Subtle structure and fluorescence signal changes of four Hg-containing complexes: Influence of the solvents and the halide ions

Four Hg(II)-containing complexes based on methylenebis(1,1′-benzimidazole) (mbbz), namely, [HgCl2(mbbz)]n (1), [HgBr2(mbbz)]n (2), [HgI2(mbbz)]n (3) and [HgI2(mbbz)]3 (4) have been synthesized and structurally characterized. Single-crystal X-ray diffraction reveals that complexes 1, 2 and 3 are isostructural exhibiting the 1-D double helical chain structures. After changing the solvent media, we obtained a trinuclear cage-like structure 4, which is isomeric with 3. Both experimental results and the theoretical calculation proved that the solvent is crucial to the structure of complexes. The fluorescence properties of the four complexes are also investigated and it is apparent that fluorescence intensity decreases as the atomic weight increases in the order of Cl−, Br− and I−. The subtle structure and fluorescence signal changes of these complexes indicate that both the solvents and halide anions have remarkable impact on the resultant complexes.