Cd(II) and Zn(II) thiocyanate coordination compounds with 3-ethylpyridine: synthesis, crystal structures and properties.

Reaction of Cd(NCS)2 and Zn(NCS)2 with 3-ethylpyridine leads to the formation of compounds of compositions M(NCS)2(3-ethylpyridine)4 (M=Cd, <bold>1-Cd</bold>; Zn, <bold>1-Zn</bold>) and M(NCS)2(3-ethylpyridine)2 (M=Cd, <bold>2-Cd</bold>; Zn, <bold>2-Zn</bold>). <bold>1-Cd</bold> and <bold>1-Zn</bold> are isotypic and form discrete complexes in which the metal cations are octahedrally coordinated by two <italic>trans</italic>-coordinating N-bonded thiocyanate anions and four 3-ethylpyridine co-ligands. In <bold>2-Cd</bold> the cations are also octahedrally coordinated but linked into chains by pairs of <italic>μ</italic>-1,3-bridging anionic ligands. <bold>2-Zn</bold> is built up of discrete complexes, in which the Zn cation is tetrahedrally coordinated by two N-bonded thiocyanate anions and two 3-ethylpyridine co-ligands. Compounds <bold>1-Cd</bold>, <bold>2-Cd</bold> and <bold>2-Zn</bold> can be prepared in a pure state, whereas <bold>1-Zn</bold> is unstable and transforms on storage into <bold>2-Zn</bold>. If <bold>1-Cd</bold> and <bold>1-Zn</bold> are heated, a transformation into <bold>2-Cd</bold>, respectively <bold>2-Zn</bold> is observed. Luminescence measurements reveal that <bold>1-Cd</bold>, <bold>2-Cd</bold> and <bold>2-Zn</bold> emit light in the blue spectral range with maxima at, respectively, 21724, 21654 and 22055 cm−1, assigned to ligand-based luminescence. [ABSTRACT FROM AUTHOR]