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K. Pavani

Bio: K. Pavani is an academic researcher from Indian Institutes of Technology. The author has contributed to research in topics: Hydrothermal synthesis & Ammonium heptamolybdate. The author has an hindex of 6, co-authored 9 publications receiving 233 citations.

Papers
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TL;DR: In this paper, the influence of the metal complex and temperature of the hydrothermal reaction on the formation of the different hybrid solids built of octamolybdate clusters is discussed, and plausible mechanisms for the self-assembly of the crystals in terms of supramolecular organization between metal complexes and soluble molybdenum precursors in the initial stages of the reaction are provided.
Abstract: The hydrothermal reaction of an aqueous ammonium heptamolybdate solution with cobalt or copper metal salts in the presence of imidazole (imi) or pyrazole (pz) in the temperature range 120–180 °C and at autogenous pressure yields four fully oxidized metal-complex-templated octamolybdates, namely [{CuI(imi)2}4(imi)2Mo8O26]·4H2O (1), (Himi)2[{CuII(imi)2}2Mo8O27] (2), [{CoII(pz)4}2(pz)2Mo8O26] (3), and [{CuII(pz)4}2Mo8O26]·2H2O (4). The single-phase nature of the solids was established by single-crystal and powder X-ray diffraction, thermal analysis, and spectroscopic techniques. Compounds 1, 3, and 4 are neutral composite solids – 1 is a discrete molecular unit while 3 and 4 are 2D sheets. Compound 2 consists of anionic chains with imidazolium counter cations. The influence of the metal complex and temperature of the hydrothermal reaction on the formation of the different hybrid solids built of octamolybdate clusters is discussed. We also provide plausible mechanisms for the self-assembly of the crystals in terms of supramolecular organization between metal complexes and soluble molybdenum precursors in the initial stages of the reaction. The magnetic properties of 2, 3, and 4 confirm the presence of Cu and Co in the divalent state with no appreciable long-range order down to 5 K, whereas 1 is diamagnetic.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

95 citations

Journal ArticleDOI
TL;DR: In this article, the role of 2-aminopyridine (2ampy) in the formation of the different solids under hydrothermal conditions is discussed, and the structures of these materials were established by single-crystal and powder X-ray diffraction techniques.
Abstract: The hydrothermal reaction of an aqueous ammonium heptamolybdate solution with first-row transition metal salts in the presence of 2-aminopyridine at around 180 °C and under autogenous pressure yields several molybdates, such as the 1D chains in (C5N2H7)4Mo8O26 (1), zero-dimensional (C5N2H7)6Mo7O24·3H2O (2), and the first synthesis of Lindgrenite [Cu3Mo2O8(OH)2 (3)] The structures of these materials were established by single-crystal and powder X-ray diffraction techniques. The crystal structures of wolframite-based MnMoO4 (4) and ZnMoO4 (5) were established by powder X-ray diffraction. The role of 2-aminopyridine (2-ampy) in the formation of the different solids under hydrothermal conditions is discussed. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

81 citations

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TL;DR: In this paper, the Anderson-Evans type solids were synthesized from an aqueous solution containing sodium molybdate, chromium chloride, cupric chloride and pyrazole at room temperature.
Abstract: The synthesis of four new Anderson-Evans type cluster based solids was carried out from an aqueous solution containing sodium molybdate, chromium chloride, cupric chloride and pyrazole at room temperature: [{Cr3O(CH3COO)6(H2O)3}2{H7CrMo6O24}]·24H2O, 1; [{Cu2(ox)(pz)4}{H7CrMo6O24}]·11H2O, 3; [{Cu(pz)2(H2O)2}{Cu2(ox)(pz)4}{H5CrMo6O24}]·8H2O, 4; and [{Cu(pz)3Cl}{Cu2(ox)(pz)4}{H6CrMo6O24}]·8H2O, 5. In 1, the discrete Anderson-Evans cluster aggregates with trimeric chromium acetate cationic complex through supramolecular interactions. In 3–5, the Anderson-Evans cluster is covalently linked into a 1D chain through oxalate bridged copper pyrazole units. In 3, the chains are further stabilized by water oligomers. In 4 and 5, the chains are covalently linked into 2D sheets by different copper pyrazole complexes. The oxalate molecules in 3–5 are probably generated in situ in the reaction medium, through a reductive coupling of dissolved carbon dioxide assisted by copper pyrazole units.

20 citations

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TL;DR: In this paper, the formation of self-assembled metal organic hybrid solids from acidified aqueous molybdate solution containing cupric ions and one of the multidentate organic ligands was studied.

16 citations

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TL;DR: In this article, two new fully oxidized polyoxovanadate cluster-based solids (C4N2S2H14)2[H2V10O28]·4H2O,1 and C4N 2S 2H14]5[H4V15O42]2·l0H 2O,2 are crystallized under self-assembly process in the presence of cysteamine.
Abstract: Two new fully oxidized polyoxovanadate cluster-based solids (C4N2S2H14)2[H2V10O28]·4H2O,1 and (C4N2S2H14)5[H4V15O42]2·l0H2O,2 are crystallized under self-assembly process in the presence of cysteamine. In both1 and2, cysteamines are oxidized forming disulphide linkages and occur as counter cations. The organic cations assemble around V10O28 cluster anions in1 whereas they aggregate around V15O42 clusters in 2· pH appears to be the structure determinant in the occurrence of decavanadate cluster in1 and pentadecavanadate in2, with the same counter cation.

15 citations


Cited by
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TL;DR: The chemistry of the pyrazole ring is summarized, and the metal coordination modes adopted by 1H-pyrazoles and their anions are reviewed, highlighting the wide structural diversity in apparently simple main group pyrazolides.
Abstract: This Perspective summarises the chemistry of the pyrazole ring, and reviews the metal coordination modes adopted by 1H-pyrazoles and their anions. Pyrazolide anions are probably the most versatile ligands in coordination chemistry, with 20 different terminal or bridging coordination modes having been identified so far. Metal cluster compounds supported by pyrazolido ligation are surveyed, concentrating on those reported during the past ten years. Highlights include the wide structural diversity in apparently simple main group pyrazolides; luminescence and charge-transfer complexes in coinage metal pyrazolide clusters; the use of robust metal pyrazolide clusters to construct liquid crystals, supramolecular materials and metal–organic frameworks; and supramolecular complexes formed by pyrazolide-supported metallacrowns.

285 citations

Journal ArticleDOI
TL;DR: These hybrid supramolecular compounds present interesting photochemical properties and spectroscopic experiments show that they not only are potential semiconductor materials but also have interesting photoluminescence phenomena, including O-->Mo [LMCT] and intraligand [pi-pi*] emissions generated by internal heavy metal effect.
Abstract: Eight members of the Ag/1,2,4-triazole/polyoxometalates (POMs) hybrid supramolecular family, namely, [Ag4(dmtrz)4][Mo8O26] (dmtrz = 3,5-dimethyl-1,2,4-triazole, 1), [Ag6(3atrz)6][PMo12O40]2·H2O (3atrz = 3-amino-1,2,4-triazole, 2), [Ag2(3atrz)2]2[HPMoVI10MoV2O40] (3), [Ag2(dmtrz)2]2[HPMoVI10MoV2O40] (4), [Ag2(trz)2]2[Mo8O26] (trz = 1,2,4-triazole, 5), [Ag2(3atrz)2][Ag2(3atrz)2(Mo8O26)] (6), [Ag4(4atrz)2Cl][Ag(Mo8O26)] (4atrz = 4-amino-1,2,4-triazole, 7), and [Ag5(trz)4]2[Ag2(Mo8O26)]·4H2O (8), were synthesized through hydrothermal reactions of 1,2,4-triazole or its derivatives with appropriate silver salts and molybdates. Crystal structure analysis reveals that the POM-dependent Ag−1,2,4-triazolate units in these hybrid compounds form a novel tetranuclear cluster (1), a unique double calix[3]arene-shaped hexamer (2), zigzag chains (5 and 6), helix chains (3, 4, and 8), and an interesting looped chain (7). A series of hydrogen bonding-based supramolecular assemblies varying among the 0-D + 0-D (1 and 2), 0-...

273 citations

Journal ArticleDOI
TL;DR: The Anderson-Evans archetype is a highly flexible POM cluster that allows modification from several point-of-views; it can incorporate a large number of different heteroatoms differing in size and oxidation state, and can incorporate inorganic and organic cations and molecules demonstrating different coordination motifs, and covalent attachment with tris(hydroxymethyl)methane ligands allows it to be combined with specific organic functionalities as mentioned in this paper.

227 citations

Journal ArticleDOI
TL;DR: With step by step increasing of the amount of organic amine, the transformation of Cu(II) ions into Cu(I) ones in different degrees in POMs-based metal-organic frameworks (MOFs) for the first time is achieved.
Abstract: Six polyoxometalate (POM)-based hybrid materials have been designed and synthesized based on octamolybdate building blocks and copper-organic units at different pH values under hydrothermal conditions, namely, [H2bbi][CuII(bbi)2(β-Mo8O26)] (1), [CuII(bbi)2(H2O)(β-Mo8O26)0.5] (2), [CuII(bbi)2(α-Mo8O26)][CuI(bbi)]2 (3), [CuIICuI(bbi)3(α-Mo8O26)][CuI(bbi)] (4), [CuI(bbi)]2[CuI2(bbi)2(δ-Mo8O26)0.5][α-Mo8O26]0.5 (5), and [CuI(bbi)][CuI(bbi)(θ-Mo8O26)0.5] (6), where bbi is 1,1′-(1,4-butanediyl)bis(imidazole). Their crystal structures have been determined by X-ray diffraction. In compound 1, the bbi ligands with bis-monodentate coordination modes link CuII cations to generate a 2D copper-organic unit with (4, 4) net, which is pillared by the (β-Mo8O26)4− anions to form a 3D framework with α-Po topology. The similar copper-organic units are connected alternately by (β-Mo8O26)4− anions to generate a 3D 2-fold interpenetrating (4,6)-connected framework with (44·62)(44·610·8) topology in compound 2. Compounds 3 and ...

211 citations

Journal ArticleDOI
TL;DR: Four inorganic-organic hybrid compounds, hydrothermally synthesized through use of the same Keggin polyoxometalate as the template and tuning the molar ratio of the bis(triazole) ligand to the Cu(II) ion, are discussed.
Abstract: Four inorganic−organic hybrid compounds, [CuI4(bte)4(SiW12O40)] (1), [CuII2(bte)4(SiW12O40)]·4H2O (2) [bte = 1,2-bis(1,2,4-triazol-1-yl)ethane], [CuI4(btb)2(SiW12O40)]·2H2O (3), and [CuII2(btb)4(SiW12O40)]·2H2O (4) [btb = 1,4-bis(1,2,4-triazol-1-yl)butane], were hydrothermally synthesized through use of the same Keggin polyoxometalate as the template and tuning the molar ratio of the bis(triazole) ligand to the CuII ion. The ratio of the bis(triazole) ligand to CuII has a crucial influence on the structures of this series. Single-crystal X-ray diffraction analyses indicate that compound 1 is constructed by tetranuclear ring-connecting chains and polymerized [Cu(bte)]+ chains, between which SiW12 anions are inserted to form a three-dimensional (3D) structure. Compound 2 shows a (44·62) two-dimensional grid sheet. The discrete SiW12 anions are sandwiched by the sheets, just like “hamburgers”. Compound 3 presents channel-like [Cu2(btb)]2+ polymerized chains, which are further connected by SiW12 anions to con...

182 citations