Hg(ii) supramolecular isomers: structural transformation and photoluminescence change

Abstract

Two pairs of Hg(II) supramolecular isomers, [HgBr₂(GAG-L)]_∞ [L = N,N′-di(3-pyridyl)adipoamide], 1, and [HgBr₂(AAA-L)]_∞, 2, and [HgI₂(GAG-L)]_∞, 3, and [HgI₂(AAA-L)]_∞, 4, have been successfully synthesized by various methods and structurally characterized by single-crystal X-ray crystallography. Complex 1 forms a one-dimensional (1D) meso-helical chain, 2 and 4 exhibit normal 1D helical chains, while 3 displays a 1D sinusoidal chain. The L ligands in 1 and 3 display GAG trans syn–syn conformation, while those in 2 and 4 adopt the AAA trans syn–syn conformation. In addition, complexes 1 and 3 can be irreversibly transformed to 2 and 4, respectively, under simple heating or hydrothermal condition. Moreover, complex 1 exhibits intense violet-blue photoluminescence in the solid state, whereas 2 and 3 display weak broad emissions in the blue-green region and 4 shows undetectable emission intensity.