Two new lead(II) coordination polymer and discrete complex containing bipyridine ligands with different positioned methyl substituents: Synthesis, characterization, crystal structure determination, and luminescent properties

چکیده مقاله

Lead(ll) coordination polymer [Pb(5,5′-dmbpy) (μ-NO ₃)₂],_n (1) and mononuclear complex [Pb(6,6′-dmbpy) (NO₃)₂] (2) (where 5,5′-dmbpy is 5,5′-dimethyl-2,2′- bipyridine and 6,6′-dmbpy is 6,6′-dimethyl-2,2′-bipyridine) were synthesized from reaction of lead(II) nitrate with 5,5′-dmbpy and 6,6′-dmbpy, respectively. Both complexes were thoroughly characterized by elemental analysis, infrared, 'H and '3C NMR, UV-Vis, emission spectroscopy, as well as single-crystal X-ray diffraction. Polymer 1 possesses one-dimensional (ID) chain structure, whilst complex 2 exhibits a discrete complex which provide an extended chain parallel to the [001] direction via weak intermolecular C-H-0 hydrogen bonding. Coordination number of Pb²⁺ in 1 and 2 are 8 and 6, respectively, with the stereochemically active lone pair, resulting in the hemidirected geometry for both complexes. The nitrate anions exhibit a tridentate chelating/bridging mode in 1, and a bi-chelating mode in 2. The supramolecular features in these complexes are guided/influenced by weak directional intermolecular C-H-0 hydrogen bonding (1 and 2) together with π- π and C-H-π (1) interactions. The luminescence studies of 1 and 2 confirmed that the position of methyl substituent on 2,2′-bipyridine rings has a profound effect on the fluorescence emissions. © Springer Science+Business Media, LLC 2011.