Exploration of Cd(ii)/pseudohalide/di-2-pyridyl ketone chemistry – rational synthesis, structural analysis and photoluminescence

Abstract

A systematic investigation of Cd(II)–(py)₂CO–X systems (X = N₃⁻, NCO⁻ and NCS⁻) was conducted, and the following cadmium(II) coordination compounds [Cd(SCN)₂{(py)₂C(OCH₃)(OH)}]_n (1), [Cd₂(SCN)₄{(py)₂C(OCH₃)(OH)}₂] (2), [Cd₄(SCN)₄{(py)₂C(OCH₃)(O)}₄] (3), [Cd₄(N₃)₄{(py)₂C(OCH₃)(O)}₄] (4), [Cd₄(N₃)₄{(py)₂C(OH)(O)}₂{(py)₂C(OCH₃)(O)}₂] (5), [Cd₄(NCO)₄{(py)₂C(OCH₃)(O)}₄] (6), [Cd₄(NCO)₄{(py)₂C(OH)(O)}₂{(py)₂C(OCH₃)(O)}₂] (7), [Cd₄(N₃)₂(NO₃)₂{(py)₂C(OH)(O)}₂{(py)₂C(OCH₃)(O)}₂] (8) and [Cd₄(NCO)₂(NO₃)₂{(py)₂C(OH)(O)}₂{(py)₂C(OCH₃)(O)}₂] (9a and 9b) were successfully synthesized and characterized by single-crystal diffraction, X-ray powder diffraction (XRPD), differential scanning calorimetry (DSC) analysis and IR spectroscopy. The fluorescence properties of 1–9 were studied in the solid state and compared to the fluorescence of di-2-pyridyl ketone. The photoluminescence behaviour of 2–9 was also investigated in acetonitrile solution. The X-ray studies demonstrated a cooperative impact of the organic ligand and auxiliary inorganic ion on the final molecular architectures of the cadmium(II) coordination compounds. Also, the essential roles of intermolecular interactions (hydrogen bonds, π–π stacking interactions and weak O⋯S contacts) in the creation of molecular architectures were discussed.