Monotheophylline and monotheophyllinato complexes of palladium(II) and their interactions with nucleosides

Abstract

The interaction of potassium tetrachloropalladate(II) with theophylline in a 1:1 molar ratio resulted in the formation of the monotheophylline (K[Pd(ThH)Cl 3]) or monotheophyllinato ([Pd(Th)Cl] 2) complexes, depending on the solvent and the acidity conditions. In the first complex, theophylline coordinates to Pd(II) as a neutral molecule through its N9 atom, while in the second as a monoanion through both its N7 and O6 atoms. Both complexes react with nucleosides, giving the complexes [Pd(Nucl)(ThH)Cl 2] and [Pd(Nucl)(Th)Cl], respectively. Those complexes with one N(1)H ionizable imino-proton undergo deprotonation and two new series of mixed ligand complexes, [Pd(Nucl − H +)(ThH)Cl] and [Pd(Nucl − H +(Th)] are formed. In the mixed ligand complexes, theophylline maintains its coordination modes. The nucleosides, on the other hand, exhibit their usual coordination sites; i.e. in the nondeprotonated complexes they coordinate only through their N7 atoms, while in the deprotonated they act as bidentate through both their N7 and O6 atoms. All complexes were characterized with elemental analyses, conductivity measurements and various spectroscopic techniques.