Luminescent Zn(NCS)2 and Cd(NCS)2 coordination compounds with pyridine derivatives: Synthesis, structures and physical properties

Abstract

Abstract Reaction of Cd(NCS)2 and Zn(NCS)2 with the co-ligands 4-benzylpyridine or 4-benzoylpyridine leads to the formation of eight new compounds, of which one crystallizes in two polymorphic modifications. The co-ligand rich compounds with the composition M(NCS)2(L)4 (M = Cd, Zn and L = 4-benzylpyridine or 4-benzoylpyridine) (1) form discrete complexes, in which the metal cations are each coordinated by four co-ligands and two N-bonded anionic ligands within slightly distorted octahedra. In the co-ligand deficient compounds (2) with the composition M(NCS)2(L)2 two structure types are observed. The Zn compounds form discrete complexes in which the Zn cations are tetrahedral coordinated (2-Zn), whereas in the Cd compounds (2-Cd) the metal cations are octahedral coordinated and linked into chains by pairs of µ-1,3-bridging thiocyanate anions. Upon heating, compounds 1 loose half of the co-ligands and transform into compounds 2. The coordination mode of the anionic ligands was also investigated by IR and Raman spectroscopy. All compounds show blue-green ligand-based luminescence with emission maxima varying between 21,857 cm−1 and 18,264 cm−1.