Syntheses, characterization, crystalline architectures and luminescence of two halidomercury(II) compounds containing a bidentate (N,O) chelator: variation in nuclearities and superstructures by varying halides

A neutral coordination polymer of chloridomercury(II) of the type ${\left[\text{Hg(bzpy)}(\mu -\text{Cl})\text{Cl}\right]}_n$ (1) and a dinuclear complex of bromidomercury(II) of the type ${\left[\text{Hg(bzpy)}(\mu -\text{Br})\text{Br}\right]}_2$ (2) (bzpy = 2-benzoylpyridine) were synthesized using a 1:1 molar ratio of ${\text{HgCl}}_2/{\text{HgBr}}_2$ and bzpy in methanolic solvent at room temperature and X-ray crystallographically characterized. Structural analyses show that each mercury(II) center in both the compounds adopts a distorted square pyramidal geometry with an ${\text{HgNOX}}_3$ [X = Cl in 1 and X = Br in 2] chromophore. Each mercury(II) center in the coordination polymer 1 is connected to two other metal(II) centers through two different chlorido bridges affording a zigzag one-dimensional (1D) chain. In the crystalline state, 1D chains in 1 are stabilized through weak non-covalent $\text{C}-\text{H}···\pi$ interactions promoting to a 2D sheet structure, and these 2D sheets, in turn, are further associated through intermolecular $\text{C}-\text{H}\cdot \cdot \cdot \text{ O}$ hydrogen bonds resulting in a 3D network structure. In 2, two bromide ions bridge two metal(II) centers to form a dinuclear entity. The dinuclear units in 2 are packed through $\pi ···\pi$ stacking and intermolecular $\text{C}-\text{H}\cdot \cdot \cdot \text{O}$ hydrogen bonds to afford a 2D sheet structure. These 2D sheets self-assemble through intermolecular $\text{C}-\text{H}\cdot \cdot \cdot \text{ Br}$ hydrogen bonds promoting to a 3D network structure. The thermally stable compounds 1 and 2 exhibit intraligand ${}^1(\pi -{\pi }^{\ast })$ fluorescence in DMF solutions at room temperature.

Graphical Abstract

The syntheses, X-ray structural analyses, spectroscopic characterizations, and thermal and luminescence properties of two halidomercury(II) compounds containing a bidentate (N,O) Schiff base chelator are delineated. The interesting variations in nuclearities and crystalline architectures in the compounds are highlighted. Different non-covalent interactions are playing crucial roles in crystal lattice stabilization and superstructure formation. .