Ag^I/V^V Heterobimetallic Frameworks Generated from Novel-Type {Ag₂(VO₂F₂)₂(triazole)₄} Secondary Building Blocks: A New Aspect in the Design of SVOF Hybrids

A series of new silver­(I)-containing MOFs [Ag₂(<i>tr</i>_<i>2</i><i>ad</i>)₂]­(ClO₄)₂ (<b>1</b>), [Ag₂(VO₂F₂)₂(<i>tr</i>_<i>2</i><i>ad</i>)₂]·H₂O (<b>2</b>), [Ag₂(VO₂F₂)₂(<i>tr</i>_<i>2</i><i>eth</i>)₂(H₂O)₂] (<b>3</b>), and [Ag₂(VO₂F₂)₂(<i>tr</i>_<i>2</i><i>cy</i>)₂]·4H₂O (<b>4</b>) supported by 4-substituted bifunctional 1,2,4-triazole ligands (<i>tr</i>_<i>2</i><i>ad</i> = 1,3-bis­(1,2,4-triazol-4-yl)­adamantane, <i>tr</i>_<i>2</i><i>eth</i> = 1,2-bis­(1,2,4-triazol-4-yl)­ethane, <i>tr</i>_<i>2</i><i>cy</i> = <i>trans</i>-1,4-bis­(1,2,4-triazol-4-yl)­cyclohexane) were hydrothermally synthesized and structurally characterized. In these complexes, the triazole heterocycle as an N¹,N²-bridge links either two adjacent Ag–Ag or Ag–V centers at short distances forming polynuclear clusters. The crystal structure of compound <b>1</b> is based on cationic {Ag₂(<i>tr</i>)₄}²⁺ fragments connected in a 2D rhombohedral grid network with (4,4) topology. The neighboring layers are tightly packed into a 3D array by means of argentophilic interactions (Ag···Ag 3.28 Å). Bridging between different metal atoms through the triazole groups assists formation of heterobimetallic Ag^I/V^V secondary building blocks in a linear V–Ag–Ag–V sequence that is observed in complexes <b>2</b>–<b>4</b>. These unprecedented tetranuclear {Ag₂(VO₂F₂)₂(<i>tr</i>)₄} units (the intermetal Ag–Ag and Ag–V distances are 4.24–4.36 and 3.74–3.81 Å, respectively), in which vanadium­(V) oxofluoride units possess distorted trigonal bipyramidal environment {VO₂F₂N}¯, are incorporated into 1D ribbon (<b>2</b>) or 2D square nets (<b>3</b>, <b>4</b>) using bitopic μ₄-triazole ligands. The valence bond calculation for vanadium atoms shows +V oxidation state in the corresponding compounds. Thermal stability and photoluminescence properties were studied for all reported coordination polymers

Ag^I/V^V Heterobimetallic Frameworks Generated from Novel-Type {Ag₂(VO₂F₂)₂(triazole)₄} Secondary Building Blocks: A New Aspect in the Design of SVOF Hybrids

A series of new silver­(I)-containing MOFs [Ag₂(<i>tr</i>_<i>2</i><i>ad</i>)₂]­(ClO₄)₂ (<b>1</b>), [Ag₂(VO₂F₂)₂(<i>tr</i>_<i>2</i><i>ad</i>)₂]·H₂O (<b>2</b>), [Ag₂(VO₂F₂)₂(<i>tr</i>_<i>2</i><i>eth</i>)₂(H₂O)₂] (<b>3</b>), and [Ag₂(VO₂F₂)₂(<i>tr</i>_<i>2</i><i>cy</i>)₂]·4H₂O (<b>4</b>) supported by 4-substituted bifunctional 1,2,4-triazole ligands (<i>tr</i>_<i>2</i><i>ad</i> = 1,3-bis­(1,2,4-triazol-4-yl)­adamantane, <i>tr</i>_<i>2</i><i>eth</i> = 1,2-bis­(1,2,4-triazol-4-yl)­ethane, <i>tr</i>_<i>2</i><i>cy</i> = <i>trans</i>-1,4-bis­(1,2,4-triazol-4-yl)­cyclohexane) were hydrothermally synthesized and structurally characterized. In these complexes, the triazole heterocycle as an N¹,N²-bridge links either two adjacent Ag–Ag or Ag–V centers at short distances forming polynuclear clusters. The crystal structure of compound <b>1</b> is based on cationic {Ag₂(<i>tr</i>)₄}²⁺ fragments connected in a 2D rhombohedral grid network with (4,4) topology. The neighboring layers are tightly packed into a 3D array by means of argentophilic interactions (Ag···Ag 3.28 Å). Bridging between different metal atoms through the triazole groups assists formation of heterobimetallic Ag^I/V^V secondary building blocks in a linear V–Ag–Ag–V sequence that is observed in complexes <b>2</b>–<b>4</b>. These unprecedented tetranuclear {Ag₂(VO₂F₂)₂(<i>tr</i>)₄} units (the intermetal Ag–Ag and Ag–V distances are 4.24–4.36 and 3.74–3.81 Å, respectively), in which vanadium­(V) oxofluoride units possess distorted trigonal bipyramidal environment {VO₂F₂N}¯, are incorporated into 1D ribbon (<b>2</b>) or 2D square nets (<b>3</b>, <b>4</b>) using bitopic μ₄-triazole ligands. The valence bond calculation for vanadium atoms shows +V oxidation state in the corresponding compounds. Thermal stability and photoluminescence properties were studied for all reported coordination polymers

Triazolyl, Imidazolyl, and Carboxylic Acid Moieties in the Design of Molybdenum Trioxide Hybrids: Photophysical and Catalytic Behavior

Three organic ligands bearing 1,2,4-triazolyl donor moieties, (<i>S</i>)-4-(1-phenylpropyl)-1,2,4-triazole (<i>trethbz</i>), 4-(1,2,4-triazol-4-yl)­benzoic acid (<i>trPhCO</i>₂<i>H</i>), and 3-(1<i>H</i>-imidazol-4-yl)-2-(1,2,4-triazol-4-yl)­propionic acid (<i>trhis</i>), were prepared to evaluate their coordination behavior in the development of molybdenum­(VI) oxide organic hybrids. Four compounds, [Mo₂O₆(<i>trethbz</i>)₂]·H₂O (<b>1</b>), [Mo₄O₁₂(<i>trPhCO</i>₂<i>H</i>)₂]·0.5H₂O (<b>2a</b>), [Mo₄O₁₂(<i>trPhCO</i>₂<i>H</i>)₂]·H₂O (<b>2b</b>), and [Mo₈O₂₅(<i>trhis</i>)₂(<i>trhisH</i>)₂]·2H₂O (<b>3</b>), were synthesized and characterized. The monofunctional <i>tr</i>-ligand resulted in the formation of a zigzag chain [Mo₂O₆(<i>trethbz</i>)₂] built up from <i>cis-</i>{MoO₄N₂} octahedra united through common μ₂-O vertices. Employing the heterodonor ligand with <i>tr/–CO</i>₂<i>H</i> functions afforded either layer or ribbon structures of corner- or edge-sharing {MoO₅N} polyhedra (<b>2a</b> or <b>2b</b>) stapled by <i>tr</i>-links in axial positions, whereas −CO₂H groups remained uncoordinated. The presence of the <i>im-</i>heterocycle as an extra function in <i>trhis</i> facilitated formation of zwitterionic molecules with a protonated imidazolium group (<i>imH</i>^<i>+</i>) and a negatively charged −CO₂^– group, whereas the <i>tr-</i>fragment was left neutral. Under the acidic hydrothermal conditions used, the organic ligand binds to molybdenum atoms either through [N–N]-<i>tr</i> or through both [N–N]-<i>tr</i> and μ₂-CO₂^– units, which occur in protonated bidentate or zwitterionic tetradentate forms (<i>trhisH</i>^<i>+</i> and <i>trhis</i>, respectively). This leads to a new zigzag subtopological motif (<b>3</b>) of negatively charged polyoxomolybdate {Mo₈O₂₅}_<i>n</i>^2<i>n</i>– consisting of corner- and edge-sharing <i>cis-</i>{MoO₄N₂} and {MoO₆} octahedra, while the tetradentate zwitterrionic <i>trhis</i> species connect these chains into a 2D net. Electronic spectra of the compounds showed optical gaps consistent with semiconducting behavior. The compounds were investigated as epoxidation catalysts via the model reactions of achiral and prochiral olefins (<i>cis</i>-cyclooctene and <i>trans</i>-β-methylstyrene) with <i>tert</i>-butylhydroperoxide. The best-performing catalyst (<b>1</b>) was explored for the epoxidation of other olefins, including biomass-derived methyl oleate, methyl linoleate, and prochiral dl-limonene