Danna Liu

Two novel Anderson-type polyoxometalate-based metal–organic complexes with high-efficiency photocatalysis towards degradation of organic dyes under UV and visible light irradiation

Two novel Anderson-type polyoxometalate (POM)-based metal–organic complexes (MOCs), namely, H{CuL0.51 [CrMo6(OH)6O18](H2O)}·0.5L1 (1) and {Cu2(L2)2[CrMo6(OH)5O19](H2O)2}·2H2O (2) (L1 = N,N′-bis(3-pyridinecarboxamide)-1,2-ethane, L2 = N,N′-bis(3-pyridinecarboxamide)-1.3-propane), were hydrothermally synthesized and structurally characterized by single-crystal X-ray diffraction, IR spectra, powder X-ray diffraction (PXRD) and thermogravimetric analyses (TGA). In complex 1, the bidentate [CrMo6(OH)6O18]3− (CrMo6) polyoxoanions bridge the CuII ions to generate a 1D Cu–CrMo6 inorganic chain, which is further connected by the μ2-bridging L1 ligands to form a 1D ladder-like chain. Complex 2 is a 3D POM-based metal–organic framework exhibiting a {412.63} topology, which is constructed from the quadridentate CrMo6 polyoxoanions and μ2-bridging L2 ligands. The flexible bis-pyridyl-bis-amide ligands with different spacer lengths have a significant effect on the final structures. In addition, pH shows great influence on the formation of the single-crystal phase. The photocatalytic activities of the title complexes on the degradation of methylene blue (MB) and rhodamine B (RhB) under UV and visible light have been investigated in detail.

Effect of polyoxoanions and amide group coordination modes on the assembly of polyoxometalate-based metal–organic complexes constructed from a semi-rigid bis-pyridyl-bis-amide ligand

A series of polyoxometalate (POM)-based metal–organic complexes constructed from a semi-rigid bis-pyridyl-bis-amide ligand have been hydrothermally synthesized and structurally characterized: [Cu2L2(PMoVI11MoVO40)(H2O)2]·2H2O (1), [Cu2L2(PWVI11WVO40)(H2O)6]·H2O (2), [Cu2L2(SiW12O40)(H2O)6]·H2O (3) and [Cu2L2(H2K2Mo8O28)(H2O)2] (4) (L = N,N′-bis(3-pyridinecarboxamide)-piperazine). Single-crystal X-ray analyses reveal that complex 1 is a 2D metal–organic architecture based on the Keggin-type [PMoVI11MoVO40]4− anions and quadrate Cu2L2 loops. Isostructural complexes 2 and 3 display 2D supramolecular networks based on 1D infinite chains, which are constructed from quadrate Cu2L2 loops and Keggin polyoxoanions. Complex 4 exhibits a 3D metal–organic framework derived from the newly-reported [K2Mo8O28]6− polyoxoanions and quadrate Cu2L2 loops. The L ligands show a μ3-bridging coordination mode (via ligation of two pyridyl nitrogen atoms and one carbonyl oxygen atom) in 1 and 4, and a μ2-bridging coordination mode (via ligation of two pyridyl nitrogen atoms) in 2 and 3, forming Cu2L2 loops in 1–4. The influence of amide group coordination modes and structural features of POMs on the structures of the title complexes has been discussed. The electrochemical properties and selective photocatalytic properties of the title complexes have been reported in this article.

pH, solvent and metal ion induced octamolybdate-based metal–organic complexes decorated with a pyridyl-carboxylate ligand containing an amide group

Three octamolybdate-based metal–organic complexes constructed from a pyridyl-carboxylate ligand containing an amide group, 3-(2-pyridinecarboxylic acid)amido pyridine (HPCAP), namely, H2{[Cu3(PCAP)4(H2O)2](β-Mo8O26)}·10H2O (1), H{[Cu(PCAP)(H2O)](β-Mo8O26)0.5} (2) and H2[Co(H2O)6][Co2(PCAP)4(γ-Mo8O26)(H2O)2]·10H2O (3), have been successfully synthesized under hydrothermal or solvothermal (methanol–water mixed solvent) conditions. Single-crystal X-ray analyses reveal that compound 1 is a 2D layer based on infinite 1D [Cu3(PCAP)4]n2n+ chains and bidentate β-Mo8O264− anions. In compound 2, 1D “thin centipede” [Cu2(PCAP)2]n2n+ chains were connected by tetradentate β-Mo8O264− anions through the Cu–O bond to form a 2D network. In compound 3, γ-Mo8O264− anions were connected by adjacent [Co2(PCAP)4(H2O)2] moieties through Co–O and Mo–N bonds forming an uncommon 1D “fat centipede” chain. The adjacent chains were further extended to a 2D supramolecular network through hydrogen bonding interactions. The title compounds represent the first examples of introducing a pyridyl-carboxylate ligand containing an amide group into the POM system. The pH value, solvent and metal ions play key roles in the construction of the final architectures and show a great influence on the structural diversities of the title compounds. The electrochemical properties of compound 1 and the photocatalysis properties of the title compounds have been reported.

Diverse polyoxometalate-based metal–organic complexes constructed by a tetrazole- and pyridyl-containing asymmetric amide ligand or its in situ transformed ligand

By introducing a tetrazole- and pyridyl-containing asymmetric amide ligand into polyoxometalate (POM) systems, four POM-based complexes, namely, H4[Cu2(TAAP)4(H2O)](Mo8O26)2·20H2O (1), H2[Co(TAAP)2(H2O)2](Mo8O26)·11H2O (2), H2[Ag4(TAAP)4(H2O)2(PMo12O40)2]·4H2O (3), and H4[Ag2(AAP)4(PW12O40)2]·2AAP·12H2O (4) (TAAP = 3-(1H-tetrazole-1-acetic acid amido) pyridine; AAP = 3-(acetic acid amido) pyridine), have been prepared under solvothermal (methanol–water mixed solvent) or hydrothermal conditions and structurally characterized. Compounds 1 and 2 are isostructural 3D structures, which are based on 3D [M(TAAP)2]n2n+ metal–organic frameworks and noncoordinated [Mo8O26]4− polyanion templates. Compound 3 exhibits a dimeric structure constructed from two Keggin [PMo12O40]3− anions and a tetranuclear [Ag4(TAAP)4(H2O)2]4+ subunit. Compound 4 exhibits a 2D supramolecular network based on 1D infinite chains, which are constructed by [PW12O40]3− and Ag-AAP subunits. In compound 4, the AAP ligand was in situ transformed from TAAP. The structural diversities show that POMs play key roles in the construction of final architectures and the in situ transformation of TAAP. The title compounds represent the first examples of introducing tetrazole- and pyridyl-containing asymmetric amide ligand into the POM system. The electrochemistry, photocatalysis and photoluminescence properties of the title compounds have been reported.

Application of flexible bis-pyrazine–bis-amide ligands to construct various polyoxometalate-based metal–organic complexes

By introducing the flexible bis-pyrazine–bis-amide ligands into a polyoxometalates (POMs) system, five POM-based metal–organic complexes, {Cu3(L1)2[CrMo6(OH)6O18]2(H2O)2}·10H2O (1), [CuL1(Mo8O26)0.5]·H2O (2), [Cu2(L1)2(HPMoVI10MoV2O40) (H2O)2]·2H2O (3), [Cu2(L1)2(SiMo12O40) (H2O)2]·2H2O (4), [Cu2(L2)2(SiMo12O40)]·2H2O (5) [L1 = N,N′-bis(2-pyrazinecarboxamide)-1,3-propane, L2 = N,N′-bis(2-pyrizinecarboxamide)-1,6-hexane], were synthesized under hydrothermal conditions and structurally characterized by single-crystal X-ray diffraction analyses, elemental analyses, IR spectra, powder X-ray diffraction (PXRD) and thermal gravimetric analyses (TG). Single-crystal X-ray analysis reveals that compound 1 is a 1D infinite ribbon-like chain with Anderson type polyanions [CrMo6(OH)6O18]3− as building blocks. Compound 2 is a 2D layer constructed from 1D helical [Cu-L1]n2n+ chains and [Mo8O26]4− anions, in which the octamolybdates also act as inorganic building blocks. Compounds 3 and 4 are isostructural, and display 2D supramolecular networks based on the 1D [Cu-L1]n2n+ chains, in which the Keggin polyanions serve as noncoordinated templates. Compound 5 is a 3D supramolecular framework constructed from the 2D [Cu-L2]n2n+ layers and the Keggin [SiMo12O40]4− polyanion templates. In compounds 1–4, the L1 ligands display the same symmetric coordination mode with two chelating sites. When lengthening the spacer of the ligand, L2 exhibits an asymmetric coordination mode in compound 5. The structural diversities of 1–5 show that the different polyoxoanions and spacer lengths of the ligands play key roles in the construction of various architectures. The title compounds represent the first examples of introducing flexible bis-pyrazine–bis-amide ligands into the POMs system. In addition, the electrochemical properties of compounds 2–5 and the photocatalytic activities of the title compounds on the degradation of methylene blue (MB) under UV, visible light and sunlight irradiation have been investigated in detail.

Four Cu(II)/Co(II) coordination polymers based on N,N′-di(3-pyridyl)sebacicdiamide: influence of different carboxylate ancillary ligands on structures and properties

Abstract Four Cu(II)/Co(II) coordination polymers, [Cu(L)(BDC)(H2O)]·3H2O (1), [Cu(L)(DNBA)2] (2), [Co(L)2(DNBA)2] (3), and [Co(L)(NIPH)(H2O)]·H2O (4) (H2BDC = 1,4-benzenedicarboxylic acid, HDNBA = 3,5-dinitrobenzoic acid, H2NIPH = 5-nitroisophthalic acid, L = N,N′-di(3-pyridyl)sebacicdiamide), have been synthesized under hydrothermal conditions. The structures of 1–4 have been determined by single-crystal X-ray diffraction analyses and 1–4 were further characterized by infrared spectroscopy and thermogravimetric analyses. Complex 1 is a 2-D polymeric layer with a 4-connected sql topology. Complex 2 displays a 1-D zigzag chain. Complex 3 possesses a 1-D double-chain structure. Complex 4 exhibits a ribbon chain based on the 1-D [Co–L]nmeso-helical chain. Adjacent layers for 1 and adjacent chains for 2–4 are further linked by hydrogen bonding or π–π stacking interactions to form 3-D supramolecular networks. The differences of carboxylates and metal ions show significant effect on the ultimate architectures of the four complexes. Thermal stabilities, fluorescent properties and photocatalytic activities of 1–4 were also studied.

Two new inorganic-organic hybrid compounds constructed from different polymolybdates and transition metal-amine subunits

Two new polyoxometalate(POM)-based hybrid compounds, [Cu(en)][H4Mo4O16]0.5(1)(en=ethylenediamine) and [Ag(3-C5H6N2)2][H2PMo12O40](2)(3-C5H6N2=3-aminopyridine), containing different transition metalamine subunits were hydrothermally synthesized and characterized by elemental analyses, infrared spectroscopy and single-crystal X-ray diffraction. For compound 1, each [H4Mo4O16]4(Mo4O16) cluster was linked to four neighboring Mo4O16 clusters through four [Cu(en)]2+ subunits to yield a (2,4)-connected 2D layer, which was further extended to a 3D supramolecular network via hydrogen bonding interactions. For compound 2, the adjacent [H2PMo12O40]– clusters were bridged by [Ag(3-C5H6N2)2]+ subunits to generate a 1D chain. The electrochemical behaviors and the photocatalytic activities of compounds 1 and 2 were studied in detail.