A series of new heteroleptic Hg(II) complexes: Synthesis, crystal structures and photophysical properties

We report the synthesis of six new heteroleptic Hg(II) complexes (1–6) with general composition [Hg(II) (bpy)L2] where bpy = 2,20-bipyridine, L = benzoic acid (1), 2-amino benzoic acid (2), 3-amino benzoic acid (3), 4-amino benzoic acid (4), 2-hydroxy benzoic acid (5), 4-hydroxy benzoic acid (6). 1, 2, 4–6 are monomer with hexa coordinated Hg(II) center whereas 3 is a zig–zag 1D-polymer with hepta-coordinated Hg (II) ion. Unlike other substituted benzoic acids, the 3-amino benzoic acid shows both –NH2 and –COOH groups having affinity towards Hg(II) centers. Therefore, on reaction of HgCl2/HgBr2 with 3-amino benzoic acid it was observed that only –NH2 group coordinates to Hg(II) center and –COOH group remains uncoordinated yielding 7 and 8. 1–6 have been characterized by elemental analysis, FT-IR, thermo gravimetric analysis as well as single crystal X-ray studies. Their photo-physical properties were also investigated and maximum quantum yield was observed for 3. Polymer 3 exhibited different fluorescence spectra in different solvents with maximum emission in chloroform. The electronic communication and geometry optimization have been performed by Density Functional Theory. 2016 Elsevier Ltd. All rights reserved.