Abstract
Five new Lanthanide(III) complexes of malonic acid (HOOC-CH2-COOH); {[Gd(C3H2O4)(H2O)4]·NO3}n (1), {[Tb(C3H2O4)(H2O)4]·NO3}n (2), {[Ho(C3H2O4)(H2O)4]·NO3}n (3), [Er(C3H2O4)(C3H3O4)(H2O)2]n (4), and {[Eu2(C3H2O4)2(C3H3O4)2(H2O)6]·4H2O}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 Pmn21. The lanthanide(III) ions are coordinated by four carboxylate and four water oxygen atoms adopting a distorted square antiprism geometry. The LnO8 square antiprisms are linked into infinite layers by malonate (C3H2) dianions sandwiching sheets of nitrate counter ions. Compound 4 contains ErO8 square antiprisms linked into a two-dimensional network by hydrogen malonate (C3H3) 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.
Highlights
A number of reports have been published on the synthesis and structures of malonate-containing lanthanide polymers, which describe the versatility of the bonding modes of the malonate group (Hansson, 1973a,b; Wenmei et al, 1992; Marrot and Trombe, 1994; Benmerad et al, 2000; Hernández-Molina et al, 2000, 2002, 2003; Doreswamy et al, 2005; Cañadillas-Delgado et al, 2006; Zhang et al, 2007; Fang et al, 2008; Chrysomallidou et al, 2010; Silva et al, 2010; Jin et al, 2012; Delgado et al, 2016)
Delgado et al reported a detailed overview on the crystal structures and topologies of these systems, as well as the molecular structures assembled by hydrogen-bonding from low-dimensional entities to higher-dimensional supramolecular architectures
In order to enhance the fundamental knowledge of structural chemistry of lanthanide-carboxylate frameworks and in view of our continuous interest in this direction (Hussain et al, 2014, 2015a,b, 2018), we report here the syntheses, characterization, crystal structures, photoluminescence, and magnetic properties of five novel lanthanide coordination polymers involving malonate ligand
Summary
In the modern hi-tech society, lanthanide-based metal-organic frameworks find a wide range of applications in several cuttingedge scientific fields, such as contrast agents (Caravan et al, 1999; Wahsner et al, 2019), catalysis (Shibasaki and Yoshikawa, 2002; He et al, 2013; Pagis et al, 2016), gas storage and purification (Reineke et al, 1999; He et al, 2013; Roy et al, 2014), magnetism (Woodruff et al, 2013; Zhu et al, 2016; Gao et al, 2018), and optoelectronic devices (Kenyon, 2002; Armelao et al, 2010; Heffern et al, 2013). The lanthanide(III) ions are coordinated by four carboxylate and four water oxygen atoms adopting a distorted square antiprism geometry. The europium complex, 5 is dinuclear having the two europium(III) ions (Eu1 and Eu2) bridged by carboxylate groups of hydrogen malonate ligands.
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