Synthesis and X-ray crystal structure analysis of 1:1 and 1:2 complexes of cisplatin with the model nucleobase 9-methyladenine in its protonated form and a unique HNO3 adduct of cis-[(NH3)2Pt(9-MeAH-N7)2]4+

9-Methyladenium, 9-MeAH+, binds to cis-(NH3)2PtII via its N7 position to give 1:1 and 1:2 complexes, both of which have been isolated. The 1:2 complex is special in that it crystallizes with additional two equivalents of HNO3 per Pt, which are located in rectangular channels. pKa values of the 9-MeAH+ ligands have been determined.