No abstract

We report the absorption, resonance Raman, and excitation spectra of mass selected cerium, praseodymium, and neodymium dimers in argon matrices. Absorption bands were found for each sample. The excitation profiles give more sensitive detail and resemble absorption spectra. Resonance Raman spectra give single progressions for which Ce2: ωe=245.4±4.2 cm−1, Pr2: ωe=244.9±1.2 cm−1, and Nd2: ωe=148.0±1.9 cm−1, ωexe=0.7±0.4 cm−1. Comparison among lanthanide dimers is discussed.

The absorption and resonance Raman spectra of yttrium dimers (Y2) in argon matrices are measured for the first time. The absorption spectrum (scattering depletion spectrum SDS) shows a weak, broad transition centered near 485 nm. Resonance Raman spectra obtained by exciting into this absorption band with several visible laser lines (465.5–496.5 nm) give a single, sharp progression with up to ten Stokes transitions. These data give ωe=184.4(4) cm−1, with ωexe=0.30(3) cm−1, leading to a spectroscopic dissociation energy of De=3.5(4) eV. Comparison of our results with several ab initio calculations adds confirmation to the assignment of the ground state of Y2 to be the Σg+1 state.

Resonance Raman spectra of rhodium trimers (Rh 3) in argon matrices have been obtained for the first time. Our samples are prepared by neutralizing a mass-filtered beam of trimer ions. Although the absorption spectrum of our optically thin samples failed to show any obvious transitions, a rich Raman spectrum was found for laser excitation wavelengths between 545 nm and 593 nm. Three fundamentals, corresponding to normal modes of a bent (C 2v) molecule can be assigned with up to four overtones in the symmetric stretch. Using standard techniques, we obtained for this mode e ϭ322.4(6) cm Ϫ1 , with e x e ϭ0.49(10) cm Ϫ1. The resulting stretching force constant is k e ϭ2.10Ϯ0.01 mdyn/Å. Assuming a Morse potential governs the symmetric stretching normal coordinate, we obtain an atomization energy of D e ϭ6.6Ϯ1.4 eV. The asymmetric stretch and bend are found at 259 cm Ϫ1 and 247.9͑8͒ cm Ϫ1 , respectively. A line at 400 cm Ϫ1 is observed, which does not fit the normal mode scheme of the ground state. This is assigned as the origin of a low lying electronic state.

The process used to prepare a functionalized dihydrobenzothiadiazole S,S-dioxide on a pilot plant scale is described. Key changes to the original synthesis included: modifying S N Ar reaction conditions between a substituted aniline and 2-fluoronitrobenzene from n-BuLi/-78 °C to KOtAm/0 to 15 °C; replacement of a NaIO 4 -RuCl 3 oxidizing system with bleach under phase transfer conditions; and a late-stage Mitsunobu reaction. The Mitsunobu reaction was used to prepare the penultimate intermediate and the process was telescoped forward through an N-Boc deprotection step that generated the active pharmaceutical ingredient. The product was efficiently extracted into the aqueous phase under acidic conditions so that the Mitsunobu byproducts could be washed away from the product with toluene. Although Mitsunobu reactions appear to be rarely used on scale, our results indicate that extraction of the API into an aqueous layer is an efficient way to separate the API from triphenylphosphineoxide and hydrazinedicarboxylate byproducts.