Mn(II) Complexes Based on Terphenyl

Subscriber access provided by UNIV OF MISSISSIPPI

Article

Polynuclear Ni(II)/Co(II)/Mn(II) Complexes Based on Terphenyl-tetracarboxylic Acid Ligand: Crystal Structures and Research of Magnetic Properties Lin Zhang, Lu Liu, Chao Huang, Xiao Han, Li'an Guo, Hong Xu, Hongwei Hou, and Yaoting Fan Cryst. Growth Des., Just Accepted Manuscript • DOI: 10.1021/acs.cgd.5b00504 • Publication Date (Web): 15 Jun 2015 Downloaded from http://pubs.acs.org on June 19, 2015

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

Crystal Growth & Design is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 27

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Crystal Growth & Design

Polynuclear Ni(II)/Co(II)/Mn(II) Complexes Based on Terphenyl-tetracarboxylic Acid Ligand: Crystal Structures and Research of Magnetic Properties Lin Zhang, Lu Liu, Chao Huang, Xiao Han, Li’an Guo, Hong Xu, Hongwei Hou*, Yaoting Fan The College of Chemistry and Molecular Engineering, Zhengzhou University, Zhengzhou, Henan, 450052, P. R. China * To whom correspondence should be addressed. Fax: (86) 371–67761744; E-mail: [email protected]

ACS Paragon Plus Environment

1


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 2 of 27

ABSTRACT: By the solvothermal reactions of a [1,1':3',1''-terphenyl]-3,3'',5,5''- tetracar -boxylic acid

(H4tpta)

with

transition

metal

ions,

three

novel

polymeric

complexes,

namely,

{[Ni2(tpta)(H2O)3]·H2O}n (1), {[Co4(tpta)2(4,4′-bpy)(H2O)3]·3H2O}n (2), {[Mn2(tpta)(H2O)2]·2H2O}n (3) have been isolated. The heterometallic clusters of these polymeric complexes are dimeric and tetrameric, respectively. 1 is comprised of dimeric paddle wheel Ni(II) units to generate a 2D structure. In complexes 2 and 3, metal ions form tetrameric units that extend via all dimensions to give 3D structures with the Schläfli symbol of (43)(43)(46·618·84) and (46)(412·53·69·74), respectively. The results of variable temperature magnetization measurements (χMT-T and χM−1-T) show that complexes 1 and 2 display unusual ferromagnetic coupling via the M-O-C-O-M bridges, while complex 3 shows predominantly antiferromagnetic behavior. The M(H) curve of 1 does not saturate until the highest field of 80 kOe, indicating the significant magnetic anisotropy in this complex system, whereas the final saturation value of 2.79 Nβ for 2 manifests the existence of typically paramagnetic property and the absence of long-range magnetic ordering. The dynamic magnetization experiments have been also carried out to further explore the magnetic behaviors of 1 and 2. There are no frequency dependences in the dynamic magnetization experiments, suggesting the absence of slow magnetic relaxation of these two complexes.

INTRODUCTION Metal-organic frameworks (MOFs) have emerged as a fast growing research topic during the past decades. Cluster-based MOFs, which is an important subset of MOFs, are of particular attention because of their intriguing structural motifs and potential applications in catalysis,1-8 gas adsorption/storage,9-12 luminescence,13-17 magnetism,18-21 etc. Magnetic cluster-based MOFs (MCMOFs) have attracted especially more interests among research communities for their significance in not only interpreting the fundamental magneto-structural correlations but also the exploration of advanced magnetic materials, such as single-molecule magnets.22-24 At present, tremendous efforts have been devoted to the rational ACS Paragon Plus Environment

2

Page 3 of 27

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


design, synthesis and the structure-magnetic behavior of MCMOFs. Despite of the great findings, it remains a long-term work for synthetic chemists to rationally tailor their network structures and predict the unique magnetic properties.25-28 Generally, such MOFs can be engineered by incorporating paramagnetic transition-metal ions and multidentate bridging organic ligands.29-32 It is found that the paramagnetic metal centers as spin carriers can effectively influence the magnetic ordering. For example, the significant single-ion magnetic anisotropy in Co2+ ions should be responsible for the tempting magnetic features of spin canting as well as slow magnetic relaxation.23,24,33 On the other hand, the versatile coordination modes of the magnetic bridges towards paramagnetic ions are anticipated guiding factors on governing the nuclearity and arrangement of metal nodes to afford varieties of SBUs and dominating the nature and strength of the superexchange interactions.34-36 Therefore, reasonable selection of ligands as magnetic mediators is a crucial way to impart cluster-based MOFs with expected magnetic properties. Bridging ligands containing carboxylate have been convinced good candidates, because they are able to bind metal ions through variable coordination modes, resulting in large amounts of polynuclear clusters.37,38 Besides, from the magnetic perspective, polycarboxylates with abundant coordination modes are capable of transmitting magnetic couplings in varying degrees. Thus, metal carboxylates can construct magnetic superexchange pathways among the metal centers and form molecular

magnets

equipped

with

interesting

magnetic

behaviors

of

antiferromagnetism,

ferromagnetism, spin canting, etal.39-44 The coactions of the magnetic nature of the paramagnetic ions and superexchange interactions by the magnetic bridges will produce a significant effect on the magnetism of the entity.45 Inspired by these ideas, our research interest focus on constructing various cluster-based frameworks with useful magnetic properties based on different paramagnetic metal centers and carboxylate functional groups. Furthermore, investigation on the magnetic properties of these MOFs is of immense importance in better comprehending their structure-magnetism relationships and can contribute to the further development of novel magnetic materials both academically and industrially.4649


3


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 4 of 27

In the present work, we have selected a [1,1':3',1''-terphenyl]-3,3'',5,5''- tetracar -boxylic acid (H4tpta) with multiple bridging modes as the main organic ligand, which can readily bind different paramagnetic centers to induce M(II)-core aggregation (M = Ni for (1), Co for (2), Mn for (3)) and lead to the magnetic interactions. Therefore, three cluster-based MOFs containing Ni2, Co4 and Mn4-clusters SBUs have been synthesized successfully, namely, {[Ni2(tpta)(H2O)3]·H2O}n (1), {[Co4(tpta)2(4,4′bpy)(H2O)3]·3H2O}n (2), {[Mn2(tpta)(H2O)2]·2H2O}n (3). Dynamic magnetization experiments of these complexes have been conducted over the range of 2−300 K. Complexes 1 and 2 exhibit predominantly ferromagnetic interactions, while 3 show weak antiferromagnetic behaviors in its measured temperature ranges.

EXPERIMENTAL SECTION Materials and Physical Measurements. All materials were acquired through commercial channels. The FT-IR spectra were performed by a Bruker-ALPHA spectrophotometer (KBr disks, 400−4000 cm-1). Elemental analyses (of C, H, N) were conducted on a FLASH EA 1112 elemental analyzer. Powder Xray diffraction (PXRD) patterns were carried out on a PANalytical X’Pert PRO diffractometer using Cu Kα1 radiation. Thermal analyses of the samples were recorded using a Netzsch STA 449C TGA instrument from ambient temperature (heating rate of 10 °C/min).

Synthesis of {[Ni2(tpta)(H2O)3]·H2O}n (1) H4tpta (0.05 mmol, 20.0 mg) and Ni(NO3)2·6H2O (0.1 mmol, 29.0 mg) were mixed in 3 mL H2O and 7 mL CH3CN. The mixture was put into a Teflon-lined stainless steel vessel (25 mL), heated to 160 °C for 3 days and cooled to ambient temperature at 5 °C/h. Light green crystals of 1 with 65 % yield (based on Ni) were collected. Anal. calcd for C22H18Ni2O12 (%): C, 44.65; H, 3.07. Found: C, 44.68; H, 3.12. IR (KBr, cm–1): 3441(m), 1616(m), 1579(m), 1521(w), 1453(m), 1363(s), 1302(w), 1247(w), 1116(m), 773(m), 731(s), 645(w), 616(w).

Synthesis of {[Co4(tpta)2(4,4′-bpy)(H2O)3]·3H2O}n (2) Dark-purple crystals of 2 with 52 % yield ACS Paragon Plus Environment

4

Page 5 of 27

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(based on Co) were obtained by employing the same reaction condition as that of 1 except that the mixture was H4tpta (0.05 mmol, 20.0 mg) and 4,4′-bpy (0.1mmol, 15.6 mg) along with Co(NO3)2·6H2O (0.1 mmol, 29.1 mg) into 4mL CH3CN, 4 mL H2O and 2 mL 1,4-dioxane. Anal. calcd for C54H40Co4N2O22 (%): C, 49.71; H, 3.09; N, 2.15. Found: C, 49.75; H, 3.12; N, 2.18. IR (KBr pellet, cm−1): 3446(m), 1613(m), 1576(w), 1427(w), 1364(s), 1110(s), 771(m), 725(s), 616(w), 571(w), 459(w).

Synthesis of {[Mn2(tpta)(H2O)2]·2H2O}n (3) Khaki crystals of 3 with 69 % yield (based on Mn) were obtained by employing the same reaction condition as that of 1 except that the mixture was H4tpta (0.05 mmol, 20.0 mg) along with MnCl2·4H2O (0.05 mmol, 10.0 mg) into 5mL CH3CN, 5 mL H2O and 2 mL THF. Anal. calcd for C22H18Mn2O12 (%): C, 45.23; H, 3.11. Found: C, 45.18; H, 3.14. IR (KBr, cm–1): 3423(s), 3060(w), 2920(w), 1614(s), 1560(s), 1429(m), 1392(s), 1371(w), 1307(w), 1256(w), 1110(s), 939(w), 893(w), 808(m), 771(s), 727(s), 645(m), 614(w), 557(w).

Crystallography. The Rigaku Saturn 724 CCD diffractomer (Mo-Kα, λ = 0.71073 Å) was used to get the crystallographic data of 1–3 at 20 ± 1 °C. All data corrections were finished by the Lorentz and polarization effects. The SHELXL-97 crystallographic software package was employed to solve and refine the structures.50 Solvent molecules for complex 2 were removed using SQUEEZE program in PLATON. The final chemical formula was determined by SQUEEZE results combining with the TGA and elemental analysis. H atoms were assigned at calculated positions and refined by a riding model. Crystal data as well as part of bond lengths and angles of 1–3 have been demonstrated in Table 1 and Table S1, respectively. Crystallographic data of 1−3 have been stored in the Cambridge Crystallographic Data Centre. CCDC numbers: 1057708−1057710.

Magnetic Susceptibility Measurements. Dynamic magnetization experiments of polycrystalline samples 1−3 were carried out with a SQUID MPMS XL-7 instrument at H = 1000 Oe over the temperature range 2−300 K. The M-H curves were obtained from - 80 to 80 kOe at 2 K. The dynamic 5 ACS Paragon Plus Environment


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 6 of 27

magnetization experiments were performed for oscillating frequencies (10000−10 Hz) at HDC = 0 Oe and HAC = 3 Oe. Diamagnetic corrections were estimated from Pascal constants.51

RESULTS AND DISCUSSION Crystal Structure of {[Ni2(tpta)(H2O)3]·H2O}n (1) 1 crystallizes in the triclinic system Pī, showing a 2D polymeric structure. As depicted in Figure 1a, the asymmetric unit includes a tpta4- anion, two independent Ni atoms, a guest H2O molecule as well as three associated H2O molecules. Ni1, Ni2 are six-coordinated and display distorted octahedral geometry. Ni1 is surrounded with four carboxylate O atoms (O3, O4, O9A ,O6B) of three tpta4- anions as well as two O atoms (O1, O2) from two coordinated H2O molecules (Ni1–O = 2.020–2.365 Å). Ni2 occurs to be coordinated to five oxygen atoms (O4, O8A, O7B，O10C and O11C) from four tpta4- ligands with a O5 of a coordinated aqua molecule (Ni2– O = 2.019–2.133 Å). In complex 1, tpta4- anion shows three different coordination fashions: η1: η1 mode, µ2-η1: η1 modes and µ2-η2: η1 mode. Based on these coordination features, two Ni(II) are linked by tpta4- ligands, forming a dinuclear {Ni2(CO2)4} secondary unit building (SBU). The distance between Ni1and Ni2 is 3.293 Å (Figure 1b). The tpta4- ligand acting as µ4-bridge links Ni1 and Ni2 ions, giving a 2D structure (Figure 1c). Moreover, topological analysis has been conducted for a better understanding of the 2D polymeric structure. If both the dinuclear cluster and the tpta4- ligand are regarded as 4connected nodes, the two-dimensional skeleton should be classified as a (4,4)-connected net with (44·62)(44·62) topology (Figure 1d).

Crystal Structure of {[Co4(tpta)2(4,4′-bpy)(H2O)3]·3H2O}n (2) 2 demonstrates a three-dimensional skeleton and crystallizes in the triclinic crystal system Pī. As depicted in Figure 2a, four Co centers occupies three different coordination environments. Both Co1 and Co4 ions are connected to four carboxylate O atoms, an oxygen atom of one aqua ligand as well as an nitrogen atom from a 4,4′-bipy molecule, exhibiting an octahedral geometry. The Co2 center lies in tetrahedral sphere, defined by three carboxylate O atoms along with an oxygen atom of one aqua ligand. The Co3 is coordinated to five ACS Paragon Plus Environment

6

Page 7 of 27

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


carboxylate oxygen atoms, showing a slightly askew trigonal-bipyramidal geometry. The Co–O/N distances fall between 1.958 and 2.361 Å.

Co1 and Co2 are connected by two µ2-η1:η1 bridging carboxylate groups to afford a binuclear [Co2(CO2)4] unit with the Co···Co distance about 3.379 Å. Meanwhile, Co3 and Co4 atoms are linked together by three carboxylate groups in µ2-η1:η1 and µ2-η2:η1 to give another Co2 unit with its Co···Co distance about 3.422 Å. Besides, Co2 and Co3 are connected to two carboxylate O atoms, which adopt a tra-tra-µ2-η1:η1-bridge coordination mode. Thus the two binuclear units are bridged to produce a Co4(COO)8 cluster as the SBU. The tpta4- ligands exhibit two kinds of connection modes to bridge Co4 SBUs to generate two different infinite 1D cluster chains (Figure 2b). The two 1D cluster chains are further held together via the Co4 SBUs to produce a 2D sheet. These 2D sheets are joined together by 4,4′-bipy molecules, resulting in a 3,8-connected 3D framework with (43)(43)(46·618·84) topological notation (Figure 2c), where the tetranuclear Co(ΙΙ) SBU are regarded as 8-connected nodes, the tpta4ligand considered as 3-connected nodes, and the 4, 4′-bipy ligands act as linkers (Figure 2d).

Crystal Structure of {[Mn2(tpta)(H2O)2]·2H2O}n (3) 3 crystallizes in the triclinic crystal system Pī, showing a three-dimensional framework. As depicted in Figure 3a, the asymmetric unit embodies two independent Mn(ΙΙ), a tpta4- anion, two associated H2O molecules and two guest H2O molecules. Mn1 is five-coordinated with four O atoms (O1A, O2, O5B, O9C) of four tpta4- anions as well as an oxygen atom (O4) of one aqua ligand; Mn2 lies in a askew octahedral geometry by connecting to four O atoms (O2, O10C, O7D, O8D) of three tpta4- ligands in the equatorial plane, one O6B of a tpta4- and one O3 of one coordinated water molecule occupying the axial sites. The Mn–O distances all lie in the normal range.52,53

The linkage of Mn1 and the adjacent Mn2 through three -O-C-O- bridges leads to a Mn2 unit with a Mn1···Mn2 distance of 3.324 Å in 3. The Mn2 units then expand symmetrically to yield a special Mn4 clusters as the SBUs, which is further linked by the tpta4- ligand through its four carboxyl groups 7 ACS Paragon Plus Environment


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 8 of 27

presenting µ2-η1:η1-bridge, µ1-η1:η1-bridge and µ3-η2:η1-chelate/bridge coordination modes, severally (Figure 3b). Thus, the tpta4- anions serve as µ4-bridges to connect four aforementioned Mn4 units, meanwhile, each Mn4 SBU is further linked to eight tpta4- anions, constructing final three-dimensional structures (Figure. 3c). Hence, as discussed above, tpta4- ligands should be considered as 4-connected nodes. Accordingly, Mn4 units could be treated as 8-connectors. As a consequence, complex 3 can be simplified as a 4,8-connected 3D framework with (46)(412·53·69·74) topological notation (Figure. 3d).

PXRD Patterns and Thermogravimetric Analysis. The PXRD patterns were conducted to confirm the phase purity of these compounds. The PXRD spectra were well comparable to the corresponding calculated ones from the single-crystal X-ray data, indicating a pure phase of each product (Fig. S1)

Thermogravimetric analyses (TGA) of 1–3 were carried out to examine their thermal stability. The primarily decreased mass 11.71 % from 115 to 350 °C for 1 manifests the release of one lattice H2O molecule along with three coordinated H2O molecules (calc. 12.16 %), and the second step weight represents the decomposition of overall framework (Fig. S2). 2 demonstrates a totally decreased weight 8.32 % at 111–152 °C, consistent with the expulsion of three guest H2O molecules as well as three associated H2O molecules (calc. 8.28 %). Its further decline in mass marks the anhydrous complex decomposition. Complex 3 lost two lattice water molecules (observed 6.62 %, calculated, 6.16 %) between 122 and 174 °C, and then the remnant starts to collapse at 407 °C.

Magnetic Studies. Temperature dependence magnetic susceptibility for these complexes have been conducted over the range of 2−300 K at 1 KOe. The χmT value for 1 is 2.52 cm3 K mol-1 at 300 K, which is slightly higher than the expected value (2.0 cm3 K mol-1) of two magnetically isolated spin-only Ni ions (S = 1/2, g = 2.0) (Figure 4a). When the temperature decreases, the χmT value increases steadily upon cooling to reach a peak at 14 K, suggesting that there exist global ferromagnetic interactions between nickel ions, which is further supported by the well-fitted χm-1 vs T plot that gives θ = +0.88 K


8

Page 9 of 27

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


and C = 2.54 cm3 K mol−1. Furthermore, below this crucial temperature of 14 K, there is a abrupt decrease of χmT, probably because of the Zeeman effect, the zero-field splitting (ZFS) effect of Ni(II), and/or some kind of intramolecular antiferromagnetic interaction.54-56 The experiment magnetic data was fitted to a binuclear-Ni(II) model derived from the Hamiltonian H = - 2JΣS1S2, with the interaction between adjacent dinuclear units considered.57,58 The parameters for the fits of complex 1 are g = 2.23, J = 2.77 cm-1, zJ′ = - 0.55 cm-1, and R = 1.06×10-4.

2 Ng 2 β 2 exp(2 J / kT ) + 5exp(6 J / kT ) χd = [ ] kT 1 + 3exp(2 J / kT ) + 5exp(6 J / kT )

χm =

χd 1 − χ d (2 zJ '/ Ng 2 β 2 )

Field-dependent magnetization measurements at 2 K were performed to further investigate the magnetic behavior. The M(H) curve of 1 constantly tends to a value of 1.58 Nβ with the increasing H, but does not saturate until the highest field of 80 kOe, which is possibly because of the significant magnetic anisotropy in the complex system (Figure 4b). The maximum M value is different from the expected net spin value for two isolated Ni(II) ions, possibly owning to the existence of significant ZFS effects or intermolecular antiferromagnetic coupling of the complex.57,59 Furthermore, the nonlinear magnetization isotherm M-H curve implies the absent long-range magnetic ordering for the absence of any hysteretic behavior. The ac magnetic susceptibility measurements carried out for oscillating frequencies (10000–10 Hz) do not show any out-of-phase signals in the measured frequency range (Figure 4c), revealing the absence of any superparamagnetic or slow magnetic relaxation. Therefore, this complex is not single-molecule magnets (SMMs).

Complex 2 exhibits an analogous magnetic behavior with 1. The χmT value for 2 at 300 K (5.70 cm3 K mol-1) is higher than the predicted 3.76 cm3 K mol-1 for two uncoupled Co(II) ions (S = 3/2, g = 2.0) (Figure 5a), possibly due to the orbital contributions between the Co(II) ions, as well as the presence of intramolecular ferromagnetic interactions.60-62 The χmT increases gradually on cooling, reaches a peak ACS Paragon Plus Environment

9


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 10 of 27

and then drops sharply at low temperature. This further confirms the latter conclusion. The following sudden decrease is mainly because of ZFS along with Zeeman interactions.55,63 It is difficult to quantitatively analyze magnetic susceptibility data in this 3D framework based on tetranuclear SBUs due to large orbital contributions between ions. The M-H curve at 2 K manifests a featureless increase with its final saturation value up to 2.79 Nβ at the highest field of 80 kOe, corresponding to the expected range for Co(II) ions. This is indicative of the existence of typically paramagnetic property and the absence of long-range magnetic ordering (Figure 5b). The conducted dynamic magnetization experiments suggest the inexistence of slow relaxation behavior since there does not appear to be any out-of-phase signals (Figure 5c).

The magnetic behavior of 3 is not the same as that of 1 and 2 (Figure 6). The χmT value is 8.56 cm3 K mol-1 at 300 K. Upon cooling, χmT value falls to 1.01 cm3 K mol-1 at 2.0 K, showing the typical antiferromagnetic behavior. The χm-1 values in the temperature range 300–6 K were fitted with the Curie-Weiss equation, giving parameters of C = 8.80 cm3 K mol-1 and θ = - 8.55 K. According to the structure of complex 3 (Figure 3a), there exist two different magnetic interactions J1 and J2 between neighboring Mn(II) atoms, representing the coupling of Mn1/Mn2 and Mn1/Mn1A, respectively. Thus, the Hamiltonian of 3 can be given as

H = - 2J1 (SMn1SMn2 + SMn2ASMn1A) - 2J2 SMn1SMn1A

The data were simulated by means of the program MAGPACK.64 The fits of complex 3 give values of J1 = - 0.48 cm-1, J2 = - 0.19 cm-1, g = 2.02, and R = 9.12×10-4. The obtained J are in accordance with others reported for similar bridging ligands.65 These results support existence of weak antiferromagnetic interactions of Mn1/Mn2 ions and very weak interactions of Mn1/Mn1A in 3.

Studies on the carboxylate bridges transferring magnetism support the fact syn−syn carboxylate bridging pattern will trigger antiferromagnetic interactions between metal ions. In contrast, anti−anti ACS Paragon Plus Environment

10

Page 11 of 27

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


and syn−anti bridging modes often lead to weak ferromagnetic or antiferromagnetic couplings.66 Looking at the carboxylate bridges between bimeric Ni(II) ions in 1, the existence of Ni-OCO-Ni with syn–anti conformations between Ni1 and Ni2 favors extremely ferromagnetic couplings. There exists one magnetic exchange pathway between bimeric Ni(II) ions with the superexchange angle Ni-OcarboxylNi of 107.31(4)°. Compared with other dinuclear Ni(II) compound with similar Ni-O-Ni magnetic exchange pathway but larger superexchange angles of about 115° exhibiting antiferromagnetic behavior, complex 1 shows absolutely different ferromagnetic coupling interactions relying on the effect of the relatively smaller exchange angles and the syn−anti carboxylate exchange pathways. 67 This conclusion is further verified by the positive value of θ (+ 0.88 K) and J constants (2.77 cm-1) evaluated for the magnetic pathways of 1. There are mainly three magnetic exchange pathways responsible for transmitting ferromagnetic exchange between Co ions for 2. One comprises two syn–anti Co-OCO-Co between Co1 and Co2. The other contains two syn–anti Co-OCO-Co and one µ2-Ocarboxyl with the CoOcarboxyl-Co angle of 101.33(5)° between Co3 and Co4. Compared with other cluster-based Co complexes with the Co-Ocarboxyl-Co angle of about 115°,68 such an angle is obviously closer to the standard angle (96 – 99°) to ascertain whether the complexes show ferromagnetic interactions.69 Thus, we can draw a conclusion that small angles often contribute to ferromagnetic interaction.70 The third one is made up of one magnetic pathways between Co2 and Co3 via the syn–anti O13-C40-O14 bridges. The distance between Co2 and Co3 is 4.608 Å, indicting very weak magnetic interactions. The obtained negative value of J (- 0.48 cm-1 and - 0.19 cm-1 ) as well as θ (- 8.55 K) of 3 provide evidence of remarkable antiferromagnetic interactions. The antiferromagnetic coupling interactions are stronger when compared with other Mn(II) complex with the same type of magnetic exchange pathway due to the shorter metal···metal separations within SBUs.

CONCLUSIONS Initially, using a polycarboxylic acid H4tpta as ligand, we have isolated three polynuclear clusters with diverse dimensions, which exhibit global ferromagnetic or antiferromagnetic properties. According ACS Paragon Plus Environment

11


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 12 of 27

to the results, carboxylate ligands with versatile coordination features play an important role in the magnetism of the obtained complexes. The magnetization curve M(H) of 2 displays different behaviors with that of 1.The M value increases constantly to reach a clear saturation at the highest field of 80 kOe, indicating a typical paramagnetic behavior of 2. In addition, dynamic magnetization experiments were also carried out to further explore their magnetic behaviors. To a certain extent, the discussion in this work will be conducive to the exploration and development of new polynuclear complexes as advanced magnetic materials. Research into the synthetic methods of novel multinuclear complexes possessing unusual magnetic properties will continue.

Acknowledgements. This work was financially supported by the National Natural Science Foundation (no 21371155) and Research Fund for the Doctoral Program of Higher Education of China (20124101110002).

Supporting Information Available: Crystallographic data in CIF format, part of bond lengths as well as bond angles, thermogravimetric analyses, PXRD patterns of 1–3 and the structural formulas of the ligands. This information is available free of charge via the Internet at http://pubs.acs.org/.


12

Page 13 of 27

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Scheme 1. The main organic ligand structure.


13


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 14 of 27

(a)

(b)

(d)

(c)

Figure 1. (a) Coordination environment of Ni2+ in 1. (b) The defined 4- and 4-connected nodes; (c) The 2D network; (d) The simplified topological net of 1.


14

Page 15 of 27

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(b)

(a)

(d)

(c)

Figure 2. (a) Coordination environment of Co2+ in 2. (b) Two different Co cluster chains bridged by tpta4-; (c) The 3D network; (d) The simplified topology of 2.


15


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 16 of 27

(b)

(a)

(d)

(c)

Figure 3. (a) Coordination environment of Mn2+ and tetranuclear SBU in 3. (b) The defined 4- and 8connected nodes; (c) The 3D framework of 3; (d) Schematic representation of the simplified topology.


16

Page 17 of 27

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(a)

(b)

(c) Figure 4. (a) The χmT-T (black) and χm-1-T plots (blue); (b) The M-H curve of 1 at 2 K; (c) The AC magnetic susceptibility at frequencies of 10000−10 Hz.


17


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 18 of 27

(b)

(a)

(c) Figure 5. (a) The χmT-T data of 2; (b) The M-H curve of 2 at 2 K; (c) The AC magnetic susceptibility at frequencies of 10000−10 Hz.


18

Page 19 of 27

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 6. The χmT-T (black) and χm-1-T plots (blue).


19


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 20 of 27

Table 1 Crystallographic data of 1–3. Complex

1

2

3

Formula

C22H18O12Ni2

C54H40N2O22Co4

C22H18O12Mn2

Fw

591.78

1304.63

584.24

Temp(K)

293(2)

293(2)

293(2)

Wavelength(Å)

0.71073

0.71073

0.71073

Crystal system

Triclinic

Triclinic

Triclinic

Space group

P -1

P -1

P -1

a (Å)

9.513(5)

9.495(0)

9.870(2)

b (Å)

9.969(2)

15.284(3)

10.291(2)

c (Å)

12.113(2)

19.639(4)

12.654(3)

α(deg)

78.90(3)

109.44(3)

111.95(3)

β(deg)

86.64(3)

93.93(3)

99.96(3)

γ(deg)

82.54(3)

103.48(3)

90.86(3)

V (Å3)

1117.1(4)

2580.1(9)

1169.7(4)

Z

2

2

2

Dc (g⋅cm-3)

1.759

1.610

1.659

µ (mm-1)

1.754

1.344

1.145

F(000)

604

1264

592

GOF on F2

1.087

0.968

1.050

R1[I>2σ(I)]a

0.0590

0.0868

0.0730

wR2 (all data)b

0.1486

0.2183

0.1940

a

R1 = ∑‫׀׀‬Fo‫׀‬-‫׀‬Fc‫׀׀‬/∑‫׀‬Fo‫׀‬. bwR2 = [∑w(Fo2 -Fc2)2/∑w(Fo2)2]1/2.


20

Page 21 of 27

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


References (1) Lee, J.; Farha, O. K.; Roberts, J.; Scheidt, K. A.; Nguyen, S. T.; Hupp, J. T. Chem. Soc. Rev. 2009, 38, 1450–1459. (2) Wu, C. D.; Hu, A.; Zhang, L.; Lin, W. J. Am. Chem. Soc. 2005, 127, 8940–8941. (3) Dance, I. J. Am. Chem. Soc. 2007, 129, 1076–1088. (4) Ni, T. J.; Xing, F. F.; Shao, M.; Zhao, Y. M.; Zhu, S. R.; Li, M. X. Cryst. Growth Des. 2011, 11, 2999–3012. (5) Han, Y. F.; Jia, W. G.; Yu, W. B.; Jin, G. X. Chem. Soc. Rev. 2009, 38, 3419–3434. (6) Dai, M.; Su, X. R.; Wang, X.; Wu, B.; Ren, Z. G. ; Zhou, X.; Lang, J. P. Cryst. Growth Des. 2014, 14, 240–248. (7) Allendorf, M. D.; Bauer, C. A.; Bhaktaa, R. K.; Houka, R. J. T. Chem. Soc. Rev. 2009, 38, 1330– 1352. (8) Cheng, D.; Khan, M. A.; Houser, R. P. Cryst. Growth Des. 2004, 4, 599–604. (9) Walton, K. S.; Snurr, R. Q. J. Am. Chem. Soc. 2007, 129, 8552–8556. (10) Pan, L.; Holson, D. H.; Ciemnolonski, L. R.; Heddy, R.; Li, J. Angew. Chem. Int. Ed. 2006, 45, 616–619. (11) Zhang, G. Q.; Yang, G. Q.; Ma, J. S. Cryst. Growth Des. 2006, 6, 375–381. (12) Lin, J. B.; Zhang, J. P.; Chen, X. M. J. Am. Chem. Soc. 2010, 132, 6654–6656. (13) Chandler, B. D.; Cramb, D. T.; Shimizu, G. K. H. J. Am. Chem. Soc. 2006, 128, 10403–10412. (14) Jin, J.; Wang, W. Y.; Liu, Y. H.; Hou, H. W.; Fan, Y. T. Chem. Commun. 2011, 47, 7461–7463.


21


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 22 of 27

(15) Pandey, M. D.; Mishra, A. K.; Chandrasekhar, V.; Verma, S. Inorg. Chem. 2010, 49, 2020–2022. (16) Lian, F. Y.; Jiang, F. L.; Yuan, D. Q.; Chen, J. T.; Wu, M. Y.; Hong, M. C. CrystEngComm. 2008, 10, 905–914. (17) Shyu, E.; Supkowski, R. M.; LaDuca, R. L. Cryst. Growth Des. 2009, 9, 2481–2491. (18) Miyasaka, H.; Julve, M.; Yamashita, M.; Clerac, R. Inorg. Chem. 2009, 48, 3420–3437. (19) Xiang, S. C.; Wu, X. T.; Zhang, J. J.; Fu, R. B.; Hu, S. M.; Zhang, X. D. J. Am. Chem. Soc. 2005, 127, 16352–16353. (20) Marino, N.; Ikotun, O. F.; Julve, M.; Lloret, F.; Cano, J.; Doyle, R. P. Inorg. Chem. 2011, 50, 378– 389. (21) Demessence, A.; Rogez, G.; Welter, R.; Rabu, P. Inorg. Chem. 2007, 46, 3423–3425. (22) Kurmoo, M. Chem. Soc. Rev. 2009, 38, 1353–1379. (23) Sun, Q.; Cheng, A. L.; Wang, Y. Q.; Ma, Y.; Gao, E. Q. Inorg. Chem. 2011, 50, 8144–8152. (24) Zhao, J. P.; Hu, B. W.; Zhang, X. F.; Yang, Q.; Fallah, M. S. E.; Bu, X. H. Inorg. Chem. 2010, 49, 11325–11332. (25) Lama, P.; Mrozinski, J.; Bharadwaj, P. K. Cryst. Growth Des. 2012, 12, 3158–3168. (26) Yi, F. Y.; Sun, Z. M. Cryst. Growth Des. 2012, 12, 5693–5700. (27) Tranchemontagne, D. J.; Mendoza-Cortés, J. L.; O’Keeffe, M.; Yaghi, O. M. Chem. Soc. Rev. 2009, 38, 1257–1283. (28) Jeffery, J. C.; Thornton, P.; Ward, M. D. Inorg. Chem. 1994, 33, 3612–3615. (29) Qiu, Y. C.; Deng, H.; Yang, S. H.; Mou, J. X.; Daiguebonne, C.; Kerbellec, N.; Guillou, O.; Batten, S. R. Inorg. Chem. 2009, 48, 3976–3981. ACS Paragon Plus Environment

22

Page 23 of 27

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(30) Xue, M.; Zhu, G. S.; Li, Y. X.; Zhao, X. J.; Jin, Z.; Kang, E. H.; Qiu, S. L. Cryst. Growth Des. 2008, 8, 2478–2483. (31) Mukherjee, S.; Gole, B.; Song, Y.; Mukherjee, P. S. Inorg. Chem. 2011, 50, 3621–3631. (32) Yang, E. C.; Liu, Z. Y.; Shi, X. J.; Liang, Q. Q.; Zhao, X. J. Inorg. Chem. 2010, 49, 7969–7975. (33) Dechambenoit, P.; Long, J. R. Chem. Soc. Rev. 2011, 40, 3249–3265. (34) Li, J. R.; Sculley, J.; Zhou, H. C. Chem. Rev. 2012, 112, 869–932. (35) Han, S. D.; Song, W. C.; Zhao, J. P.; Yang, Q.; Liu, S. J.; Li, Y.; Bu, X. H. Chem. Commun. 2013, 49, 871–873. (36) Zeng, Y. F.; Hu, X.; Liu F. C.; Bu, X. H. Chem. Soc. Rev. 2009, 38, 469–480. (37) Zhang, Y. B.; Zhou, H. L.; Lin, R. B.; Zhang, C.; Lin, J. B.; Zhang, J. P.; Chen, X. M. Nat. Commun. 2012, 3, 642. (38) Mondal, K. C.; Kostakis, G. E.; Lan, Y.; Anson, C. E.; Powell, A. K. Inorg. Chem. 2009, 48, 9205– 9213. (39) Maji, T. K.; Sain, S.; Mostafa, G.; Lu, T. H.; Ribas, J.; Monfort, M.; Chauhuri, N. R. Inorg. Chem. 2003, 42, 709–716. (40) Huang, S. L.; Weng, L. H.; Jin, G. X. Dalton Trans. 2012, 41, 11657–11662. (41) Mereacre, V.; Ako, A. M.; Clerac, R.; Wernsdorfer, W.; Hewitt, I. J.; Anson, C. E.; Powell, A. K. Chem. Eur. J. 2008, 14, 3577–3584. (42) Zheng, Y. Z.; Tong, M. L.; Zhang, W. X.; Chen, X. M. Angew. Chem., Int. Ed. 2006, 45, 6310– 6314. (43) Zeng, M. H.; Zhang, W. X.; Sun, X. Z.; Chen, X. M. Angew. Chem., Int. Ed. 2005, 44, 3079–3082. ACS Paragon Plus Environment

23


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 24 of 27

(44) Konar, S.; Mukherjee, P. S.; Zangrando, E.; Lloret, F.; Chaudhuri, N. R. Angew. Chem. Int. Ed. 2002, 41, 1561–1563. (45) Yang, E. C.; Liu, Z. Y.; Wu, X. Y.; Chang, H.; Wang, E. C.; Zhao, X. J. Dalton Trans. 2011, 40, 10082–10089. (46) Mahata, P.; Natarajan, S.; Panissod P.; Drillon, M. J. Am. Chem. Soc. 2009, 131, 10140–10150. (47) Zeng, M. H.; Zhou, Y. L.; Wu, M. C.; Sun, H. L.; Du, M. Inorg. Chem. 2010, 49, 6436–6442. (48) Li, D. S.; Zhao, J.; Wu, Y. P.; Liu, B.; Bai, L.; Zou, K.; Du, M. Inorg. Chem. 2013, 52, 8091–8098. (49) Cheng, X. N.; Xue, W.; Lin J. B.; Chen, X. M. Chem. Commun. 2010, 46, 246–248. (50) Sheldrick, G. M. Acta Crystallogr. 2008, A64, 112. (51) E. König, Magnetic Properties of Coordination and Organometallic Transition Metal Compounds; Springer: Berlin, 1966. (52) Liu, Y. Y.; Li, H. J.; Lv, X. F.; Hou, H. W.; Fan, Y. T. Cryst. Growth Des. 2012, 12, 3505–3513. (53) Yang, L. R; Zhang, H. M.; You, Q. Q.; Wu, L. Z.; Liu, L.; Song, S. CrystEngComm. 2013, 15, 7505–7514. (54) Nakajima, H.; Katsuhara, M.; Ashizawa, M.; Kawamoto, T; Mori, T. Inorg. Chem. 2004, 43, 6075– 6082. (55) Georgopoulou, A. N.; Raptopoulou, C. P.; Psycharis, V.; Ballesteros, R.; Abarca, B.; Boudalis, A. K. Inorg. Chem. 2009, 48, 3167–3176. (56) Ouellette, W.; Prosvirin, A. V.; Valeich, J.; Dunbar, K. R.; Zubieta, J. Inorg. Chem. 2007, 46, 9067–9082. (57) An, G. Y.; Ji, C. M.; Cui, A. L.; Kou, H. Z. Inorg. Chem. 2011, 50, 1079–1083. ACS Paragon Plus Environment

24

Page 25 of 27

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(58) Duan, L. M.; Xie, F. T.; Chen, X. Y.; Chen, Y.; Lu, Y. K.; Cheng, P.; Xu, J. Q. Cryst. Growth Des. 2006, 6, 1101–1106. (59) Maurice, R.; Verma, P.; Zadrozny, J. M.; Luo, S.; Borycz, J.; Long, J. R.; Truhlar. D. G.; Gagliardi. L. Inorg. Chem. 2013, 52, 9379–9389. (60) Huang, F. P.; Tian, J. L.; Gu, W.; Liu, X.; Yan, S. P.; Liao, D. Z.; Cheng, P. Cryst. Growth Des. 2010, 10, 1145–1154. (61) Wöhlert, S.; Tomkowicz, Z.; Rams, M.; Ebbinghaus, S. G.; Fink, L.; Schmidt, M. U.; Näther, C. Inorg. Chem. 2014, 53, 8298–8310. (62) Yang, F.; Li, B. Y.; Xu, W.; Li, G. H.; Zhou, Q.; Hua, J.; Shi, Z.; Feng, S. H. Inorg. Chem. 2012, 51, 6813–6820. (63) Serna, Z. E.; Urtiaga, M. K.; Barandika, M. G.; Corte´s, R.; Martin, S.; Lezama, L.; Arriortua, M. I.; Rojo, T. Inorg. Chem. 2001, 40, 4550–4555. (64) Borras-Almenar, J. J.; Clemente-Juan, J. M.; Coronado, E.; Tsukerblat, B. S. Inorg. Chem. 1999, 38, 6081–6088. (65) Lv, X. F.; Liu, L.; Huang, C.; Guo, L. A.; Wu, J.; Hou, H. W.; Fan, Y. T. Dalton Trans. 2014, 43, 15475–15481. (66) Li, H. J.; Yao, H. C.; Zhang, E. P.; Jia, Y. Y.; Hou, H. W.; Fan, Y. T. Dalton Trans. 2011, 40, 9388–9393. (67) Niu, C. Y.; Zheng, X. F.; Wan, X. S.; Kou, C. H. Cryst. Growth Des. 2011, 11, 2074–2088. (68) Wang, S. N.; Bai, J. F.; Li, Y. Z.; Pan, Y.; Scheer, M.; You, X. Z. CrystEngComm. 2007, 9, 1084– 1095. (69) Gomez-Garcia, C. J.; Coronado, E.; Borras-Almenar, J. J. Inorg. Chem. 1992, 31, 1667–1673. ACS Paragon Plus Environment

25


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 26 of 27

(70) Sakiyama, H.; Suzuki, T.; Ono, K.; Ito, R.; Watanabe, Y.; Yamasaki, M.; Mikuriya, M. Inorg. Chim. Acta. 2005, 358, 1897–1903.


26

Page 27 of 27

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


For Table of Contents Use Only

Polynuclear Ni(II)/Co(II)/Mn(II) Complexes Based on Terphenyl-tetracarboxylic Acid Ligand: Crystal Structures and Research of Magnetic Properties Lin Zhang, Lu Liu, Chao Huang, Xiao Han, Li’an Guo, Hong Xu, Hongwei Hou*, Yaoting Fan Three novel cluster-based MOFs have been successfully isolated under hydrothermal conditions by the reaction of polycarboxylate ligand H4tpta together with Ni(II)/Co(II)/Mn(II) salts. Mangnetic studies of the complexes demonstrate that Ni(II)/Co(II) complexes display unusual ferromagnetic coupling via the M-O-C-O-M bridges, while Mn(II) complex shows predominantly antiferromagnetic behavior.


27

Mn(II) Complexes Based on Terphenyl

Recommend Documents