New thiocyanatocadmates with bidentate N-heterocyclic molecules as the templating agents: synthesis and structural characterization

Abstract

The room-temperature reactions between CdX₂, NH₄SCN and bidentate N-heterocyclic molecules in acidic C₂H₅OH/H₂O solutions yielded five new thiocyanatocadmates, [H₂bpp][CdCl₂(SCN)₂] (bpp = 1,3-bis(4-piperidyl)propane) 1, [H₂bpe][CdBr₂(SCN)₂] (bpe = 1,2-bis(4-pyridyl)ethane) 2, [H₂(4,4′-dtdpy)][Cd₂(SCN)₆] (4,4′-dtdpy = 4,4′-dithiodipyridine) 3, [H₂(4,4′-dtdpy)][CdBr₂(SCN)₂] 4 and [H(2,2′-dtdpy)][Cd(SCN)₃] (2,2′-dtdpy = 2,2′-dithiodipyridine) 5. It is noteworthy that (i) in compound 3, Cd²⁺ and SCN⁻ aggregate together to form two types of ribbons with H₂(4,4′-dtdpy)²⁺ as the templating agent; (ii) in compound 5, 2,2′-dtdpy is monoprotonated, and the anion [Cd(SCN)₃]⁻ shows a 2D honeycomb-like layer structure; (iii) in compounds 1–4, the N-heterocyclic molecules still act as the linkers to extend the inorganic anions into 1D or 2D supramolecular networks via weak hydrogen-bonded interactions with piperidyl/pyridyl N atoms as the acceptors, although they are diprotonated. In ethanol solution, all of the title compounds emit light upon excitation.