AUTHOR=Hussain Sajjad , Chen Xuenian , Harrison William T. A. , Ahmad Saeed , Elsegood Mark R. J. , Khan Islam Ullah , Muhammad Shabbir 

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

JOURNAL=Frontiers in Chemistry

VOLUME=7

YEAR=2019

URL=https://www.frontiersin.org/journals/chemistry/articles/10.3389/fchem.2019.00260

DOI=10.3389/fchem.2019.00260

ISSN=2296-2646

ABSTRACT=<p>Five new Lanthanide(III) complexes of malonic acid (HOOC-CH<sub>2</sub>-COOH); {[Gd(C<sub>3</sub>H<sub>2</sub>O<sub>4</sub>)(H<sub>2</sub>O)<sub>4</sub>]·NO<sub>3</sub>}<sub><italic>n</italic></sub> (<bold>1</bold>), {[Tb(C<sub>3</sub>H<sub>2</sub>O<sub>4</sub>)(H<sub>2</sub>O)<sub>4</sub>]·NO<sub>3</sub>}<sub><italic>n</italic></sub> (<bold>2</bold>), {[Ho(C<sub>3</sub>H<sub>2</sub>O<sub>4</sub>)(H<sub>2</sub>O)<sub>4</sub>]·NO<sub>3</sub>}<sub><italic>n</italic></sub> (<bold>3</bold>), [Er(C<sub>3</sub>H<sub>2</sub>O<sub>4</sub>)(C<sub>3</sub>H<sub>3</sub>O<sub>4</sub>)(H<sub>2</sub>O)<sub>2</sub>]<sub><italic>n</italic></sub> (<bold>4</bold>), and {[Eu<sub>2</sub>(C<sub>3</sub>H<sub>2</sub>O<sub>4</sub>)<sub>2</sub>(C<sub>3</sub>H<sub>3</sub>O<sub>4</sub>)<sub>2</sub>(H<sub>2</sub>O)<sub>6</sub>]·4H<sub>2</sub>O}<sub><italic>n</italic></sub> (<bold>5</bold>) were synthesized and characterized by elemental, infrared spectral, and thermal analyses. The structures of compounds <bold>1</bold>–<bold>5</bold> were determined by single crystal X-ray diffraction technique. The X-ray analysis reveals that compounds <bold>1</bold>, <bold>2</bold>, and <bold>3</bold> are isostructural and crystallized in the orthorhombic space group <italic>Pmn</italic>2<sub>1</sub>. The lanthanide(III) ions are coordinated by four carboxylate and four water oxygen atoms adopting a distorted square antiprism geometry. The LnO<sub>8</sub> square antiprisms are linked into infinite layers by malonate (C<sub>3</sub>H<sub>2</sub><inline-formula><mml:math id="M1" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msubsup><mml:mrow><mml:mtext>O</mml:mtext></mml:mrow><mml:mrow><mml:mn>4</mml:mn></mml:mrow><mml:mrow><mml:mn>2</mml:mn><mml:mo>-</mml:mo></mml:mrow></mml:msubsup></mml:math></inline-formula>) dianions sandwiching sheets of nitrate counter ions. Compound <bold>4</bold> contains ErO<sub>8</sub> square antiprisms linked into a two-dimensional network by hydrogen malonate (C<sub>3</sub>H<sub>3</sub><inline-formula><mml:math id="M2" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msubsup><mml:mrow><mml:mtext>O</mml:mtext></mml:mrow><mml:mrow><mml:mn>4</mml:mn></mml:mrow><mml:mrow><mml:mo>-</mml:mo></mml:mrow></mml:msubsup></mml:math></inline-formula>) anions and malonate dianions. The europium complex, <bold>5</bold> is dinuclear having the two europium(III) ions (Eu1 and Eu2) bridged by carboxylate groups of hydrogen malonate ligands. The europium ions in <bold>5</bold> 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 <bold>1–5</bold> 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 <bold>1–4</bold> are in good agreement with those expected for the free ions, while the data for <bold>5</bold> indicates that low-lying excited states contribute to the observed moment. The compound <bold>1</bold> 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.</p>