Frequency comb Vernier spectroscopy for broadband, high-resolution, high-sensitivity absorption and dispersion spectra

A femtosecond frequency comb provides a vast number of equidistantly spaced narrow band laser modes that can be simultaneously tuned and frequency calibrated with 15 digit accuracy. Our Vernier spectrometer utilizes all of theses modes in a massively parallel manner to rapidly record both absorption and dispersion spectra with a sensitivity that is provided by a high finesse broadband optical resonator and a resolution that is only limited by the frequency comb line width while keeping the required setup simple.     

Trinuclear first row transition metal complexes of a hexapyridyl, trialkoxy 1,3,5-triarylbenzene ligand

Trinuclear complexes of Mn(II), Fe(II), Co(II), Ni(II), Cu(II), and Zn(II) were synthesized using a ligand architecture based upon a 1,3,5-triarylbenzene core decorated with six pyridines and three alkoxide moieties. Characterization via X-ray diffraction, NMR, and magnetism studies is discussed.     

Bimetallic effects on ethylene polymerization in the presence of amines: inhibition of the deactivation by Lewis bases

Dinickel complexes supported by terphenyl ligands appended with phenoxy and imine donors were synthesized. Full substitution of the central arene blocks rotation around the aryl-aryl bond and allows for the isolation of atropisomers. The reported complexes perform ethylene polymerization in the presence of amines. The inhibiting effect of polar additives is up to 250 times lower for the syn isomer than the anti isomer. Comparisons with mononuclear systems indicate that the proximity of the metal centers leads to the observed inhibitory effect on the deactivation of the catalysts.     

The Chiral Glycine Enolate Derivative from 1-Benzoyl-2-(tert-butyl)-3-methyl-1,3-imidazolidin-4-one is Alkylated in the 5-Position with Relative Topicity lk. Preliminary Communication

An overall enantioselective substitution of the R-group of an α-hydroxy- or α-amino acid 1 [R? CH(XH)COOH] by another R-group is possible through heterocycles 2 obtained from 1 with pivaladehyde ( 1 → 7 ). The rac- and the (S)-(+)-heterocycles 8 (title compounds of type 5 ) are prepared from glycine and O-benzyl-(S)-serine, respectively. Their enolates (cf. 9 , type 6 ) are alkylated with iodomethane, iodobutane, 2-iodopropane, benzyl bromide, and acetone to give the trans-disubstituted imidazolidinones 10 with ≥ 95% diastereoselectivity. The configuration of the products is established by chemical correlation with alanine, phenylalanine, and valine.     

1H and 13C nuclear magnetic resonance study of (D3)-trishomocuban-4-ol and (D3)-trishomocubanone

The complete assignments of the ¹H and ¹³C NMR spectra for (D₃)-trishomocuban-4-ol (3) and (D₃)-trishomocubanone (4) are reported. The difference between the ¹H and ¹³C chemical shifts of 3 and 4 and those of the hydrocarbon (D₃)-trishomocubane, and the substituent effect of the hydroxy group, can be adequately explained by the unique stereochemistry of these compounds.