Ultrafast Photofragmentation of Ln(hfac)3 with a Proposed Mechanism for forming High Mass Fluorinated Products

Abstract

The photo-induced dissociative-ionization of lanthanide complexes Ln(hfac)3 (Ln = Pr, Er, Yb) is studied using intense ultrafast transform limited (TL) and linearly chirped laser pulses in a time-of-flight (TOF) mass spectrometry setup. Various fluorine and Ln-containing high-mass fragments were observed in this experiment, including the molecular parent ion, which have not been seen with previous studies relying on relatively long-duration laser pulses (i.e., ns or longer). These new high-mass observations provide important formerly missing information for deducing a set of photo-fragmentation mechanistic pathways for Ln(hfac)3. An overall ultrafast control mechanism is proposed by combining insights from earlier studies and the fragments observed in this research to result in three main distinct photo-fragmentation processes: (a) ligand-metal charge transfer, (b) CF3 elimination, and (c) C-C bond rotation processes. We conclude that ultrafast dissociative-ionization could be a promising technique for generating high-mass fragments for potential use in material science applications.

Theoretical Modeling (Sparkle RM1 and PM7) and Crystal Structures of the Luminescent Dinuclear Sm(III) and Eu(III) Complexes of 6,6,7,7,8,8,8- Heptafluoro-2,2-dimethyl-3,5-octanedione and 2,3-Bis(2-pyridyl)pyrazine: Determination of Individual Spectroscopic Parameters for Two Unique Eu3+ Sites

“…However, the peaks corresponding to the molecular fragments Ln­(fod) 2 bpp and Ln­(fod) 2 (bpp) 2 are apparent in the spectra. The easy splitting of CF 3 fragments and the possible migration of fluorine atoms , results in various types of molecular fragments.…”

Mechanochemical Syntheses of Ln(hfac)3(H2O)x (Ln = La-Sm, Tb): Isolation of 10-, 9-, and 8-Coordinate Ln(hfac)n Complexes

“…Lanthanide β-diketonate complexes are often studied for their magnetic − and optical properties. − The versatility afforded by the variety of commercially available β-diketone ligands combined with the structurally isomorphous nature of lanthanide cations allows for delineation of structure–function relationships while also facilitating diverse applications . More specifically, the fluorinated β-diketone 1,1,1,5,5,5-hexafluoroacetylacetone (Hhfac) ligand imparts volatility. − Although complexes of the type Ln­(hfac) 3 (H 2 O) x have been known for over 50 years, only the single-crystal structures of the later lanthanides Tb, Ho, Er, and Dy are currently known. The early lanthanides (La-Nd) have differing hydration numbers and are structurally different based on powder X-ray diffraction (PXRD) patterns compared to later lanthanides .…”

Ultrafast control of the LnF+/LnO+ ratio from Ln(hfac)3

“…The latter agrees well with the C-C bond rotation pathway described in our previous study. 25 The final fragment yields after the completion of the entire optimal pulse shape gives rise to an enhanced PrF + /PrO + ratio, which was not observed for the compressed TL pulse in Fig. 4 that instead minimizes the same ratio.…”

“…A discussion of the full mass fragmentation pattern can be found in ref. 25. The relative photofragment yields of PrO + and PrF + were optimized with shaped fs laser pulses during adaptive feedback control experiments.…”

“…In our previous study of Ln(hfac) 3 , 25 we showed that intense femtosecond laser pulses can generate a variety of high mass fluorine-containing metal fragments, indicating that two of the three ligands are involved in metal fluorination. In this paper, in contrast with previous other studies, 11 we observed large LnO + peaks with the precursors Pr(hfac) 3 , Er(hfac) 3 , and Yb(hfac) 3 .…”