Measurement of theg-factor of the 21 + state of192Pt in an external magnetic field

Theg-factor of the 2₁ ⁺ state of¹⁹²Pt has been measured by the IPAC technique in an external magnetic field as:g(2₁ ⁺,¹⁹²Pt)=+0.287(17). An additional IPAC experiment with an¹⁹²IrFe sample was performed with the same level in order to investigate the hyperfine field. The result:ω _L τ(2₁ ⁺,¹⁹²PtFe)=0.1115(9) gives the hyperfine field:B _hf ^4.2k (PtFe)=126.8(71) T. The result of an LTNO experiment with the same level is compatible with the assumption that 100% of the¹⁹²Ir atoms were on unique sites.     

Geometric aspects influencing N-NTB transition - implication of intramolecular torsion

Herein we report a comprehensive study on novel carbonyl- and ethenyl-linked symmetric dimers that combine synthesis, mesomorphic properties and molecular modelling. The study has been focused on the impact of geometry imposed by the linkage group on the incidence of the twist-bend nematic (N_TB) phase. Comparison of the mesomorphic properties of these two series complemented with computational studies of conformational space around the linkage group points molecular curvature and intramolecular torsion plays important role in the appearance of the N_TB phase and can be regarded as the basic structural requirements for design of new twist-bend nematogen materials.     

Wasseruntersuchung

Ohne Zusammenfassung     

Sulfur Ylide Promoted Synthesis of N‐Protected Aziridines: A Combined Experimental and Computational Approach

A range of N‐protected aziridines [N‐Tosyl (N‐Ts), N‐2‐trimethylsilylethanesulfonamide (N‐SES), N‐tert‐butoxycarbonylamido (N‐Boc), and N‐o‐nitrobenzenesulfonamide (oNs)] were prepared in moderate to good yield and with high enantiomeric excess of both isomers starting from N‐protected imines, using a sulfonium salt derived from Eliel’s oxathiane. The diastereoselectivities of the reactions are influenced by the imine N‐protecting group, the imine substituent, and the sulfide structure. An unusual cis selectivity was observed in the formation of N‐tosyl‐2‐phenyl‐3‐tert‐butylaziridine and N‐o‐trimethylsilylethanesulfonamide‐2‐phenyl‐3‐tert‐butylaziridine, which was explained by using computational models. The analysis suggests that betaine formation in the case of N‐tosyl‐tert‐butylaldimine aziridination using oxathiane benzyl sulfonium ylide 1 ′ is reversible and that the selectivity is determined at the rotation step, which is unusual for semistabilized ylide aziridination. We have shown herein that the steric bulk of an imine substituent, in combination with a sterically demanding sulfonium ylide, can also affect the reversibility of the reaction. This is the first example of this sort involving aziridinations using semistabilized ylides.