Luminescent Polymeric Dispersions and Films Based on Oligonuclear Lanthanide Clusters

Abstract

The successful embedding of different amounts and types of hydrophobic rare earth clusters (Ln = Y, Pr, Eu, Sm, Nd) in various polymer matrices via miniemulsion polymerization is presented. The resulting cluster‐polymer hybrid nanoparticles are spherical in shape and possess a narrow size distribution, as investigated by photon cross correlation spectroscopy (PCCS) and transmission electron microscopy (TEM). The exact Ln‐content in the nanoparticles is exemplarily investigated for Eu‐ and Nd‐containing polymer dispersions via inductively coupled plasma‐optical emission spectrometry (ICP‐OES). As a result of encapsulation more than 1000 mg · L−1 of the hydrophobic Ln‐cluster are successfully dispersed in water. The photophysical properties of the emulsion show the successful avoidance of water from the vicinity of the clusters. Furthermore, a very efficient energy transfer from the ligand and polymeric unit to Eu3+ ions can be observed in dispersion. Based on the different glass transition temperatures (Tg) of the applied polymers, monolayers of the nanoparticles and efficient luminescent thin polymer films are obtained by spin coating. magnified image

Rare‐Earth Metal Oxo/Hydroxo Clusters – Synthesis, Structures, and Applications

“…The published spectra are well resolved, also showing the other transitions, whereas the spectra of the terbium(III) cluster are less clear. [50][51][52] [Eu 5 (OH) 5 (Ph 2 acac) 10 ] was also successfully embedded into a polymer matrix by the so-called miniemulsion technique. [51] Direct miniemulsions are heterophase systems including a (polymerizable) organic phase.…”

“…We and others have established the synthesis of pentanuclear lanthanide hydroxo clusters by treatment of the trichlorides of the smaller lanthanides [LnCl 3 ·(H 2 O) n ] (n = 6, 7) with dibenzoylmethane (Ph 2 acacH) in organic solvents in the presence of an organic base such as triethylamine or KOtBu. Another route to these compounds is by treatment of [Ln(Ph 2 acac) 3 10 ] (Ln = Y, [10] Nd, [49] Eu, [50][51][52][53] Tb, [52] Dy, [54] Ho, [53] Er, [49,55] Yb; [49] Scheme 3), in which the lanthanide atoms build up a square pyramidal scaffold by occupying its vertices (Figure 6), were obtained. In each of these structures, the square base face of the pyramid is capped by one μ 4 -oxygen atom, whereas its four triangular faces are capped by one μ 3 -oxygen moiety each.…”

“…[50][51][52] [Eu 5 (OH) 5 (Ph 2 acac) 10 ] was also successfully embedded into a polymer matrix by the so-called miniemulsion technique. [51] Direct miniemulsions are heterophase systems including a (polymerizable) organic phase. Through the use of this technique the monomer is finely dispersed in water and thus forms micellar structures.…”

“…[49] Since europium and terbium usually show emission in the visible region their pentanuclear clusters have been studied most intensively. [50][51][52] The europium cluster [Eu 5 (OH) 5 (Ph 2 acac) 10 ] exhibits very strong red luminescence at 612 nm, based on a 5 D 0 → 7 F 2 transition. The published spectra are well resolved, also showing the other transitions, whereas the spectra of the terbium(III) cluster are less clear.…”

“…[37] Beside the usage of alkoxides as ligands, such pentanuclear cluster compounds with other ligands, such as dibenzoylmethane and functionalized versions of it, are also known. [10,[49][50][51][52][53][54][55] According to Evans et al, the reaction between europium metal and 2,6-diisopropylphenol in propan-2-ol leads to the formation of pentanuclear complex H 5 [Eu 5 O 5 (OC 6 H 3 iPr 2 -2,6) 6 -(NCCH 3 ) 8 ] after recrystallization from acetonitrile. [56] This mixedvalence compound features the known square pyramidal cluster core with four Eu II ions at the basal positions and one Eu III ion at the apex.…”