Formation and Structure of Cinchona Alkaloid (Bis-2,3-naphthalenediyl)orthoborate Salts

Maciej Kubicki, Teresa Borowiak, Krystyna Gawrońska, and Jacek Gawroński Department of Chemistry, Adam Mickiewicz University, Grunwaldzka 6, 60-780 Poznan, Poland Reprint requests to Dr M.Kubicki. Fax +48(0)-61-8658008. E-mail [email protected] Z. Naturforsch. 55 b, 1083-1088 (2000); received August 4, 2000 Cinchona Alkaloids, Association Modes, Hydrogen Bonds A series of (bis-2,3-naphthalenediyl)orthoborate salts of Cinchona alkaloids has been syn­ thesized 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 dihydroquinidine salt show that in non-polar solvents it exists as a tightly held ion pair. The crystal structure of the cinchonidine salt proves the existence of ions in the solid state. The protonation takes place at the quinuclidine nitrogen atom. The hydrogen bonds connect cation and anion into one recognizable unit. Additional hydrogen bonds (with hydroxy group as a hydrogen donor and quinoline nitrogen atom as an acceptor) form infi­ nite chains of cations along the [001] direction. There are cavities in the crystal structure that are partially filled by solvent molecules (acetone).