Two Windmill-Shaped Ln18 Nanoclusters Exhibiting High Magnetocaloric Effect and Luminescence.

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.

Two SiO44--Templated Ln23Ni20 Clusters with Magnetic Cooling and Stability.

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.

Two POM-based compounds containing Zn-capped Keggin anions as decent heterogeneous catalysts for sulfur oxidation and CO2 cycloaddition reactions.

Carbon dioxide (CO2) and the combustion of sulfide in gasoline are the main causes of air pollution. A great deal of attention has been paid to solving the problem and the catalytic reaction seems to be a decent choice. Due to the high-density of Lewis acidic active sites, polyoxometalates are undoubtedly an ideal choice for the sulfur oxidation reaction. With the reasons foregoing, two novel Zn-capped polyoxometalate-based organic-inorganic hybrids, {[α-PMoV2MoVI10O39(OH)Zn2][bbbm]3}·0.5C2H5OH (1) and TBA2{[ε-PMoV8MoVI4O37(OH)3Zn4][phim]3} (2) ((where bbbm = 1-(4-imidazol-1-ylbutyl) imidazole) and phim = 2-phenylimidazole) were successfully obtained by hydrothermal synthesis. In the two compounds, the N-donor ligands in a monodentate or bidentate coordination mode are directly connected to the Keggin anions by Zn-capped atoms, forming an extended one-dimensional chain. It is noteworthy that compound 2 ends up with an interesting spiral infinite chain possibly thanks to the TBA+ cations residing in gaps as structure-directing agents. Simultaneously, the catalytic properties indicate that compounds 1 and2 as efficient heterogeneous catalysts display a decent catalytic activity in the sulfur removal process. Especially, 2 enabled satisfying catalytic oxidation of dibenzothiophene (DBT) to produce more valuable dibenzothiophene sulfone (DBTO2) at 55 °C, and the conversion almost reached 99%. Besides, compound 2 also shows satisfactory catalytic effectiveness in the oxidation of various epoxides in the CO2 cycloaddition reaction, which suggests that compound 2 has the potential to function as a dual functional material with tremendous prospects in sulfur oxidation and carbon dioxide cycloaddition for the first time.

Efficiently increasing low-field magnetic entropy by incorporating SO32- into Gd22Ni21 clusters.

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.

A new family of boat-shaped Ln8 clusters exhibiting the magnetocaloric effect and slow magnetic relaxation.

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.

Two Ni-Substituted Trilacunary Keggin-Type Polyoxometalates: Syntheses, Crystal Structures, NLO Studies, and Magnetic Properties.

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.

A Purely Inorganic Quasi-Keggin Polyoxometalate for Photocatalytic Conversion of Carbon Dioxide to Carbon Monoxide.

A pure inorganic cluster, H47 Na2 Co4 Mo24 (PO4 )11 O72 ⋅ 15H2 O (denoted as {Co4 Mo24 }), has been successfully synthesized by hydrothermal method. Notably, the assembly of a central {Co2 PO4 } tetrahedron and four peripheral {Co[P4 Mo6 ]} fragments gives rise to a rare "quasi-Keggin" structure of {Co4 Mo24 }, in which Co linkers continue to bridge adjacent substructures, resulting in the generation of 3D framework with large cavities. Benefitting from the combination of strong reductive {P4 Mo6 } units and Co active centers, the photocatalytic system with {Co4 Mo24 } as heterogeneous catalyst exhibits excellent activity for CO2 conversion to CO, offering the CO formation rate of 1848.3 µmol g-1 h-1 with high selectivity of 97.0 %. Besides, thermogravimetric and X-ray diffraction analysis confirm that {Co4 Mo24 } can maintain stable during the photocatalytic reaction process.

Two three-dimensional polyanionic clusters [M(P4Mo6)2] (M = Co, Zn) exhibiting excellent photocatalytic CO2 reduction performance.

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.

Two Polyoxometalate-Based Hybrid Compounds Modified by Iron Schiff Base Complexes: Syntheses, Crystal structures, Cyclic Voltametric Studies and Nonlinear Optical Properties.

Two new polyoxometalate (POM)-based hybrid compounds modified by a Schiff base, [Fe(DAPSC)(H2 O)2 ]2 [HPMo2 V Mo10 VI O40 ] ⋅ 5H2 O (1) and [Fe(DAPSC)(H2 O)]2 [HPV3 IV Mo4 V Mo7 VI O42 ] ⋅ 6H2 O (2), (DAPSC=2,6-diacetylpyridine bis-(semicarbazone)), have been successfully constructed from typical Keggin POMs, iron ions, and DAPSC ligands under hydrothermal condition. Structural analysis demonstrates that the Fe-Schiff base ligand units are free from polyacid anions in compound 1. While in compound 2, the Fe-Schiff base ligand units are bridged with polyacid anions via Fe-O bonds to emerge a stable double-supported skeleton. Noticeably, owing to the introduction of vanadium in H5 PMo10 V2 O40 ⋅ 32.5H2 O, a divanadium-capped configuration is shaped in compound 2. Besides, the third-order nonlinear optical (NLO) properties of two compounds were explored. It should be noted that both compounds 1 and 2 have two-photon absorption properties, which indicates that the two compounds are potential nonlinear optical materials.

Two 3D Mn-based coordination polymers: synthesis, structure and magnetocaloric effect.

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.