Paramagnetic 19 F NMR and Electrospray Ionization Mass Spectrometric Studies of Substituted Pyridine Complexes of Chromium(III): Models for Potential Use of 19 F NMR to Probe Cr(III)-Nucleotide Interaction

The synthesis and characterization of chromium basic carboxylate complexes, [Cr (O CR) L ] , containing trifluoroacetate, 3-fluoropyridine, 3-trifluoromethylpyridine, and 4-trifluoromethylpyridine are described. The substituted pyridine ligands are used as models of DNA bases to determine whether F NMR would be a potentially useful probe of the binding of Cr to DNA. The F NMR resonances of the coordinated ligands, while broadened by delocalization of unpaired electron density from the S=3/2 chromic centers, are readily discernable, and the contact shifts are of sufficient magnitude that the signals from coordinated and free ligands can easily be differentiated. Thus, F NMR appears to be a potentially useful probe of the binding of Cr to DNA containing F-labeled bases. Additionally, electrospray MS is shown to be a convenient method to establish the identity of chromium basic carboxylate assemblies.