ABSTRACT
The self-assembly of the high-nuclearity Ln-exclusive nanoclusters is challenging but of significance due to its aesthetically pleasing architectures and far-reaching latent applications in magnetic cooling technologies. Herein, two novel high-nuclearity lanthanide nanoclusters were successfully synthesized under solvothermal conditions, formulated as {[Gd18(IN)20(HCOO)8(µ6-O)(µ3-OH)24(H2O)4]·4H2O}n and {[Eu18(IN)16(HCOO)8(CH3COO)4(µ6-O)(µ3-OH)24(H2O)4]·5H2O}n (abbreviated as Gd18 and Eu18, HIN = isonicotinic acid). Both of them possess novel and exquisite windmill-shaped cationic cores in the family of high-nuclearity Ln-exclusive nanoclusters. Remarkably, the adjacent second building units are interconnected into a three-dimensional (3D) metal-organic framework by IN- ligands. As expected, the abundant existence of GdIII ions endows Gd18 with a favorable magnetic entropy change at 2.0 K for ΔH = 7.0 T (-ΔSmmax = 40.0 J kg-1 K-1), and Eu18 displays the typical luminescence of EuIII ions.
ABSTRACT
Assembling and studying high-nuclearity 3d-4f metal clusters represent a pregnant and challenging research hotspot. Based on anionic template and ligand-controlled hydrolytic methods, two heterometallic metal clusters, formulated as [Gd23Ni20(DTA)20(CO3)4(CH3COO)6(SiO4)4(CH3CH2OH)2(µ3-OH)33(µ2-OH)4(H2O)16]·Cl2·30H2O and [Eu23Ni20(DTA)20(CO3)4(CH3COO)6(SiO4)4(CH3CH2OH)2(µ3-OH)33(µ2-OH)4(H2O)16]·Cl2·46H2O (abbreviated as Gd23Ni20, Eu23Ni20, H2DTA = thiodiglycolic acid), are successfully obtained, which both feature similar double-shell-shaped structures with a Ni20 building unit encapsulating a Ln23 aggregation. The structural analysis illustrates that the SiO44- anion, serving as the anionic template in this work, is reported for the second time in 3d-4f metal clusters. In terms of the magnetic properties, large amounts of Gd3+ and Ni2+ ions contribute to the MCE of compound Gd23Ni20, along with 38.15 J kg-1 K-1 at ΔH = 7.0 T for 2.0 K. It is worth mentioning that compound Gd23Ni20 exhibits an excellent magnetic entropy change at low fields (-ΔSm = 19.10 J kg-1 K-1 at 2.0 K for ΔH = 2.0 T). In addition, Gd23Ni20 exhibits preferable solvent and thermal stability.
ABSTRACT
The distinct nanosized cluster Gd22Ni21 was isolated using a mixture of anions (SO32- and SO42-) as templates, and to the best of our knowledge, this was the first such 3d-4f cluster to have been developed. Additionally, of a number of 3d-4f heterometallic clusters, Gd22Ni21 showed the largest low-field magnetic entropy change (26.1 J kg-1 K-1) at 2.0 K and ΔH = 2.0 T.
ABSTRACT
Designing and synthesizing lanthanide clusters have always been a research hotspot. Herein, three lanthanide clusters with the formula [Ln8(IN)14(µ3-OH)8(µ2-OH)2(H2O)8]·xH2O (Ln = 1-Gd and x = 11; Ln = 2-Dy and x = 8; Ln = 3-Eu and x = 8) have been isolated in the presence of isonicotinic acid under solvothermal conditions. Structural analysis indicates that those three compounds are isostructural, featuring boat-shaped {Ln8} metal frameworks. Magnetic measurements reveal that 1-Gd exhibits a larger MCE with the maximum -ΔSm value of 31.77 J kg-1 K-1 at 2 K for ΔH = 7 T, while 2-Dy displays slow magnetization relaxation. Besides, the photoluminescence properties of 3-Eu were investigated.
ABSTRACT
Two Ni-substituted polyoxometalates (NiSPs), [Ni6(Py)6(H2O)5(µ3-OH)3(PW9O34)]2·10H2O (1), [Ni7(Py)6(Im)(H2O)5O(WO4)(µ3-OH)3(H2PW9O34)]·3H2O (2) (Py = pyridine, Im = imidazole), were successfully hydrothermally synthesized. Compounds 1 and 2 have significantly different configurations by introducing different amounts of imidazole ligands. For compound 1, two malposed {Ni6(Py)6PW9} units that are face to face are bridged by two Ni-O-W bonds to constitute an isolated dimeric structure. Differently, the {Ni7(Py)6(Im)PW9}2 dimer in compound 2 connects with four adjacent dimers by four {WO4} groups in an interesting two-dimensional (2-D) arrangement. The magnetism of compounds 1 and 2 was studied, and magnetic test results demonstrated that both compounds have ferromagnetic interactions between the nickel centers. Meanwhile, the third-order nonlinear optical (NLO) measurements indicated that compound 1 can serve as potential nonlinear optical materials.
ABSTRACT
Two captivating {P4Mo6}-based compounds, formulated as (H2bbi)2{[Co2(bbi)][Co2.33(H2O)4][H9.33CoP8Mo12O62]}·4H2O (1) and (H2bbi){[Zn(Hbbi)]2[Zn0.75(bbi)][K2Zn(H2O)4][H8.5ZnP8Mo12O62]} (2) [bbi = 1,1'-(1,4-butanediyl)bis(imidazole)], were successfully synthesized under hydrothermal conditions. Structural analysis demonstrates that compounds 1 and 2 are constructed from hourglass-shaped structures [M(P4Mo6O31)2]n- (M = Co, Zn), which are all made up of molybdophosphates and one transition metal ion as the central connecting node. Compounds 1 and 2 feature three-dimensional (3D) frameworks, which are all connected to form a 3D structure by metal ions and bbi ligands. More interestingly, compound 1 exhibits higher catalytic activity than 2 in CO2 photoreduction due to the suitable energy band structure of Co species in {P4Mo6} clusters. The CO yield was 3261 µmol g-1 with high selectivity in 8 h for compound 1 in photocatalytic CO2 reduction, which is highly promising in the photocatalytic field. Additionally, the photoluminescence properties of 2 were investigated.
ABSTRACT
The maximum exposure of polyoxometalates (POMs) is of great significance to enhance the catalytic performance of HKUST-1 with incorporated Keggin-type POMs. Herein, two phosphovanadomolybdates were encapsulated into the HKUST-1 via a hydrothermal method to obtain two polyoxometalate-based metal-organic frameworks, formulated as [Cu12(BTC)8(H2O)12][H4PMo11VO40]@(H2O)30 (1) and [Cu12(BTC)8(H2O)12][H5PMo10V2O40]@(H2O)49 (2). Single-crystal X-ray diffraction analysis indicates that two compounds contain unique high-nuclearity water clusters without organic counter cations. The octahedral-shaped water cluster (H2O)30 was constructed from square-pyramid-shaped (H2O)5 for compound 1, while the huge cage-shaped water cluster (H2O)49 of compound 2 consisted of crown-like (H2O)8 and one water molecule, which substitute the organic counter cations involved in the structural construction. More importantly, after removing the water clusters via simple heat treatment, the active sites of the two compounds were fully exposed, leading to good catalytic activities for both benzene hydroxylation reaction and oxidative desulfurization. Furthermore, the catalytic test confirmed that compound 2 may be a bifunctional heterogeneous catalyst with great promise for both benzene hydroxylation and oxidative desulfurization.
ABSTRACT
Two isomorphic heterometallic 3d-4f cluster-based materials, formulated [Gd8Cr4(IN)18(µ3-O)2(µ3-OH)6(µ4-O)4(H2O)10]·13H2O (1) and [Tb8Cr4(IN)18(µ3-O)2(µ3-OH)6(µ4-O)4(H2O)10]·13H2O (2) (abbreviation: {Ln8Cr4}: Ln = Gd3+ (1); Tb3+ (2); HIN = isonicotinic acid), were achieved by hydro-/solvothermal method through using the ligand HIN. X-ray diffraction analysis illustrates eight lanthanide ions (Ln = Gd3+, Tb3+) and four transition-metal ions (Cr3+) of {Ln8Cr4} were constructed from two classical "drum-like" {Ln4Cr2} structures associated by organic ligands HIN, displaying a one-dimensional wave chain structure, which is rare. The magnetic properties of {Gd8Cr4} were inspected and showed the existence of antiferromagnetic coupling interactions between contiguous metal ions. On top of this, the magnetic entropy change of ΔS m can attain 23.40 J kg-1 K-1 (44.90 mJ cm-3 K-1) at about 3 K and ΔH = 7 T. Besides, fluorescence measurements of {Tb8Cr4} display typical characteristic Tb-based luminescence.
ABSTRACT
Two three-dimensional (3D) coordination polymers, namely MnII 6(CH3COO)2(HCOO)2(IN)8(C4H8O)2(H2O) and MnIII 6MnII 12(µ3-O)6(CH3COO)12(IN)18(H2O)7.5 (abbreviated as Mn II 6 and Mn II 12 Mn III 6 respectively; HIN = isonicotinic acid), were synthesized by the reaction of Mn(CH3COO)2·4H2O and isonicotinic acid under solvothermal conditions. Magnetic studies revealed that antiferromagnetic interactions may be present in compounds Mn II 6 and Mn II 12 Mn III 6 . Moreover, the values of -ΔS m (26.27 (Mn II 6 ) and 37.69 (Mn II 12 Mn III 6 ) J kg-1 K-1 at ΔH = 7 T) are relatively larger than those of the reported Mn-based coordination polymers. This work provides a great scope in the magnetocaloric effect (MCE) of pure 3d-type systems.
ABSTRACT
Carbon dioxide (CO2) and sulfides in gasoline are the main causes of air pollution. Considerable attention has been devoted to solving the problems, and the catalytic reaction seems to be a good choice. Owing to the high density of Lewis acid (LA) active sites and large numbers of open methoxide groups, polyoxovanadates (POVs) are an undisputed option as a heterogeneous catalyst for the CO2 cycloaddition reaction and catalytic oxidation of sulfides. On the basis of the above, a series of V8 clusters, [(C2N2H8)4(CH3O)8VIV8O12]·CH3OH (V8-1a), [(C2N2H8)4(CH3O)4VIV4VV4O16]·4CH3OH (V8-1), [(C3N2H10)4(CH3O)4VIV4VV4O16]·5H2O (V8-2), [(C6N2H14)4(CH3O)4VIV4VV4O16]·5CH3OH·2H2O (V8-3), have been legitimately designed and triumphantly isolated. In the synthesis process, three different kinds of Lewis bases (LBs), ethanediamine, 1,2-diaminopropane, and 1,2-cyclohexanediamine, were used to modify LA {V8} clusters to form four diverting windmill-shaped configuration. Among them, the vanadium atoms in V8-1a are +4 valence of VIV, while the vanadium atoms in V8-1-3 are mixed valence states of VIV and VV. Magnetic property investigation indicates that the antiferromagnetic coupling interactions between VIV ions all exist in the four compounds. The compound V8-1 also demonstrated high catalytic activity in the cycloaddition of CO2 to several epoxides under relatively mild conditions (70 °C, 0.5 MPa). More importantly, the reaction pressure 0.5 MPa is the lowest among the high nuclear polyoxometallates (POMs). Furthermore, V8-1 also has an excellent catalytic conversion for the oxidation of sulfides. The catalytic tests manifested that V8-1 was a very efficient difunctional heterogeneous catalyst for CO2 cycloaddition reaction and catalytic oxidation of sulfides.
ABSTRACT
Two novel and fascinating high-nuclearity lanthanide-transition (4f-3d) heterometallic clusters were obtained based on an anion-template (Cl-) and ligand-controlled approach, formulated as [Gd40Ni44(CO3)12(CH3COO)4(IDA)44(C2O4)(µ2-O)4(µ3-OH)60(µ3-O)6(H2O)12]·Cl10·20H2O (abbreviated as Gd40Ni44, 1) and [Eu40Ni44(CO3)12(CH3COO)6(IDA)44(C2O4)(µ2-O)4(µ3-OH)62(µ3-O)4(H2O)12]·Cl10·23H2O (abbreviated as Eu40Ni44, 2), where H2IDA = iminodiacetic acid and H2C2O4 = oxalic acid. Structural analysis exhibits that the compounds 1 and 2 were both constructed by two enticing bowl-like anion units Ln20Ni22, featuring peanut-like structures. Besides, the assembly of Ln20Ni22 was templated by five Cl- ions. Magnetically, compound 1 shows a significant magnetocaloric effect, with -ΔSm = 36.05 J kg-1 K-1 at 3 K for ΔH = 7 T.
ABSTRACT
The unpredictability of the polyoxometalate (POM) coordination model and the diversity of organic ligands provide more possibilities for the exploration and fabrication of various novel POM-based materials. In this work, a series of POM-based lanthanide (Ln)-Schiff base nanoclusters, [Ln(H2O)2(DAPSC)]2[Ln(H2O)3(DAPSC)]2[(SiW12O40)]3·15H2O (Ln = Sm, 1; Eu, 2; Tb, 3), have been successfully isolated by the reaction of classical Keggin POMs, a Ln3+ ion, and a Schiff-base ligand [2,6-diacetylpyridine bis(semicarbazone), abbreviated as DAPSC]. Both the hindrance effect of the organic ligand and charge balance endow the cluster with fascinating structural features of discrete and linear arrangement. The title compounds with dimensions of ca. 4 × 1 × 1 nm3 are first trimeric polyoxometalate-based nanosized compounds, constructed by saturated POM anions (SiW12O404-, denoted as SiW12). Moreover, the properties (stability, electrochemistry, third-order nonlinear optics, and magnetism) of the compounds have also been studied.
