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 = 2,2′-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.