Speciation, Luminescence, and Alkaline Fluorescence Quenching of 4-(2-methylbutyl)aminodipicolinic acid (H2MEBADPA)

4-(2-Methylbutyl)aminodipicolinic acid (H2MEBADPA) has been synthesized and fully characterized in terms of aqueous phase protonation constants (pKa\u27s) and photophysical measurements. The pKa\u27s were determined by spectrophotometric titrations, utilizing a fully sealed titration system. Photophysical measurements consisted of room temperature fluorescence and frozen solution phosphorescence as well as quantum yield determinations at various pH, which showed that only fully deprotonated MEBADPA2– is appreciably emissive. The fluorescence of MEBADPA2– has been determined to be quenched by hydroxide and methoxide anions, most likely through base-catalyzed excited-state tautomerism or proton transfer. This quenching phenomenon has been quantitatively explored through steady-state and time-resolved fluorescence measurements. Utilizing the determined pKas and quenching constants, the fluorescent intensity of MEBADPA2– has been successfully modeled as a function of pH

Optical Properties of Lanthanide Squarates

Two types of lanthanide squarate hydrates of formulae Eu(C$\text{}_{4}$O$\text{}_{4}$)(HC$\text{}_{4}$O$\text{}_{4}$)(H$\text{}_{2}$O)$\text{}_{6}$·H$\text{}_{2}$O (compound I) and [Ln$\text{}_{2}$(C$\text{}_{4}$O$\text{}_{4}$)$\text{}_{3}$(H$\text{}_{2}$O)$\text{}_{8}$] where Ln = Eu and Gd (compound II) were investigated. The optical properties of crystals I and selected spectral data of compound II are reported and confronted with earlier studies of europium complexes type II. Excitation and emission spectra were measured at 77 K. Effect of polymeric structure on spectroscopic properties is considered and correlated with the structural data. Cooperative intrachain interactions between metal ions coupled via squarate anions were pointed and cooperative absorption was recorded. To check the presence of the Eu$\text{}^{2+}$ traces, the EPR and γ-irradiation measurements were applied. Raman spectra of the compound II (where Ln = from Sm to Lu) were measured in the range 50-500 cm$\text{}^{-1}$. Positions of the bands were considered in function of ionic radius of lanthanide ion. The above, together with the data from excitation spectra, allows to localize the Ln-O bands. Vibronic components in electronic spectra were elucidated and assigned

Stereoselectivity Effect on Tb(III)-Eu(III) Energy Transfer in Complexes with Glutamic Acid and Alanine

The effect of stereoselectivity on energy transfer between Tb(III) and Eu(III) in crystals with glutamic acid and alanine was investigated. It was found that the stereoselectivity significantly changes the energy transfer in these systems. The theoretical model for the selective dependent energy transfer processes in lanthanide systems is developed and the nature of processes occurring in both systems under investigation briefly discussed

Vibronic Transitions in Centrosymmetric [Eux\text{}_{x}La1−x\text{}_{1-x}(AP)6\text{}_{6}](ClO4\text{}_{4})3\text{}_{3} Crystals

The optical excitation and emission spectra of Eu(III) in [Eu$\text{}_{x}$La$\text{}_{1-x}$(AP)$\text{}_{6}$](ClO$\text{}_{4}$)$\text{}_{3}$ centrosymmetric complex were measured. The vibronic transitions were observed in excitation and emission spectra. Following the vibrational analysis' of the infrared and Raman spectra of [Pr$\text{}_{x}$La$\text{}_{1-x}$(AP)$\text{}_{6}$](ClO$\text{}_{4}$)$\text{}_{3}$, the assignment of [Eu$\text{}_{x}$La$\text{}_{1-x}$(AP)$\text{}_{6}$](ClO$\text{}_{4}$)$\text{}_{3}$ vibronics was given The concentration effect on excitation and emission spectra was investigated. It was found that the vibronic intensities were changed upon the concentration effect. The intensive charge transfer bands were observed in blue region. Their intensities decreased with increasing concentration