Effect of Ligand Deuteration on the Decay of Eu3+(5D0) in Tris(2,2,6,6-tetramethyl-3,5-heptanedionato)europium(III)

Charge-transfer excited states of π- and 4f-orbitals for development of luminescent Eu(III) complexes

Transition metal complexes provide photofunctional properties through the charge transfer excited states of their metal ion and organic ligand components. Recently, there are increasing reports on the charge transfer excited states of the ligand (π)- and 4f-orbitals of lanthanide complexes, where the latter are shielded by filled 5s² and 5p⁶ orbitals. This area of research is relatively unestablished; thus, the study of photo-excited organic-lanthanide charge transfer would lead to the construction of next-generation photofunctional metal complexes. In this review, we summarize the latest research progress in photofunctional materials using the charge transfer excited states of lanthanide complexes, and discuss the photophysical/theoretical analyses of these charge transfer excited states.

Long-Range LMCT Coupling in EuIII Coordination Polymers for an Effective Molecular Luminescent Thermometer*

A design for an effective molecular luminescent thermometer based on long-range electronic coupling in lanthanide coordination polymers is proposed. The coordination polymers are composed of lanthanide ions Eu^III and Gd^III , three anionic ligands (hexafluoroacetylacetonate), and a chrysene-based phosphine oxide bridges (6,12-bis(diphenylphosphoryl)chrysene). The zig-zag orientation of the single polymer chains induces the formation of packed coordination structures containing multiple sites for CH-F intermolecular interactions, resulting in thermal stability above 350 °C. The electronic coupling is controlled by changing the concentration of the Gd^III ion in the Eu^III -Gd^III polymer. The emission quantum yield and the maximum relative temperature sensitivity (S_m ) of emission lifetimes for the Eu^III -Gd^III polymer (Eu:Gd=1:1, Φ_tot =52 %, S_m =3.73 % K^-1 ) were higher than those for the pure Eu^III coordination polymer (Φ_tot =36 %, S_m =2.70 % K^-1 ), respectively. Enhanced temperature sensing properties are caused by control of long-range electronic coupling based on phosphine oxide with chrysene framework.

Theoretical study, and infrared and Raman spectra of copper(II) chelated complex with dibenzoylmethane

There are some discrepancies in both the vibrational assignments and in the metal-ligand (M-L) bond strengths predicted in the previous studies on the copper (II) chelated complex of dibenzoylmethane, Cu(dbm)2. Also, there is a lack of theoretical structure, Raman spectrum and full vibrational assignment for Cu(dbm)2 in the literatures. Density functional theory (DFT) at the B3LYP level and also MP2 calculations using different basis sets, besides Natural Bond Orbital (NBO) and Atoms-in-Molecules (AIM) analyses, have been employed to investigate the effect of methyl substitution with the phenyl group on the stabilities of bis(acetylacetonate) copper (II), Cu(acac)2, and Cu(dbm)2 complexes and the electron delocalization in their chelated rings. Measured solid phase infrared and Raman bands for Cu(dbm)2 complex have been interpreted in terms of the calculated vibrational modes and detailed assignment has been presented. We concluded that, theoretically, the results of charge transfer studies, and experimentally, in-phase symmetric O-Cu-O stretching mode of these complexes are very useful measures for M-L bond strength. The electron delocalization in the chelated rings and the M-L bond strength in Cu(dbm)2 are concluded to be higher than those in Cu(acac)2. The calculated geometries and vibrational results are in good agreement with the experimental data.

Assembly of hydrophobic shells and shields around lanthanides

Luminescent lanthanide complexes have been developed, based on the assembly of bulky ligands around the lanthanide ion, to provide shell-type protection of the ion from coordinated solvent molecules. Aryl-functionalised imidodiphosphinate ligands (tpip and Metpip) provide a bidentate anionic site that leads to hexa-coordinate lanthanide complexes in which the aryl groups surround the ion. There are twelve phenyl groups around the lanthanide that act as "remote" (from the binding site) sensitisers for the metal ion. It is shown that these ligands are suitable for sensitising luminescence for all the lanthanides that emit in the visible range, namely, SmIII, EuIII, TbIII, DyIII. A "builtin" shield on the ligand is designed to provide a complete block of the approach of water to the lanthanide ion. The synthesis of the ligands and their lanthanides complexes as well as detailed photophysical studies of the complexes in solution and in the solid-state are presented.