Two cluster-based metal–organic frameworks with selective detection of Hg2+ ion and magnetic properties

Abstract

Two cluster-based metal–organic frameworks {[Cd₅L₄Br₁₀]·2(CH₃)₂NH}_n (1) and {[Mn^III₃OL(TA)₃]F·sol}_n (2) (L = 1,3,5-tris(benzimidazol-1-ylmethyl)-2,4,6-trimethylbenzene, TA = terephthalate anion) containing a semi-rigid tribenzimidazol-based ligand were synthesized and characterized. Single crystal X-ray analyses show that the structure of 1 contains pentanuclear cadmium clusters with an interesting four-fan shape, in which each μ₂-Br interlinks two crystallographically unique Cd atoms, while 2 contains a trimanganese cluster with three Mn³⁺ ions present in an equilateral triangle distribution. Furthermore, 1 exhibits highly selective fluorescent detection of trace Hg²⁺, with the detection limit of 5.26 × 10⁻⁷ M⁻¹. 2 shows antiferromagnetic interactions between Mn³⁺ ions.