Syntheses, structures and properties of two dinuclear mercury(II) iodide compounds containing tetradentate tripodal amine/pentadentate N-donor Schiff base: Control of molecular and crystalline architectures by varying ligand matrices

Abstract

Two dinuclear mercury(II) iodide complexes of the types [(L1)Hg(μ-I)HgI3] (1) and [Hg2(L2)(I)4] ⋅H 2O (2) [L1 =tris(2-aminoethyl)amine and L2 = N,N′-(bis-(pyridin-2-yl)benzylidene)diethylenetriamine] have been synthesized and characterized using microanalytical, spectroscopic, thermal and other physicochemical results. Structures of both the compounds are solved by X-ray diffraction measurements. Structural analyses show that one mercury (II) centre in 1 adopts a distorted tetrahedral geometry with an HgI4 chromophore surrounded by four iodides, while the other has a distorted trigonal bipyramidal environment with an HgN4I chromophore bound by four N atoms of L1 and one bridging iodide. Pentadentate Schiff base (L2) in 2 shows unusual binucleating bis(bidentate) behaviour to bind two different mercury(II) centres—Hg1 with an HgN3 I 2 chromophore in a distorted square pyramidal geometry and Hg2 with an HgN2 I 2 chromophore in a tetrahedral environment. Weak intermolecular N–H ⋅⋅⋅I hydrogen bonds in 1 and cooperative C–H ⋅⋅⋅π and π⋅⋅⋅π interactions in 2 promote dimensionalities. The Schiff base complex, 2, shows intraligand (π– π*) fluorescence in DMF solution at room temperature, whereas compound 1 containing tripodal amine is fluorescent-inactive.