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An unprecedented bird-nest high-nuclear molybdenum(V) cobalto-phosphate nanosized wheel modified by imidazole (im) and pyridine (py), {[H55 (Mo24 O48 )(Co4 O)2 Co16 (PO4 )42 (py)6 (EtOH)2 (H2 O)11 ]- @[(Him)2 (Hpy)]}(N-Et-py)(H2 PO4 )(py)7 (EtOH)⋅12 H2 O (1), has been successfully synthesized by self-assembly. The anionic huge wheel consists of two rare {Co4 O} squares, four {Co4 } tetramers, four {Mo4 } tetramers and four {Mo2 } dimers, linked by bridging oxygen atoms and [PO4 ] groups and encloses two imidazolium cations and a protonated pyridium for charge balance. Surprisingly, 1 represents the first twisted wheel-shaped cluster with a record high-nuclear molybdenum(V) cobalto-phosphate. The delocalized electron effects of the cluster are enhanced with the help of coordinated py ligands, which endows 1 with an excellent third-order nonlinear optical (NLO) response. Additionally, 1 also shows a better photocatalytic water oxidation activity than Co(NO3 )2 with the O2 production of 205 μmol during 6 h in the absence of the [Ru(bpy)3 ]2+ photosensitizer.

Two new Schiff-base modified vanadium complexes, [VIVO(C7 H5O)2(N2C6H10)] (1) and [VVO2(C7H5O)(N2C6H12)] (2), were synthesized under hydrothermal conditions, in which salicylaldehyde and cyclohexanediamine were used directly to form Schiff-base ligands during the reactions. The structures of 1 and 2 were characterized by EA, FT-IR, UV-vis, SCXRD and PXRD, EPR spectroscopy and magnetic susceptibility measurement. Due to the good optical activity of Schiff-base ligands and the existence of conjugated benzene rings in 1 and 2, the delocalized electronic effects between Schiff-base ligands and vanadium can be improved. Therefore, the third-order non-linear optical (NLO) properties of these complexes were investigated. The results of the open aperture Z-scan tests show that the two-photon absorption (TPA) cross-sections (σ) of the complexes are 1033 and 1041GM, respectively, which indicated that they both have potential applications as NLO materials.

Two hourglass-type molybdophosphate hybrids with the formulas [Cd(H2O)2DABT]4[Cd(H7P4Mo6O31)2]·19H2O (1) and (C2H5OH)(C3H5N2)6[Co3(H6P4Mo6O31)2]·H2O (2) (DABT= 3,3′-diamino-5,5′-bis(1H-1,2,4-triazo...

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 ΔSm 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.

Chemical fixation of CO2 into C1 source, as a general approach, can effectively alleviate the emission of greenhouse gases. Whereas, the challenge posed by the need for efficient catalysts with high catalytic active sites still exists. In this work, we reported a series of new hexavanadate clusters, [(C6H6ON)2(C2H8N2)2(CH3O)6VIV6O8] (V6-1), [(C6H6ON)2(C3H10N2)2(CH3O)6VIV6O8] (V6-2), [(C6H6ON)2(C6H14N2)2(CH3O)6VIV6O8] (V6-3) and [(C6H6ON)2(C4H11N2O)2(CH3O)4VIV6O8] (V6-4), assembled by 2-aminophenol and four different kinds of Lewis bases (LB), ethanediamine(en), 1,2-diaminopropane, 1,2-cyclohexanediamine and N,N′-bis(2-hydroxyethyl)ethylenediamine(ben) together. Among them, the basic unit {V6} cluster featured Z-shaped configuration represents a bran-new example of hexanuclear vanadium clusters. Remarkably, the catalytic tests demonstrated that V6-1 as catalyst displays high catalytic activity in the cycloaddition for the CO2 fixation into cyclic carbonates by virtue of open V sites. As expected, for oxidative desulfurization of sulfides, V6-1 also exhibits satisfied catalytic effectiveness. Furthermore, the recycling test confirmed that catalyst V6-1 may be a bifunctional heterogeneous catalyst with great promise for both CO2 cycloaddition and oxidative desulfurization reactions.

A three-dimensional polymolybdate-based metal-organic framework (POMOF) consisting of Zn-e-Keggin unit and organic linker, {[PMo8VMo4VIO37(OH)3Zn4][BPE]2}·[BPE] (1), was successfully obtained by the hydrothermal method. Compound 1 is composed of Zn-e-Keggin units and BPE ligands, featuring a fascinating 5-fold interpenetrating framework with dia topology. The catalytic performance of compound 1 was investigated, and experiments showed that 1 could effectively facilitate the cycloaddition reaction of CO2 with epoxides as Lewis acid heterogeneous catalyst. Moreover, compound 1 also was studied as LIBs anode material, and it showed reversible capacity of 546 mA h g-1 at 100th cycle.

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 [Gd40Ni4...

Two enantiomorphic MgII -based metal-organic frameworks, {MgL(H2 O)2 }n (1-D and 1-L) (where H2 L=2,2'-bipyridyl-4,4'-dicarboxylic acid) have been synthesized by solvothermal reaction without any chiral auxiliary. The single-crystal X-ray measurement and the structural analysis indicate that both 1-D and 1-L possess 2-fold interpenetrated frameworks with different left- and right-handed helical chains simultaneously, which serve as chiral source, thus transmitting chirality over the whole frameworks. The fluorescence measurements reveal that they exhibit a strong quenching response to nitrobenzene and could be potentially used as a chemical sensor. Owing to the accessible Lewis acidic sites in channels, they display high catalytic efficiency for cycloaddition reaction of CO2 with epoxides and could be reused five times without losing activity.

Polyoxovanadates (III) are important class of polyoxometalates in molecular magnetism field, and particularly the systems which contain vanadium(III) centers. To date, only very few highly reduced vanadium polynuclear complexes were reported, which remains a significant challenge to synthesize novel polyoxovanadates, owing to the characteristics of easily oxidized vanadium(III). Herein, two unprecedented petaloid chiral octanuclear polyoxovanadates, l- and d-[H2N(CH3)2]12.5(H3N(CH2)2NH3)(H3O)1.5(VIIIμ2-OH)8(SO4)16·2H2O (L-, D-V8), have been successfully obtained by solvothermal method without any chiral auxiliary. Both L- and D-V8 compounds contain the motif eight-membered ring (Vμ2-O)8(SO4)16 constituted of three different chiral entangled loops with the V atoms as nodes. Bond valence calculation (BVC) analysis indicates that all the V ions existed in L, D-V8 are +3 value. The magnetic behavior of compounds indicated ferromagnetic coupling between vanadium(III) ions. To our knowledge, it is the first chi...

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 new bifunctional isolated hybrid compounds, [e-PMoV8MoVI4O37(OH)3Zn4][iql]4·6H2O (1) and [e-PMoV8MoVI4O38(OH)2Zn4][bipy]3[(CH3COO)(bipy)2Zn]·2H2O (2) (where iql = isoquinoline and bipy = 2,2′-bipyridine), based on Zn-e-Keggin were successfully synthesized by self-assembly under hydrothermal conditions. It is interesting to note that acetate in 2 acted as a linker connecting the e-Keggin anion with the one Zn atom (Zn5) and enabled the e-Keggin anion to coordinate with more bipy ligands, culminating with a larger isolated system, which is the first reported isolated cluster of Zn5PMo12. Meanwhile, compounds 1–2 show great electrochemical behaviors and excellent electrocatalytic activity for the degradation of NaNO2. In addition, compound 2 displays better third-order NLO performance than 1 due to the presence of more conjugated rings, with a TPA cross section (σ) of 1819 GM, which suggests that compound 2 has the potential to function as a bifunctional material with tremendous prospects.

Two three-dimensional (3D) coordination polymers, namely MnII6(CH3COO)2(HCOO)2(IN)8(C4H8O)2(H2O) and MnIII6MnII12(μ3-O)6(CH3COO)12(IN)18(H2O)7.5 (abbreviated as MnII6 and MnII12MnIII6 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 MnII6 and MnII12MnIII6. Moreover, the values of −ΔSm (26.27 (MnII6) and 37.69 (MnII12MnIII6) 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.

Temperature usually occupies a crucial position in the construction of chiral compounds. By controlling the temperature of the reaction system, chiral and non-chiral compounds can be designed and synthesized. Given the above, three new chiral and non-chiral compounds based on copper(II) monosubstituted polyoxoanions and Cu(en) complexes (en = ethylenediamine), D/L-[Cu(H2O)(en)2]2{[Cu(H2O)2(en)][SiCuW11O39]}·5H2O (1, D-1 and L-1) and [Cu(H2O)(en)2]{[Cu(en)2]2[SiCuW11O39]}·2.5H2O (2), were successfully synthesized under hydrothermal conditions. The main synthesis conditions of compound 1 (D-1 and L-1) and compound 2 are the same, however, the only difference is that the reaction temperatures are 80 °C and 140 °C, respectively. What's more, compounds 1 and 2 can form a 1D chiral chain by Cu–O and W/Cu–O–W/Cu bonds, respectively, and further obtain a 3D-supramolecular framework through hydrogen bonding interaction. Meanwhile, due to the asymmetry of chiral compound 1, optical second-harmonic generation (SHG) was used to investigate the second-order nonlinear optical effect and it was found that the observed SHG efficiency of compound 1 is 0.3 times that of urea. To further investigate the chiral properties, D-1 and L-1 were used in the electrochemical enantioselective sensing of D-/L-tartaric acid (D-/L-tart) molecules, respectively, which demonstrates that D-1 and L-1 have a good application prospect in sensing chiral substances.

Two isolated polyoxovanadogermanates, [Cd(C2H8N2)2]2{[Cd(C2H8N2)]2[Ge8V12O40(OH)8](H2O)}·7H2O (1, V12Ge8) and {[Cd(C2H8N2)2][Cd(C2H8N2)(H2O)]}{[Cd(C2H8N2)2][Cd(C2H8N2)]2Ge8V12O40(OH)8(H2O)}2·4H2O (2, V24Ge16), have been hydro-/solvothermally synthesized and structurally characterized. All the V ions existed in compounds 1 and 2 are demonstrated in the valence of +4 by bond valence calculation (BVC). Notably, it is the first time to investigate the nonlinear optical (NLO) properties of vanadium-based heteropolyacids and obtain strong two photon responses. The results of open aperture Z-scan based on the two compounds manifest that they are the highest value among the reported polyoxovanadates and may be a decent potential NLO materials. At the same time, the electrochemical and electrocatalytic properties of compounds 1 were also measured in detail. More interestingly, the ratio of compounds 1 and 2 in solvent thermal synthesis can be regulated by adjusting the proportion of mixed solvents, which provides a fresh idea and method for the investigation of polyoxometalate chemistry.

Two pairs of novel chiral chromium lanthanide compounds, formulated as l- and d-[Gd4 Cr4 (IN)10 (μ3 -OH)4 (μ4 -O)4 (H2 O)12 ]⋅[IN]2 ⋅8 H2 O (1 and 3), and l- and d-[Dy4 Cr4 (IN)11 (μ3 -OH)4 (μ4 -O)4 (H2 O)8 ]⋅[IN]⋅1.5 H2 O (2 and 4) (HIN=isonicotinic acid) have been successfully synthesized and characterized. Structural analysis reveals that four Ln3+ ions and four Cr3+ ions connect with each other and yield a "tower-like" [Ln4 Cr4 ] skeleton. Apart from the above featuring an aesthetically charming structure, circular dichroism (CD) spectra confirm that compounds 1 and 3, 2 and 4 are enantiomers. To the best of our knowledge, these are the largest chiral chromium lanthanide compounds. In addition, magnetic interaction shows that Gd (the mixture of 1 and 3) exhibits significant cryogenic magnetocaloric effect (MCE) with -ΔSm =18.08 J kg-1 K-1 (34.69 mJ cm-3 K-1 ). Also, the observed second-harmonic generation efficiencies of [Gd4 Cr4 (IN)10 (μ3 -OH)4 (μ4 -O)4 (H2 O)12 ]⋅[IN]2 ⋅8 H2 O and [Dy4 Cr4 (IN)11 (μ3 -OH)4 (μ4 -O)4 (H2 O)8 ]⋅[IN]⋅1.5 H2 O are 0.3 and 0.4 times that of urea, respectively.

Despite wide potential applications of Gd-clusters in magnetocaloric effect (MCE) owing to f7 electron configuration of Gd(III), the structural improvement in order to enhance MCE remains difficult. A new approach of the situ hydrolysis of acetonitrile is reported, and the slow release of small ligand CH3COO– is realized in the design and synthesis of high-nuclearity lanthanide clusters. A large lanthanide-exclusive cluster complex, [Gd60(CO3)8(CH3COO)12(μ2-OH)24(μ3-OH)96(H2O)56](NO3)15Br12(dmp)5·30CH3OH·20Hdmp (1-Gd60), was isolated under solvothermal conditions. To the best our knowledge, cluster 1 possesses the high metal/ligand ratio (magnetic density) and the largest magnetic entropy change (−ΔSmmax = 48.0 J kg–1 K–1 at 2 K for ΔH = 7 T) among previously reported high-nuclearity lanthanide clusters.

A series of lanthanide compounds, [Ln8(CH2OHCH2OH)8(SO4)12]·m(C2H7N)·nH2O (Ln = Gd (1), Sm (2), Tb (3), La (5), m = 2, n = 2; Ln = Eu (4), m = 0, n = 8), which contain Ln8 rings by sulfate and glycol as the ligand have been synthesized and characterized. Besides, small organic amine and l-tartaric acid act as dual templating roles during the synthetic process. Magnetic investigation of compound 1 reveals the existence of weak antiferromagnetic interactions between GdIII ions and the data of magnetic entropy change (−ΔSm) is 36.86 J K–1 kg–1 (108.55 mJ cm–3 K–1) for ΔH = 7 T at 2.0 K, which is comparatively large among GdIII based compounds. Additionally, because of the excellent luminescence properties of SmIII, TbIII, and EuIII, compounds 2–4 were investigated.

Three new nickel-cluster-substituted polyoxometalates (POMs), [Ni6(H2O)9(μ3-OH)3(HSiW9O34)]2·12H2O (1), [Ni(en)(H2O)3][Ni6(H2O)3(en)2L(μ3-OH)3(HSiW9O34)]2·9H2O (2) (en = ethylenediamine; L = C7H5O2 = benzoic acid) and [Ni6(L')6(CH3COO)(H2O)3(μ3-OH)3(HPW9O34)]2·9H2O (3) (L' = C5NH5 = pyridine) were successfully isolated under hydro-/solvothermal conditions. 1-3 were structurally characterized by single-crystal XRD, elemental analyses, PXRD, IR, and TGA. Compound 1 mainly consists of a pair of {Ni6SiW9} fragments and some water molecules. Interestingly, the whole structure can be regarded as the connection of {Ni6SiW9} and another unit rotated 180° through Ni-O-W bonds, forming a dimeric structure {Ni6SiW9}2. Compounds 2 and 3 also have an {Ni6XW9}2 (X = Si, P) dimer, but there is a big difference in the connection between {Ni6SiW9} units. On this basis, mono-dentate conjugated organic ligands (benzoic acid (L) and pyridine (L')) were successfully introduced. It is noteworthy that pyridine molecules were first integrated into {Ni6SiW9}-based clusters and 3 features the highest number of organic ligands (six pyridines per Ni6) in the reported {Ni6XW9}-based clusters. The introduction of organic ligands to compounds 2 and 3 can bring about better third-order nonlinear optical properties. Magnetic research indicated the existence of ferromagnetic interactions in 2-3.

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.

An eight-membered ring petal-shaped cluster [V8ⅣO8(CH3O)16(C2O4)](C6NH16)2(CH3OH)2 (V8) has been successfully designed and synthesized via hydrothermal method. Structure analysis revealed that each vanadium atom was in an octahedral geometrical configuration six-coordinated, two adjacent vanadium atoms were linked by oxygen atoms on oxalic acid to form a ring. The selective sulfur oxidation experiments reveal that V8 had good catalytic activity under mild conditions, and the removal rate of phenyl sulfide was >99% within 4 h at 40 °C. In addition, the open aperture Z-scan test of V8 was carried out and found that V8 also has latent application value as nonlinear optical (NLO) material.

Based on {e-PMoV8MoVI4O40Zn4} POM units, two novel organic–inorganic hybrids, [TBA]2[H3PMoV8MoVI4O40Zn4]2[4-pyim]6·7H2O (1) (4-pyim = 4-(imidazol-2-yl)pyridine) and [H3PMoV8MoVI4O40Zn4][2-pyim]4·3H2O (2) (2-pyim = 2-(imidazol-2-yl)pyridine), have been triumphantly gained under the hydrothermal conditions via self-assembly method. Compound 1 is made up of two Zn-e-Keggin units jointed by two Zn O bonds, which modified by three 4-pyim ligands, respectively, to form a dimer, while compound 2 consists of a Zn-e-Keggin unit coordinated with four 2-pyim ligands. The coordination mode of the different ligands causes a change in the number of ligands coordinated on each Zn-e-Keggin unit, resulting in the formation of dimers and monomers. What’s more, the third-order non-linear optical (NLO) properties of the two compounds were detected in detail due to the existence of a large number of conjugated organic ligands. Compound 1 has a superiority over compound 2 in NLO performance and the two-photon absorption (TPA) cross section (σ) are 7320 GM for 1 and 1573 GM for 2, which is attributed to the fact that 1 own more conjugated organic ligands. The NLO testing results of compound 1 and 2 show that Zn-e-Keggin unit can provide a good NLO response through combining with conjugated organic ligands, indicating that it is a wally choice for NLO materials. Furthermore, the electrochemistry properties of two compounds were also amply explored.

Two pure enantiomers of polyoxovanadate clusters [(L-/D-C4O6H2)2V4O8]·2C6N2H18 (abbreviated as 1-L and 1-D) have been synthesized by a two-step method. During the two-step synthesis process, we first carried out the solvothermal synthesis and then evaporated the solvent, ending up with orange-yellow crystals. The unique chiral architectures are built up by a single chiral ligand (tartaric acid) and polyoxovanadium. The chiralities of the products were confirmed by circular dichroism (CD) spectra. Due to the presence of protonated free tetramethyl ethylenediamine (TMEDA) cations, the adjacent clusters and TMEDA cations can be connected by hydrogen-bonding interactions. The {V4} cluster linked adjacent clusters via hydrogen bonds to form a 3D supramolecular network. The open aperture Z-scan spectra of two compounds show that molecular TPA cross-section σ of 1-L and 1-D are 1412 and 1094 GM, respectively, which illustrate that they feature decent third-order NLO properties and may have great potential applications as NLO materials.

Triazole, similarly to imidazole, makes a prominent contribution to the proton conductivity of porous materials. To investigate the effects of triazole-based ligands in polyoxovanadates (POVs) on proton conduction, we designed and synthesized two decavanadate-based POVs, [Zn3(C2H4N4)6(H2O)6](V10O28)·14H2O (1) and [Zn3(C2H3N3)8(H2O)4](V10O28)·8H2O (2) constructed from the ligands 3-amino-1,2,4-triazole and 1H-1,2,4-triazole, respectively, via an aqueous solution evaporation method. Surprisingly, complex 1 obtained a superior proton conductivity of 1.24 × 10−2 S cm−1 under 60 °C and 98% RH, which is much higher than that of complex 2. Furthermore, due to the contribution of the conjugate properties of the ligands to the third-order nonlinear optical (NLO) properties, we also studied its two-photon responses and achieved satisfactory results.