Highly luminescent and stable lyotropic liquid crystals based on a europium β-diketonate complex bridged by an ethylammonium cation

Abstract

Soft lanthanide luminescent materials are impressive because of their tunable and self-assembling characteristics, which make them an attractive emerging materials field of research. In this report, novel luminescent lyotropic liquid crystals (LLCs) with four different mesophases have been fabricated by a protic ionic liquid (IL) based europium β-diketonate complex EA[Eu(TTA)] (EA = ethylammonium, TTA = 2-thenoyltrifluoro-acetone) and an amphiphilic block copolymer (Pluronic P123). The protic IL, ethylammonium nitrate (EAN), was used as both the solvent and linkage to stabilize the doped complexes. Analyses by single-crystal X-ray diffraction for EA[Eu(TTA)] and Fourier transform infrared spectroscopy for the LLC materials reveal convincingly that the ethylammonium cations establish an effective connection with both the carbonyl group of the β-diketonate ligand and the EO blocks of the amphiphilic block copolymer P123 via strong hydrogen bonding interactions. Due to this, an extremely long decay time of the excited state is obtained in EA[Eu(TTA)] and excellent photostability of the luminescent LLCs could be achieved. The long-period ordered structures of the luminescent LLCs have been investigated by small-angle X-ray scattering measurements and the best luminescence performance was found in the most organized mesophase. Noteworthy, the LLCs could yield an effective confining effect on the europium complex accompanied by a sizeable elongation of the excited-state lifetime and an enhancement of the energy transfer efficiency, which reaches a remarkably high value of 52.6%. More importantly, the modulated luminescence properties observed in the four mesophase structures offer the potential and powerful possibility for these unique composite LLCs to be used in the fabrication of soft luminescent materials with tunable functions.

Luminescent Poly(vinylidene fluoride)‐Based Inks for Anticounterfeiting Applications

“…In particular, it points out that [Bmim] + contributes to the decrease of the nonradiative transition probability with respect to that of PVDF/Na[Eu(tta) 4 ]. We note that the lifetime values reported for [Bmim][Eu(tta) 4 ] and Na[Eu(tta) 4 ] were 0.521 ms [ 68 ] and 0.289 ms, [ 31 ] respectively.…”

“…The fivefold increase in the [Bmim] + ‐based material is another experimental argument supporting the active role of [Bmim] + in protecting the Eu 3+ ions from nonradiative channels. The higher absolute emission quantum yield of PVDF/[Bmim][Eu(tta) 4 ] can be correlated with the formation of a hydrogen bond between the CH group of a [Bmim] + ion and a CO group of the tta − ligand, which, according to Yi et al, [ 68 ] leads to the improvement of the energy transfer efficiency due to a decrease in the nonradiative transition deactivation. The boost in luminescence and stability in europium β‐diketonate materials induced by the formation of hydrogen bonds with imidazolium ions was also reported by other authors.…”

The Influence of Different Ammonium Cations on the Optical Properties of Tetrakis GdIII and EuIII Complexes

“…The ground state geometry of the complexes was determined using the Sparkle/RM1 44 and Sparkle/PM6 45 methods implemented in the Mopac2012 software 47 ( Figures 5 and 6, and Figures S3 and S4, SI section). The average Eu−O distance bond obtained by X-ray diffraction for [Eu(b-dik) 4 ]complexes is 2.3878 Å, 55,[57][58][59][60][61][62] while using the Sparkle/RM1 and Sparkle/PM6 we obtained 2.4589 (2.98% error) and 2.4306 Å (1.79% error), respectively. 60,[62][63][64][65][66][67] Therefore, the Sparkle/PM6 method gave better values for the Eu-O distance bond than the Sparkle/ RM1 in this case.…”

Luminescent Sodium Deoxycholate Ionogel Induced by Eu3+ in Ethylammonium Nitrate

“…Upon the ionogel formation, this peak position was shifted to 3440 cm –1 , which was caused by reconstruction of hydrogen bonding due to gel formation. 35 The previous stronger hydrogen bonding in NaDC powder was weakened because of the coordination of carboxylate group to Eu 3+ . Besides, the peak difference (Δν) between asymmetric (ν as ) and symmetric (ν s ) stretchings of carboxylate groups can reflect the coordination modes of them in NaDC with Eu 3+ .…”