Three 3D coordination polymers based on [1,1′:4′,1′′-terphenyl]-2′,4,4′′,5′-tetracarboxylate demonstrating magnetic properties and selective sensing of Al3+/Fe3+over mixed ions

Abstract

Three three-dimensional (3D) coordination polymers with the formulae [Cd(TPTC)_0.5(H₂O)₂] ·DMA (1), [Co₂(TPTC)(H₂O)_1.5(CH₃OH)_0.5] (2), and [Mn₂(TPTC)(H₂O)(DMA)]·DMA (3) (TPTC = [1,1′:4′,1′′-terphenyl]-2′,4,4′′,5′-tetracarboxylate acid) were solvothermally synthesized. They were characterized by thermogravimetric analyses, IR spectroscopy, X-ray powder diffraction, and single crystal X-ray diffraction. 1 features a 3D porous coordination polymer formed from Cd-carboxylate chains and the TPTC bridges. In 2 and 3, the uniform metal–carboxylate chains with triple bridges, (μ-EO-H₂O)(μ-syn,syn-COO)₂ and (μ-EO-H₂O/DMA)(μ-syn,syn-COO)₂ (EO = end-on), were extended by the TPTC arms. Complex 1 displayed strong fluorescent emission in the visible region. Interestingly, the emission intensities of 1 were increased upon the addition of Al³⁺ and quenched upon the addition of Fe³⁺, even in mixtures of ions. Thus, 1 can act as a useful material for sensing Fe³⁺ and Al³⁺ ions. The magnetic studies of 2 and 3 show that antiferromagnetic interactions between the Co(II) and Mn(II) centers exist.