Thiophene Based Europium β-Diketonate Complexes: Effect of the Ligand Structure on the Emission Quantum Yield

Abstract

The synthesis and the molecular and photophysical characterization, together with solid state and solution structure analysis, of a series of europium complexes based on β-diketonate ligands are reported. The Eu(III) complex emission, specifically its photoluminescence quantum yield (PL-QY), can be tuned by changing ligands which finely modifies the environment of the metal ion. Steady-state and time-resolved emission spectroscopy and overall PL-QY measurements are reported and related to geometrical features observed in crystal structures of some selected compounds. Moreover, paramagnetic NMR, based on the analogous complexes with other lanthanides, are use to demonstrate that there is a significant structural reorganization upon dissolution, which justifies the observed differences in the emission properties between solid and solution states. The energy of the triplet levels of the ligands and the occurrence of nonradiative deactivation processes clearly account for the luminescence efficiencies of the complexes in the series.

Circularly polarized luminescence under near-UV excitation and structural elucidation of a Eu complex

“…The experimental set-up employed to record the CPL spectra is described in the ESI. We notice that the solid state luminescence is enhanced with respect to the solution one, this is in agreement with previous observations, 27 although no ultimate explanation has been put forward. Possibly, crystal packing on one hand and solvation on the other may account for both total luminescence and CPL enhancement in solid state samples.…”

Near‐IR Emitting Iridium(III) Complexes with Heteroaromatic β‐Diketonate Ancillary Ligands for Efficient Solution‐Processed OLEDs: Structure–Property Correlations

“…[21] Complexes 2 and 3,compared to 1,show larger extinction coefficients (e)i nt he range l = 350-400 nm because of the overlap of the original diketonate ligand (Hdtdk and Htta) absorption bands. [22] In the region l = 450-600 nm the absorption shape of 1, 2,a nd 3 is similar and undergoes ablue shift in the sequence 1, 3, 2.Since the ligands (iqbt and diketonates) do not absorb in that region, we assign these bands to 1,3 MLCT (d-p*) transitions resulting from the coordination of the Ir III center with the iqbt ligand. Weak bands in the region of l > 600 nm (Figure 2a,i nset) are assigned to ground-state excitation into the lowest triplet state (S 0 !T 1 ;T able 1and see below for TDDFT analysis).…”

Interfacial interactions of hard polyelectrolyte-stabilized luminescent colloids with substrates

“…The particular importance of the lanthanide complexes with ␤-diketonates as ancillary ligands for sensing arises from their well-known sensitizing effect on lanthanide-centered luminescence or so-called "antennae effect" arisen from a ligandto-metal energy transfer [15,[18][19][20][21][22][23][24]. These complexes exhibit high binding capacity towards additional ligands, which results from an incomplete coordination sphere of lanthanide ions due to their high coordination numbers [18][19][20][21][22][23][24]. Unfortunately, a majority of luminescent lanthanide complexes are poor soluble in water, which restricts their application in sensing.…”