Comparative Analysis Of Luminescent Properties Research Articles

Why are the luminescent properties of the mononuclear and binuclear Eu/Tb-2-hydroxybenzoate complexes with 1,10-phenanthroline so different? An experimental-theoretical study

This study presents a comprehensive investigation into the structural and luminescent properties of lanthanide 2-hydroxybenzoate compounds, focusing on Eu3+ and Tb3+ ions in both single and mixed systems. The X-ray structures of (Hphen)2[Eu2(2-OHBz)8(H2O)2]·2H2O (1a·2H2O) and [Eu(2-OHBz)3(phen)2]·PhMe (2a·PhMe) were determined, where 2-OHBz: 2-hydroxybenzoate and phen: 1,10-phenantroline, revealing triclinic crystal structures with distinct coordination geometries. Compound 1a·2H2O displayed a centrosymmetric dinuclear anion with a coordination number of eight for each Eu3+ center, while compound 2a·PhMe exhibited a neutral mononuclear complex with a decacoordinated Eu3+ center. A comparative analysis of luminescent properties between these compounds unveiled significant differences in the nonradiative decay rates of the 5D0 level of Eu3+ ions, suggesting potential luminescence-quenching channels. The investigation is extended to mixed Eu3+-Tb3+ systems, demonstrating efficient Tb3+ to Eu3+ energy transfer, especially at room temperature. Three models, including two novel ones proposed in this study, were considered to rationalize energy transfer in the mixed systems. Our theoretical-experimental investigation reveals that variations in lifetimes of the emitting level 5D0 of Eu-2-OHBz mononuclear and binuclear complexes, or mixed Eu/Tb-2-OHBz complexes, with 1,10-phenanthrolines, primarily result from multiphonon decay processes; however, low-energy ligand-to-metal charge transfer (LMCT) states play a key role in suppressing luminescence in the binuclear complex compare to the mononuclear ones.

New Magnesium(II), Aluminum(III), and Gallium(III) 12-Crown-4-Porphyrinates: Synthesis, Structure, and Luminescent Properties

New meso-tetra(benzo-12-crown-4)-substituted magnesium(II), aluminum(III), and gallium(III) porphinates are obtained. The structure of complexes is established using the data of electron absorption spectroscopy and MALDI TOF mass spectrometry. Comparative analysis of luminescent properties (energies of fluorescent transitions and fluorescence quantum efficiency) of metal porphyrinates and free meso-tetra(benzo-12-crown-4)-substituted porphyrin in a dimethylformamide solution at 25°C. It is found that the obtained metal porphyrinates are characterized by rather intense fluorescent radiation, as well as solubility in organic media of very different polarities, which allows considering new complexes as potential luminescent sensors for metal cations and as luminescent agents of metal cation interphase transfer.

The effect of the core morphology of Eu(III)-doped nanoparticles on the ion exchange versus energy transfer between Eu(III) in the core and Cu(II) ions at the interface

The report represents the comparative analysis of luminescent properties of Eu(III) complex in colloids of silica-coated and layer-by-layer-fabricated nanoparticles. The diverse morphologies of these nanoparticles greatly affect their photophysical properties. The interfacial binding with d-ions exemplified by Cu(II) and the contributions of the ion exchange and energy transfer processes between Eu(III) ions confined within polymeric coating and Cu(II) ions at the interface of nanoparticles also depend on their morphology. The silica coating of Eu(III) complex does not prevent it from the efficient ion displacement by the interfacial Cu(II) ions, which results in the irreversible quenching of Eu(III)-centered luminescence. The lack of the ion exchange and the predominant energy transfer between Eu(III) ions in the core and interfacial Cu(II) ions are revealed in the colloids of Eu(III) complex reprecipitated from organic to aqueous solution and coated by the layer-by-layer-fabricated polyelectrolyte multilayer. The obtained results represent the synthetic route of the insertion of Cu(II) ions into the polyelectrolyte multilayer fabricated onto Eu(III) complex.