Incorporating palladium in the first coordination sphere of acetato-bridged lanthanoid complexes, [Pd Ln (H O) (AcO) ]⋅2 AcOH (Ln=Gd (1), Y (2), Gd Y (3), Eu (4)), led to significant bonding interactions between the palladium and the lanthanoid ions, which were demonstrated by experimental and theoretical methods. We found that electron density was donated from the d Pd ion to Gd ion in 1 and 3, leading to the observed slow magnetic relaxation by using local orbital locator (LOL) and X-ray absorption near-edge structure (XANES) analysis. Field-induced dual slow magnetic relaxation was observed for 1 up to 20 K. Complex 3 and frozen aqueous and acetonitrile solutions of 1 showed only one relaxation peak, which confirms the role of intermolecular dipolar interactions in slowing the magnetic relaxation of 1. The slow magnetic relaxation occurred through a combination of Orbach and Direct processes with the highest pre-exponential factor (τ =0.06 s) reported so far for a gadolinium complex exhibiting slow magnetic relaxation. The results revealed that transition metal-lanthanoid (TM-Ln) axial interactions indeed could lead to new physical properties by affecting both the electronic and magnetic states of the compounds.
Oligothiophene-based liquid crystals having a wide luminescent color variation exhibit reversible luminescent color changes induced by mechanical shearing and subsequent aging at ambient temperature.
A heterometallic Tb-Pt complex, [Tb Pt (SAc) (H O) ] (SAc=thioacetate), was synthesized. Dual emission was modulated by the presence of a heterometallic Tb-Pt bonding environment. The heterometallic Tb-Pt bond lowers the symmetry of the Tb ion and enhanced the emission efficiency. In addition, the Tb-Pt complex shows field-induced multiple magnetic relaxation pathways. Furthermore, it served as an antenna for the observed dual emission. In other words, the heterometallic Tb-Pt bond has a significant effect on the luminescence and magnetic properties of the complex.
Lanthanide
(Ln) based luminescent materials are experiencing an increasing interest
in their applications in several fields. In this study, we report
a series of new lanthanide-oligomeric brush films, supported on quartz
substrates and prepared using a layer-by-layer method (LbL). Oligomeric
brush films are composed of small oligomers from our previously reported
coordination polymers [x-EuL] and [x-TbL] (with x = 1, 3, and 5 generations of Ln complexes),
which are grown perpendicularly from a carboxylate self-assembled
monolayer. Oligomers composed of our previously described helical
lanthanide complex LnL (Ln: Eu and Tb) as a luminescent moiety and
benzene-1,4-dicarboxylate acid (bdc) used as a linker. Mixed films
having the fifth-generation Ln complexes composed of equimolar mixture
of Eu and Tb ions were prepared. Oligomeric brush films are highly
transparent and exhibited a colored emission under UV irradiation.
Pure Ln (Eu or Tb) films showed a strong luminescence from the Ln
ions. Their luminescent properties depended on the number of lanthanide
layers in the films composed of the first to third generations of
lanthanide complexes. Then, the increase of the complex layers induced
no difference in the luminescent properties. An energy transfer from
Tb to Eu ions in the mixed films indicated a short distance between
lanthanide ions of a fifth layer. The structural analysis together
with the observed luminescent properties and some previous studies
allowed to clarify the disposition of the oligomers in the films.
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