One-dimensional coordination polymers of whole row rare earth tris-pivalates

Diverse Coordination Chemistry of the Whole Series Rare-Earth L-Lactates: Synthetic Features, Crystal Structure, and Application in Chemical Solution Deposition of Ln2O3 Thin Films

Rare-earth (RE, Ln) carboxylates are widely studied as precursors of RE oxide-based nanomaterials; however, no systematic studies of RE L-lactates (HLact = 2-hydroxypropanoic acid) have been reported to date. In the present work, a profound structural investigation of RE L-lactates is carried out. A family of RE lactate complexes of the general formula LnLact3∙nH2O (Ln = La, Ce-Nd, Sm-Lu, Y; n = 2-3) are synthesized and characterized by CHN, TGA, and FTIR as well as by powder and single-crystal XRD methods.The existence of four novel structural types (1-Ln-4-Ln) is revealed. Compounds of the 1-Ln type (Ln = La, Ce, Pr) exhibit a chain polymeric structure, whereas 2-Ln-4-Ln compounds are molecular crystals consisting of dimeric (2-Ln; Ln = La, Ce-Nd) or monomeric (3-Ln-Ln = Sm-Lu, Y; 4-Ln-Ln = Sm-Gd, Y) species. The crystal structures of 1-Ln-4-Ln compounds are discussed in terms of their coordination geometry and supramolecular arrangement. Solutions of yttrium and lanthanum lactates with diethylenetriamine are applied for the chemical deposition of Y2O3 and La2O3 thin films.

Partially Ordered Lanthanide Carboxylates with a Highly Adaptable 1D Polymeric Structure

A new family of 14 isostructural [Ln(piv)₃(en)]_∞ lanthanide pivalate (piv⁻, 2,2-dimethylpropanoate) complexes with ethylenediamine (en) was synthesized by a topology-preserving transformation from 1D coordination polymers [Ln(piv)₃]_∞. The crystal structures of the compounds were determined by single-crystal and powder X-ray diffraction, which demonstrated that despite the regular ligand arrangement within the chains, the latter are intricately packed within the partially ordered crystal, as only two of four ligands are strictly bound by the translational symmetry. The peculiarities of the lanthanide coordination environment were explored by total X-ray scattering with pair distribution function analysis. Periodic DFT calculations revealed the chain stabilization by intrachain H-bonds and weak interchain interactions. Noticeably, the energy difference was infinitesimally small even between the two considered extreme variants of ordered packing, which is in line with the disturbed packing order of the chains. The luminescent properties of Eu and Tb complexes were investigated in order to prove the energy transfer between lanthanide ions within the heterometallic complex. This opens up the prospect of creating new materials for optical applications. The heterometallic compound Eu_0.05Tb_0.95(piv)₃(en) was synthesized, and was found to demonstrate temperature-dependent luminescence with a linear dependence of the thermometric parameter I(Eu)/I(Tb) within the temperature range from −80 °C to 80 °C, and had a maximum relative sensitivity value of 0.2%/K.

Single-Source Precursors for Chemical Solution Deposition of Up-Converting NaLnF4 Thin Films

Novel single-source precursors based on sodium and lanthanide pentafluoropropionates have been developed for chemical solution deposition of NaLnF4 thin films (Ln = Y, Yb, Er, Tm). A series of [Ln2(pfp)6Qn] (Q = H2O, diglyme) and mixed-metal NaLn(pfp)4Qn were synthesized and characterized by X-ray diffraction (XRD) and thermogravimetric analysis (TG-DTA). Thermal decomposition of individual Na(pfp) and Ln(pfp)3 occurs at different temperatures while single-source NaLn(pfp)4 decomposes with the transformation to NaLnF4 in a single stage at 280 °C. Further crystallization of NaLnF4 was studied by variable-temperature powder XRD, which shows two phase transformations from cubic NaLnF4 to hexagonal NaLnF4 at 310 °C and back to a high-temperature cubic phase at 560 °C. The thin films of NaY0.78Yb0.2Er0.02F4 prepared by the dip-coating technique on Al2O3 substrates showed intense up-converting luminescence in green and blue regions under 980 nm excitation.

A Family of Lanthanide Hydroxo Carboxylates with 1D Polymeric Topology and Ln4 Butterfly Core Exhibits Switchable Supramolecular Arrangement

The unique family of coordination polymers [Ln₄(OH)₂(piv)₁₀(H₂O)₂]_∞ of 11 lanthanides (Ln = La-Er) has been prepared by a simple solution method based on controlled hydrolysis. The ribbon-like polymeric structure consisting of connected tetranuclear clusters and supported by pivalate ligands and a framework of H-bonds has been revealed by single-crystal X-ray diffraction. While the compounds demonstrate similar PXRD patterns and unit cell parameters, the joint single-crystal XRD and pair distribution function data suggest the significant local structure change along the lanthanide series. The compounds exist as two packing polymorphs (α and β) with similar ribbon geometry, but different supramolecular arrangement of the ribbons. Dehydration of either polymorph does not disturb the tetranuclear core but leads to a translational symmetry loss along the ribbon and a transformation of the 3D-ordered crystal into a 2D-ordered mesostructure. Rehydration of the mesostructure leads to the β polymorph (except La and Ce), allowing the deliberate switching between the polymorphs via dehydration-rehydration evidenced by means of powder X-ray diffraction, pair distribution function analysis, and density functional theory calculations. Ab initio calculations reveal significant magnetic anisotropy of Ln³⁺ ions with ferro- and antiferromagnetic interactions within tetranuclear [Ln₄(OH)₂(piv)₁₀(H₂O)₂] species. Magnetic susceptibility measurements demonstrated antiferromagnetic coupling, slow magnetic relaxation for Dy, Ho, and Er complexes, and field-induced single-chain magnetism for the Dy compound.