Temperature and Pressure Dependence of Excitation Spectra as a Probe of the Solution Structure and Equilibrium Thermodynamics of a Eu(III) Complex Containing a Modified dota Ligand

Abstract

The temperature and pressure dependence of the 7F0 → 5D0 and 7F1 → 5D0 excitation spectra for aqueous solutions of Eu(III) with racemic-tetra(α-carboxyethyl)DOTA have been measured. Individual excitation and emission peaks have been assigned to square antiprism (SAP) and twisted square antiprism (TSAP) isomers of the complex, and the variation of relative peak areas as a function of temperature and pressure have been used to estimate the enthalpy and volume change associated with the isomer equilibrium. The effects of temperature on the initial state populations have been treated explicitly, although for the data presented, these effects are within the uncertainty of the measurement. The results show that the SAP isomer of Eu(ceDOTA) is the more compact, more ordered, and lower enthalpy structure, consistent with previous NMR experiments on the differences in the observed rate of water exchange for the isomeric species.

Lighting Up Two-Dimensional Lanthanide Phosphonates: Tunable Structure–Property Relationships toward Visible and Near-Infrared Emitters

“…29 As such, there is a one-to-one correspondence between the number of bands associated with the 5 D0→ 7 F0 transition in the PL spectrum and the number of distinct Eu III environments. 29,62 Gaussian deconvolution of this band reveals a single Eu III local environment for all Eu-phosphonates, which is in good agreement with the crystallographic data.…”

“…Firstly, the observation of a single component for the 5 D0→ 7 F0 transition confirms that there is only one unique crystallographic site in each material. 29,62 Secondly, for Eu-Naph, splitting of the 49,71 The triplet state energies were estimated from the 77 K phosphorescence spectra and were found to be 21,097 cm -1 for 1-naphthalene phosphonic acid and 22,624 cm -1 for 4biphenyl phosphonic acid, respectively ( Figure S7b,d, Supporting Information). Figure 6 shows the corresponding energy level diagram for Ln-Naph and Ln-Biphen (Ln = Eu III , Tb III ).…”

On the use of high-pressure to study the speciation, solvation, and excited state energetics of luminescent lanthanide complexes

“…It should be noted that the resolution of the dye laser used in this study is 0.03 nm. In a recent study for a macrocyclic complex involving Eu(III) and a modified DOTA-type ligand we have also looked at the wavelength position of the 7 F 1 → 5 D 0 excitation spectrum [4]. In this work it was also noticed that the wavelength peak positions changed very little with increases in pressure.…”

“…Luminescence and excitation spectroscopy involving Eu(III) has been particularly useful in studies aimed at determining the structure and speciation of solution complexes, since the sharp excitation and luminescence transitions may often be analyzed in terms of specific solution species. In a number of recent studies [4][5][6][7][8][9], for example, we have shown how one may determine useful energetic parameters and thermodynamic properties from the measurement of excitation and luminescence spectra under conditions of variable temperature and pressure.…”

Investigation of the Structure and Dynamics of Regioisomeric Eu³⁺ and Gd³⁺ Chelates of NB-DOTMA: Implications for MRI Contrast Agent Design

“…SAP and TSAP chelates can be distinguished from one another by any technique which probes the magnitude of the axial ligand field, A 2 0 . [104][105][106] This parameter is larger for Chapter 1: Introduction…”