From discrete molecules to one-dimensional coordination polymers containing Mn(II), Zn(II) or Cd(II) pyridine-2-aldoxime building unit

The syntheses, spectroscopic characterization and crystal structures for eight coordination compounds [Cd(HCO2)2(pya)2] (1), {[M(bdc)(pya)].1.5DMF}n (M = Mn(II), Zn(II), Cd(II) (2–4), [Zn(SO4)(pya)(H2O)3](H2O) (5), [(ZnSO4)2(pya)4] DMF.2H2O (6), [Zn(SO4)(pya)(H2O)2]n (7), and [Cd(SO4)(pya)(H2O)]n (8) [pya = pyridine-2-aldoxime, bdc = 1,4-benzenedicarboxylate, DMF = N,N′-dimethylformamide] are reported. Compounds 1–4 and 6 contain two, while 5, 7, and 8 contain one neutral pya ligand coordinated in a chelate mode to the metal center through the Npyridyl and Noxime atoms. The dicarboxylic bdc anions provide an access to 1D polymeric arrays in 2–4. The hybrid sulfates including discrete mononuclear (5), binuclear (6), and 1D polymeric (7, 8) coordination arrays were obtained due to different binding modes of coordinated sulfate anion. While solid state fluorescence of new polymeric compounds 2–4 is similar to that of the H2bdc ligand, a rare dual emission is observed for compounds 7 and 8. According to TD-DFT calculations, emission at 400 and 650 nm originates from nπ∗ and ππ∗ states of the pya ligand respectively.

Graphical abstractThe syntheses, spectroscopic characterization and crystal structures for eight coordination compounds [Cd(HCO2)2(pya)2] (1), {[M(bdc)(pya)]·1.5DMF}n (M = Mn(II), Zn(II), Cd(II) (2–4), [Zn(SO4)(pya)(H2O)3](H2O) (5), [(ZnSO4)2(pya)4]·DMF·2H2O (6), [Zn(SO4)(pya)(H2O)2]n (7), and [Cd(SO4)(pya)(H2O)]n (8) [pya = pyridine-2-aldoxime, bdc = 1,4-benzenedicarboxylate, DMF = N,N′-dimethylformamide] are reported. Compounds 1–4 and 6 contain two, while 5, 7, and 8 contain one neutral pya ligand coordinated in a chelate mode to the metal center through the Npyridyl and Noxime atoms. The dicarboxylic bdc anions provide an access to 1D polymeric arrays in 2–4. The hybrid sulfates including discrete mononuclear (5), binuclear (6), and 1D polymeric (7, 8) coordination arrays were obtained due to different binding modes of coordinated sulfate anion. The fluorescence properties of new polymeric compounds 2–4 and 7, 8 recorded in the solid state at room temperature are reported.Figure optionsDownload full-size imageDownload as PowerPoint slide