Syntheses, Structures, and Properties of Two-Dimensional Alkaline Earth Metal Complexes with Flexible Tripodal Tricarboxylate Ligands

Two new coordination polymers [Ca 3 (bta) 2 (H 2 O) 8 ]·3H 2 O ( 1 ) and Ba 3 (bta) 2 (H 2 O) 8 ( 2 ) were obtained by self-assembly of the corresponding metal carbonate with a flexible tripodal ligand, benzene-1,3,5-triacetic acid (H 3 bta), and their structures were determined by single-crystal X-ray diffraction studies. The results revealed that complex 1 crystallizes in the triclinic space group P 1̄ with a = 8.3045(10) Å, b = 10.4883(10) Å, c = 11.0184(16) Å, α = 102.703(3)°, β = 100.001(4)°, γ = 108.842(7)°, V = 854.36(18) Å 3, and Z = 1; compound 2 is in the monoclinic space group C 2/c with a = 23.4363(8) Å, b = 6.9782(3) Å, c = 21.7150(8) Å, β = 111.4480(10)°, V = 3305.4(2) Å 3, and Z = 4. Complexes 1 and 2 have two-dimensional network structures, and each bta 3- ligand coordinates to Ca(II) or Ba(II) atoms using two of three carboxylate groups adopting different coordination modes: μ 3 -η 2:η 2 -bridging and μ 2 -η 2:η 1 -bridging coordination modes in 1 or μ 3 -η 2:η 2 -bridging and μ 3 -η 2:η 1 -bridging coordination modes in 2 . The noncoordinated carboxylic group forms hydrogen bonds with an adjacent network to generate a three-dimensional structure. The luminescence properties of 1 and 2 were investigated and found that the complexes showed photoluminescence in the solid state at room temperature.