V.A. Kudryashova

Charge transfer bands in the luminescence excitation spectra of isomeric pyridinedicarboxylic salts of europium

Abstract The ligand–cation charge transfer band was observed in the region of 360–400 nm of the luminescence excitation spectrum of europium salt of 3,4-pyridinedicarboxylic acid but was absent in the spectra of europium 2,6- and 2,3-pyridinedicarboxylic salts. It was due to higher efficiency of the energy transfer through the charge transfer state conditioned by increased polarizability of the ligand of the former compound. Energy transfer through the excited ligand–lanthanide charge transfer state may explain the effect of the quenching of luminescence by the redox-sensitive lanthanide ions.

Charge transfer bands in the Eu3+ luminescence excitation spectra of isomeric europium pyridine-dicarboxylates

A ligand-cation charge transfer band was observed in the region of 360–400 nm in the Eu3+ luminescence excitation spectrum of europium 3,4-pyridine-dicarboxylates, but was absent in the spectra of europium 2,6-and 2,3-pyridine-dicarboxylates. This band is due to noticeable energy transfer through a charge-transfer state formed owing to the high polarizability of the ligand in the former compound. Energy transfer through the excited ligand-lanthanide charge-transfer state can explain the well-known effect of luminescence quenching by redox-sensitive lanthanide ions.

Influence of ligand architecture on the structure of coordination centre in dimeric europium carboxylates with 1,10-phenanthroline

Abstract Methods of optical spectroscopy and X-ray crystallography data were used to examine the effect of architecture of carboxylate anions on structure of the Eu3+ coordination centre in europium carboxylates with 1,10-phenanthroline Eu(RCOO)3·Phen. Luminescence spectra of europium acetate, nitropropionate, benzoate, naphthylcarboxylates, phenylacetates, phenoxyacetate, triphenylpropionate were investigated. A few of europium carboxylates with 2,2′-bipyridine Eu(RCOO)3·Bpy and europium salts Eu(RCOO)3·nH2O were also studied. Vibrational IR and Raman spectra of phenylacetate family were analyzed. The crystal structure of nitropropionate Eu(NO2C2H4COO)3·Phen was solved by X-ray diffraction method. The predominant influence of steric hindrances on Eu3+ coordination centre was observed at increase of the size of aromatic fragment of carboxylate anions. It was demonstrated, that introduction of the methylene bridges between the carboxylic group and aromatic rings of ligand weakens the effect of steric factor.