Syntheses, structures, and properties of two-dimensional alkaline earth metal complexes with flexible tripodal tricarboxylate ligands

Two new coordination polymers [Ca-3(bta)(2)(H2O)(8)].3H(2)O (1) and Ba-3(bta)(2)(H2O)(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 (1) over bar with a = 8.3045(10) Angstrom, b = 10.4883(10) Angstrom, c = 11.0184(16) Angstrom, a = 102.703(3)degrees, beta = 100.001(4)degrees, gamma =.108.842(7)degrees, V = 854.36(18) Angstrom(3), and Z = 1; compound 2 is in the monoclinic space group C2/c with a = 23.4363(8) Angstrom, b = 6.9782(3) Angstrom, c = 21.7150(8) Angstrom, beta = 111.4480(10)degrees, V = 3305.4(2) Angstrom(3), and Z = 4. Complexes I 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: mu(3)-eta(2):eta(2)-bridging and mu(2)-eta(2):eta(1)-bridging coordination modes in 1 or mu(3)-eta(2):eta(2)-bridging and mu(3)-eta(2):eta(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.