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)(Py 2 TTz) 1.5 (H 2 O)]·2H 2 O·DMF ( 1 ) and [Co(oba)(Py 2 TTz)(H 2 O) 4 ]·2H 2 O ( 2 ) have been synthesized under solvothermal conditions [H 2 oba = 4,4′-oxybis(benzoic acid) and Py 2 TTz = 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) Å 3 , Z = 8. Compound 2 crystallizes in the monoclinic crystal system, space group C 2/ c , with a = 33.816(3), b = 6.2697(6), c = 13.5821(13) Å, β = 96.393(3)°, V = 2861.7(5) Å 3 , Z = 4. The oba 2− dianions link two Ni atoms through unidentate carboxylate moieties in a μ 1 − η 1 : η 0 coordination mode. Compound 1 features a three-dimensional (3D) framework structure with Py 2 TTz and oba 2− 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 Py 2 TTz ligands. It is noteworthy that the dicarboxylate ligands oba 2− 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.