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

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.