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

Three new cadmium(II) complexes, [Cd(5,5'-dmbipy)(2)(eta(2)-NO3)(2)] (1), [Cd(6-mbipy)(2)(eta(2)-NO3)(eta-NO3)] (2) and [Cd(6,6'-dmbipy)(2)(eta(2)-NO3)][Cd(6,6'-dmbipy)(eta(2)-NO3)(3)] (3) were prepared from the reaction of Cd(NO3)(2)center dot 4H(2)O 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 degrees C, respectively. The three complexes were thoroughly characterized by elemental analysis, IR, UV-Vis, H-1 and C-13{H-1}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 center dot center dot center dot O hydrogen bonding (1-3), pi center dot center dot center dot pi stacking (1-2) and C-H center dot center dot center dot pi interaction (1-2), 3D supramolecular structures are assembled in these compounds. (C) 2016 Elsevier B.V. All rights reserved.