Structure and magnetic properties of two new lanthanide complexes with the 1-((E)-2-pyridinylmethylidene)semicarbazone ligand

High-yield synthesis of heavy rare earth(III) anhydrous solvates: known, new, and unexpected products

Ten anhydrous rare-earth (RE) chloride solvates were prepared by dehydration of RECl3·6H2O with triethylorthoformate (teof) in O-donor solvents as an accessible and general synthetic route. Reactions are quick, safe, mild, easily reproducible, and cost-effective. They run at room temperature or under reflux to give high-yield, pure crystalline products that are either new, such as [Gd2Cl4(μ-Cl)2(PriOH)6] (1) and [{GdCl(μ-Cl)2(thf)2}∞] (2), or obtained for the first time from teof, such as [GdCl3(thf)4] (3), trans-[MCl2(thf)5]trans-[MCl4(thf)2], M = Gd (4), Dy (6), and Y (7), [YbCl3(thf)3] (8), and [MCl3(dme)2], M = Gd (5), Dy (9), and Er (10). Structural and spectroscopic characterization is presented for all products, and variable-temperature magnetic susceptibility data are discussed for the Dy3+ complexes 6 and 9. The latter behaves as a field-induced single-ion magnet for which theoretical (ab initio) and experimental data allowed a non-trivial assignment of overlapping high- (Orbach, Ueff 139 cm-1) and low-temperature (Raman, weff 46.8(2) cm-1) magnetic relaxation mechanisms (1 kOe field). Besides the main products, unanticipated Lewis and redox reactivity led to serendipitous 11, [({Gd3Cl4(μ-Cl)4(μ-H3CCOO)(C3H8O2)(PriOH)4}·PriOH)∞], and 12, [{(thf)2Cl2Gd(μ-Cl)2(μ3-O2)Gd(thf)3}2]·3thf, whose formation is discussed. The final RE3+ anhydrous complexes serve as valuable starting materials for numerous substitution reactions in coordination and organometallic chemistry.

Unlocking same-sign CPL: solvent effects on spectral form and racemisation kinetics in nine-coordinate chiral europium(III) complexes

Understanding the factors that shape the circularly polarised luminescence (CPL) emission profiles of europium(III)-based CPL emitters to have specific sign properties, e. g. monosignate individual CPL transitions, is key to design novel complexes for applications ranging from advanced security inks to bio-probes for live cell imaging. In order to correlate structure and spectral characteristics, a photophysical and kinetic investigation has been conducted on a series of coordinatively saturated nine-coordinate europium(III) systems based on 1,4,7-triazacyclononane. We highlight that lanthanide emission is sensitive to changes in the ligand field by showing the linear dependence of total emission intensity ratios as a function of solvent polarity, for europium(III) complexes displaying an internal charge transfer (ICT) excited state. This sensitivity increases by a factor of 20 when studying changes in CPL spectra, rendering these complexes accurate probes of local polarity. Solvent polarity, solvent-specific effects, and the nature of the chromophores' coordinating donor atoms strongly influence the kinetic stability of europium(III) complexes with respect to enantiomer interconversion. Notably, we show that the choice of donor groups to coordinating to europium(III) and the nature and polarity of the solvent affects the rate of racemisation, leading to systems with very long half-lives at room temperature in non-polar media.

Five Dinuclear Lanthanide Complexes Based on 2,4-dimethylbenzoic Acid and 5,5'-dimethy-2,2'-bipyridine: Crystal Structures, Thermal Behaviour and Luminescent Property

A series of new complexes, [Ln (2,4-DMBA)3(5,5'-DM-2,2'-bipy)]2 (Ln = Sm(1), Eu (2)), [Pr (2,4-DMBA)3 (5,5'-DM-2,2'-bipy)]2·0.5(C2H5OH) (3), [Ln (2,4-DMBA)3 (5,5'-DM-2,2'-bipy)]2·0.5(2,4-DMBAH)·0.25(5,5'-DM-2,2'-bipy) (Ln = Tb (4), Dy (5)) (2,4-DMBA = 2,4-dimethylbenzoate, 5,5'-DM-2,2'-bipy = 5,5'-dimethy-2,2'-bipyridine) were synthesized via hydrothermal reaction conditions. The complexes were characterized through elemental analysis, Infrared spectra (IR), Raman (R) spectra, UV-Vis spectra, single X-ray diffraction. Single crystal data show that complexes 1-5 are binuclear complexes, but they can be divided into three different crystal structures. The thermal decomposition mechanism of complexes 1-5 were investigated by the technology of simultaneous TG/DSC-FTIR. What's more, the luminescent properties of complexes 1-2 and 4 were discussed, and the luminescence lifetime (τ) of complexes 2 and 4 were calculated.

High-Coordinate Mononuclear Ln(III) Complexes: Synthetic Strategies and Magnetic Properties

Single-molecule magnets involving monometallic 4f complexes have been investigated extensively in last two decades to understand the factors that govern the slow magnetization relaxation behavior in these complexes and to establish a magneto-structural correlation. The prime goal in this direction is to suppress the temperature independent quantum tunneling of magnetization (QTM) effect via fine-tuning the coordination geometry/microenvironment. Among the various coordination geometries that have been pursued, complexes containing high coordination number around Ln(III) are sparse. Herein, we present a summary of the various synthetic strategies that were used for the assembly of 10- and 12-coordinated Ln(III) complexes. The magnetic properties of such complexes are also described.

The crystal structure of bis(μ2-5,7-dichloroquinolin-8-olato-κ3N,O:O)-tetrakis(5,7-dichloroquinolin-8-olato-κ2N,O)bis(methanol-κ1O)dieuropium(III) — toluene (1/1), C63H39Cl12Eu2N6O8

C63H39Cl12Eu2N6O8, triclinic, P1̄ (no. 2), a = 10.720(5) Å, b = 12.232(5) Å, c = 14.267(5) Å, α = 65.288(32)°, β = 71.325(5)°, γ = 88.067(5)°, V = 1599.1(11) Å3, Z = 1, Rgt(F) = 0.0358, wRref(F2) = 0.0785, T = 293(2) K.

Multi-color electrochromism from coordination nanosheets based on a terpyridine-Fe(ii) complex

A new metal complex electrochromic nanosheet with multiple color electrochromism, fast switching speed and excellent cyclic stability was prepared controllably by the liquid–liquid interface self-assembly method.