Magnetic and Luminescent Properties of Isostructural 2D Coordination Polymers Based on 2-Pyrimidinecarboxylate and Lanthanide Ions

Abstract

<jats:p>A couple of isostructural coordination polymers with the general formula [Ln4(pymca)4(AcO)8]n have been obtained from reactions between pyrimidine-2-carboxylate (pymca) ligand and rare-earth ions (Ln = Dy (1), Nd (2)). These two-dimensional compounds have been characterized and the crystal structures have been solved by single-crystal X-ray diffraction technique, resulting in layers along the bc plane based on pymca and acetate anions that act as bridging ligands between metal atoms. Given that pymca and acetate anions possess carboxylate and hetero-nitrogen groups, it is possible to build a coordination polymer whose metal centers have a nine coordination. Furthermore, static and dynamic magnetic measurements of compound 1 reveal the lack of single molecule-magnet (SMM) behavior in this system due to the following two effects: (i) the ligand field does not stabilize magnetic ground states well separated from excited states, and (ii) anisotropy axes are not collinear, according to results with Magellan software. On another level, luminescent properties of compounds 1 and 2 are attributed to singlet π-π* transitions centered on pymca ligand as corroborated by time-dependent density functional theory (TD-DFT) calculations.</jats:p>

Metal-Organic Framework vs. Coordination Polymer—Influence of the Lanthanide on the Nature of the Heteroleptic Anilate/Terephtalate 3D Network

“…Most of the ligands used are carboxylates derivatives due to their hard base behavior [2]. Among them, oxalate [15], succinate [16] and some other aliphatic linkers were used [17], but most of the reported examples contain aromatic linkers such as squarate [18,19], 1,4-benzenedicarboxylate (usually called terephthalate) [20], 1,3,5-benzene-tricarboxylate [21] or more extended π-conjugated linkers [22,23], and more recently imidazole [24][25][26], pyridine [27] or pyrimidine-based bridging ligands [28]. Alternatively, derivatives of 2,5-dihydroxy-1,4-benzoquinone, usually called anilates, have been extensively used in the last decade to prepare CPs with either transition metal ions [29,30] or lanthanides [31].…”

A 1D helical eco-friendly Mn(II) halide coordination polymer: Luminescent properties involving resonant energy transfer and magnetic characterization

“…In particular, luminescent halide-based coordination polymers are identified as a new and ideal candidate for WLEDs due to their wide range of structural diversity and exotic optical functionalities. Their various self-assembly modes, multiple emitting centers, and their friendly environments, that benefit from the combination of organic ligands and non-toxic metal nodes, makes them a highly emissive candidate [25][26][27][28][29][30][31] . Besides, the short coordination links between organic ligands and inorganic entities as well as the nature of the organic linkers will foster the appearance of resonance energy transfer (FRET) which is the main responsible for the WL emission process 33 .…”

Exploring the Slow Magnetic Relaxation of a Family of Photoluminescent 3D Lanthanide–Organic Frameworks Based on Dicarboxylate Ligands

“…The problem lies on the fact that lanthanide elements have very high and variable coordination numbers, which brings us to the issue that the coordination geometries and the LnOF topologies are difficult to control [15]. Instead, once a dominant architecture is achieved and the factors affecting the structural variability are isolated [16][17][18], it allows obtaining an isostructural family of lanthanide-based materials in which a comparative analysis of a specific property may be accomplished.…”