Robert G. Ghirardelli

Oral toxicity of the cyclic polyethers--12-crown-4, 15-crown-5, and 18-crown-6--in mice.

Abstract The acute and chronic oral toxicities of a homologous series of three crown ethers in mice have been studied. The LD50 values and the partition coefficients (octanol/water) of the compounds have been determined. The LD50 values are as follows: 12-crown-4, 3.15 g/kg; 15-crown-5, 1.02 g/kg; and 18-crown-6, 0.71 g/kg. The compounds follow a general trend of increasing toxicity with increasing ring size and water solubility. There appears to be no cumulative effect of daily ingestion of small amounts (one-half to one-third the LD50 value) of the compounds over a 2-week period.

Ion pairing in metal nitrate complexes of optically active crown ethers detected by circular dichroism

Abstract The detection by circular dichroism of ion pair formation in the lithium nitrate complexes of two new optically active crown ethers is described.

Optical Activity (CD and CPL) as a Probe of Ion Pairing and Solution Structure of Macrocycle Complexes

The nature, significance and methods of evaluating ion pairing effects are reviewed, particularly with respect to the complexes of crown ethers and related macrocycles. The application of chiroptical techniques, specifically circular dichroism (CD) and circularly polarized luminescence (CPL), to the investigation of ion pairing and related solution structural phenomena in complexes of chiral crown ethers with alkali, alkaline earth, transition metal and lanthanide ions is described. The use of induced optical activity of crown substituent π → π* transitions, cation d → d and f → f transitions and anion n → π* transitions is illustrated. Emphasis is placed on recent results of the use of NO 3 - and NO 3 - n → π* CD as a probe of ion pairing in alkali and alkaline earth complexes of four chiral derivatives of 18-crown-6 in chloroform and on related studies in various solvents of the f → f CPL of europium(III) nitrate, Perchlorate and chloride complexes of the same macrocycles. Structural deductions based on the chiroptical results are correlated with total luminescence, vibrational spectroscopy, conductance and crystal structure data, as appropriate.