Cobalt(II) and nickel(II) complexes based on 2,5-di(pyridine-4-yl)thiazolo[5,4-d]thiazole and dicarboxylate ligands: synthesis, structures and properties

Abstract Two metal coordination polymers [Ni(oba)(Py2TTz)1.5(H2O)]·2H2O·DMF (1) and [Co(oba)(Py2TTz)(H2O)4]·2H2O (2) have been synthesized under solvothermal conditions [H2oba = 4,4′-oxybis(benzoic acid) and Py2TTz = 2,5-di(pyridine-4-yl)thiazolo[5,4-d]thiazole]. Crystals of compound 1 belong to the orthorhombic system, space group Ibam, with a = 38.928(8), b = 7.7113(14), c = 28.508(6) Å, V = 8558(3) Å3, Z = 8. Compound 2 crystallizes in the monoclinic crystal system, space group C2/c, with a = 33.816(3), b = 6.2697(6), c = 13.5821(13) Å, β = 96.393(3)°, V = 2861.7(5) Å3, Z = 4. The oba2− dianions link two Ni atoms through unidentate carboxylate moieties in a μ1 − η1:η0 coordination mode. Compound 1 features a three-dimensional (3D) framework structure with Py2TTz and oba2− ligands. In compound 2, the central cobalt ion is in an octahedral geometry, which is defined by four oxygen atoms from four different coordinated water molecules and two nitrogen atoms from two different Py2TTz ligands. It is noteworthy that the dicarboxylate ligands oba2− with four oxygen atoms do not directly coordinate with the cobalt ion, and only act as a counter-anion. The luminescence properties of 1 and 2 were also investigated.