The present work demonstrates a new fully regenerative, molecular machine-like "ON-OFF-ON" chemosensor based on a b-carboline molecule "OFF-ON-OFF" cycle. It behaves as a molecular lock that requires a hydrogen sulfate (HSO 4 À ) ion as"key" to open the lock and a fluoride (F À ) ion as "hand" that removes the key from the lock to close the lock. The reversibility and reusability of sensor for the detection of hydrogen sulfate and fluoride ions were tested for six cycles. Experimental and computational studies reveal that the proton transfer process from hydrogen sulfate (HSO 4 À ) ion to the pyridinic nitrogen atom of norharmane leading to the formation of a hydrogen bonded ion pair (HBIP) provides the optical changes in the visible region that are advantageous for real time and on-site application.[a] S.

Der Einbau großer Anteile an Al (bis 29%) verändert die lR‐Charakteristik von BaF2/ThF4‐Gläsern stark.

Vibrational Spectroscopy of Pb/Mn/Ga Fluoride Glasses.

The kinetics of the anation reaction of cis-diaquo-bis-oxalatochromate(III) ion by DL-alanine has been studied spectrophotometrically inthe pH range 3.8 to 7.3, where DLalanine remains in zwitterionic form. A second-order rate law has been established. Reaction rates in three different ethanol-water mixtures were measured. In each solvent medium the anation rate is higher as compared to water exchange reaction at a particular temperature. The activation parameters (AH # and AS #) in different ethanol-water mixtures were obtained from Eyring plots. AG#(A/-/# -TAS ~) values were calculated in each solvent medium and compared with that of the isotopic water exchange process. A reaction mechanism involving the Ss2 path has been suggested~ Keywords. Anation; bis-oxalato-diaquo-chromate(III) ion; amino acid; associative mechanism.