Syntheses, crystal structures, and photoluminescence of three cadmium(II) coordination complexes based on bipyridine ligands with different positioned methyl substituents

• Three new complexes of [Cd(5,5′-dmbipy)2(η2-NO3)2], [Cd(6-mbipy)2(η2-NO3)(η-NO3)] and [Cd(6,6′-dmbipy)2(η2-NO3)][Cd(6,6′-dmbipy)(η2-NO3)3] were obtained and fully characterized.
• The [Cd(5,5′-dmbipy)2(η2-NO3)2] and [Cd(6-mbipy)2(η2-NO3)(η-NO3)] complexes have discrete structure.
• The asymmetric unit of [Cd(6,6′-dmbipy)2(η2-NO3)][Cd(6,6′-dmbipy)(η2-NO3)3] complex include cationic and anionic parts.
• Photoluminescence studies show that the three complexes exhibit strong luminescence.

Three new cadmium(II) complexes, [Cd(5,5′-dmbipy)2(η2-NO3)2] (1), [Cd(6-mbipy)2(η2-NO3)(η-NO3)] (2) and [Cd(6,6′-dmbipy)2(η2-NO3)][Cd(6,6′-dmbipy)(η2-NO3)3] (3) were prepared from the reaction of Cd(NO3)2·4H2O with 5,5′-dmbipy (5,5′-dimethyl-2,2′-bipyridine), 6-mbipy (6-methyl-2,2′-bipyridine) and 6,6′-dmbipy (6,6′-dimethyl-2,2′-bipyridine) ligands in a mixture of CH3CN and CH3OH (1:1) at 40 °C, respectively. The three complexes were thoroughly characterized by elemental analysis, IR, UV–Vis, 1H and 13C{1H}NMR spectroscopy and their structures were studied by the single-crystal diffraction method. We are interested in influencing the structure, as well as the optical properties of the complexes by means of changing the position of the methyl substituent on the bipyridine (bipy) ring, which is to be determined using X-ray crystal structure determination and luminescence studies. These studies revealed that upon coordination to Cd(II) the luminescent intensity is enhanced in comparison with the related unbound ligands. Furthermore, through intermolecular weak interactions, for example, C–H⋯O hydrogen bonding (1–3), π⋯π stacking (1–2) and C–H⋯π interaction (1–2), 3D supramolecular structures are assembled in these compounds.

Three new cadmium(II) complexes, [Cd(5,5′-dmbipy)2(η2-NO3)2], [Cd(6-mbipy)2(η2-NO3)(η-NO3)] and [Cd(6,6′-dmbipy)2(η2-NO3)][Cd(6,6′-dmbipy)(η2-NO3)3] (where 5,5′-dmbipy is 5,5′-dimethyl-2,2′-bipyridine, 6-mbipy is 6-methyl-2,2′-bipyridine and 6,6′-dmbipy is 6,6′-dimethyl-2,2′-bipyridine) have been synthesized. These three complexes were thoroughly characterized by elemental analysis, IR, 1H and 13C{1H}NMR, UV–Vis and luminescence spectroscopy. Moreover; their single-crystal structures were studied by X-ray diffraction method.Figure optionsDownload as PowerPoint slide