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Absorption difference and comparative absorption spectrophotometric studies on praseodymium(III) and fluorouracil, fluorocytosine, fluoroadenine, fluorothymine, fluorouridine, fluorocytidine, fluoroadenosine and fluorothymidine systems at pH approximately 5.5 and in different stoichiometries in 80% DMF medium have been carried out. Magnitudes of spectral parameters, viz. Coulombic (Fk), spin-orbit (zeta 4f), nephelauxetic (beta), bonding (b), intensity (T lambda Judd-Ofelt), and oscillator strength (P) and their variation have provided information on the binding mode of these biomolecules in terms of outer and inner sphere complexation, degree of covalency and extent of 4f orbital involvement. Preliminary ultrasonic studies have indicated that these biomolecules behave as structure breakers, hence weak ligands in aqueous medium, while strengthening water structure in semi-nonaqueous medium. The analysis of the isolated solid complexes has suggested octa- and nona-coordination for praseodymium(III) in fluorinated nucleic bases and fluorinated nucleoside complexes.

A simple, specific and reliable 1H-NMR spectroscopic method for the quantitative determination of the optical purity of indacrinone is described. After conversion of the S(+)- and R(-)-enantiomers to their methyl ester derivatives, they were coordinated with chiral europium(III) or praseodymium(III) shift reagents in CCl4/C2HCl3 (2:1). The optical purity was calculated from the relative intensities of the enantiomeric resonance signals for the protons of the methyl groups at position C(2) of the indanone ring. Mean +/- SD (n = 6) recoveries of S(+)-indacrinone from synthetic enantiomeric mixtures amounted to 99.75 +/- 0.63% when using europium(III) and 100.01 +/- 0.55% when using praseodymium(III).