Synthesis and characterization of a novel Europium(III) complex with a one-dimensional chain-like structure

Abstract

By means of a solvothermal reaction of isonicotinic acid and europium perchlorate, a novel europium(III) complex, i.e. catena-[tri(μ2-isonicotinato-O,O′)-(biaqua-europium(III))-(triperchlorate)-(monohydrate)], [Eu(HIA)3(H2O)2]n·3n(ClO4)·nH2O (1; HIA ​= ​isonicotinic acid), was obtained. The molecular structure of complex 1 was characterized by single-crystal X-ray crystallography. Complex 1 crystallized in the space group Pī of the triclinic system with a ​= ​9.5500(2), b ​= ​10.9680(3), c ​= ​15.1214(4) Å, α = 104.299(2)°, β = 91.532(2)°, γ = 111.310(2)°, V ​= ​1417.92(6) Å3, C18H21Cl3EuN3O21, Mr ​= ​873.69, Z ​= ​2, Dc ​= ​2.046 ​g/cm3, μ(MoKα) ​= ​2.595 ​mm−1 and F(000) ​= ​864. The europium(III)) ions are coordinated by eight oxygen atoms (of which six come from six HIA ligands and two come from two water molecules) and displays a EuO8 square antiprismatic geometry. The adjacent europium(III) ions are interlinked by four or two μ2-bridging HIA ligands to generate an infinite one-dimensional (1-D) –Eu–(HIA)4–Eu–(HIA)2–Eu–(HIA)4–Eu– chain running along the a axis. The chains are further connected by π···π stacking and hydrogen bonding interactions to yield a three-dimensional (3-D) supramolecular network. Complex 1 exhibits red photoluminescence emission bands at 593 ​nm, 617 ​nm and 699 ​nm, which are originated from the 5D0 → 7F1, 5D0 → 7F2 and 5D0 → 7F4 characteristic transitions of europium(III) ions. It has CIE chromaticity coordinates of (0.5742, 0.3275). A solid-state UV/Vis diffuse reflection spectrum shows that complex 1 has a band gap of 5.02 ​eV with a direct transition process.