trimer.

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10.1021/cg801208z CCC: $40.75 2009 American Chemical SocietyPublished on Web 04/07/2009

For 1, the first outstanding structure feature is the linearCu3(OH)2(CO2)4 trimer with each copper pairs only bridged byone OH- group. Within it, the two terminal copper ions showthe tetrahedral geometry, whereas the middle copper ions issquare coordinated. The Cu-Cu distance and Cu-O-Cu anglesare Cu1-Cu2/3.27 Å and Cu1-O1-Cu2/116.62°, respectively.In the literature, only one 1D compound has a similar linearCu3(OH)2(CO2)4 fragment;8 however, in it, each copper pair isbridged not only by one OH- group but also by one carboxylate.Moreover, all the copper ions in it are square-coordinated. Thus,it is clear that the present linear Cu3(OH)2(CO2)4 trimer is uniqueand unprecedented.

Another outstanding structure feature is the moganite net with2-fold interpenetration built on two distinct copper nodes. As shownin Figure 2, each linear nic ligand acts as linker, and then eachcopper ion becomes to be 4-connected node. And the 3D matrixcan be easily constructed by connecting Cu nodes together, yieldinga 4-connected net (Figure 2). The topology analysis via Topos40program9 suggests moganite net with the (42 ·62 ·82)(4 ·64 ·84)2

topology symbol, where the ratio of two kinds of copper nodes isCu(tetrahedron)/Cu(square) ) 2:1. Furthermore, two identicalmoganite nets interpenetrate each other (type Ia), as illustrated inFigure 3.

As we know, moganite, a newly recognized mineral, is closelyrelated to quartz and presents the second most abundant crystallinematerial in the Earth’s crust because of its considerable techno-logical importance. The construction of such net is somewhatdifficult, as it requires two distinct 4-connected nodes. Until now,only a few cases have been reported to adopt such a topology.10 In2004, Loye and co-workers reported a highly rare moganite netbuilt on two distinct copper nodes, although all the copper ions areoctahedrally coordinated. In comparison, the copper ions in the

present case are four-coordinated and allow 2-fold interpenetration.In contrast to the reported moganite nets, the present one is thefirst (3d metal)-based moganite net with 2-fold interpenetration.

Besides its outstanding structural features, the present one alsoholds unique and unprecedented magnetic properties. The temper-ature-dependent magnetic susceptibility data of polymer 1 weremeasured for crystal samples at an applied magnetic field of 2000Oe in the temperature range of 2-300 K. The �MT value at roomtemperature is 0.96 cm3 mol-1 K, comparable with the expectedvalue of 1.13 cm3 mol-1 K for three Cu(II) centers as isolatedmagnetic source. At 300-50 K, the �MT value increases from 0.96to 1.05 cm3 mol-1 K, indicating the very weak ferromagneticbehavior. Below 50 K, the �MT value drops abruptly until 0.72 cm3

mol-1 K at 2 K, because of intermolecular antiferromagneticinteractions and/or other factors (such as zero field splitting). Thisweak ferromagnetic interactions can be further supported by thefitting of �M ) C/(T - θ) at 2-300 K with C )0.98 cm3 mol-1 K,θ ) +2.0 K. (Figure 4.)

Obviously, the magnetic property of 1 can be treated as a lineartrinuclear system mediated by OH- group. As the two terminalcopper atoms are symmetry-related, then only one couplingconstant, J, is involved. The best fitting at 2-300 K upon theCu2-J-Cu1-J-Cu2 mode with the consideration of other factors(θ) gives J ) +0.71 cm-1, g )2.01, TIP ) 350 × 10-6 cm3 mol,θ )-1.8 K, F ) 0.1, where J is a coupling constant, θ other factors,g Zeeman factor, TIP temperature-independent paramagnetism, andF paramagnetic impurities.3 The detailed Heisenberg Hamiltonianand the derivation of theoretical equations of magnetic susceptibilityare listed in Scheme 1.3

Usually, as discussed above, the magnetic nature for Cu(II) ionsmediated by OH- groups can be estimated by orthogonalized ornatural magnetic orbital approach, as well as Goodenough-Kanamorirules.3,11 For the system containing the square, pyramidal, oroctahedral Cu(II) ions, their interaction between pairs of magneticorbital is Jb1b1

, then the well-defined linear correlation between Jand R, J ) -74R + 7270, reported by Hatfield and Hodgson, canbe utilize to evaluate the magnetic nature and the interaction strength

Figure 2. Schematic description of the moganite net built on tetrahedraland square copper nodes.

Figure 3. View of 2-fold interpenetrating moganite net.

Figure 4. Experimental (black) and simulated (red) �MT vs T and �M

vs T plots of 1.

Scheme 1.

H)-2J(SCu1Cu2 + SCu1Cu2A)+

�g(SCu1 + SCu2 + SCu2A)H

xm ) Ng2�2

4k(T- θ){1+ exp(2J ⁄ kT)+ 10exp(3J ⁄ kT)1+ exp(2J ⁄ kT)+ 2exp(3J ⁄ kT) } ×

(1-F)+ [3Ng2�2

4kT ]F+TIP

(1)

2048 Crystal Growth & Design, Vol. 9, No. 5, 2009 Communications

of magnetic orbital. In 1, this special trimer comprises one squareand two tetrahedral Cu(II) ions and it belongs to the above-mentioned d magnetic correlation. Then the ferromagnetic interac-tions within this Cu3(µ2-OH)2(CO2)4 trimer is expected, which iswell-consistent with the experimental results.

In conclusion, herein, a new topological framework is preparedby the hydrothermal self-assembly of CuCl and Hnic in the presenceof HClO4. Notably, it holds two outstanding features: (a) it presentsthe first (3d metal)-based, 2-fold interpenetrating moganite net; (b)it shows the first d, viz. Cu(square)-Cu(tetrahedron), magneticcorrelation.

Acknowledgment. This work was supported by the NationalNatural Science Foundation of China (50572040).

Supporting Information Available: XRD studies (PDF) and crystaldata in CIF format. This material is available free of charge via theInternet at http://pubs.acs.org.

References

(1) (a) Charlot, M. F.; Verdaguer, M.; Journaux, Y.; Loth, P. D.; Daudey,J. P. Inorg. Chem. 1984, 23, 3802. (b) Glerup, J.; Goodson, P. A.;Hodgson, D. J.; Michelsen, K. Inorg. Chem. 1995, 34, 6255. (c)Castillo, O.; Luque, A.; Julve, M.; Lloret, F.; Roman, P. Inorg. Chim.Acta 2001, 315, 9. (d) Castillo, O.; Luque, A.; Julve, M.; Lloret, F.;Roman, P. Inorg. Chem. Commun. 2001, 4, 350. (e) Pellaux, R.;Schmalle, H. W.; Huber, R.; Fischer, P.; Hauss, T.; Ouladdiaf, B.;Decurtins, S. Inorg. Chem. 1997, 36, 2301.

(2) (a) Crawford, W. H.; Richardson, H. W.; Wasson, J. R.; Hodgson,D. J.; Hatfield, W. E. Inorg. Chem. 1976, 15, 2107. (b) de Loth, P.;

Darudey, J. P.; Astheimer, H.; Walz, L.; Haase, W. J. Chem. Phys.1985, 97, 4884.

(3) Kahn, O. Molecular Magnetism; Wiley-VCH: New York, 1993.(4) (a) King, P.; Clerac, R.; Anson, C. E.; Coulon, C.; Powell, A. K. Inorg.

Chem. 2003, 42, 3492. (b) Ruiz, R.; Alemany, P.; Alvarez, S.; Cano,J. J. Am. Chem. Soc. 1997, 119, 1297.

(5) An aqueous solution (8 mL) of CuCl (1mmol) and Hnic (1 mmol)with 0.5 mL of HClO4 (70%) was sealed in a Teflon reactor and heatedat 200°C for 7 days, and then cooled to room temperature at 3°C/h.Subsequently, blue crystals were obtained in 85% yield based on Hnic.Element anal. (%) Calcd for 1: C, 40.42; H, 2.54; N, 7.85. Found: C,40.51; H, 2.47; N, 7.68.

(6) Waizumi, K.; Takuno, M.; Fukushima, N.; Masuda, H. J. Coord. Chem.1998, 44, 269.

(7) Crystallographic data for 1: C24H18Cu3N4O10, monoclinic, P2(1)/c, Z) 2, T ) 298(2) K, a ) 5.9567(12) Å, b ) 20.497(4) Å, c ) 10.180(2)Å, � ) 111.70(3)°, S ) 1.119, R1 ) 0.0379, wR2 ) 0.101.

(8) Chen, H.-J.; Zhang, J.; Feng, W.-L.; Fu, M. Inorg. Chem. Commun.2006, 9, 300.

(9) (a) Blatov, V. A.;http://www.topos.ssu.samara.ru/ (2006). (b) Blatov,V. A.; Shevchenko, A. P.; Serezhkin, V. N. J. Appl. Crystallogr. 2000,33, 1193.

(10) (a) O’Keeffe, M.; Yaghi, O. M. Reticular Chemistry StructureResource; Arizona State University: Tempe, AZ, 2005; http://okeeffe-ws1.la.asu.edu/rcsr /home.htm. (b) Ramsden, S. J.; Robins, V.;Hungerford, S.; Hyde, S. T.epinet.anu.edu.au (2006). (c) Su, C.-Y.;Smith, M. D.; Goforth, A. M.; zur Loye, H.-C. Inorg. Chem. 2004,43, 6881. (d) Zhang, L.; Li, Z.-J.; Qin, Y.-Y.; Zhang, J.; Cheng, J.-K.; Yin, P.-X.; Yao, Y.-G. CrystEngComm 2008, 10, 655.

(11) (a) Goodenough, J. B. Phys. ReV. 1995, 100, 564. (b) Kanamori, J. J.Phys. Chem. Solids 1959, 10, 87.

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