Four-State Molecular Shuttling of [2]Rotaxanes in Response to Acid/Base and Alkali-Metal Cation Stimuli.

In this study, we synthesized [2]rotaxanes possessing three recognition sites-a dialkylammonium, an alkylarylamine, and a tetra(ethylene glycol) stations-in their dumbbell-like axle component and dibenzo[24]crown-8 (DB24C8) as their macrocyclic component. These [2]rotaxanes behaved as four-state molecular shuttles: i) under acidic conditions, the DB24C8 unit encircled both the dialkylammonium and alkylarylammonium stations; ii) under neutral conditions, the dialkylammonium unit was the predominant station for the DB24C8 component; iii) under basic conditions, when both ammonium centers were deprotonated, the alkylarylamine unit became a suitable station for the DB24C8 component; and iv) under basic conditions in the presence of an alkali-metal cation, the tetra(ethylene glycol) unit recognized the DB24C8 component through cooperative binding of the alkali-metal ion. In addition, we observed that the [2]rotaxanes exhibited selective recognition for metal cations. These shuttling motions of the macrocyclic component proceeded reversibly.

Sellmeier and thermo-optic dispersion formulas for the extraordinary ray of 5 mol. % MgO-doped congruent LiNbO(3) in the visible, infrared, and terahertz regions.

This paper reports the high-accuracy Sellmeier and thermo-optic dispersion formulas for the extraordinary ray of 5 mol. % MgO-doped congruent LiNbO(3) that provide excellent reproduction of the temperature-dependent quasi-phase-matching conditions in the 0.39-4.95 µm and 150-270 µm ranges. We believe that these equations would be highly useful for designing the frequency conversion system based on periodically poled MgO-doped LiNbO(3)