pH Dependent Structural Diversity of Metal Complexes with 5-(4H-1,2,4-Triazol-4-yl)benzene-1,3-dicarboxylic Acid

A ligand 5-(4H-1,2,4-triazol-4-yl)benzene-1,3-dicarboxylic acid (H2L) with N- and O-donors was successfully applied to construct a series of coordination complexes [Cu3(μ3-OH)2(HL)4]n (1), [Co(HL)2(H2O)4]·3H2O (2), [Ni(HL)2(H2O)4]·3H2O (3), [Mn(HL)2]n (4), {[Cu2(L)2(μ-OH2)2]·3H2O}n (5), {[Co2(L)2(μ-OH2)2]·3H2O}n (6), {[Ni2(L)2(μ-OH2)2]·3H2O}n (7), and {[Mn(L)(μ-OH2)]·2H2O}n (8) under hydrothermal conditions. By adjusting the reaction pH, H2L ligand is partially deprotonated to give HL– form in 1–4 and completely deprotonated to afford L2– form in 5–8. The structural analyses revealed that complex 1 is a three-dimensional (3D) (3,3,5,6)-connected framework with Point (Schlafli) symbol of (4.6.8)2(42.65.83)2(42.66.86.10)(42.6)2, while 2 and 3 are discrete mononuclear complexes which are extended by hydrogen bonds to form 3D frameworks. The (3,6)-connected 3D framework of 4 is defined as a metal–organic replica of anatase (ant) net with Point (Schlafli) symbol of (42.6)2(44.62.88.10). Complexes 5–7 are isost...