Multinuclear magnetic resonance and X-ray characterization of platinum(II) complexes with substituted-1,2,4-triazolo [1,5-a]pyrimidines Iwona Lakomska a,⇑ , Kamil Hoffmann a , Tadeusz Muzioł a , Jerzy Sitkowski b a Faculty of Chemistry, Nicolaus Copernicus University, Gagarina 7, 87-100 Torun ´, Poland b National Institute of Medicines, Chełmska 30/34, 00-725 Warszawa, Poland highlights  Platinum(II) coordination compound as potent anticancer agent.  15 N NMR can be used to determinate a coordination mode of triazolopyrimidine.  X-ray determination. article info Article history: Received 22 July 2013 Received in revised form 28 September 2013 Accepted 8 October 2013 Available online 15 October 2013 Keywords: Platinum(II) complex Triazolopyrimidine 15 N NMR, X-ray abstract Mononuclear, square-planar platinum(II) complexes having general formula cis-[PtI 2 (L) 2 ], where L = 7-isobutyl-5methyl-1,2,4-triazolo[1,5-a]pyrimidine (ibmtp) (1), 5,7-diethyl-1,2,4-triazolo[1,5-a] pyrimidine (detp) (2), 5,6,7-trimethyl-1,2,4-triazolo[1,5-a]pyrimidine (tmtp) (3) and 5-methyl-1,2, 4-triazolo[1,5-a]pyrimidin-7(4H)-one (HmtpO) (4) have been synthesized and characterized by infrared and multinuclear magnetic resonance ( 1 H, 13 C, 15 N, 195 Pt) spectroscopy. The solid-state structure of cis-[PtI 2 (dptp) 2 ]2dmf (5) has been determined by X-ray diffraction method. X-ray structure and spectroscopical parameters revealed that the heterocyclic ligands are coordinated to platinum(II) ion via N(3). Ó 2013 Elsevier B.V. All rights reserved. 1. Introduction Cisplatin is one of the most effective anticancer drugs that are currently used to treat various types of human cancer. However, the medical application of these drug has been greatly hampered by poor solubility in aqueous solution, drug resistance and several side effects. Those clinical inconveniences in the cisplatin chemotherapy prompted the design and synthesis of more effective and less toxic platinum anticancer drugs. Therapeutic properties of novel platinum(II) complexes can be improved by replacement the stable amine molecules with different N-donors ligands or by substitution of the chloride ions with other ionic groups [1]. In the original formulation of platinum anticancer drugs structure–activity relationships iodido is also the preferred leaving group. It is expected to depart slowly from platinum coordination sphere, leading to more sluggish DNA modification [2]. Following this research line, Casini and Quirog have been investigated the reactivity of cis and trans diiodido platinum(II) compounds contained aliphatic amines with biomolecules such as: cyto- chrome c or modified amino acid [3]. Both series of platinum(II) complexes manifested pronounced cytotoxic effects with the trans isomers being generally more effective than their cis counterparts. Additionally, cell cycle analysis revealed different modes of action for these complexes with respect to cisplatin. In reference to the examined interactions of received complexes with biomolecules, they observed that trans complexes are markedly less reactive than their cis isomers with model amino acids and peptides. In addition, the cis compounds manifest a peculiar reactivity, which involves the release of the amine ligands and retention of the iodides upon biomolecule binding. Interestingly, the most cytotoxic trans com- plexes are less reactive with model peptides but more efficient in binding to nucleic acids with respect to the cis analog. On the other hand, Rochon’s group have been studied diiodido Pt(II) complexes on general formula: cis and trans-[PtI 2 (A) 2 ], where A = primary, secondary or aromatic amines, using 195 Pt NMR [4–6]. In most cases, signals of cis complexes were detected at lower fields than for the trans isomers. The smallest differences between 0022-2860/$ - see front matter Ó 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.molstruc.2013.10.021 ⇑ Corresponding author. Tel.: +48 56 6114510. E-mail address: iwolak@chem.umk.pl (I. Lakomska). Journal of Molecular Structure 1056–1057 (2014) 146–151 Contents lists available at ScienceDirect Journal of Molecular Structure journal homepage: www.elsevier.com/locate/molstruc