engleski

Crystallographic studies of three dioxomolybdenum(VI) polymorphs and a supramolecular square complex

Polymorphs based on dioxomolybdenum(VI) complexes are still scarce and only the structures of the trimorph [MoO2(C12H8N2O2) (CH3OH)] and of the dimorph [MoO2(C9H9NO2) (C9H11NO2)], containing the {; ; ; MoO2}; ; ; 2+ unit were reported so far.1, 2, 3 Here we report on crystallographic studies of three dioxomolybdenum(VI) polymorphs [MoO2(L)(EtOH)] (1, 1 or 1) and two metal-organic supramolecular isomers: coordination polymer [MoO2(L)]n and molecular square inclusion complex [MoO2(L)]4CH2Cl24CH2Cl2 (L2− = 4- methoxy-2-oxybenzaldehyde isonicotinylhydrazoate). Three polymorphic forms 1, 1 and 1 were synthesized by the reaction of H2L with [MoO2(acac)2] in ethanol. Removal of the coordinated ethanol molecule upon grinding or heating led to the solid-state transformation into the supramolecular coordination polymer. Supramolecular polymer can also be obtained by self-assembly reaction after dissolution of 1, 1 or 1 in ethanol. The square inclusion complex was obtained by conversion of 1, 1 or 1 in dichloromethane or by reaction of [MoO2(acac)2] with H2L in CH2Cl2, at ambient temperature. In all compounds the molybdenum atoms exhibit distorted octahedral coordination spheres. The ligand is coordinated in the dianionic form to the cis-{; ; ; MoO2}; ; ; 2+ core via the O, N, O donor atoms the remaining sixth coordination site is occupied either by the oxygen atom from the ethanol molecule or by the nitrogen atom of the izonicotinyl moiety of the neighboring molecule forming discrete cyclic assemblies, molecular squares. A common feature of all three polymorphic forms is the association of the molecules by hydrogen bonds into centrosymmetric dimers. Intermolecular interactions and their role in the supramolecular architecture formation will be discussed

dioxomolybdenum(VI) polymorphs ; crystallographic studies

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