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

authors	Lysenko, AB; Senchyk, GA; Domasevitch, KV; Kobalz, M; Krautscheid, H; Cichos, J; Karbowiak, M; Neves, P; Valente, AA; Goncalves, IS
nationality	International
journal	INORGANIC CHEMISTRY
keywords	OLEFIN EPOXIDATION; STRUCTURAL ELUCIDATION; CRYSTAL-STRUCTURES; DIOXOMOLYBDENUM(VI) COMPLEXES; CYCLOOCTENE EPOXIDATION; HYDROTHERMAL SYNTHESIS; OPEN-FRAMEWORKS; OXIDES; LIGAND; PRECURSORS
abstract	Three organic ligands bearing 1,2,4-triazolyl donor moieties, (S)-4-(1-phenylpropy1)-1,2,4-triazole (trethbz), 4-(1,2,4-triazol-4-yl)benzoic acid (trPhCO(2)H), and 3-(1H-imidazol-4-y1)-2-(1,2,4-triazol-4-yl)propionic acid (trhis), were prepared to evaluate their coordination behavior in the development of molybdenum(VI) oxide organic hybrids. Four compounds, [Mo2O6(trethbz)(2)]-H2O (1), [Mo4O12(trPhCO(2)H) center dot 0.5 H2O (2a), [Mo4O12(trPhCO(2)H)(2)]center dot H2O (2b), and [Mo8O25(trhisH)(2)(trhisH)(2)]center dot 2H(2)O (3), were synthesized and characterized. The monofunctional tr-ligand resulted in the formation of a zigzag chain [Mo2O6(trethbz)(2)] built up from cis-{MoO4N2} octahedra united through common mu(2)-O vertices. Employing the heterodonor ligand with tr/-CO2H functions afforded either layer or ribbon structures of corner- or edge-sharing {MoO5N} polyhedra (2a or 2b) stapled by tr-links in axial positions, whereas -CO2H groups remained uncoordinated. The presence of the im-heterocycle as an extra function in trhis facilitated formation of zwitterionic molecules with a protonated imidazolium group (imH(+)) and a negatively charged -CO2- group, whereas the tr-fragment was left neutral. Under the acidic hydrothermal conditions used, the organic ligand binds to molybdenum atoms either through [N-N]-tr or through both [N-N]-tr and mu(2)-CO2- units, which occur in protonated bidentate or zwitterionic tetradentate forms (trhisH' and trhis, respectively). This leads to a new zigzag subtopological motif (3) of negatively charged polyoxomolybdate {Mo8O25}(n)(2n-) consisting of corner- and edge -sharing cis-{MoO4N2} and {MoO6} octahedra, while the tetradentate zwitterrionic trhis 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 (cis-cyclooctene and trans-beta-methylstyrene) with tert-butylhydroperoxide. The best -performing catalyst (1) was explored for the epoxidation of other olefins, including biomass -derived methyl oleate, methyl linoleate, and prochiral DL-limonene.
publisher	AMER CHEMICAL SOC
issn	0020-1669
isbn	1520-510X
year published	2017
volume	56
issue	8
beginning page	4380
ending page	4394
digital object identifier (doi)	10.1021/acs.inorgchem.6b02986
web of science category	Chemistry, Inorganic & Nuclear
subject category	Chemistry
unique article identifier	WOS:000399625600018