title: Mechanochemical Synthesis of 3d Transition-Metal-1,2,4-Triazole Complexes as Precursors for Microwave-Assisted and Thermal Conversion to Coordination Polymers with a High Influence on the Dielectric Properties.
abstract: The complexes [MCl2 (TzH)4] (M=Mn (1), Fe (2); TzH=1,2,4-1H-triazole) and [ZnCl2 (TzH)2] (3) have been obtained by mechanochemical reactions of the corresponding divalent metal chloride and 1,2,4-1H-triazole. They were successfully used as precursors for the formation of coordination polymers either by a microwave-assisted reaction or by thermal conversion. For manganese, the conversion directly yielded 1∞ [MnCl2 TzH] (4), whereas for the iron-containing precursor, 1∞ [FeCl2 TzH] (6), was formed via the intermediate coordination polymer 1∞ [FeCl(TzH)2]Cl (5). For cobalt, the isotypic polymer 1∞ [CoCl(TzH)2]Cl (7) was obtained, but exclusively by a microwave-induced reaction directly from CoCl2 . The crystal structures were resolved from single crystals and powders. The dielectric properties were determined and revealed large differences in permittivity between the precursor complexes and the rigid chain-like coordination polymers. Whereas the monomeric complexes exhibit very different dielectric behaviour, depending on the transition metal, from "low-k" to "high-k" with the permittivity ranging from 4.3 to >100 for frequencies of up to 1000 Hz, the coordination polymers and complexes with strong intermolecular interactions are all close to "low-k" materials with very low dielectric constants up to 50 °C. Therefore, the conversion procedures can be used to deliberately influence the dielectric properties from complex to polymer and for different 3d transition-metal ions.
authors.affiliation: Institut für Anorganische Chemie, Universität Würzburg, Am Hubland, 97074, Würzburg, Germany), Fax: (+49) 931-31-88724.
authors.forename: Franziska A
authors.initials: FA
authors.lastname: Brede
authors.affiliation: Institut für Anorganische Chemie, Universität Würzburg, Am Hubland, 97074, Würzburg, Germany), Fax: (+49) 931-31-88724.|Fachbereich Chemie, Universität Marburg, Hans-Meerwein-Straße, 35043, Marburg, Germany.
authors.forename: Johanna
authors.initials: J
authors.lastname: Heine
authors.affiliation: Institut für Chemische Technologie der Materialsynthese, Universität Würzburg, Röntgenring 11, 97070, Würzburg, Germany.
authors.forename: Gerhard
authors.initials: G
authors.lastname: Sextl
authors.affiliation: Institut für Anorganische Chemie, Universität Würzburg, Am Hubland, 97074, Würzburg, Germany), Fax: (+49) 931-31-88724. k.mueller-buschbaum@uni-wuerzburg.de.
authors.forename: Klaus
authors.initials: K
authors.lastname: Müller-Buschbaum
keywords: coordination polymers; mechanochemistry; microwave chemistry; permittivity; transition metals