Thermochimica Acta, 89 (1985) 141-149 Elsevier Science Publishers B.V., Amsterdam ~ Printed in The Netherlands 141 INFLUENCE OF IONIC STRENGTH ON STABILITY CONSTANTS OF Ag(I), Zn(II), Cd(I1) AND Hg(I1) COMPLEXES WITH SOME 4-AMINO-5-NITROSO-PYRIMIDINE DERIVATIVES M.N. MORENO-CARRETERO Department of Inorganic Chemistry, Unioersicv College, 2307/- Jaen (Spain) J.M. SALAS-PEREGRIN * Department of Inorganic Chemistcv, Faculty of Sciences, University of Granada, 18071 -Grunadu (Spain) (Received 7 January 1985) ABSTRACT The stability constants, K,, of the complexes formed by 4-amino-2.6-dioxo-3-methyl-5- nitroso-1,2,3.6-tetrahydro-pyrimidine (LH), 4-amino-1.3-dimethyl-2.6-dioxo-5-nitroso- 1,2,3,6-tetrahydro-pyrimidine (RH) and 4-amino-1,6-dihydro-l-methyl-2-methoxy-5-nitroso- 6-oxo-pyrimidine (JH) with Ag(I). Zn(l1). Cd(I1) and Hg(II) ions. in aqueous media at different ionic strengths and 25°C. have been calculated by Bjerrum’s method. From the data obtained, thermodynamic stability constants have been calculated. in each case, using the Debye-HBckeI limit law and adjusting log K, vs. fi values at a parabolic equation by least-squares methods. The log KF values. calculated by both methods. are in good agreement. INTRODUCTION Recently, the importance of metal ions to the vital functions in living organisms, and, hence, their health and well-being, has become increasingly apparent [l-5]. For this reason, and, especially, because of the chem- iotherapeutic effects that some of these complexes have shown [6-121, the study of interactions between metal ions and components of nucleic acids (pyrimidine and purine derivatives and their nucleosides and nucleotides) has been tackled by numerous investigators, yielding, as a consequence, a great number of publications in recent years [13,14]. As a continuation of our research about the stability of metal-pyrimidine complexes in aqueous solutions [15], we report in this paper the influence of ionic strength of the medium on the stability constants of Ag(I), Zn( II), * To whom all correspondence should be addressed. 0040-6031/85/$03.30 0 1985 Elsevier Science Publishers B.V.