Syntheses, structures, and properties of two luminous mercury(II) halide compounds containing a tetradentate N-donor Schiff base

A 1D coordination polymer [Hg2(L)Br4]n (1) and one dinuclear compound [Hg2(L)I4] (2) [L = N,N′-(bis(pyridin-2-yl)benzylidene)ethane-1,2-diamine] are isolated using a 2:1 M ratio of HgBr2/HgI2 and Schiff base (L) in methanol–acetonitrile solution mixture and X-ray crystallographically characterized. Structural analyses show that in 1 1D chain is formed through binucleating bis(bidentate) bridging behavior of L and asymmetric Hg-(μ-Br)2-Hg bridges in an alternate fashion; one terminal bromide unit completes the distorted square pyramidal geometry around each mercury(II). In 2, two mercury(II) centers are connected by bis(bidentate) bridging behavior of L and two iodides bound to each metal(II) center remain as terminal resulting in a discrete dinuclear entity with distorted tetrahedral geometry. Weak intermolecular Hg⋯I and I⋯I interactions in 2 promote dimensionality. In DMF solutions, 1 and 2 display intraligand 1(π–π∗) fluorescence.

► Two mercury(II) halide compounds with a Schiff base are isolated and characterized.
► X-ray structures show interesting variations in coordination motifs and nuclearities.
► Thermogravimetric analyses show their thermal stability and decomposition pattern.
► The compounds display 1(π–π∗) fluorescence in DMF solutions.