Molecular and Polymer Ln2M2 (Ln = Eu, Gd, Tb, Dy; M = Zn, Cd) Complexes with Pentafluorobenzoate Anions: The Role of Temperature and Stacking Effects in the Structure; Magnetic and Luminescent Properties

Abstract

Varying the temperature of the reaction of [{Cd(pfb)(H2O)4}+n·n(pfb)−], [Ln2(pfb)6(H2O)8]·H2O (Hpfb = pentafluorobenzoic acid), and 1,10-phenanthroline (phen) in MeCN followed by crystallization resulted in the isolation of two type of products: 1D-polymers [LnCd(pfb)5(phen)]n·1.5nMeCN (Ln = Eu (I), Gd (II), Tb (III), Dy (IV)) which were isolated at 25 °C, and molecular compounds [Tb2Cd2(pfb)10(phen)2] (V) formed at 75 °C. The transition from a molecular to a polymer structure becomes possible because of intra- and intermolecular interactions between the aromatic cycles of phen and pfb from neighboring tetranuclear Ln2Cd2 fragments. Replacement of cadmium with zinc in the reaction resulted in molecular compounds Ln2Zn2 [Ln2Zn2(pfb)10(phen)2]·4MeCN (Ln = Eu (VI), Tb (VIII), Dy (IX)) and [Gd2Zn2(pfb)10(H2O)2(phen)2]·4MeCN (VII). A new molecular EuCd complex [Eu2Cd2(pfb)10(phen)4]·4MeCN (X)] was isolated from a mixture of cadmium, zinc, and europium pentafluorobenzoates (Cd:Zn:Ln = 1:1:2). Complexes II-IV, VII and IX exhibit magnetic relaxation at liquid helium temperatures in nonzero magnetic fields. Luminescent studies revealed a bright luminescence of complexes with europium(III) and terbium(III) ions.

Single-Ion Magnet and Photoluminescence Properties of Lanthanide(III) Coordination Polymers Based on Pyrimidine-4,6-Dicarboxylate

“…Among all these interesting properties, magnetism and luminescence have gained an increasing interest due to the potential of CPs to behave as single-molecule magnets (SMMs) [23][24][25][26] and solids-state lighting materials (organic light-emitting diodes, OLEDs) [27], by taking advantage of previous properties, respectively. Inside this sorts of materials, those built up from the coordination of organic ligands to lanthanide(III) ions have shown enormous potential during the last years owing to their particular electronic structure, which being hardly disturbed by the ligand field in the crystal structure, affords the aforementioned properties to the resulting CP [28][29][30][31].…”

Cadmium-Inspired Self-Polymerization of {LnIIICd2} Units: Structure, Magnetic and Photoluminescent Properties of Novel Trimethylacetate 1D-Polymers (Ln = Sm, Eu, Tb, Dy, Ho, Er, Yb)

“…In all these examples, as in the present study, the high ionic radius of Cd II and its ability to form a large number of coordination bonds at least contributed to the polymerization of Cd x Ln 2 ( x = 1 or 2) moieties and, in some cases, were the main driving force behind the formation of coordination polymers. As expected, molecular complexes with Cd x Ln y pivalate cores were formed upon the addition of “capping ligands”, which blocked the coordination sites of Cd II ions and prevented the formation of coordination bonds between these ions and pivalate oxygen atoms from the neighboring units [ 39 , 41 , 43 , 48 , 49 , 50 ]. Among the heterometallic Cd-Ln carboxylates that do not contain specific capping ligands, only the compound [Cd 2 Eu(bzo) 6 (NO 3 )(MeCN) 2 (THF) 2 ] (bzo − = 3,5-di- tert -butylbenzoate anion) had a molecular structure, and the coordination positions of the terminal Cd II ions were blocked by coordinated THF and MeCN molecules [ 51 ].…”

“…Thus, cadmium ions induce the polymerization of Cd 2 Ln fragments with the formation of polymeric Ln-Cd pivalates. A similar situation was previously observed for complexes [Ln 2 M 2 (pfb) 10 (phen) 2 ] (Ln = Eu, Gd, Tb, Dy; M = Zn, Cd; pfb - is the anion of pentafluorobenzoic acid): Ln 2 Zn 2 complexes had a discrete molecular structure, while the Ln 2 Cd 2 species were molecular or 1D polymers as a result of changes in the functionality of bridging carboxylate groups and π-π interactions between aromatic fragments (pfb anion and phen ligand) of neighboring tetranuclear fragments [ 48 ]. Similarly, 1D polymer [CdEu 2 (pfb) 8 (Etypy)(H 2 O) 2 ] n (Etypy = 3-ethynylpyridine) was reported, where Cd II ion adopted coordination number 7 and could be bound in the chain [ 39 ].…”

Structure and assembly mechanism of a centipede-shaped high-nuclear Dy14Cu12heterometallic nanocluster

“…Lanthanide-containing high-nuclear clusters are attracting increasing interest due to their aesthetic nano-scaled structures and their potential applications in fields such as catalysis, information storage, optical devices, and bioactivity. [1][2][3][4][5][6][7] However, reasonable design and assembly of these clusters are still a huge challenge due to diverse coordination configurations of lanthanide ions and their variable self-assembly pathways. The common method is to assemble metal ions into the anticipated structures using well-designed organic ligands with a special geometry and size and multiple coordination groups which contribute a significant role in the construction of high-nuclear heterometallic clusters.…”