Novel Lanthanide Luminescent Materials Based on Complexes of 3-Hydroxypicolinic Acid and Silica Nanoparticles

Abstract

New lanthanide complexes of 3-hydroxypicolinic acid (HpicOH) were prepared: [Ln(H 2 O)-(picOH) 2 (µ-HpicO)]‚3H 2 O (Ln ) Eu, Tb, Er). The complexes were characterized using photoluminescence, infrared, Raman, and 1 H NMR spectroscopy, and elemental analysis. The crystal structure of [Eu(H 2 O)(picOH) 2 (µ-HpicO)]‚3H 2 O 1 was determined by X-ray diffraction. Compound 1 crystallizes in a monoclinic system with space group P2 1 /c and cell parameters a ) 9.105(13) Å, b ) 18.796(25) Å, and c ) 13.531(17) Å, and ) 104.86(1) deg. The 3-hydroxypicolinate ligands coordinate through both N,O-or O,O-chelation to the lanthanide ions, as shown by X-ray and spectroscopic results. Photoluminescence measurements were performed for the Eu(III) and Tb(III) complexes; the Eu(III) complex was investigated in more detail. The Eu(III) compound is highly luminescent and acts as a photoactive center in nanocomposite materials whose host matrixes are silica nanoparticles.

Synthesis, Characterisation and Luminescent Properties of Lanthanide‐Organic Polymers with Picolinic and Glutaric Acids

“…10 %, with a corresponding k r value of 0.253 ms -1 . These values, lifetimes and quantum efficiency values, although lower when compared with those obtained by Sendor et al for the europium picolinato, [8] are of the same order of magnitude as those obtained for the Eu 3+ emission in the 3-hydroxypicolinato [7] and 2-hydroxynicotinato complexes.…”

“…2 ] complex has been estimated assuming that only nonradiative and radiative processes are essentially involved in the depopulation of the excited state, as already reported. [7,28] We obtained a q value of ca. 10 %, with a corresponding k r value of 0.253 ms -1 .…”

“…[5] More recently, as part of our own studies of metal complexes with aromatic ambidentate ligands, [6] we began to exploit the coordination chemistry of 3-hydroxypicolinic acid and its derivatives in the synthesis of a series of lanthanide complexes and we investigated the role of this ligand in the photoluminescence of such complexes. [7] Picolinic acid complexes of lanthanides, particularly those of Eu 3+ and Tb 3+ , show interesting photoluminescent behaviour because energy transfer from the aromatic groups close to the lanthanide ions may enhance the luminescent efficiency of the ion. [8] Even dispersed in solid matrices they can produce efficient luminescent materials, such as those in SiO 2 nanoparticles obtained by the sol-gel method.…”

“…[8] Even dispersed in solid matrices they can produce efficient luminescent materials, such as those in SiO 2 nanoparticles obtained by the sol-gel method. [7] Therefore, in principle, it should be possible to fine tune the luminescence of such nanocomposites by working out the coordination chemistry of the Ln complexes. Lanthanide coordination polymers, including those synthesised in the presence of dicarboxylato ligands have attracted considerable interest and many examples can be found in the literature.…”

Biofunctional Composites of Polysaccharides Containing Inorganic Nanoparticles

“…Silica encapsulation normally involves the growth of SiO 2 shells, very often following the hydrolysis of tetraethylortosilicate precursor, in the presence of the above mentioned fluorophores. The literature offers a number of examples of nanoparticles comprising amorphous silica encapsulating fluorophores, these include organic dyes (Ow et al, 2005), lanthanide complexes (Granadeiro et al, 2010;Soares-Santos et al, 2003), gold clusters (Guével et al, 2011) and quantum dots (Darbandi et al, 2005), among other luminescent systems (Burns et al, 2006). Silica coating of fluorophores provides a large surface area for which a number of functionalization procedures that are well known in chemistry can be directly applied.…”