Using alkaline-earth metal ions to tune structural variations of 1,3,5-benzenetricarboxylate coordination polymers.

Alkaline-earth metal ions were used to tune four new heterometallic frameworks, {[Cd(2.07)Mg(0.93)(BTC)(2)(H(2)O)(4)]·2H(2)O}(n) (1), {[Cd(2)Ca(BTC)(2)(H(2)O)(4)]·2H(2)O}(n) (2), {[Cd(2)Sr(BTC)(2)(H(2)O)(5)]·H(2)O}(n) (3) and [Cd(6)Ba(3)(BTC)(3)(H(2)O)(10)](n) (4) (H(3)BTC = 1,3,5-benzenetricarboxylic acid), synthesized from H(3)BTC and the corresponding metal salts. Single-crystal X-ray analysis shows that compound 1 is a three-dimensional (3D) framework based on heterometallic Cd-O-Cd-O-Mg inorganic chain subunits, compounds 2 and 3 are basically isostructural and feature a 3D framework based on Ca(II) or Sr(II) polyhedrons decorated with Cd-O-Cd inorganic chains. Compound 4 is a 3D framework templated by disordered inorganic hydrate Ba(II) ions, and also features inorganic Cd-O-Cd chains, which are connected together through corner sharing with the {Cd(1)O(6)} polyhedrons by {Ba(1)O(6)} polyhedrons, giving rise to a rare heterometallic 3D inorganic skeleton. Moreover, the solid-state fluorescence of compounds 1-4 and NLO properties of compounds 2-4 have also been investigated at room temperature.