Complexes of azathioprine, a biologically active mercaptopurine derivative, with Pt(II), Pd(II), Rh(III), Ru(III) and Ag(I)

In order to possibly elucidate the prevailing factors determining the binding sites in the interactions of azathioprine (AZAH), a biologically active 6-mercaptopurine derivative, with the platinum group and other heavy metals, we probed the binding sites of AZAH with Pt(II), Pd(II), Rh(III), Ru(III), and Ag(I) by using 1H and 195Pt NMR, ESR, and IR spectroscopic techniques as well as magnetic susceptibility measurements and mass spectrometry. The altered coordination behavior of AZAH with respect to the parent 6-mercaptopurine, with sulfur no longer being the primary binding site, was ascertained. In the Pt(II), Rh(III), and Ru(III) complexes, 1H NMR data imply coordination of the metal through the N(3) and N(9) positions of the purine ring, while in the case of the Pt(II) compound, 195Pt NMR data further ascertain AZAH binding in a bridging mode through ring nitrogens. As opposed to the aforementioned metals, in the Pd(II) and Ag(I) compounds, 1H NMR data suggest binding via the N(9) position of deprotonated AZAH. Conductivity measurements for all compounds, except for that of Pt(II), showed a nonelectrolyte behavior in solution; the presence of ionic nitrate in the Pt(II) compound was further ascertained by IR spectroscopy. The coordination sphere of the metal in the cases of the Pt(II) and Pd(II) compounds is completed by ammonia and water molecules, respectively, while in those of the Rh(III) and Ru(III) compounds is completed by chloride bridge. For the Ru(III) compound, the latter is confirmed by magnetic susceptibility measurements.

Synthesis, spectroscopic and magnetic resonance studies of mercury (II) and methylmercury (II) complexes of azathioprine, a biologically active mercaptopurine derivative

Synthetic and spectroscopic studies of the Hg(II) and MeHg(II) complexes of azathioprine (AZA), a biologically active 6-mercaptopurine derivative, were undertaken. The altered coordination behavior of AZA with respect to the parent mercaptopurine, with sulfur no longer being the primary donor atom, was confirmed. As concluded by the 1H NMR, 13C NMR, and IR spectroscopic data, Hg(II) binds to the N(9) position of deprotonated AZA, while in the MeHg(II) compound, coordination occurs through the N(3) and N(9) positions of the purine ring. The values of the coupling constants 2J (199Hg-1H), 1J(199Hg-13C) for the MeHg(II) compound further support complexation via nitrogen atoms of the purine. Elemental analyses confirmed the compounds to be Hg(AZA)2 (1) and [(MeHg)2(AZA)](NO3) (2); conductivity measurement values show that 1 is a nonelectrolyte and 2 is a 1:1 electrolyte. Furthermore, the FAB-MS of the compounds confirms direct binding of the metal to the ligand, and in the case of the MeHg(II) compound, the successive loss of one and two MeHg(II) moieties can be clearly observed.

Mono-vitamin B6 complexes of palladium(II) and their interactions with nucleosides

The interactions of potassium tetrachloropalladate(II) with the B6 vitamins pyridoxal, pyridoxine, and pyridoxamine in 1:1 molar ratio have been studied. From DMF solutions, the ionic trichloro (pyridoxal or pyridoxine) palladates(II) were isolated. Pyridoxamine, on the other hand, in aqueous solutions gave the dimeric complex bis [mu-chloro-pyridoxaminato-palladium(II)]. In the first two complexes, the ligands coordinated to palladium through their pyridine nitrogen while, in the last one, pyridoxamine acted as a chelating ligand through its phenolic oxygen and aminomethyl nitrogen. All three complexes reacted with nucleosides, yielding the complexes [Pd(PL)(Nucl)Cl2], [Pd(PN)(Nucl)Cl2], and [Pd(PM-H+)(Nucl)Cl], respectively. Those complexes with one ionizable N(1)H imino proton underwent deprotonation, and the new mixed ligand complexes [Pd(PL)(Nucl-H+)Cl], [Pd(PN)(Nucl-H+)], and [Pd(PM-H+)(Nucl-H+)] were formed. In all mixed ligand complexes, the B6 vitamins maintained their coordination modes. The nucleosides, on the other hand, exhibited their usual coordination sites, i.e., in the nondeprotonated complexes, purine nucleosides coordinated only through their N7 atom. In the deprotonated complexes, they acted as bidentate ligands and coordinated through their N7 and O6 atoms. All complexes were characterized with elemental analyses, conductivity measurements, and various spectroscopic techniques.

Gold complexes of purine and pyrimidine nucleosides

the reactions of chloroauric acid (HAuCl4) with inosine=ino, guanosine=guo, triacetylinosine=trino, triacetylguanosine=trguo, and cytidine=cyd were studied. Complexes of AU(III) and AU(I) with these nucleosides have been isolated from the reactions at different pH values in aqueous and in methanolic solutions. The Au(I) complexes were obtained by reducing Au(III) with 1-ascorbic acid in aqueous solutions. All the isolated complexes were characterized by elemental analyses, conductivity measurements, IR, 1H nmr, and esr spectra. The Au(III) complexes correspond to the general formulae [Au(nucl)2Cl2]Cl, Au(nucl)Cl3, and Au(nucl-H+Cl2, while the Au(I)complexes are of the au(nucl)2Cl type, where nucl represents the above nucleosides. In the complex with the composition (AucydCl2]2 that was isolated from aqueous solutions, the Au atom is believed to be in the (II) oxidation state. Possible structures for all the isolated complexes based on the experimental data are proposed and discussed.