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Abstract
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Palladium-based complexes are closely related to their platinum analogues, due to their structural similarities and significant overlap of coordination chemistry for the two metals. A series of novel palladium complexes have been synthesized which exhibit promising activity against tumor cell lines. In several cases the palladium complexes have exhibited better antitumor activity than their platinum counterparts [1]. One of the early synthesized palladiumbased complexes is [Pd{(C5H4N)2CH(2-C5H4NS)}Cl2] (1; see Figure 1) that has been characterized by X-ray crystallography [2]. In this work we report a theoretical study on the interaction of 1 (after removing one Cl-) with guanine, at BP86/def2-TZVP level of theory. Since the guanine has three possible binding sites with the transition metal, all isomers and conformers of 1-guanine complexes were optimized. The calculated relative free energies and interaction energies between 1 and guanine showed that the preferred binding site of guanine to Pd atom in complex 1 (similar to cisplatin) is N7. To investigate the nature of interaction between 1 and guanine, the EDA-NOCV and NBO analyses were also performed on 1-guanine complex. The results of energy decomposition analysis show that the interaction between 1 and guanine is more electrostatic (~62% ) than covalent (~33%) and contribution of dispersion forces is ~5%.
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