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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.

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.

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 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.

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.