Solvothermal self-assembly of seven lanthanide(III) coordination polymers using diphenic acid and 1,10-phenanthroline as co-ligands: Efficient detection of picric acid and Cu2+ ions in aqueous medium by europium based coordination polymer

Abstract

Lanthanide based coordination polymers (Ln-CPs) act as efficient chemo-sensors on interaction with the target analyte and show a detectable variation in their optical properties. This work demonstrates interaction of metal ions and nitroaromatic compounds with Eu based CP resulting in quenching of luminescence emission intensity. Approaching towards this aim, seven iso-structural lanthanide coordination polymers having the formulae, [Ln(diphen)1.5(1,10-phen)(H2O)] where Ln = Sm (1), Gd (3), Dy (5), {[Ln(diphen)1.5(1,10-phen)(H2O)]·OH} Ln = Eu (2), Er (7) and {[Ln(diphen)1.5(1,10-phen)(H2O)]·CH3CN·H2O} Ln = Gd (4), Ho (6) (diphen = diphenic acid, 1,10-phen = 1,10 Phenanthroline), were assembled solvothermally by using diphenic acid and 1,10-Phenanthroline as ligands. These lanthanide coordination polymers were characterized by Single-crystal X-ray diffraction, FTIR, Powder X-ray diffraction, Thermogravimetric analysis, UV–visible spectroscopy and Photoluminescence. The CPs 1–7 possess one-dimensional (1D) infinite chain-like structures which crystallize in the monoclinic C2/c space group. The photoluminescence properties of CP 2 exhibit its sensing ability to detect some toxic nitroaromatic compounds and d-block metal ions. However, CP 2 shows highly sensitive behavior for the recognition of Cu2+ and picric acid as indicated by efficient luminescence quenching with the low limit of detection. Other metal ions (viz., Cr3+, Cu2+, Co2+, Zn2+, Mn2+, Ni2+, Cd2+, and Hg2+), and nitro compounds (viz., PA, m-DNB, p-NP, p-NA and NB) were also screened for sensing potential of CP 2.