Tuning the Subunits and Topologies in Cluster-Based Cobalt–Organic Frameworks by Varying the Reaction Conditions

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Article

Tuning the Subunits and Topologies in Cluster-based Cobalt-Organic Frameworks by Varying the Reaction Conditions

Jiong-Peng Zhao, Wei-Chao Song, Ran Zhao, Qian Yang, Bo-Wen Hu, and Xian-He BuCryst. Growth Des., Just Accepted Manuscript • DOI: 10.1021/cg4002626 • Publication Date (Web): 31 May 2013

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Tuning the Subunits and Topologies in Cluster-based Cobalt-Organic

Frameworks by Varying the Reaction Conditions

Jiong-Peng Zhao,†, ‡ Wei-Chao Song,

† Ran Zhao,

† Qian Yang,

† Bo-Wen Hu,

† and Xian-He Bu*

,†

†Department of Chemistry, and TKL of Metal and Molecule-based Materials Chemistry, Nankai University,

Tianjin 300071, China

‡School of Chemistry and Chemical Engineering, Tianjin University of Technology, Tianjin 300384, China

___________________________________________________________________________________

* Corresponding author. E-mail: [email protected]. Fax: +86-22-23502458 Tel: +86-22-23502809.

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ABSTRACT

Different ways of anions introduction were applied to construct cluster-based frameworks owning to the

versatile coordination ability of formate anion and its sensitivity to the pH value of the reaction system.

Three tetra-, penta- and hexanuclear clusters based cobalt-organic frameworks [Co2(L)3(HCO2)•MeOH]n

(1), [Co5(L)6(OH)2(NO3)2•2H2O]n (2) and [CoL(HCO2)]n (3) (L = (E)-3-(pyridin-3-yl)acrylate), have been

successfully synthesized. In these complexes, each CoII-cluster is linked by twelve L ligands with different

connectivities to generate unique topological nets. In 1, two formate anions link four CoII ions forming a

tetranuclear cluster, and each of the tetranuclear clusters is connected to eight neighbors by L ligands

giving an 8-connected 36418536 net. In 2, the pentanuclear cluster is formed by five CoII ions linked through

two OH- and six carboxylate groups, which are further connected by L ligands to afford a pcu (primitive

cubic lattice) net. Different from 1 and 2, complex 3 is a two-fold interpenetrating pcu net based on

hexanuclear clusters, which are formed by the linkage of six CoII ions with six syn,syn,anti- formate anions

and six syn-syn carboxylate groups. Magnetic studies indicated that domain antiferromagnetic interactions

exist between CoII ions, and spin competition exists in 2 and 3.

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Introduction

Great efforts have been devoted to the rational design and synthesis of metal-organic frameworks

(MOFs), especially those constructed from polynuclear metallic units, which offer the potential for unique

properties, such as host-guest, luminescence, magnetism, catalysis, and so on. The synthetic challenge is to

increase and control the degree of the nuclearity of metal clusters.1-2 In additon, it is also a big challenge to

construct high-nuclearity-cluster based MOFs in pursuit of multifunctional materials and understand the

mechanism of the formation of high-nuclearity clusters.3 As a new type of molecule materials, one of the

advantages of MOFs is that some basic units, the so called secondary building units (SBUs), could be used

to assemble novel structures and enhance their properties through organic linker design and SBUs

selection.4 Among the reported organic linkers, the most efficient ligands are carboxylate ligands and

N-donor ligands. And SBUs with different geometries, such as, paddlewheel dimers M2(O2CR)4,5a-5c

trimers M3O(O2CR)6,5d,5e tetramers M4O(O2CR)6,

6a M4O(O2CR)8,6b high nuclear clusters7 and chain

structures,8 have been fabricated. The understanding of the formation of the SBUs, as well as the

coordination habit of the linkers, is necessary to the tailored design of MOFs.

Some small inorganic anions, such as O2-, OH- and X- (X = halogen), play important roles in the

formation of stable clusters.5,9 It should be noted that the introduction of inorganic anions is not the only

method to construct clusters. Small carboxylate, which could link metal ions in various ways, may be good

candidates to replace the small inorganic anions in the formation of clusters.10-11 Besides the applied anions,

syntheses conditions, such as pH, reactant ratios, temperature and solvents, can all affect the final structure

of SBUs and framework with giving organic ligands.12

In this work, the attempt to synthesize novel cluster based cobalt-organic frameworks with the

assistance of formate anion and (E)-3-(pyridin-3-yl)acrylate as bridge ligands was carried out. Fortunately,

three new complexes, [Co2(L)3(HCO2)•MeOH]n (1), [Co5(L)6(OH) 2(NO3)2•2H2O]n (2) and [CoL(HCO2)]n

(3) (L = (E)-3-(pyridin-3-yl)acrylate), with tetra-, penta- and hexanuclears as SBUs were obtained. In

complexes 1 and 3, the formate anions participate in the coordination and the formation of multinuclear

clusters. In 2, the formate anion does not coordinate to metal ions but adjusts the pH of the system, and an

OH- involved pentanuclear cluster is formed. In all these three complexes, each cluster is linked by twelve

L ligands to form various topological nets: 8-connected net, pcu (primitive cubic lattice) net and two-fold

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interpenetrating pcu net for 1, 2 and 3, respectively. Magnetic studies indicated that domain

antiferromagnetic interactions exist between the CoII ions in these complexes.

Experimental Section

Materials and Physical measurements

All the chemicals used for synthesis are of analytical grade and commercially available.

Co(HCO2)2·4H2O was synthesized by dissolving cobalt carbonate in formic acid and then concentrating.

Elemental analyses (C, H, N) were performed on a Perkin-Elmer 240C analyzer. The X-ray powder

diffraction (XRPD) was recorded on a Rigaku D/Max-2500 diffractometer at 40 kV, 100 mA for a

Cu-target tube and a graphite monochromator. IR spectra were measured on a Tensor 27 OPUS (Bruker)

FT-IR spectrometer with KBr pellets. Simulation of the XRPD spectra was carried out by the single-crystal

data and diffraction-crystal module of the Mercury (Hg) program available free of charge via the Internet at

http://www.iucr.org

Magnetic data were collected using crushed crystals of the sample on a Quantum Design MPMS-XL

SQUID magnetometer equipped with a 5T magnet. The data were corrected using Pascal's constants to

calculate the diamagnetic susceptibility; an experimental correction for the sample holder was applied.

Synthesis of 1: A mixture of Co(HCO2)2•4H2O (1.5 mmol), HL (HL= (E)-3-(pyridin-3-yl)acrylic

acid) (0.75mmol), MeOH (10 mL) was sealed in a Teflon-lined autoclave and heated to 140°C. After

maintained for 48 h, the reaction vessel was cooled to room temperature in 12 h, red crystals were collected

with ca 30% yield based on HL. FT-IR (KBr pellets, cm-1): 3467, 1650, 1581, 1466, 1429, 1387, 1129,

1033, 880, 848, 789, 614. Anal. Calcd for C26H23Co2N3O9: C, 48.84; H, 3.63; N, 6.57%. Found: C, 48.76;

H, 3.49; N, 6.74%.

Synthesis of 2: A mixture of Co(NO3)·6H2O (1.5 mmol), HL (0.75mmol), NaHCO2 (1 mmol) and

MeOH (10 mL) was sealed in a Teflon-lined autoclave and heated to 140 °C. After maintained for 48 h, the

reaction vessel was cooled to room temperature in 12 h, red crystals were collected with ca 30% yield

based on HL. FT-IR (KBr pellets, cm-1): 3447, 1647, 1559, 1541, 1507, 1474, 1457, 1399, 1123, 1034,

977, 699, 647. Anal. Calcd for C48H42Co5N8O22: C, 41.85; H, 3.07; N, 8.13%. Found: C, 41.97; H, 3.25; N,

7.84%.

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Synthesis of 3: A mixture of Co(NO3)·6H2O (1 mmol), HL (1mmol), NaHCO2 (1 mmol) and DMF

(10 mL) was sealed in a Teflon-lined autoclave and heated to 140 °C. After maintained for 48 h, the

reaction vessel was cooled to room temperature in 12 h, red crystals were collected with ca 30% yield

based on HL. FT-IR (KBr pellets, cm-1): 3467, 1650, 1581, 1466, 1387, 1129, 1033, 880, 848, 789, 614.

Anal. Calcd for C9H7CoNO4: C, 42.88; H, 2.80; N, 5.56%. Found: C, 42.71; H, 2.71; N, 5.65%.

X-ray Data Collection and Structure Determinations. X-ray single-crystal diffraction data for

complexes 1-3 were collected on a Rigaku SCXmini diffractometer at 293(2) K with Mo-Kα radiation (λ =

0.71073 Å) by ω scan mode. The program Rigaku CrystalClear13a was used for integration of the

diffraction profiles. All the structures were solved by direct methods using the SHELXS program of the

SHELXTL package and refined by full-matrix least-squares methods with SHELXL(semi-empirical

absorption corrections were applied using SADABS program).13b Metal atoms in each complex were

located from the E-maps and other non-hydrogen atoms were located in successive difference Fourier

syntheses and refined with anisotropic thermal parameters on F2. The hydrogen atoms of the ligands were

generated theoretically onto the specific atoms and refined isotropically with fixed thermal factors. Table 1

shows crystallographic crystal data and structure processing parameters. Selected bond lengths and bond

angles are listed in Table 2.

(Insert Table 1 and Table 2)

Results and Discussion

Synthesis

Reacting ligand HL with the corresponding metal salts and sodium formate in different solvent give

birth to complexes 1-3 with tetra-, penta- and hexanuclear clusters as SBUs (Scheme 1). Directly

assembling the ligand L and cobalt formate in MeOH afford tetranuclear clusters based complex 1. In 1, the

ratio of formate anions and L is 1 : 3, which may be ascribed to the low solubility of cobalt formate in

MeOH. And adding formate anions and cobalt ions in the reaction by using sodium formate and cobalt

nitrate instead of cobalt formate, complex 2 was obtained based on a pentanuclear clusters as SBUs. In

forming 2, the formate anions are not coordinated to metal ions but only adjust the pH value of the system,

which create double hydroxyl anions bridged pentanuclear clusters. And it is worth noting that the nitrate

anions coordinate to the unsaturated coordinated positions of cobalt ions for charge balance in forming the

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pentanuclear clusters in 2. The formate anions could coordinate to cobalt ions giving a hexanuclear clusters

based complex 3 with DMF not MeOH as solvent, in which the contents of formate is increased with a ratio

of formate : L as 1 : 1. It indicates that the concentration of the formate anions in the reaction systems of 3

is higher than that of 1. And the L ligands in the complexes take the roles of assisting the formation of the

cluster and linking the clusters into 3D framework.

(Insert Scheme 1)

Description of crystal structures

[Co2(L)3(HCO2)•MeOH]n (1). Single-crystal X-ray diffraction analysis of 1 reveals that 1 crystallizes

in the monoclinic space group P21/n (see Table 1 for more information about the unit cell) and has a 3D

framework structure. The asymmetric unit of 1 contains one unique formate anion, three L ligands, two

CoII ions and one lattice MeOH molecule. The Co1 ion is coordinated by five oxygen atoms and one

nitrogen atom from four L ligands and one formate anion forming a distorted octahedral configuration

(Figure 1a). The Co2 ion is coordinated by five L ligands and one formate anion forming a CoN2O4

distorted octahedral coordination geometry. The formate anion takes anti,anti mode linking two CoII ions

with bond lengths of [Co1-O2 = 2.038(4) Å], [O1-Co2iii = 2.023(4) Å, and Co1…Co2iii distance about

5.870 Å. The first L ligand coordinates to three CoII ions in which the nitrogen atom coordinates to Co1v

with bond length of [N1-Co1v = 2.117(5) Å] and the carboxylate group chelates to Co1 and bridges to Co2

in syn,syn,anti κO3,O4:κO4 mode with bond lengths of [Co1-O3 = 2.148(4) Å, Co1-O4 = 2.274(4) Å and

Co2-O4 = 2.131(4) Å] and Co1…Co2 distance about 3.555 Å. The second L ligand coordinates to Co1,

Co2 and Co2iv using the syn,syn carboxylate and the nitrogen atom with bond lengths of [Co1-O6 =

2.059(4) Å, Co2-O5 = 2.044(4) Å and N2-Co2iv = 2.179(5) Å. The third L ligand has the same

coordination mode with the second one but coordinates to Co2vi, Co1vi and Co2 using the carboxylate

group and the nitrogen atom with bond lengths of [O7-Co2vi = 2.083(4) Å, O8-Co1vi = 2.024(4) Å and

Co2-N3 = 2.163(5) Å]. In this way the carboxylate groups of three different types of L ligands link Co1

and Co2 ions giving Co2 dimer. The dimer is further linked by two formate anions, which are anti-parallel

to each other to form a tetranuclear cluster (Figure 1b). Each tetranuclear unit is expanded by the linkage of

twelve L ligands (four of the each type) to form a 3D network. However, the first and second type ligands

take double-bridges mode linking the neighboring clusters. Through these L ligands, each tetranuclear

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cluster is connected to eight neighbors to afford a 36418536 8-connected net with the cluster as the unique

node (Figure 1c).14,15

(Insert Figure 1 and Figure 2)

[Co5(L)6(OH)2(NO3)2•2H2O]n (2). Complex 2 crystallizes in the triclinic space group P-1, and the

asymmetric unit of 2 contains one unique hydroxyl anion, three L ligands, one nitrate anion, two and a half

CoII ions, and one lattice water molecule. The Co1 ion is located at the inverse center and coordinated by

six oxygen atoms form four carboxylate groups and two hydroxyl anions with bond lengths of [Co1-O9 =

2.051(7) Å, Co1-O6 = 2.112(7) Å and Co1-O4 = 2.134(7) Å]. The Co2 ion is coordinated by four L ligands,

one hydroxyl anion and one nitrate anion forming a CoN1O5 distorted octahedral coordination

configuration with normal bond lengths in the range of 2.036(7)-2.222(8) Å (Figure 2a and 2b). The Co3

ion is coordinated by four oxygen atoms and two nitrogen atoms from five L ligands and one hydroxyl

anions with bond lengths in the range of 2.042(7)-2.276(8) Å. The first type of L ligand takes µ3 mode

linking Co1, Co2 and Co3iv with the syn,syn carboxylate group (O1, O2) and the nitrogen atom (N1)

(Figure 2a). The second type of L ligand takes µ4 mode coordinating to four CoII ions (Co1, Co2, Co3i and

Co3v) in which Co1, Co2, Co3i are coordinated by the carboxylate groups in syn,syn,anti µ3-κO3: κO4:

κO4 mode with bond angle of [Co1-O4-Co2 = 90.0(3)°]. The third type of L ligand has the similar

coordination mode with the second one but links Co1, Co2, Co3i and Co2ii. In the third type of L ligand,

the O6 atom takes µ2 bridging mode linking Co1 and Co3i with bond angle of [Co1-O6-Co3i = 90.8(3) °].

The nitrate anion takes the unsaturated site of Co2 in monodentate mode. The hydroxyl anion takes µ3

bridging mode coordinating to Co1, Co2 and Co3 with bond angles of [Co1-O9-Co2 = 97.8(3)°,

Co1-O9-Co3 = 99.5(3)° and Co2-O9-Co3 = 127.3(3)°] and Co1…Co2, Co2…Co3, Co1…Co3 distance

about 3.080 Å, 3.658 Å, 3.127 Å to form an irregular metal triangle. Two metal triangles connect to each

other with a common vertex Co1 to give rise to a bow-tie shaped Co5(µ3-OH)2 unit, in which all of the CoII

ions lie in a perfect plane for the symmetry reason (Figure 2b).16 Although the Co5 units expand through

twelve L ligands like 1, every couple of clusters are linked by two L ligands with the same type, thus each

cluster is connected to six neighbors. The whole framework could be described as a pcu-type topological

net with the Co5 cluster as node (Figure 2c).17

[CoL(HCO2) ]n (3). Complex 3 is a two-fold interpenetrating 3D framework based on hexanuclear

clusters and crystallizes in the trigonal space group R-3. The asymmetric unit of 3 contains one formate

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anion, one L ligand and one CoII ion. The Co1 ion is six coordinated by five oxygen atoms and one

nitrogen atom from three formate anions and three L ligands (Figure 3a). The L ligand coordinates to three

CoII ions with the nitrogen atom and two oxygen atoms of the syn,syn carboxylate group with bond lengths

of [Co1-O1 = 2.045(6) Å, Co1ii-O2i = 2.090(6) Å and Co1-N1iv = 2.163(7) Å]. The formate anion takes

syn,syn,anti mode coordinating to three CoII ions (Co1, Co1i and Co1v) with bond lengths of [Co1i-O4 =

2.115(6), Co1-O3 = 2.121(6) Å and Co1v-O4 = 2.126(6) Å]. The bond angle of the µ2 oxygen atom is

[Co1i-O4-Co1v = 114.5(2) °]. Six formate anions link six CoII ions forming a hexaprismane with the nearest

Co…Co distance about 3.566 Å (Figure 3b). This hexaprismane is reinforced by six carboxylate groups

(Figure 3c).18 Similar to that of 1 and 2, each Co6 unit expands through twelve L ligands to form a 3D

framework. Every couple of neighboring Co6 units are connected by two L ligands, thus a six connected

pcu net based on the node of Co6 unit is obtained.17

(Insert Figure 3 and Figure 4)

Different from that of 2, the framework of complex 3 is interpenetrating and could be described as a

two-fold interpenetrating pcu topological net (Figure 3d). It is worth noting that both the formate anion and

the L ligand connect to three CoII ions. If the connections in the Co6 units are also taken into consideration,

the whole framework would be described as a two-fold interpenetrating 3,6-connected 3-nodal net with the

Schläfli notation of {42;6}2{47;66;82} (Figure 4).

Magnetic Studies

Magnetic measurements were carried out on crystalline samples of complexes 1-3 (phase purity of

these samples was confirmed by XRPD, Figure S1). As discussed above, these compounds are structurally

featured by multinuclear clusters, which are interlinked by the long pyridin-3-ylacryl groups, thus the

magnetisms of these complexes reflect the characters of their clusters.

(Insert Figure 5)

The magnetic susceptibility of 1 was collected under an external field of 1000 Oe in the temperature

range of 2-300 K. The χm and χmT vs T plots are shown in Figure 5a, accounting for the tetranuclear cluster

Co4. The χmT product decreases smoothly with cooling from room temperature to 100 K and then it drops

quickly to 1.70 cm3 mol-1 K at 2 K. This phenomenon indicates that antiferromagnetic coupling exist

between the CoII ions in 1. The value of χm has a peak at about 5 K, which suggests an antiferromagnetic

phase transition at low temperature. The best-fit parameters from the magnetic data in the temperature

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range of 100-300 K through the Curie–Weiss law (Figure S2) give θ = -34.90 K and C = 16.03 cm3Kmol-1,

which is consistent with the values expected for four magnetically isolated high spin octahedral CoII ions

with spin-orbit coupling, which contribute a negative Weiss constant of about -20 K.2a,19 The

field-dependent magnetization at 2 K (Figure 5b) clearly corroborates the antiferromagnetic interaction in 1.

The M/Nβ increases linearly with the field and reaches 8.00 Nβ at 5 T, which is close to the saturation value

for four octahedral CoII ions (8.4-10 Nβ).2a,16,19 In the tetranuclear cluster of 1, the carboxylate group and

formate ion in syn,syn or anti,anti mode would conduct antiferromagnetic coupling, and the carboxylate

group in syn,syn,anti κO3,O4:κO4 mode also transfer antiferromagnetic interaction for the Co1-O4-Co2

angle of 107.59(16)°.20 Finally, the weak antiferromagnetic coupling transferred by L ligands.

(Insert Figure 6)

As shown in Figure 6a, the tendency of the χm vs T and χmT vs T plots of 2 (collected under 1000 Oe)

are similar to that of 1, indicating the domain antiferromagnetic interaction between the CoII ions in 2.

However, the χm plot has no peak, which excludes the antiferromagnetic phase transition above 2 K. It is

interesting that the Curie plot has two linear regions with different slopes: a high temperature (HT) region

from 300 to 50 K and a low temperature (LT) region from 50 to 2 K. Structurally, 2 could be considered as

magnetically isolated pentanuclear clusters with weak interactions between neighbors. However, the

spin-orbit coupling effects of CoII ions make it difficult to evaluate the exchange parameters between CoII

ions. In the pentanuclear clusters, domain antiferromagnetic interaction could be conducted by the

syn,syn,anti carboxylate group and the oxygen bridge with Co-O-Co angle larger than 90°.20 The best-fit

parameters of the magnetic data through the Curie–Weiss law (Figure S2) are θHT = -53.09 K, CHT = 16.64

cm3Kmol-1, θLT = -2.47 K and CLT = 5.28 cm3Kmol-1. The θHT obtained from the HT region is consistent

with five isolate high spin octahedral CoII ions with spin-orbit coupling, and its negative value indicates a

dominant antiferromagnetic interaction. It is worthwhile to note that spin competition is possible to exist in

the pentanuclear cluster for the triangle arrangement of CoII ions with antiferromagntic interaction. The

degree of frustration quantified by f = |θHT|/TN is 26 (53.09/2), sugessting strong spin competition.21

However, if the contribution of spin-orbit coupling to θHT is excluded, the f value of 1 would be much

smaller.23 Due to the unequal couplings in the triangle, the Curie plot presents at low temperature and gives

a ferrimagnet like behavior. The magnetization versus field plot at 2 K (Figure 6b), in which M/Nβ reaches

a value of 3.0 Nβ at 50 kOe, which is larger than the expected saturation value of 2.1-2.5 Nβ for one CoII

ion in an octahedral environment with S = 1/2 and g = 4.1-5.0.2a,16,19 These results indicate that in the

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pentanuclear cluster, the spins of the five CoII ions are not well compensated. No obvious typical rise of a

ferrimagnetic complex is observed in the χmT vs T plot of 2 at low temperature, which may be due to the

existence of small antiferromagnetic interaction between clusters or the frustration in the pentanuclear

clusters.

(Insert Figure 7)

The magnetic susceptibility of 3 were collected under a external field of 2000 Oe in the temperature

range of 2-300 K, and the χm vs T and χmT vs T plots are shown in Figure 7a, accounting for the hexanuclear

cluster Co6. Starting from room temperature, the χmT product decreases smoothly with cooling until 150 K,

and below 100 K, it decreases quickly to 10.70 cm3mol-1K at 8 K. Below 8 K, it drops suddenly to 6.30 cm3

mol-1K at 2 K. These results indicate antiferromagnetic coupling between the CoII ions in 3. However there

is no peak in the χm vs T plot excluding the antiferromagnetic phase transition above 2 K. The best-fit

parameters from the magnetic data in the temperature range of 50-300 K through the Curie–Weiss law

(Figure S2) are θ = -24.38 K and C = 20.31 cm3 K mol-1, which are consistent with the values of six high

spin CoII ions with spin-orbit coupling. The field-dependent magnetization at 2 K (Figure 7b) clearly

corroborates the antiferromagnetic interaction in 3. The M/Nβ value does not follow the Brillouin curve and

reaches 12.84 Nβ at 5 T, which is close to the saturation value of six octahedral CoII ions about 12.5-15 Nβ.

2a,16,19 In the hexanuclear cluster, there are two kinds of interaction between CoII ions. Between neighboring

CoII ions, antiferromagnetic coupling would be conducted by the syn,syn carboxylate group, syn,syn

formate ion and bridging oxygen atom with a Co-O-Co angle of 114.5(2)°. Antiferromagnetic interaction

can also be conducted by the formate ion in syn,anti mode between the couple of CoII ions with one interval.

Thus there are antiferromagnetic triangles antiferromagnetic coupled in the cluster. The degree of

frustration quantified by f = |θ|/TN is 12.19 (24.38/2). However, the frustration in 3 could not be emphasized

too much, because the interaction between the CoII ions with one interval are weaker than that between

neighbors and the negative θ value also contains the contribution of the spin-orbit coupling in CoII ions.22

Conclusion

Three cobalt-organic frameworks based on tetra-, penta- and hexanuclear clusters as building blocks

with different topologies have been constructed by the deliberate selection of the reaction condition with

the aid of formate anions. Due to the significant variety of the CoII cluster nodes and their geometries, it is

clear that there remains great potential for the discovery of cluster based metal-organic frameworks with

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the application of formate anions. The connection of clusters suggests that the increase of the number of the

ligands linked to a small cluster does not always give high connected nets because neighboring clusters

may be linked through multi-bridges reducing the connection number of the whole framework. In addition,

magnetic studies indicated that domain antiferromagnetic interaction exists between CoII ions and spin

competition exists in 2 and 3.

Acknowledgments. This work was supported by the NNSF of China (21031002, 21290171, 21101114),

and the 973 Program of China (2012CB821700).

Supporting Information Available: X-ray crystallographic data for complexes 1, 2 and 3 in CIF format

and Fig. S1-S2. These materials are available free of charge via the Internet at http://pubs.acs.org.

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Captions to Scheme and Figures

Scheme 1. The synthesis conditions of the complexes and structure of the clusters as well as the role of the

anions.

Figure 1. a) The coordination modes of the metal ions and linkage of the ligands in 1. b) The polyhedron

view of tetranuclear cluster in 1. c) The 8-connected topological net of 1 with the tetranuclear

cluster as node. Symmetry codes: (i) −x+3/2, y−1/2, −z+3/2; (ii) x, y−1, z; (iii) −x+1, −y+1,

−z+1; (iv) −x+2, −y+1, −z+1; (v) x, y+1, z; (vi) −x+3/2, y+1/2, −z+3/2.

Figure 2. a) The linkage of the ligands in 2. b) The coordination mode of the CoII ions in the pentanuclear

structure in 2. c) The pcu topological net of 2 with the pentanuclear cluster as node. Symmetry

codes: (i) −x, −y+1, −z; (ii) −x, −y+2, −z; (iii) x−1, y, z; (iv) −x, −y, −z+1; (v) x+1, y, z.

Figure 3. a) The coordination modes of the metal ions and linkage of the ligands in 3. b) The hexanuclear

cluster constructed by the formate anions and CoII ions. c) The connections of the hexanuclear

cluster and L ligands. Only the carboxylate groups and nitrogen atoms of the L ligands are

shown for clarity. d) The two-fold interpenetrating pcu topological net of 3 with the hexanuclear

cluster as node. Symmetry codes: (i) y, −x+y, −z+1; (ii) x−y, x, −z+1; (iii) −y, x−y, z; (iv) −y+1/3,

x−y−1/3, z+2/3; (v) −x+y, −x, z; (vi) −x+y+2/3, −x+1/3, z−2/3.

Figure 4. View of the 3,6-connected 3-nodal topological net of 3 from different directions: a) from c

direction and b) a direction.

Figure 5. a) Plots of χm and χmT vs T at 0.1 T of 1. Inset: the χm vs T at 2-50 K. b) The field-dependent

magnetizations plots (M/ Nµβ vs H) plots of 1 at 2 K (triangles), and the solid line is guided for

eye.

Figure 6. a) Plots of χm and χmT vs T at 0.1 T of 2. b) The field-dependent magnetizations plots (M/ Nµβ vs

H) plots of 2 at 2 K.

Figure 7. a) Plots of χm and χmT vs T at 0.2 T of 3. b) The field-dependent magnetizations plots (M/ Nµβ vs

H) plots of 3 at 2 K (triangles), and the solid line is guided for eye. Inset: the topological

structure (solid line) and the exchange ways (dashed) of the hexanuclear cluster of 3.

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Table 1. Crystal data and structure refinement details for 1-3.

1 2 3

Chemical formula C26H23Co2N3O9 C48H42Co5N8O22 C9H7CoNO4

Formula weight 639.34 1377.55 252.09

Space group P21/n P-1 R-3

a (Å) 15.182(3) 10.975 (2) 22.575(12)

b (Å) 9.7285(1) 12.139 (2) 22.575(12)

c (Å) 19.240(4) 13.728 (3) 11.483(2)

α / deg 90 67.25 (3) 90

β / deg 100.61(3) 80.94 (3) 90

γ / deg 90 70.26 (3) 120

V / Å3 2793.2(1) 1586.8 (5) 5068(4)

Z 4 1 18

GOF 1.157 1.04 1.147

D/g cm–3 1.520 1.442 1.487

µ / mm–1 1.244 1.36 1.516

T / K 293 293 293

R a / wR

b 0.0771/0.1388 0.112/0.294 0.0995/0.2430

a R = Σ||Fo| − |Fc|| / Σ|Fo|;

b Rw = [Σ[w(Fo2 − Fc

2)2] / Σw(Fo2)2]1/2.

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Table 2. Selected bond lengths [°] and angles [Å] for 1-3.

1

Co1—O8i 2.024 (4) Co2—O1iii 2.023 (4)

Co1—O2 2.038 (4) Co2—O5 2.044 (4)

Co1—O6 2.059 (4) Co2—O7i 2.083 (4)

Co1—N1ii 2.117 (5) Co2—O4 2.131 (4)

Co1—O3 2.148 (4) Co2—N3 2.163 (5)

Co1—O4 2.274 (4) Co2—N2iv 2.179 (5)

Co2—O4—Co1 107.59 (16)

(i) −x+3/2, y−1/2, −z+3/2; (ii) x, y−1, z; (iii) −x+1, −y+1, −z+1; (iv) −x+2, −y+1, −z+1

2

Co1—O9i 2.051 (7) Co2—N3ii 2.150 (9)

Co1—O9 2.051 (7) Co2—O5 2.156 (7)

Co1—O6 2.112 (7) Co2—O4 2.222 (8)

Co1—O6i 2.112 (7) Co3—O1 2.042 (7)

Co1—O4i 2.134 (7) Co3—O9 2.047 (7)

Co1—O4 2.134 (7) Co3—O3i 2.105 (7)

Co2—O9 2.036 (7) Co3—N2iii 2.131 (10)

Co2—O2 2.050 (7) Co3—N1iv 2.190 (9)

Co2—O10 2.097 (11) Co3—O6i 2.276 (8)

Co2—O9—Co3 127.3 (3) Co3—O9—Co1 99.5 (3)

Co2—O9—Co1 97.8 (3) Co1—O4—Co2 90.0 (3)

Co1—O6—Co3i 90.8 (3)

(i) −x, −y+1, −z; (ii) −x, −y+2, −z; (iii) x−1, y, z; (iv) −x, −y, −z+1

3

Co1—O1 2.045 (6) Co1—O3 2.121 (6)

Co1—O2i 2.090 (6) Co1—O4iii 2.126 (6)

Co1—O4ii 2.115 (6) Co1—N1iv 2.163 (7)

Co1i—O4—Co1v 114.5 (2)

(i) y, −x+y, −z+1; (ii) x−y, x, −z+1; (iii) −y, x−y, z; (iv) −y+1/3, x−y−1/3, z+2/3;

(v) −x+y, −x, z

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Scheme 1

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Fig. 1.

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Fig. 2.

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Fig. 3.

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Fig. 4.

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Fig. 5.

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Fig. 6.

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Fig. 7.

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Synopsis

Tuning the Subunits and Topologies in Cluster-based Cobalt-Organic Frameworks by

Varying the Reaction Conditions

Jiong-Peng Zhao,†, ‡ Wei-Chao Song,

† Ran Zhao,

† Qian Yang,

† Bo-Wen Hu,

† and

Xian-He Bu*,†

Three cobalt-organic frameworks based on tetra-, penta- and hexanuclear clusters as

building blocks with various topologies have been constructed by the deliberate selection of

the reaction condition with the aid of formate anions.

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Documents

Tuning the Subunits and Topologies in Cluster-Based Cobalt–Organic Frameworks by Varying the Reaction Conditions