Supramolecular coordination polymers of La(III), Ce(III), Sm(III), Gd(III) and Eu(III) decorated with rigid 5-hydroxy-1,3-benzenedicarboxylate and flexible hexane-1,6-dicarboxylate linkers: Syntheses, structures, DFT study, luminescence and magnetic properties

Abstract

Five new coordination polymers (CPs) with the formula [Ln (hip) (adip)0.5(H2O)2]n·nH2O [Ln=La (1), Ce (2), Sm (3) and Gd (4)] and [Ln2(hip)2 (adip)(H2O)4]n·2nH2O [Ln=Eu (5)] were synthesized by self-assembly of lanthanide salts with rigid [5-hydroxyisophthalic acid (H2hip)] and flexible [adipic acid (H2adip)] linkers under solvothermal condition. The CPs 1–4 crystallizes in monoclinic C2/c space group, whereas CP 5 has triclinic P1¯ space groups respectively. The CPs 1–4 exhibit 1D linear ladder shaped extension with the linkage of lanthanide carboxylate chains having the backbone of H2hip and H2adip ligands, whereas CP 5 shows linear orthogonally twisted ladder shaped chains. The 1D linear ladder chains are grafted into three dimensional (3D) supramolecular frameworks via significant π–π and hydrogen bonding interactions. The DFT calculations support structures adopted by polymers. The CPs 3 (Sm) and 5 (Eu) emit strong ligand sensitized characteristic f–f luminescence emission. The CP 4 exhibit weak ferromagnetic interactions at low temperatures.