title: Synthesis and characterization of two polymorphic crystalline phases and an amorphous powder of nickel(II) bisimidazolate.
abstract: Nickel(II) bisimidazolate is polymorphic. Depending on the synthetic strategy adopted, two crystalline phases (alpha- and beta-Ni(im)(2)) or an amorphous material of the same composition can be prepared. The thermodynamically stable alpha-Ni(im)(2) phase, which can be prepared in water at elevated temperatures, contains a two-dimensional polymer (of nearly square meshes) with square-planar NiN(4) chromophores and exo-bidentate imidazolate ligands bridging nickel atoms that are ca. 5.73 A apart. The beta-Ni(im)(2) phase can be kinetically stabilized at lower temperatures, but the structural complexity and the lack of single crystals prevented its full structural characterization, even in the presence of an indexed powder diffraction pattern. The spectroscopic features of these crystalline phases are compared with those of the amorphous material.
authors.affiliation: Dipartimento di Scienze Chimiche, Fisiche e Matematiche, Università dell'Insubria, via Valleggio 11, 22100 Como, Italy. norberto.masciocchi@uninsubria.it
authors.forename: Norberto
authors.initials: N
authors.lastname: Masciocchi
authors.forename: Fulvio
authors.initials: F
authors.lastname: Castelli
authors.forename: Paul M
authors.initials: PM
authors.lastname: Forster
authors.forename: Maya M
authors.initials: MM
authors.lastname: Tafoya
authors.forename: Anthony K
authors.initials: AK
authors.lastname: Cheetham