Ion size dominated 1D and 2D Salen lanthanide coordination complexes and their luminescence

Exploring the Oxidation States of Neptunium with Schiff Base Coordination Complexes

A pair of neptunium Schiff base coordination complexes, Np^VIO₂L(MeOH) and Np^IVL₂ {H₂L = N,N'-bis[(4,4'-diethylamino)salicylidene]-1,2-phenylenediamine}, have been synthesized and analyzed by several characterization methods including single-crystal X-ray diffraction, electronic absorption, ¹H NMR, cyclic voltammetry, and theoretical interpretation. Structural analysis reveals that Np^VIO₂L(MeOH) and Np^IVL₂ are isomorphous with the previously reported U^VIO₂L(MeOH) and M^IVL₂ (M = Pu, Ce, U, Th) complexes, respectively, allowing for a direct comparison across the series. The reduction of Np^VIO₂L(MeOH) in situ or direct synthesis from a (Np^VO₂)⁺ source shows evidence of a pentavalent neptunyl (Np^VO₂L)_x^n- species as determined by UV/vis/NIR and ¹H NMR spectroscopy. The synthesis of (Np^VO₂L)_x^n- directly from a (Np^VO₂)⁺ starting material gives a similar spectrum. Theoretical analysis offers insight into the electronic structure for a better understanding of the bonding patterns and relative stability of the different oxidation states. Computational results show that the Np-L covalent interactions in Np^IVL₂ are similar to those in the Np^VIO₂L(MeOH) complex, indicating that neither the presence of the axial oxo ligands nor the oxidation state significantly modify the nature of the Np-L bonds.

Experimental and Theoretical Comparison of Transition-Metal and Actinide Tetravalent Schiff Base Coordination Complexes

A series of homoleptic tetravalent transition-metal and actinide Schiff-base coordination complexes, ML₂ {M = Zr, Hf, Th, U; L = N, N'-bis[(4,4'-diethylamino)salicylidene]-1,2-phenylenediamine}, have been synthesized that feature a rigid phenyl backbone. These complexes create the opportunity for comparing a series of complexes containing metal cations in the formal IV+ oxidation state by structural, spectroscopic, and theoretical analysis that also incorporate the previously reported Ce(IV) and Pu(IV) analogues. X-ray crystallographic analysis reveals that all complexes are isomorphous and feature a co-facial ligand geometry. TD-DFT and other quantum mechanical methods were used to explore bonding differences across between the complexes, and resulting calculated absorbance spectra for ML₂ are in good agreement with the experimental data. The computational results also suggest that U(IV) and Pu(IV) analogs have more covalent character in their bonding than found with the other metal cations reported here.

Schiff-base coordination complexes with plutonium(iv) and cerium(iv)

The synthesis and characterization of a Pu(iv) salen complex reveals the stabilization of the +4 oxidation state with respect to that observed with Ce(iv).

A Novel 3D Salen Neodymium Framework with Near-Infrared (NIR) Properties

The reaction of N,N′-bis(3-hydroxy)ethylene-1,2-diamine (H2salen) with Nd(NO3)3·6H2O and NdCl3·6H2O yields a novel lanthanide complex, namely, Nd(salen)2(NO3)2Cl (1). X-ray crystallographic analysis revealed that H2salen effectively functions as a bridging ligand forming a kind of novel 3D structure complex which is constructed by Salen ligands and mixed lanthanide counter-ions without π–π stacking and hydrogen bond interactions. This is the first Salen-type 3D lanthanide complex to be constructed in this way. The near-infrared (NIR) properties of 1 in the solid state were also studied.

First Orange Fluorescence Composite Film Based on Sm-Substituted Tungstophosphate and Its Electrofluorochromic Performance

We chose a Sm-containing sandwich-type tungstophosphate K3Cs8[Sm(PW11O39)2]·10H2O (SmPW11) as a molecular dyad, which contains photoluminescence and electrochromism components in a skeletal structure, and investigated its electrofluorochromic performance both in solution and in composite films. First, the electrochemical activity and luminescence property of SmPW11 were studied in different pH solutions to determine the optimal pH solution medium; and then, the electrofluorochromic performance of SmPW11 was investigated under the optimized pH solution medium. Subsequently, the composite films containing SmPW11 were prepared on quartz substrates and conductive ITO substrates through a layer-by-layer (LbL) assembly method, using PDDA and PEI as molecular linkers. Characterization methods of the composite films include UV-vis spectra, fluorescence spectroscopy, cyclic voltammetry (CV), bulk electrolysis with coulometry, chronoamperometry, X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). Finally, in situ UV-vis and fluorescence spectroelectrochemical systems were used to research electrofluorochromic properties for the composite films under electrochemical modulation. The results indicate that the composite films display not only orange luminescence emission but also reversible orange luminescence switching behaviors manipulated by the redox process of tungstophosphate species PW11 via the energy transfer between the orange luminescence component Sm and electroreduced species of tungstophosphate PW11.

A series of lanthanide(iii) complexes constructed from Schiff base and β-diketonate ligands

Four type lanthanide(iii) complexes constructed from Schiff base and β-diketonate ligands have been synthesized by the same method. The structures were determined by single crystal X-ray crystallographic studies, and their luminescence properties were determined.