SOLVENT EFFECT ON 2ND-SPHERE COORDINATION OF FERRIOXAMINE-B WITH SUBSTITUTED 18-CROWN-6 AND 30-CROWN-10 CROWN-ETHERS IN DICHLOROMETHANE AS COMPARED TO CHLOROFORM

Stability constants for the second-sphere association of picrate and p erchlorate salts of ferrioxamine B (FeHDFB+) with the substituted crow n ethers (CE) 18-crown-6, cis-dicyclohexano-18-crown-6, benzo-18-crown -6, dibenzo-18-crown-6 and dibenzo-30-crown-10 were determined in dich loromethane and compared with corresponding data collected in chlorofo rm. The stability of the supramolecular assembly {FeHDFB+,CE,X-} is in creased in wet CH2Cl2 compared to wet CHCl3 by 0.21 to 0.74 log units. This represents a deviation from the expected trend of higher host-gu est stability constants in a less polar solvent. The complexity of the molecular recognition process is discussed in the context of the role of the solvent in relation to the role of the cation and anion, and t heir hydration shells, and the crown ether structure, in determining t he stability of the supramolecular assembly.