Thermochemistry of the gaseous fluorides of samarium, europium, and thulium

Abstract

The gaseous mono-, di-, and trifluorides of the lanthanide metals samarium, europium, and thulium were characterized thermochemically from high temperature equilibrium studies carried out by mass spectrometry. Reaction enthalpies and entropies were derived using second-law analysis throughout, and the results were used to evaluate the enthalpies of formation and bond dissociation energies (BDE) of the gaseous fluorides, and to obtain approximate values for the electronic entropies of the MF and MF2 species. The dissociation energies of the monofluorides D°0(SmF)=134 kcal/mole, D°0(EuF)=129 kcal/mole, and D°0(TmF)=121 kcal/mole, all ±2 kcal/mole, are in good agreement with values predicted by the Rittner electrostatic model, whereas values in the polyatomic fluorides show considerable variation and do not seem to follow any clear trends. Although the BDE values in some instances differ from previous estimates, their sums yield trifluoride heats of atomization that are in close accord with values derived from the vaporization thermodynamics of the solid trifluorides.

Ab Initio Studies on the Structures and Vibrational Frequencies of Rare Earth Fluorides LnFn (Ln = Er, Tm; n = 1, 2, 3) and Their Positive Ions and an Assessment of Their Ionization and Dissociation Energies

“…In this case one of the Ln−F bonds is considerably elongated (by ∼0.7 Å), and also this structure possesses imaginary frequencies. This indicates that positive trifluoride ions are not stable, which is in accordance with experimental findings. ,, …”

“…The values were corrected for zero-point vibrational energy. Also listed are some experimental results available in the literature. , In the case of the trifluorides only vertical ionization energies were presented. The calculated ionization energies for ErF 3 and TmF 3 are equal, while the MP2 values are rather higher, by 1.4 eV.…”

“…We see that they are closer to our MP2 values. The values of dissociation energies quoted in column c and d were derived from gaseous equilibrium studies carried out by mass spectrometry. , For all fluorides they can be compared with our MP2 dissociation energies.…”

Bond dissociation energies of low-valent lanthanide hydroxides: lower limits from ion–molecule reactions and comparisons with fluorides

“…Experimental BDEs for small metal-containing molecules, including neutral and cationic LnX 0/+ , are mostly from high-temperature equilibria. 75 Measured or estimated ionization energies in conjunction with eqn (2) provide BDEs for cations from neutrals. 58 Although traditional experimental approaches have provided seminal information, the extreme conditions of high-temperature and reactive gases impose formidable challenges.…”

Dipole allowed transitions in GdF: A four-component relativistic general open-shell configuration interaction study

“…The electronic spectra of lanthanide fluorides have been investigated experimentally by several groups. [1][2][3][4][5][6][7] In particular, Kaledin et al 7 performed an intensive investigation of the GdF molecule. Most of the excited states of GdF up to about 3.0 eV above the ground state have been characterized by them.…”