Syntheses and crystal structures of new dinuclear lanthanide complexes based on 3-(4-hydroxyphenyl)propanoic acid: Hirshfeld surface analyses and photoluminescence sensing

A series of ten new lanthanide complexes, [Ln2(PA)6(bipy)2]·4H2O·2bipy (Ln = Eu 1, Tb 2, Ce 3, Gd 4, Nd 5, Pr 6, Sm 7, Yb 8) and [Ln2(PA)6(bipy)2]·4H2O (Ln = Ce 9 and Er 10) (HPA = 3-(4-hydroxyphenyl)propanoic acid and bipy = 2,2'-bipyridine), have been synthesized and characterized using microanalyses, FTIR and single crystal X-ray diffraction. The complexes 1-8 and 10 are isostructural and contain two crystallographically equivalent Ln3+ ions having coordination number 9 with distorted monocapped square-antiprism geometries in which the PA ligand adopts bridging, bidentate chelating, and tridentate chelating bridging modes to coordinate with Ln3+ ions, while 9 possess tricapped trigonal prism geometry where only bridging, bidentate chelating modes are adopted by PA ligands. All the complexes display 2D supramolecular layered framework held by weak C-H···π, π···π and O-H···O intermolecular interactions. These interactions have been validated with the aid of Hirshfeld surface analyses. Additionally, emission studies indicated that amongst all the complexes, 1 and 2 can act as luminescent sensors for the detection of nitrobenzene and Cu2+ ion. The limit of detection (LOD) for both 1 and 2 against nitrobenzene are 3.66 and 3.71 ppm, respectively while against Cu2+ ion, they are 2.11 and 2.99 ppm for 1 and 2, respectively.