7-[(7S)-7-Aza-niumyl-5-aza-spiro-[2.4]hept-5-yl]-8-chloro-6-fluoro-1-[(1S,2R)-2-fluoro-cyclo-prop-yl]-4-oxo-1,4-dihydroquinoline-3-carboxyl-ate methanol monosolvate.

Sitafloxacin is a newly developed fluoro-quinolone anti-bacterial drug. The crystal studied, C(19)H(18)ClF(2)N(3)O(3)·CH(3)OH, consists of one mol-ecule of sitafloxacin and one methanol solvent mol-ecule. The mol-ecule of sitafloxacin is a zwitterion with a protonated primary amine group and a deprotonated carboxylate group.

Tetracyanoresorcin[4]arene as a pH dependent artificial acetylcholine receptor.

This communication describes the facile synthesis of tetracyanoresorcin[4]arene and its high and pH dependent affinities toward biologically important acetylcholine in the physiological pH region.

Tetracyanoresorcin[4]arene ion channel shows pH dependent conductivity change.

A pH sensitive artificial ion channel, tetracyanoresorcin[4]arene, whose pK(a1) to pK(a3) are around pH 7, was synthesized. Conductivities for potassium ion were increased by the progress of dissociation at the channel mouth.