Formation and structure of cinchona alkaloid (bis-2,3-naphthalenediyl)orthoborate salts

A series of (bis-2,3-naphthalenediyl)orthoborate salts of Cinchona alkaloid s has been synthesized and characterized. The interactions between ions in the salts have been studied by means of circular dichroism spectroscopy and X-ray crystal structure determination. The CD spectra of the dihydroquinid ine salt show that in non-polar solvents it exists as a tightly held ion pa ir. The crystal structure of the cinchonidine salt proves the existence of ions in the solid state. The protonation takes place at the quinuclidine ni trogen atom. The hydrogen bonds connect cation and anion into one recogniza ble unit. Additional hydrogen bonds (with hydroxy group as a hydrogen donor and quinoline nitrogen atom as an acceptor) form infinite chains of cation s along the [001] direction. There are cavities in the crystal structure th at are partially filled by solvent molecules (acetone).