Complexes of palladium(II) with theophylline-7-acetic acid

The complexes trans-[Pd(tpH)2Cl2], tpH = theophylline-7-acetic acid; cis- and trans-[Pd(tpH)(BH)Cl2],BH=adenine (adH), guanine (guaH) or cytosine (cytH); and trans-[Pd(tpH)(B′H)Cl2] and [Pd(tp)(B′H)Cl], B′H = inosine (inoH) or guanosine (guoH) have been prepared and characterised by elemental and thermal analyses, electronic, infrared, 1H and 13C NMR spectroscopic studies. Coordination through the imidazole nitrogen, N9 and in some cases additional coordination through the acetate oxygen are demonstrated. The complexes with the theophylline-7-acetate anion are dimeric involving the bridging of theophylline-7-acetate anion. Extended Hückel molecular orbital (EHMO) calculations on tpH and structurally related xanthines indicate N9 of tpH is the most probable binding site which also agrees with the experimental results. The anticancer activity studies on the complex cis- [Pd(tpH)(cytH)Cl2] against Dalton's lymphoma in Swiss mice indicate that the complex possesses marginal activity. © 1990.