Mononuclear, Tetra-, Penta- 3d Molecular Clusters Based on the

Mononuclear, Tetra-, Penta- 3d Molecular Clusters Based on the Variability of SS-1,2-Bis(1H-benzimidazole-2-yl)-1,2-ethanediol Ligand Arising from Hydroponic and Hydrothermal Conditions: Structure, Crystal Growth, and Magnetic Properties

CRYSTAL GROWTH & DESIGN 2009 VOL. 9, NO. 3 1402–1410

Yan-Ling Zhou,†,‡ Fa-Yan Meng,† Jian Zhang,‡ Ming-Hua Zeng,*,† and Hong Liang*,†,‡ Key Laboratory of Medicinal Chemical Resources and Molecular, Guang Xi Normal UniVersity, Guilin 541004, China, and Department of Chemistry and Chemical Engineering, Central South UniVersity, Changsha 410083, P. R. China ReceiVed June 19, 2008; ReVised Manuscript ReceiVed NoVember 17, 2008

ABSTRACT: Four compounds Co(SS-H2bzimed-H)2 · CH3OH · 2H2O (1), Zn4(SS-H2bzimed-H)4(NO3)4 · 5H2O (2), Co5(HbzimedH)6Cl4 · 2.5H2O (3), Ni5(Hbzimed-H)6Cl4 · 4H2O (4) (SS-H2bzimed ) SS-1,2-bis(1H-benzimidazole-2-yl)-1,2-ethanediol; Hbzimed ) 1,2-bis(1H-benzimidazol-2-yl)-1,2-ethenol) have been synthesized by methods of alternative hydroponic and hydrothermal reactions, and their crystal structures were determined. Room temperature reaction of SS-H2bzimed with Co(NO3)2 · 6H2O yielded compound 1 which crystallizes in the chiral orthorhombic space group C2221, where SS-H2bzimed ligands act as facially tridentate ligands through both bis-benzimidazole nitrogen atoms and one deprotonated hydroxyl group. By using Zn(NO3)2 · 6H2O instead of Co(NO3)2 · 6H2O, under refluxed stirring at 80 °C, compound 2 was obtained similarly to 1 which crystallizes in the chiral monoclinic space group C2, showing a Zn4[µ3-O]4 cubic core constructed by four monodeprotonated, µ3-κN,O:κO,O′:κN′,O′-SS-H2bzimed ligands. Under 140 °C at hydrothermal conditions, the SS-H2bzimed ligand unexpectedly changes to Hbzimed by an in situ intramolecular dehydration coupling reaction, and the neonatal ligands bridge metal systems into two kinds of rare single crystal microtubes constructed by a trigonal bipyramid M5[µ-O]6 (M ) CoII: 3, NiII: 4) core where each apical Oh metal atom is linked to equatorial Td metal atoms through six µ2-κN,O:κN′,O-Hbzimed-H ligands. Magnetic studies show that 3 exhibits spin-canting behavior below 10 K, whereas 4 shows only simple antiferromagnetic coupling. Such magnetic behavior of 3 mainly arises from Oh-Td mixed geometries of pentameric Co(II) ions, which can result in relatively noncompensated moments, according to different efficient spins of Co(II) at very low temperature and the Dzyaloshinski-Moriya interaction. A discussion of the coordination properties of H2bzimed ligands upon different geometries of the central ions, and a probable mechanism for in situ reaction of ligand and the formation of single crystal microtubes is provided. Introduction In recent years, polynuclear clusters of 3d transition-metal ions continue to attract a great deal of interest, such as the architectural beauty of their structures, and their new and fascinating magnetic properties.1,2 The design of molecular clusters is highly influenced by factors such as the coordination nature of the metal ion, the structural characteristics of the organic ligand, the reaction condition, and other possible influences, which provides a possible approach to the controlled assembly of polynuclear compounds with systematically tunable interesting properties.1-4 However, truly rational design of these cluster structures still remains a largely elusive goal; recent research has demonstrated the dramatic influence of rigid bridging ligands (e.g., benzotriazole) that impose the geometry on the resultant cluster,3 and flexible organic bridging ligands (e.g., alkyl alcohols) that impose little or no geometry.4 Research has also been extended to include bridging ligands constructed from rigid and flexible groups into the synthesis of magnetic molecular clusters, such as a commonly used ligand containing the pyridyl-type of spacer with heterocycles and alkoxide functions, as good chelating/bridging groups to favor the formation of polynuclear products.2,5 Very recently, we have been investigating Co(II) and Ni(II) complexes constructed by the (1H-benzimidazol-2-yl)-methanol, which usually form cubane-based structures and favor ferromagnetic coupling through * To whom correspondence should be addressed. E-mail: zmh@ mailbox.gxnu.edu.cn. Fax: 86 773 5846-279. † Guang Xi Normal University. ‡ Central South University.

µ3-O-bridges and toward the single-molecule magnets (SMMs) behavior.2 Such SMMs are individual molecules that possess a significant barrier (vs kT) to magnetization relaxation and thus exhibit the ability to function as magnets below their blocking temperatures (TB). Herein, we choose an analogous SS-1,2bis(1H-benzimidazole-2-yl)-1,2-ethanediol (SS-H2bzimed) with two rigid benzimidazole rings and two flexible hydroxyls groups, to serve as a chelating/bridging ligand to bring 3d metal ions into molecular clusters. To the best of our knowledge, the crystal structures of metal-organic complexes with SS-H2bzimed ligand have not been well explored to date, in comparison with other semirigid benzimidazole based bridging ligands.6 Actually, only two research groups showed that this ligand could adopt different bridging modes (Scheme 1), with the alcohol group coordinated to Cu(II) and Ni(II) atoms.7 On the other hand, it is well-known that the vast majority of cluster compounds were produced through the “conventional” techniques-mixed metal ion and ligands in a common solvent at a temperature limited by the boiling point of that solvent at atmospheric pressure.1 With the development of new preparative routes for the synthesis of clusters under nonambient conditions, recently a few groups have explored the hydro(solvo)thermal method to cluster.8 This technique has demonstrated in particular increasing success in providing alternative pathways to cluster with in situ ligand syntheses, which not only provides a powerful synthesis method for organic ligands that cannot normally be obtained by traditional methods, but also represents a potential new direction for novel coordination compounds.8,9 A fascinating aspect for synthetic inorganic chemists is preparing new

10.1021/cg800649a CCC: $40.75  2009 American Chemical Society Published on Web 01/21/2009

Mononuclear, Tetra-, Penta- 3d Molecular Clusters

Crystal Growth & Design, Vol. 9, No. 3, 2009 1403

Scheme 1. Coordination Modes for Ligand SS-H2bzimed and Hbzimed

cluster compounds in the same ligand under different reaction conditions. Obviously, research on the molecular clusters of the chiral, multifunctional SS-H2bzimed ligand, with different metal ions is interesting work under a different synthesis method. Herein, we describe the synthesis and characteristics of four compounds, Co(SS-H2bzimed-H)2 · CH3OH · 2H2O (1), Zn4(SSH2bzimed-H)4(NO3)4 · 5H2O (2), Co5(Hbzimed-H)6Cl4 · 2.5H2O (3), and Ni5(Hbzimed-H)6Cl4 · 4H2O (4), which show various coordination modes of ligand SS-H2bzimed and the factors favoring the formation of these complexes under different reaction conditions, as well as a probable mechanism of ligand reaction and single crystal microtubes for compounds 3 and 4 under hydrothermal conditions. Furthermore, we demonstrate the totally different magnetic behavior of isostructural compounds 3 and 4. Experimental Section Materials and Physical Measurements. The reagents and solvents employed were commercially available and used as received without further purification. The C, H, and N microanalyses were carried out with an Elementar Vario-EL CHNS elemental analyzer. The TG analysis was performed on Pyris Diamond TG/DTA. The FT-IR spectra were recorded from KBr pellets in the range 4000-400 cm-1 on a Bio-Rad FTS-7 spectrometer. Temperature and field-dependent magnetic measurements were carried out on a SQUID-MPMS-XL-7 magnetometer. Diamagnetic corrections were made with Pascal’s constants. Co(SS-H2bzimed-H)2 · CH3OH · 2H2O (1). SS-H2bzimed (0.125 mmol) was dissolved in methanol solution (5 mL), and a solution of Co(NO3)2 · 6H2O (0.25 mmol) in H2O (5 mL) was added dropwise. The mixture was stirred at room temperature for 30 min, and then filtered. The filtrate was allowed to slowly concentrate by evaporation at room temperature. Three days later, red crystals were obtained, and the crystals were washed with water (yield ca. 17% based on CoII). Anal. Calcd. (%) for C33H34CoN8O7: C, 55.54; H, 4.80; N, 15.70; found C, 55.55; H, 4.82; N, 15.79%. IR data for 1 (KBr, cm-1): 3238(s), 1621(m), 1593(m), 1470(m), 1450(m), 1274(m), 921(m), 744(m). Zn4(SS-H2bzimed-H)4(NO3)4 · 5H2O (2). SS-H2bzimed (0.125 mmol) was dissolved in methanol solution (5 mL), and a solution of Zn(NO3)2 · 6H2O (0.25 mmol) in H2O (5 mL) was added dropwise. The pH value was adjusted to 8.5 with triethylamine. A white precipitate was formed. The suspension was maintained at 80 °C by refluxed stirring for 5 h. The cooled solution was filtered and was allowed to slowly concentrate by evaporation at room temperature. One week later, pale-yellow crystals were obtained. The crystals were washed with ether and dried (yield ca. 16% based on ZnII). Anal. Calcd. (%) for C64H62N20O25Zn4: C, 43.36; H, 3.52; N, 15.80; Found C, 43.41; H, 3.56; N, 15.72%. IR data for 2 (KBr, cm-1): 3432(s), 2351(m), 1625(m), 1453(m), 1384(m), 1108(m), 1487(m), 742(m). Co5(Hbzimed-H)6Cl4 · 2.5H2O (3). SS-H2bzimed (0.125 mmol) in a CH3OH solution (3 mL) was added to a water solution (4 mL) of

CoCl2 · 6H2O (0.25 mmol) and 0.05 mL of triethylamine dropwise to the mixed solution (5 mL) for 15 min at room temperature. The reactants were sealed in a 15-mL Teflon-lined autoclave heated at 140 °C for 5 days and then cooled to room temperature at a rate of 10 K h-1. Then red block solid single crystals were obtained along with purple powder. The crystals were picked out, washed with distilled water, and dried in air (yield ca. 32.2% based on CoII). Anal. Calcd. (%) for C96H71Co5N24O8.5Cl4: C, 54.05; H, 3.35; N, 15.76; Found C, 54.28; H, 3.41; N, 15.70%. IR data for 3 (KBr, cm-1): 3424(s), 1609(m), 1541(m), 1453(m), 1399(v), 1049(m), 994(m), 747(m). Ni5(Hbzimed-H)6Cl4 · 4H2O (4). This compound was prepared in a manner similar to 3 in a water/methanol mixture using NiCl2 · 6H2O and SS-H2bzimed, to give dark red both solid single crystals suitable for structural analysis (yield ca. 33.7% based on NiII). Anal. Calcd. (%) for C96H74N24Ni5O10Cl4: C, 53.40; H, 3.45; N, 15.57; Found C, 53.59; H, 3.50; N, 15.50%. IR data for 4 (KBr, cm-1): 3398(s), 1611(m), 1543(m), 1453(m), 1399(m), 1067(m), 994(m), 747(m). Single microtubular crystals Co5(Hbzimed-H)6Cl4 · 2.5H2O (3′). In the preparation of compound 3, we often at one time obtain block solid 3 and microtubular single crystals 3′; the latter’s surfaces are much crisper and rougher. In order to probe the factors that may affect the formation of the microtubular single crystals, a series of experiments were designed with variable hydrothermal conditions: the length of heating time, temperatures and pH, and particular experimental approaches (refer to the section Formation of Single Crystal Microtubes). In addition, the microtubular single crystals for 4 are also obtained at similar conditions. X-ray Crystallography. Diffraction data were collected on a Bruker Smart Apex CCD diffractometer with graphite monochromated Mo KR radiation (λ ) 0.71073 Å), and the absorption corrections were applied by SADABS.10 The structures were solved by direct methods and refined using the full-matrix least-squares technique with SHELXL97.10 Some of solvate molecules and anions show disordering over crystallographically imposed symmetry positions. Therefore, fractional occupancy was assigned and restrained refinement was applied. The Flack parameters for chiral structures are 0.01(3) (1), and 0.03(1) (2).10c Experimental details of the X-ray analyses are provided in Table 1. Selected bond distances and angles are listed in Table 2. CCDC Nos. 684672, 684673, 684674, and 684675 for 1-4, respectively, contain the supplementary crystallographic data for this paper. These data can be obtained free of charge via http://www.ccdc.can.ac.uk/conts/retrieving.html (or from the Cambridge Crystallographic Centre, 12 Union Road, Cambridge CB21EZ, UK; Fax: (+44)1223-336-033; or e-mail: [email protected]).

Results and Discussion Crystal Structure of 1. Single-crystal X-ray diffraction analysis reveals that compound 1 crystallizes in a chiral orthorhombic space group C2221. In the asymmetry unit, there are two neutral mononuclear Co1(SS-H2bzimed-H)2 and Co2(SSH2bzimed-H)2 molecules, two methanol and four water mol-

1404 Crystal Growth & Design, Vol. 9, No. 3, 2009

Zhou et al.

Table 1. Summary of Crystallographic Data for 1-4 compound

1

2

3 (solid)

4

3′ (tubular)

formula fw T (K) cryst syst space group a (Å) b (Å) c (Å) V/Å3 Z Dcalcd/ g cm-3 µ/ mm-1 R1a [I g 2(I)] wR2a (all data)

C33H34CoN8O7 713.61 298(2) orthorhombic C2221 14.466(1) 31.255(3) 33.094(3) 14963(3) 8 1.267 0.513 0.1059 0.2750

C66H68Co2N16O14 1776.88 293(2) monoclinic C2 27.772(3) 14.678(2) 19.408(2) 7752.8(1) 4 1.519 1.311 0.0542 0.1171

C96H71Co5N24O8.5Cl4 2133.22 173(2) monoclinic P2(1)/n 13.041(1) 26.434(2) 28.561(3) 9669.9(2) 4 1.461 0.918 0.0712 0.1923

C96H74N24Ni5O10Cl4 2159.05 293(2) monoclinic P2(1)/n 13.089(6) 26.676(1) 28.874(1) 9865.2(8) 4 1.450 1.011 0.0703 0.2026

C96H71Co5N24O8.5Cl4 2133.22 293(2) monoclinic P2(1)/n 13.154(1) 26.640(3) 28.592(3) 9832.9(2) 4 1.410 0.900 0.0932 0.2100

a

R1 ) ∑|Fo| - |Fc|/∑|Fo|; wR2 ) [∑w(Fo - Fc2)2/∑w(Fo2)2]1/2.

ecules (Figure 1).11 In each mononuclear molecule, the Co(II) ion octahedrally coordinated by two monodeprotonated SSH2bzimed ligands forms a distorted octahedral coordination sphere. Both the SS-H2bzimed anions act as tridentate ligands (Scheme 1, VII) through the two benzimidazole nitrogens and one hydroxyl oxygen and form a seven-membered chelate ring, which is essentially the same as in the complexes of 1,2-bis(2benzimidazolyl)-ethane,7c showing that coordination of the alcohol function has not distorted the seven-membered chelate ring. The coordination and bond geometries of Co1(SSH2bzimed-H)2 and Co2(SS-H2bzimed-H)2 are very similar and show only slight changes in bond distances and angles. The average Co-N bond distances are 2.085 and 2.070 Å, and Co-O bond distances are 2.263 and 2.257 Å, respectively. The average N-Co-N angle is 2.21° smaller (95.26 vs 97.47 °) in Co1(SS-H2bzimed-H)2 than in Co2(SS-H2bzimed-H)2. Bond distances and angles within the SS-H2bzimed anions have expected values. The Co1-Co2 distance in the compound 1 is 13.801 Å. The presence of three intermolecular hydrogen bonding interactions depending on the donor group in the lattice form the complex hydrogen bonding 3D networks of compound 1 (Figure S2, Supporting Information): each peripheral ligand of a mononuclear molecule has two nitrogen atoms of NH groups that behave as donors to the oxygen atom of hydroxyl (2.87-3.02 Å) of ligand in neighboring mononuclear molecules, and solvent water (2.88-2.92 Å), as well as methanol (2.90 Å) molecules as acceptors (type A); the oxygen atoms of protonated hydroxyl of ligand act as donors toward solvate water molecules in the range of 2.74-2.77 Å (type B); the oxygen atoms of water molecules behaving as donors are involved in extensive hydrogen bonding with neighboring solvent water molecules behaving as acceptors (type C). In addition, the solvent molecules (MeOH and H2O) occupy channels between the mononuclear molecules, filling up the remaining unoccupied space in the crystal lattice. Crystal Structure of 2. Single-crystal X-ray crystallographic studies reveal that compound 2 crystallizes in a chiral monoclinic space group C2, which is made up of tetravalent cubic-type [Zn4(SS-H2bzimed-H)4]4+ species and four nitrate anions and five lattice water molecules. The Zn4O4 cubane is constructed by four Zn(II) ions and four alkoxo oxygen atoms from the four ligands each at alternating corner (Figure 2), where each Zn(II) ion is coordinated in a distorted octahedral geometry by two benzimidazole N atoms (Zn-N ) 2.004(2)-2.153(1) Å), three µ3-alkoxo oxygen atoms (Zn-O ) 2.004(2)-2.153(1) Å), and one alkyl hydroxyl oxygen atom (Zn-O ) 2.215(1) Å) with ligands. Each ligand is monodeprotonated and bridge three znic ions, four bound on one side, and the conformation may be described as µ3-κN,O:κO,O′:κN′,O′ (Scheme 1, VII), similar

to the observed mode in rac-[Cu4(H2bzimed-2H)(H2bzimedH)4]6+, but dramatically different from the well-documented series of [Cu4(SS-H2bzimed-H)4]4+ cube-based complexes with the ligand adopting a µ2-κN,O:κN′,O-H2bzimed-H coordinating mode (Scheme 1, V).7a This result further supports the idea that the H2bzimed ligand possesses a considerable variety of coordinating modes for different metal ions under appropriate conditions. The cuboidal core is distorted with all the Zn-O-Zn angles in the range (98 ( 2)° (Table 2). The Zn · · · Zn separations in 2 are 3.128-3.493 Å, which is comparable to those found in related Zn4O4 cubane-like complexes.12 The crystal packing of this compound can be described as the juxtaposition of four tetranuclear entities per unit cell (Figure S2, Supporting Information), and free nitrate groups and crystallization water molecules are localized between the tetranuclear entities. Three dominating kinds of intermolecular hydrogen bonds also exist. Type A is nitrogen atoms of NH groups behaving as donors to the oxygen atom of nitrate anions (2.721(2)-2.823(3) Å), and solvent water (2.88-2.91 Å) as acceptors; type B is the oxygen atoms of hydroxyl of ligand acting as donors toward the oxygen atom of nitrate anions, and solvent water (2.88-2.91 Å) as acceptors in the range of (2.931(1)-3.100(2) Å). Furthermore, there are other medium hydrogen bonds between the guest water molecules and nitrate anions (type C). These interactions play a vital role in the consolidation of the solid structure and results in the cooperative self-assembly of the final three-dimensional supermolecular network of 2.13 Comparing the hydrogen bonding of compounds 1 and 2, we found that they have the same kinds of donors for hydrogen bonding, while the acceptors are different mainly by the variety of modes of coordination and the presence of free nitrate anions in the latter. To the best of our knowledge, compound 2 is the first example of a zinc(II) complex of the H2bzimed ligand, although several 3d metal coordination complexes have been structurally characterized.7 Crystal Structure of 3 and 4. The hydrothermal reaction of SS-H2bzimed with CoCl2 · 6H2O in methanol/water (1:2) gave red crystals of 3. X-ray single crystal structural analysis for solid crystal 3 revealed that the SS-H2bzimed ligands had undergone an in situ intramolecular dehydration coupling reaction to form Hbzimed during the hydrothermal process as shown in Scheme 2.6b,14 Like other hydroxyl benzimidazoles such as 1,2-bis(1methylbenzimidazol-2-yl)-1,2-ethanediol, 1,2-bis(1-methylbenzimidazol-2-yl)-ethanol,7 Hbzimed may act as a rigid, facially coordinating tridentate ligand, with the alcohol group coordinated to metal ions. The compound 3 is composed of a tetravalent cluster [Co5(Hbzimed-H)6]4+ (Figure 3), four counteranions Cl-, and two and a half-solvent water molecules. The cation cluster has a D3 symmetry, and is constructed by six planar Hbzimed-H



Table 2. Selected Bond Lengths (Å) and Bond Angles (deg) for 1-4 Compound 1 Co1-O1 Co1-N1 Co1-N5 Co2-O6 Co2-N9 Co2-N13 N1-Co1-O4 N1-Co1-N5 N5-Co1-O4 O4-Co1-N3

2.433(2) 2.027(1) 2.092(1) 2.254(1) 2.142(1) 2.004(2) 88.0(4) 97.4(4) 82.3(3) 174.1(4)

Co1-O4 Co1-N3 Co1-N7 Co2-O7 Co2-N12 Co2-N15 O7-Co2-O6 N12-Co2-N9 N9-Co2-O6 N9-Co2-O7

2.093(9) 2.103(2) 2.117(1) 2.260(1) 2.046(1) 2.088(1) 99.0(5) 96.1(5) 80.3(3) 171.5(4)

Compound 2 Zn1-O2 Zn1-O7 Zn1-N3 Zn2-O1 Zn2-O4 Zn1-N7 Zn3-O3 Zn3-O6 Zn3-N5 Zn4-O2 Zn4-O5 Zn4-N1 Zn1-O2-Zn2 Zn4-O4-Zn3 N11-Zn1-N3 N7-Zn2-N13 N5-Zn3-N15 N9-Zn4-N1

2.131(5) 2.222(5) 2.068(6) 2.288(5) 2.313(4) 2.011(6) 2.411(6) 2.016(5) 2.030(6) 2.062(5) 2.315(5) 2.126(6) 96.4(2) 95.1(2) 105.8(3) 109.2(2) 107.4(2) 108.0(3)

Zn1-O6 Zn1-O8 Zn1-N11 Zn2-O2 Zn2-O8 Zn1-N13 Zn3-O4 Zn3-O8 Zn3-N15 Zn4-O4 Zn4-O6 Zn4-N9 Zn2-O1-Zn3 Zn4-O4-Zn3 N3-Zn1-O2 N13-Zn2-O8 N5-Zn3-O3 N9-Zn4-O5

2.222(5) 2.121(5) 2.021(6) 2.065(5) 2.136(5) 2.077(6) 2.416(5) 2.041(5) 2.094(6) 1.999(5) 2.431(5) 2.070(7) 95.2(2) 100.4(2) 77.0(2) 77.6(2) 75.1(2) 76.5(2)

Compound 3 Co1-O1 Co1-O3 Co1-N5 Co2-O1 Co2-N3 Co3-O4 Co3-O6 Co3-N19 Co4-O3 Co4-N11 Co5-O2 Co1-O1-Co2 Co1-O3-Co4 Co2-O5-Co3 N9-Co1-N1 N17-Co2-N3 N19-Co3-N23 N11-Co4-N13 N7-Co5-N21

2.182(5) 2.179(5) 2.094(6) 1.967(5) 1.964(6) 2.156(5) 2.188(5) 2.042(6) 1.946(5) 1.968(6) 1.955(5) 114.4(4) 122.5(2) 120.4(2) 103.5(3) 101.4(3) 103.1(2) 104.6(3) 101.6(3)

Ni1-O1 Ni1-O3 Ni1-N5 Ni2-O1 Ni2-N3 Ni3-O4 Ni3-O6 Ni3-N19 Ni4-O3 Ni4-N11 Ni5-O2 Ni5-N7 Ni1-O1-Ni2 Ni1-O3-Ni4 Ni2-O5-Ni3 N15-Ni1-N7 N3-Ni2-N13 N11-Ni3-N21 N17-Ni4-N1 N5-Ni5-N19

2.127(3) 2.151(4) 2.052(4) 1.953(3) 1.943(5) 2.137(4) 2.128(4) 2.010(5) 1.952(3) 1.957(5) 1.952(4) 1.944(5) 119.1(2) 119.9(2) 120.6(2) 98.1(2) 97.9(2) 99.0(2) 101.1(2) 98.8(2)

Co1-O2 Co1-N1 Co1-N9 Co2-O5 Co2-N17 Co3-O5 Co3-N15 Co3-N23 Co4-O4 Co4-N13 Co5-O6 Co1-O2-Co5 Co3-O4-Co4 Co3-O6-Co5 N9-Co1-O2 N17-Co2-O5 N23-Co3-O4 O4-Co4-N13 N7-Co5-O2

2.156(5) 2.053(6) 2.041(6) 1.964(4) 1.968(6) 2.176(4) 2.084(6) 2.078(6) 1.977(5) 1.971(6) 1.965(5) 119.1(2) 121.1(2) 120.4(2) 91.9(2) 95.0(2) 94.4(2) 95.2(2) 95.1(2)

Compound 4 Ni1-O2 Ni1-N1 Ni1-N9 Ni2-O5 Ni2-N17 Ni3-O5 Ni3-N15 Ni3-N23 Ni4-O4 Ni4-N13 Ni5-O6 Ni5-N21 Ni1-O2-Ni5 Ni3-O4-Ni4 Ni3-O6-Ni5 N3-Ni2-O4 N3-Ni2-O1 O3-Ni3-N11 N1-Ni4-O1 N5-Ni5-O2

2.176(4) 2.030(4) 2.027(4) 1.943(4) 1.960(5) 2.149(4) 2.127(3) 2.045(5) 1.951(4) 1.937(3) 1.946(4) 1.945(5) 119.9(2) 117.7(2) 117.3(3) 116.6(2) 93.2(2) 92.6(2) 78.1(2) 93.2(2)

ligands around the M5[µ-O]6 core, and cobalt(II) centers arranged at the apexes of a trigonal bipyramid in which each octahedral CoII (Co1, Co3) ions are coordinated by three benzimidazole N atoms, three µ2-alkoxide oxygen atoms with monodeprotonated alcohol function from Hbzimed-H, and each tetrahedral CoII (Co2, Co4, Co5) ion by two benzimidazole N atoms, two µ2-alkoxide oxygen atoms with monodeprotonated alcohol functions from ligands residing in the equatorial triangular plane. Therefore, each Co(II) ion is bridged by an µ2-alkoxide bridge atom from each of the six µ2-κN,O:κN′,OHbzimed-H ligands. The coordination sites do not have regular geometries, as is common for cobalt(II), and the Co-O, Co-N bond distances are 1.946-2.188, 1.954-2.094 Å, respectively, which are consistent with those reported for related complexes.15 Co-O-Co bridge angles are a little large, falling in a range of 114.4-122.5° for Co · · · Co dominant antiferromagnetic exchange.2,15 It is note of that the structural motif belongs to the increasing [M5] family, for which no mixed geometry of trigonal bipyramid [Co5] member has been reported until now.12 Like other [M5] clusters, the structure is represented by a closestpacking arrangement of donor nitrogen/oxygen and Co atoms.12 Compounds 1 and 2, and the cationic clusters of compound 3 are also not well isolated, and are linked via H-bonding which involves the Cl- anions (Figure S4, Supporting Information). The dominating interaction involves two types: the N atoms of NH groups behaving as donors toward the Cl- anions (2.78-3.07 Å), with the solvate water molecules in the range of 2.96-3.10 Å (type A), and water molecules behaving as donors are involved in extensive hydrogen bonding with the guest water molecules and Cl- anions in the range of 2.80-3.12 Å (type C). It is of note that type B hydrogen bonding is not found in this structure because of the absence of protonated hydroxyls. There are also disordered molecules of water (2.78-3.01 Å) and Cl- anions in the crystal lattice, lying in the vicinity of the H-bond between anions. This extended intercluster H-bonded network results in close nearest neighbor contacts of 9.84 Å between metal ions at the edges of the clusters (Co · · · Co). Changing CoCl2 to NiCl2 under similar reaction conditions, dark red single crystals along with some single crystal microtubes of produced 4 were acquired, which are very different from the familiar green nickel compounds and have the same structure as 3 (Figure S3, Supporting Informatiom); however, it has more one point half-solvate water molecules than 3 in the crystal lattice, leading to a more complicated H-bond supernetwork than that of 3 (Figure S4, Supporting Information), and results in close nearest neighbor contacts of 9.94 Å between metal ions at the edges of the clusters (Ni · · · Ni). These interactions clearly lead to a certain extent to correlation among the cationic clusters and the weak but effective intermolecular magnetic exchange interactions would be anticipated and should not be negligible. Crystal Structure of 3′. We especially chose the single microtubular crystal of complex 3′ (Table 1) to characterize using X-ray single-crystal diffraction analysis and found the quality of its X-ray diffraction data as good as that of collected solid single crystals of compound 3. The coordination and bond geometries of 3 and 3′ are very similar and show only slight changes in bond distances and angles (Table S1, Supporting Information). It is of note that only a few examples of studies report such a microtubular metal-organic architecture with sufficiently high crystal quality at all length scales from macroscopic down to the molecular level.6b,7b This observation may be informative in understanding the macroscopical growth


Zhou et al.

Figure 1. The coordination environment of CoII in compound 1.

Figure 2. The coordination environment of ZnII (left) and the unit of Zn4O4 core (right) showing the bridging mode adopted by ligand SS-H2bzimed-H for compound 2; some of hydrogen atoms are omitted for clarity.

Scheme 2. The Probable Mechanism of the in Situ Formation for the Ligand Hbzimed

drawback of the microtube single crystal which does not affect the determination of its microcosmic X-ray single-crystal structure. The Formation of Single Crystal Microtubes. How are the rare single crystal microtubes of compounds 3 and 4 formed during the synthesis processing? Under our alternative experiments, we found that reaction heating time plays a vitally important role in the formation of microtubular single crystals (Figure 4). With a reaction heating time of 72 h, only a little rodlike solid crystals formed; with a 120 h growing period, some small rod crystals just started to form holes at the top, some became hollow with channels not completely developed, and some evolved into well-shaped tubes; with a prolonged reaction heating time of 240 h, a great deal of high quality microtubular single crystals are observed. Meanwhile, we found that microtubular single crystals can be produced with temperatures

varying from 140 to 160 °C with pH between 5 and 7. No crystals were found when the pH of mixtures is higher than 7 or below 5. It is clear that tubular morphology is not the initial crystal growing shape; therefore, tube shape evolution may undergo a slow transformation process depending on the growth of the rodlike precursors. Recently, the concentration depletion at the surfaces of the cylindrical seeds mechanism6a,7b and the helical belt template mechanism were used to account for the formation of single crystal microtubes.16 Here, we think the first mechanisms work in the formation of the present microtubular single crystals based on our above experimental results, namely, owing to the very slow rate to form the clusters which depend upon neonatal in situ ligand Hbzimed reacting with metal ions, and not enough clusters provided to fast crystal packing through supermoleclar interaction and the growth of the rodlike crystals, and leading to undersaturation in the central part of the growing



Figure 3. The coordination environments of CoII5 unit (left) and the highlighted Co5O6 core and bridging mode adopted by ligand Hbzimed-H for compound 3; all hydrogen atoms have been omitted for clarity.

regions of rodlike crystals. Thus, the continuous feeding of clusters on the surface of rodlike crystals can diffuse into two directions: circumferential diffusion and diffusion parallel to the tubular axis, resulting in formation of tubular architectures, and the concentration depletion at the surfaces of cylindrical seeds. Discussion for Structure. The ligand used in this work is interesting from a structural point of view (Scheme 1); we can conclude that the coordination modes of SS-H2bzimed are changeable when assembling with a given metal atom and are vital for the clusters formation. In compound 2-4, the benzimidazole nitrogen atoms incline to coordinate to the metal atom and impose the geometry on the resultant cluster, and the anionic nature of the flexible hydroxyl group leads to a cluster complex. However, the hydroxyl groups exhibit different binding fashions (see Scheme 1). For compound 1, the simple chelating and unidentate mode of the flexible hydroxyl group is observed (mode VI). For the cubic structure of 2, the chelating, unidentate, and trans tridentate fashions of the two hydroxyls are detected all together, expanding the metal nodes to generate a Zn4O4 cubic core, where ligands adopt a bent µ3-κN,O:κO,O′:κN′,O′ bridging fashion (mode VII) and actually fills four metal coordination positions. More interestingly, the SS-H2bzimed was converted in situ into Hbzimed via intramolecular dehydration coupling during a hydrothermal reaction to prepare a pentacluster of 3 and 4. Obviously, limited by the enol group, the structure of the Hbzimed ligand is more rigid than H2bzimed, and will impose the geometry on the resultant trigonal bipyramid [Co5] cluster core by being able to adopt different binding modes and relative asymmetric orientations of the benzimidazole nitrogen and hydroxyl group (mode VIII). The coordination geometry of the central metal ion may also have a significant effect on the final structure. As demonstrated by the comparison of 2 with rac-[Cu4(H2bzimed-H)4]4+, the coordination of the copper ions is strongly distorted from octahedral, so the above Cu(II) compound of the ligand adopts a µ2-κN,O:κN′,O coordinating mode (Scheme 1, V) in order to allow the Cu(II) to coordinate. It should also be noted that the higher pH value and reaction temperature create more opportunities to introduce deprotonation of hydroxyl groups in molecular cluster structures and lead to ligand in situ reactions.9 Thermogravimetric Analysis of 3 and 4. Thermogravimetric analysis (TGA) was carried out to examine the thermal stability

of compounds 3 and 4. The crushed single-crystal samples were heated up to 1000 °C in N2 at a heating rate of 10 °C min-1. The TGA curves for 3 show that the first weight loss of 2.0% between 25 and 53 °C corresponds to the loss of 2.5 water molecules (ca. 2.0% calc 2.1%) per molecular unit (Figure S6, Supporting Information). It is somewhat surprising that this occurs below the boiling point of water. We attribute this facile loss to the low degree of hydrogen bonding holding the water in the crystal lattice. This is followed by a loss of 7.0% from 70-330 °C, corresponding to the loss of 4 equiv of hydrochloric acid (ca. 7.0% calc 7.1%). The four mobile protons of the benzimidazole ligands presumably transfer to chlorine anions, liberating four HCl molecules. At this stage, an intermediate of neutral pentacluster should be present. Between 340 and 646 °C, the anhydrous natural pentacluster entity decomposes and forms by losing six C6H4 fragments per pentanuclear unit. At last, a large weight loss of 37% occurred at 650-1000 °C, which shows that the organic ligands are not completely decomposed under a high temperature at N2 atmosphere. For 4, the first weight loss of 3.2% between 25 and 60 °C corresponds to the loss of four water molecules (ca. 3.2% calc 3.0%), showing the guest water molecules escape more slowly from the limited porosity in 4 than the water molecules located between clusters of 3. The other three steps for the loss of weight are similar to 3. The above thermal behaviors may be attributed to their structural features. The organic ligands of compounds 3 and 4 are difficult to decompose completely may be attributed to the presence of rigid ligands possessing µ2-κN,O:κN′,O-Hbzimed-H bridging coordinated modes, and the cationic clusters themselves have approximate D3 symmetry. Magnetic Studies for 3 and 4. Magnetic susceptibility measurements carried out on crushed single crystals of 3 with an applied field of 1000 Oe revealed a χmT value of 12.34 cm3 mol-1 K (per Co5) at room temperature (Figure 5). Upon lowering the temperature, χmT first gradually decreases to a minimum value of 4.92 cm3 K mol-1 at 14.1 K, and then abruptly increases to a sharp maximum value of 6.19 cm3 K mol-1 at 9.1 K, and finally decreases more rapidly on further cooling. The molar magnetic susceptibility in the temperature range 50-300 K obeys the Curie-Weiss law [χm ) C/(T θ)], i.e., C ) 13.61 cm3 mol-1 K and θ ) - 29.3(1) K, consistent with the presence of five CoII ions (Figure S7, Supporting Information). The largely negative θ value suggests


Figure 4. The series of optical microscope images of microtubular and solid single crystals for compounds 3 (top) and 4 (bottom) with different reaction times: (a) 3 days, (b) 5 days, (c) 10 days, showing the tetragonal hollow.

Figure 5. Plot of χmT vs T for 3 and temperature dependence of χm at different fields (inset).

Figure 6. Plot of ac susceptibility shown as χ′ vs T and χ′′ vs T for 3.

a dominant antiferromagnetic coupling between CoII ions within the pentameric entity, and the single-ion behavior of octahedral CoII contributes somewhat to the θ value. The field-dependence of χm vs. T curves at different fields shows a pronounced field dependence of the low-temperature phase, with a larger increase of χm values at a small field (inset in Figure 5), which is an indication that the source of an obvious spontaneous moment is probably spin canting.17 Indeed, the AC magnetic susceptibility data confirm the presence of net magnetization as the data show a peak in the χ′′m (out-of-phase) signals below 10 K (Figure 6). The position of the maxima shows a very slight frequency dependence within the range of 1-997 Hz that is indicative of spin canting behavior.1a,18 In addition, the shift of the peak temperature (Tp) of χ′ can be quantified as φ ) ∆Tp/ [Tp∆(log f)] ) 0.006, which is comparable to a spin-glass rather

Zhou et al.

Figure 7. Plots of zero-field cooled magnetization (ZFC), field-cooled magnetization (FC) in a field of 20 Oe, and field dependence of magnetization from 0-7 T at 2 K (inset) for 3.

Figure 8. Plot of χmT Vs T and field dependence of magnetization at 2 K (inset) for complex 4.

than a superparamagnet (φ > 0.1). Such is also consistent with the presence of the bifurcation point between the field-cooled/ zero-field-cooled magnetization curves (Figure 7).18 Furthermore, the shapes of the M/H plots are quite like those of a recently reported canted-spin antiferromagnet,19 in which the M value increases rapidly at low fields, with no obvious saturation observed up to 7 T (Figure 6, inset). The maximum value observed of 4.85 Nβ per Co5 formula unit is very close to the resultant moment of two CoOct, assuming an effective S ) 1/2, and three CoTd, assuming an effective S ) 3/2 at low temperatures (Figure 3, right), since octahedral Co(II), the effect of spin orbit coupling usually yields a Kramers S ) 1/2 state at low temperature with an anisotropic g-tensor and a moment of 2.2 µB per Co(II). The cluster configurations necessary to give this total moment are two octahedral sites (vvv) that are antiferromagnetically coupled to three tetrahedral sites (v). The compound exhibits a hysteresis loop at 1.8 K (Figure S8, Supporting Information) with a small remnant magnetization (MR) of ca. 381 Oe and a coercive field (HC) around 95 Oe and the spin canting angle R is estimated to be about 0.4° through sin(R) ) MR/gµBS.1a,20 There are different magnetic pathways, such as a strong superexchange within the pentamer by µ2-alkoxide bridges, weak intercluster interactions facilitated by the hydrogen bonds per cluster between the benzimidazole N atoms, Cl anions, and H2O guest molecules of neighboring cluster molecules, and the dipole-dipole coupling through the space between the large cationic clusters. All these pathways have to be AF, and superexchange within the pentamers is expected to be much stronger than the dipolar coupling between these features. Thus,



the origin of this magnetic ordering can be attributed to a weak magnetic ordering, the so-called canting. Due to zero-field splitting, and the more common complications arising from spin-orbital interactions, which is a frequent source of difficulty in the interpretation of magnetic data for Co(II) complexes. The magnitude of the coupling constants in the penta-cluster of 3 cannot be calculated by conventional methods. To evaluate the interactions, with the molecular field approximation, and an admittedly simple model, a least-squares fit of the observed magnetic data based on the theoretical expression of a pentamer with antiferromagnetic interactions was made (eq 1, Figure 3 right). The isotropy spin Hamiltonian for trigonal bipyramid pentamer in 3 is given in the equation as follows:

ˆ ex ) -2J1(Sˆ1Sˆ2 + Sˆ1Sˆ4 + Sˆ1Sˆ5 + Sˆ3Sˆ2 + Sˆ3Sˆ5 + Sˆ3Sˆ4) H (1) Then, E(S ′ , SA, SB) ) -J1(S ′ (S ′ + 1) - SA(SA + 1) - SB(SB + 1))

where

SA ) S1 + S3 ;SB ) S2 + S4 + S5 ;S ′ ) SA + SB Nβ2g2 χ′ ) 3kT

∑ S ′ (S ′ + 1)(2S ′ + 1)e-E(S )⁄kT ∑ (2S ′ + 1)e-E(S )⁄kT

χm )

(2) Conclusion

χ 1 - 2zJχ/Nβ2g2

following parameter values: g ) 2.16, J1 ) -2.17 cm-1, zJ′ ) -1.44 cm-1, R ) 3.8 × 10-4 for plot of χmT vs T. This result showed a relatively strong antiferromagnetic intrapentamer Ni(II) interaction, and the J1 value is comparable to those previously reported for Ni(II) complexes with similar bridges.9,21 However, it needs to be kept in mind that this simulation for 4 is only qualitative, and it is difficult to explain intercluster interactions. Obviously, the intercluster magnetic interactions of the almost completed compensated Ni5O6 core that contribute to the bulky magnetic behaviors are insignificant and different from compound 3. The cobalt(II) compound reveals obvious spin canting behavior with the effective intercluster interactions contributing to the bulky cooperative magnetic behaviors due to relatively noncompensated moments of Co5O6 core and the anisotropy effects originate from the single ion and/or the interaction, some similar to other high spin and previously reported high-nuclearity cluster compounds.21 Nonetheless, 3 and 4 provide the relative evidence for the origin of spin canting (at least, in the CoII systems) and demonstrate the importance of remanent spins in the cationic clusters upon intercluster magnetic interactions, especially, the dipole-dipole coupling at very low temperature. With the correlation in a 3D molecular arrangement, the intercluster interaction, albeit very weak, can perturb the bulky cooperative magnetic behaviors.22,23

(3)

where five intrapentamer Co · · · Co interactions (J1) are nearly equilateral because of the molecule possession along the C3 axis (Co1 · · · Co3), J′ is an interpentamer exchange interaction, and z is the number of nearest neighbors of the pentamer. By varying g, J1, J′, and minimizing the residual R ) Σ(χobsT - χcalT)2/ Σ(χobsT)2 or R ) [Σ(χobs - χcalc)2/Σ(χobs)2], the best nonlinear least-squares fittings of the theoretical and expression to the experimental data can be made for complex 3 (eq S1, Supporting Information). The model provides a proper fit of χm/T variation over the temperature range of 50-300 K, with a discrepancy that does not exceed experimental uncertainty. The closest agreement between theory and experiment comes from use of the following parameter values: g ) 2.67, J1 ) -2.22 cm-1, and zJ′ ) -0.309 cm-1, R ) 2.8 × 10-4 for the plot of χmT vs T (Figure 5). These results support antiferromagnetic coupling intraclusters and interclusters exchange. The values of exchangeparameters in the two above models are comparable to those previously reported for Co(II) complexes with similar bridges.17,18b Obviously, the magnetic behavior of this compound at T > 50 K is dominated by intracluster exchange interactions. A plot of χmT vs T for 4 is shown in Figure 8. This plot is typical for a simple antiferromagnetic system, without any other important features. The χmT value (for five NiII ions) is 5.19 cm3 mol-1 K at 300 K, a typical value for NiII ions with g > 2.00, and decreases in an unremarkable fashion to 0.6 cm3 mol-1 K at 2 K. At low temperature the χmT values are independent of the field employed (in contrast with the CoII system), and there is no signal in the ac susceptibility measurements (Figure S9, Supporting Information). The pronounced slope of the M/H curve indicates antiferromagnetic coupling with the value of 1.31 µB per Ni5 formula unit at 7 T. According to the similar magnetic exchange in compound 4, the same magnetic fit treatment method as that in complex 3 can be used here (eq S2, Supporting Information). A leastsquares fit of the data above 50 K comes from the use of the

In summary, we reported a set of molecular clusters based on different 3d ions (NiII, CoII, ZnII) with SS-H2bzimed and in situ intramolecular dehydrated offspring-Hbzimed ligands. Among them, the CoII and NiII pentanuclear motif shows that the first example of mixed geometry of the trigonal bipyramid [M5] member belongs to the increasing [M5] family. Furthermore, it is noted that rare single crystal microtubes of the two pentanuclear compounds were acquired during in situ synthesis. The unprecedented in situ intramolecular dehydration coupling reaction of SS-H2bzimed ligand provides a new way in higher temperature routes-solvothermal methods for generating more complicated metal clusters from simpler ones, and may affect clusters of crystal growth speed at different directions, as a result, leading to the formation of for example tubular crystals. More interestingly, isostructural pentanuclear clusters 3 and 4 have totally different bulky magnetic properties. The former has an unexpected magnetic ordering from spin-canted antiferromagnetic coupling depending on this single-ion effect, but the latter displays simple antiferromagnetic coupling resulting from the less noncompensated moments. Hence, this study highlights that homometallic Co(II) clusters with Oh-Td mixedgeometries can result in relatively obvious noncompensated moments, according to different efficient spins of Co(II) at very low temperatures, in spite of antiferromagnetic intracluster interactions, and further influence the bulky cooperative magnetic behaviors through weak intercluster interactions. Acknowledgment. This work was supported by NSFC (Nos. 20871034, 20561001), and the Program for New Century Excellent Talents in University of the Ministry of Education China and GuangXi Province (NCET-07-217, RC2007005) as well as Fok Ying Tung Education Foundation (No. 111014). Supporting Information Available: Crystal data (CIF file and additional structural plots), synthesis of the ligand SS-1,2-bis(1Hbenzimidazole-2-yl)-1,2-ethanediol; the coordination environments of CoII and the unit of Ni5O5 showing the angle bridging mode adopted by ligand Hbzimed-H for compound 4; packing diagram of unit cell of compounds 1-3; χM-1 vs T curve for compound 3; in-phase and


Zhou et al.

out-of-phase curves for compound 4; Thermogravimetric analysis of 3 and 4. This material is available free of charge via the Internet at http:// pubs.acs.org. (11)

References (1) (a) From the Molecular to the Nanoscale: Synthesis, Structure, and Properties; Fujita, M., Powell, A., Creutz, C., Eds.; Elsevier-Ltd.: Oxford, 2004; Vol. 7. (b) Gatteschi, D.; Sessoli, R. Angew. Chem., Int. Ed. 2003, 42, 268. (c) Humphrey, S. M.; Wood, P. T. J. Am. Chem. Soc. 2004, 126, 13236. (d) Stamatatos, T. C.; Abboud, K. A.; Wernsdorfer, W.; Christou, G. Angew. Chem., Int. Ed. 2007, 46, 884. (e) Schelter, E. J.; Karadas, F.; Avendano, C.; Prosvirin, A. V.; Wernsdorfer, W.; Dunbar, K. R. J. Am. Chem. Soc. 2007, 129, 8139. (f) Milios, C. J.; Inglis, R.; Vinslava, A.; Bagai, R.; Wernsdorfer, W.; Parsons, S.; Perlepes, S. P.; Christou, G.; Brechin, E. K. J. Am. Chem. Soc. 2007, 129, 12505. (2) (a) Zeng, M.-H.; Yao, M.-X.; Liang, H.; Zhang, W.-X.; Chen, X.-M. Angew. Chem., Int. Ed. 2007, 46, 1832. (b) Zhou, Y.-L.; Yao, M.-X.; Zeng, M.-H.; Liang, H. Unpublished work. (3) (a) Tabernor, J.; Jones, L. F.; Heath, S. L.; Muryn, C.; Aromı´, G.; Ribas, J.; Brechin, E. K.; Collison, D. Dalton Trans. 2004, 975. (b) Collison, D.; Mcinnes, E. J. L.; Brechin, E. K. Eur. J. Inorg. Chem. 2006, 2725. (c) Boudalis, A. K.; Sanakis, Y.; Clemente-Juan, J. M.; Donnadieu, B.; Nastopoulos, V.; Mari, A.; Coppel, Y.; Tuchagues, J. P.; Perlepes, S. P. Chem. Eur. J. 2008, 14, 2514. (4) (a) Brechin, E. K. Chem. Commun. 2005, 5141. (b) Boskovic, C.; Gudel, H. U.; Labat, G.; Neels, A.; Wernsdorfer, W.; Moubaraki, B.; Murray, K. S. Inorg. Chem. 2005, 44, 3181. (c) Manoli, M.; Prescimone, A.; Bagai, R.; Mishra, A.; Murugesu, M.; Parsons, S.; Wernsdorfer, W.; Christou, G.; Brechin, E. K. Inorg. Chem. 2007, 46, 6968. (d) Langley, S.; Helliwell, M.; Sessoli, R.; Teat, S. J.; Winpenny, R. E. P. Inorg. Chem. 2008, 47, 497. (5) (a) Yang, E. C.; Hendrickson, D. N.; Wernsdorfer, W.; Nakano, M.; Zakharov, L. N.; Sommer, R. D.; Rheingold, A. L.; Ledezmagairaud, M.; Christou, G. J. Appl. Phys. 2002, 91, 7382. (b) Ako, A. M.; Hewitt, I. J.; Mereacre, V.; Cle´rac, R.; Wernsdorfer, W.; Amson, C. E.; Powell, A. K. Angew. Chem., Int. Ed. 2006, 45, 4926. (6) (a) Zhang, X.-L.; Guo, C.-P.; Yang, Q.-Y.; Wang, W.; Liu, W.-S.; Kang, B.-S.; Su, C.-Y. Chem. Commun. 2007, 4242. (b) Zhang, X.L.; Guo, C.-P.; Yang, Q.-Y.; Lu, T.-B.; Tong, Y.-X.; Su, C.-Y. Chem. Mater. 2005, 126, 3576. (c) Su, C.-Y.; Goforth, A. M.; Smith, M. D.; Zur Loye, H.-C. Inorg. Chem. 2003, 42, 5685. (d) Su, C.-Y.; Yang, X.-P.; Kang, B.-S.; Mark, T. C. W. Angew. Chem., Int. Ed. 2001, 40, 1725. (7) (a) Katharina, I.; Patrick, F.; Christina, A.; Gerald, B.; Silvio, D.; Alan, F. W. Inorg. Chem. 2005, 44, 3896. (b) Feng, S.-S.; Zhu, M.-L.; Lu, L.-P.; Guo, M.-L. Chem. Commun. 2007, 4785. (c) Katharina, I.; Fabienne, G.; Alan, F. W.; Gerald, B.; Patrick, F.; Silvio, D. Dalton Trans. 2007, 332. (d) Katharina, I.; Vanessa, B.; Craig, J. M.; Alan, F. W.; Gerald, B.; Patrick, F.; Silvio, D. Dalton Trans. 2002, 3899. (8) Laye, R. H.; McInnes, E. J. L. Eur. J. Inorg. Chem. 2004, 2811. (9) Chen, X.-M.; Tong, M.-L. Acc. Chem. Res. 2007, 40, 162. (10) (a) SMART, version 5.0; Bruker AXS: Madison, WI, 1998. SAINT plus, version 6.0; Bruker AXS: Madison, WI, 1999. SHELXTL,

(12) (13) (14) (15) (16) (17)

(18)

(19)

(20) (21) (22)

(23)

version 6.1; Bruker AXS: Madison, WI, 2001. (b) Blessing, R. Acta Crystallogr., Sect. A 1995, 51, 33. (c) Flack, H. D.; Bernadinelli, G. Acta Crystallogr., Sect. A 1999, 55, 908. (a) Chen, X.-M.; Huang, X.-Y.; Xu, Y.-J.; Zhu, Y.-J. J. Chem. Crystallogr. 1995, 25, 605. (b) Chen, C.-N.; Zhu, H.-P.; Huang, D.G.; Wen, T.-B.; Liu, Q.-T.; Liao, D.-Z.; Cui, J.-Z. Inorg. Chim. Acta 2001, 320, 159. Tong, M.-L.; Zheng, S.-L.; Shi, J.-X.; Tong, Y.-X.; Lee, H. K.; Chen, X.-M. Dalton Trans. 2002, 1727. Steiner, T. Angew. Chem., Int. Ed. 2002, 41, 48. Zhang, X.-M.; Hou, J.-J.; Wu, H.-S. Dalton Trans. 2004, 3437. Matthews, C. J.; Thompson, L. K.; Parsons, S. P.; Xu, Z.-Q.; Miller, D. O.; Heath, S. L. Inorg. Chem. 2001, 40, 4448. Mo, M.-S.; Zeng, J.-H.; Liu, X.-M.; Yu, W.-C.; Zhang, S.-Y.; Qian, Y.-T. AdV. Mater. 2002, 14, 1658. (a) Murrie, M.; Teat, S. J.; Stoeckli-Evans, H.; Gu¨del, H. U. Angew. Chem., Int. Ed. 2003, 115, 4801. (b) , Angew. Chem., Int. Ed. 2003, 42, 4653. (c) Yao, M.-X.; Zeng, M.-H.; Zou, H.-H.; Zhou, Y.-L.; Liang, H. Dalton Trans. 2008, 2428. (d) Gutschke, S. O. H.; Price, D. J.; Powell, A. K.; Wood, P. T. Angew. Chem., Int. Ed. 1999, 38, 1088. (a) Zeng, M.-H.; Wu, M.-C.; Liang, H.; Zhou, Y. L.; Chen, X.-M.; Ng, S. W. Inorg. Chem. 2007, 46, 7241. (b) Chen, H.-J.; Mao, Z.-W.; Gao, S.; Chen, X.-M. Chem. Commun. 2001, 2320. (c) Zeng, M.-H.; Feng, X.-L.; Zhang, W.-X.; Chen, X.-M. Dalton Trans. 2006, 5294. (d) Zeng, M.-H.; Wang, B.; Wang, X. Y.; Zhang, W.-X.; Chen, X.M.; Gao, S. Inorg. Chem. 2006, 45, 7069. (e) Zeng, M.-H.; Zhang, W.-X.; Sun, X.-Z.; Chen, X. M. Angew. Chem., Int. Ed. 2005, 44, 3079. (f) Zeng, M.-H.; Feng, X.-L.; Chen, X.-M. Dalton Trans. 2004, 2217. (a) Liu, F.-C.; Zeng, Y.-F.; Jiao, J.; Bu, X.-H.; Zhang, H.-J.; Ribas, J.; Batten, S. R. Inorg. Chem. 2006, 45, 2776. (b) Li, J.-R.; Yu, Q.; Tao, Y.; Bu, X.-H.; Ribas, J.; Batten, S. R. Chem. Commun. 2007, 2290. (c) Zeng, Y.-F.; Liu, F.-C.; Zhao, J.-P.; Cai, S.; Bu, X.-H.; Ribas, J. Chem. Commun. 2006, 2227. (d) Gala´n-Mascaro´s, J. R.; Dunbar, K. R. Angew. Chem., Int. Ed. 2003, 42, 2289. Kahn, O. Molecular Magnetism; VCH Publishers: New York, 1993; p 322. King, P.; Cle´rac, R.; Wernsdorfer, W.; Anson, C. E.; Powell, A. K. Dalton Trans. 2004, 2670. (a) Shaw, R.; Tidmarsh, I. S.; Laye, R. H.; Breeze, B.; Helliwell, M.; Brechin, E. K.; Heath, S. L.; Murrie, M.; Ochsenbein, S.; Gu¨del, H. U.; McInnes, E. J. L. Chem. Commun. 2004, 1418. (b) Yang, E. C.; Wernsodorfer, W.; Zakharov, L. N.; Karaki, Y.; Yamaguchi, A.; Isidro, R. M.; Lu, G.-D.; Wilson, S. A.; Rheingold, A. L.; Ishimoto, H.; Hendrickson, D. N. Inorg. Chem. 2006, 45, 529. (c) Larionova, J.; Gross, M.; Pilkington, M.; Andres, H.; Evans, H. S.; Gu¨del, H. U.; Decurtins, S. Angew. Chem., Int. Ed. 2000, 39, 1605. (a) Salah, M. B.; Vilminot, S.; Andre´, G.; Richard-Plouet, M.; Mhiri, T.; Takagi, S.; Kurmoo, M. J. Am. Chem. Soc. 2006, 128, 7972. (b) Taliaferro, M. L.; Selby, T. D.; Miller, J. S. Chem. Mater. 2003, 15, 3602.

CG800649A

Mononuclear, Tetra-, Penta- 3d Molecular Clusters Based on the

Recommend Documents