Synthesis, Thermal, Structural Analyses, and Photoluminescent Properties of a New Family of Malonate-Containing Lanthanide(III) Coordination Polymers

Five new Lanthanide(III) complexes of malonic acid (HOOC-CH(2)-COOH); {[Gd(C(3)H(2)O(4))(H(2)O)(4)]·NO(3)}(n) (1), {[Tb(C(3)H(2)O(4))(H(2)O)(4)]·NO(3)}(n) (2), {[Ho(C(3)H(2)O(4))(H(2)O)(4)]·NO(3)}(n) (3), [Er(C(3)H(2)O(4))(C(3)H(3)O(4))(H(2)O)(2)](n) (4), and {[Eu(2)(C(3)H(2)O(4))(2)(C(3)H(3)O(4))(2)(H(2)O)(6)]·4H(2)O}(n) (5) were synthesized and characterized by elemental, infrared spectral, and thermal analyses. The structures of compounds 1–5 were determined by single crystal X-ray diffraction technique. The X-ray analysis reveals that compounds 1, 2, and 3 are isostructural and crystallized in the orthorhombic space group Pmn2(1). The lanthanide(III) ions are coordinated by four carboxylate and four water oxygen atoms adopting a distorted square antiprism geometry. The LnO(8) square antiprisms are linked into infinite layers by malonate (C(3)H(2) [Formula: see text]) dianions sandwiching sheets of nitrate counter ions. Compound 4 contains ErO(8) square antiprisms linked into a two-dimensional network by hydrogen malonate (C(3)H(3) [Formula: see text]) anions and malonate dianions. The europium complex, 5 is dinuclear having the two europium(III) ions (Eu1 and Eu2) bridged by carboxylate groups of hydrogen malonate ligands. The europium ions in 5 are nine-coordinate and exhibit a distorted monocapped square antiprism geometry. All the structures are consolidated by O–H⋯ O hydrogen bonds. The photoluminescence spectra of 1–5 exhibit characteristic emissions in the visible region. The IR spectra and thermal data are consistent with the structural results. The room-temperature effective magnetic moments for 1–4 are in good agreement with those expected for the free ions, while the data for 5 indicates that low-lying excited states contribute to the observed moment. The compound 1 was further subjected to quantum computational calculations to explore its optoelectronic properties including; density of states (DOS), dielectric function, refractive index, extinction coefficient, and absorption spectrum, to highlight the possible applications of such materials in the optoelectronics.