Sublimation Behavior of Tris(2,2,6,6-tetramethyl-3,5-heptanedionato)lanthanoid(III)

Abstract

Two fundamental experiments (to determine vapor pressures and vacuum sublimation-recrystallizing temperature zones) were undertaken on a series of remarkably volatile and thermally stable lanthanoid(III) chelates of 2,2,6,6-tetramethyl-3,5-heptanedione (Ln(thd)3) in order to obtain information about their sublimation behavior. Vapor pressures of these chelates were measured from 100 to 150 °C by means of a modified Knudsen effusion technique. Vacuum sublimation-recrystallizing temperatures were determined by using a sublimation apparatus with a continuous temperature gradient along its sublimation tube. The obtained enthalpies of sublimation were classified into three groups (La to Gd, Tb and Dy, and Ho to Lu), and the vacuum sublimation-recrystallizing temperature zones were divided into two sets (La to Tb, and Dy to Lu). The Tb and Dy chelates were also found to change thermally from a dimeric form to a monomeric form at a definite temperature. These results are explained in terms of the two different crystallizing forms of Ln(thd)3 chelates. Furthermore, the regularity in their sublimation behavior is discussed as a function of the atomic numbers of the lanthanoid metals, using thermochemical considerations.

Vapor Pressures of the Copper and Yttrium β-Diketonate MOCVD Precursors

“…The Cu(TMHD) 2 vapor pressures of Waffenschmidt et al 6 are about a factor of 4 lower than our results, while the data for Y(TMHD) 3 show a markedly lower temperature dependence. For Y(TMHD) 3 , the effusion pressures of Amano et al 3 are a factor of 4 or more lower than our results, although the slopes are compatible. The single points reported by Erbil et al 4 are about a factor of 2 higher than the present results, while similar points listed in the Strem Chemicals, Inc. catalog 11 are higher by factors of 32 and 76 for Cu-(TMHD) 2 and Y(TMHD) 3 , respectively.…”

“…Earlier determinations of the vapor pressures of Cu-(TMHD) 2 and Y(TMHD) 3 were obtained by mass-loss effusion 3 and transpiration 5,6 methods; one method 4 was not clearly stated. Comparisons of the present results with literature values [3][4][5][6] are shown in Figures 4 and 5; extrapolation of our data up to the vicinity of the melting point (denoted "MP"; 198 °C for Cu(TMHD) 2 ; 170 °C for Y-(TMHD) 3 ) is shown by the dotted line. As can be seen, there is a considerable spread among the various determinations.…”

“…Of interest here are the β-diketonate complexes of copper and yttrium, Cu-(TMHD) 2 (c) (TMHD: 2,2,6,6-tetramethyl-3,5-heptanedionato, C 11 H 19 O 2 ), and Y(TMHD) 3 (c). Published vapor pressure data for these materials [2][3][4][5][6][7] show considerable scatter or are available at only one temperature. In one instance, 7 the vapor pressures were reported in graphical form only and are of limited quantitative use.…”

Synthesis of multifunctional multiferroic materials from metalorganics

“…This tendency is stronger for the lighter lanthanides due to their larger ionic radius [42]. Tb(thd) 3 and Dy(thd) 3 are reported to undergo irreversible change from a dimeric form to monomeric form upon heating at 147 • C and 115 • C, respectively [76].…”