High-resolution ESI Mass Spectrometry Research Articles

Synthesis, structural characterization and anion binding studies of palladium macrocycles with hydrogen-bonding ligands

The reactions between [Pd(P-P)(OTf)2] (where P-P=dppp or dppf) and two different bipyridyl ligands (=1,3-bis(4-pyridylmethyl)urea and=1,3- bis(pyridinylmethyl)benzenedicarboxamide) containing hydrogen-bonding units have been studied. The X-ray crystal structures of three of these assemblies have been solved showing them to be the [2+2] metallo-macrocycles [Pd(P-P)(n)]2(OTf)4 [P-P=dppp, n=1, (); P-P=dppp, n=2, (); P-P=dppf, n=1, ()]. To confirm whether the dimeric assembly of one of these species () is retained in solution, several investigations have been carried out. 1H NMR studies in DMSO and high resolution ESI mass spectrometry have shown that is in equilibrium with a larger [3+3] metallo-macrocycle. The equilibrium between these two species can be modified by changing the temperature, concentration or solvent. Also, addition of certain anions (e.g. [H2PO4]-) to the mixture shifts the equilibrium favoring the formation of the [2+2] metallo-macrocycle over the [3+3] (initially present in a larger proportion).

Thiocolchicine−Podophyllotoxin Conjugates: Dynamic Libraries Based on Disulfide Exchange Reaction

A dynamic combinatorial library of thiocolchicine-podophyllotoxin derivatives based on the disulfide bond exchange reaction is described. The influence of a biological target on the composition of the reaction mixture has been demonstrated. Use of high-resolution ESI mass spectrometry to evaluate the composition of the mixture shows promise for the design of new large libraries. The biological evaluation demonstrates that formation of a divalent compound affords a new chemical entity whose biological activity is not merely the sum of the single ligands activities, thus reflecting a different interaction with the biological target.