New hybrid Cd(ii) compounds: synthesis and structural characterization

Abstract

In an acidic solution, the room-temperature reactions of CdX₂ (X⁻ = Cl⁻, Br⁻ or CH₃COO⁻) and organic N-heterocyclic molecules with or without SCN⁻/SeCN⁻/dca⁻ (dca⁻ = dicyanamide) created the five new hybrid Cd(II) compounds [H₂(4,4′-dtdpy)]₂[CdBr₄]SO₄·2.5H₂O (dtdpy = dithiodipyridine) 1, [H(2,2′-dtdpy)]₂[CdBr₄] 2, [(Hbim)₂CdCl₂(SCN)₂] (bim = 2,2′-biimidazole) 3, [H₂(pip)][Cd(SCN)₄] (pip = piperazine) 4 and [CdL₂] (L = HNC(OH)N⁻CN) 5. X-ray single-crystal diffraction analysis revealed that: (i) compound 1 is a double salt of [H₂(4,4′-dtdpy)]SO₄ and [H₂(4,4′-dtdpy)][CdBr₄], [H₂(4,4′-dtdpy)]SO₄ shows a two-dimensional (2D) supramolecular layer structure and [H₂(4,4′-dtdpy)][CdBr₄] is distributed in the space between the supramolecular layers; (ii) compounds 2 and 3 are mononuclear molecular entities. Of those, 2,2′-dtdpy and bim were only in situ monoprotonated; (iii) compound 4 contains a 2D supramolecular layered structure which is based on [Cd(SCN)₄]²⁻ chains with H₂(pip)²⁺via N_SCN⋯N_pip interactions; (iv) the three-dimensional (3D) compound 5 exhibits a rutile-related (4·6²)₂(4²·6¹⁰·8³)-topology. The ligand L originates from the in situ nucleophilic addition of H₂O with one –CN group of dca⁻. Upon excitation, the solid-state compounds 3 and 4 emit blue light, and the solid-state compound 5 emits violet light.