SALT-BRIDGE FORMATION BY CINCHONA ALKALOIDS - QUININIUM SALICYLATE MONOHYDRATE

C20H25N2O2+C7H5O3-.H20, M(r) = 480.56, orthorhombic, P2(1)2(1)2(1), a = 6.957 (2), b = 17.108 (1), c 20.477 (6) angstrom, V = 2437 (1) angstrom3, Z = 4, D(m) = 1.30 (1), D(x) = 1.31 g cm-3, lambda(Cu Kalpha) = 1.5418 angstrom, mu = 7.194 cm-1, F(000) = 1024, T = 293 K, R = 0.0341 for 2507 reflections. Hydrogen bonds link the quininium cation, salicylate anion and water molecule to form an eleven-membered ring which can be compared to salt-bridge clusters observed in myoglobin. The effect of protonation on the quinuclidine geometry is discussed.