Direct Evidence for the Polymeric Structure of Some Platinum-blue Complexes in Aqueous Solution

Abstract

<jats:title>Abstract</jats:title><jats:p> The anticancer active compound, cis-dichloro-diammine platinum (II), and the biomolecules cytosine and thymine form paramagnetic complexes in aqueous solution. The electron spin resonance spectra which can be attributed to paramagnetic platinum, exhibit large anisotropy in frozen solution as well as in liquid solution. This fact can be explained by assuming poly-meric structures also in liquid solution.</jats:p>

Temperature Dependent ESR Studies on Platinum Pyrimidine “Blues”: Evidence for a Structural Instability ?

“…The same holds true for their detailed molecular structure, as structure analysis is severely impeded by the fact that the compounds have never been obtained in the crystalline form. It is generally assumed, however, that the "blues" form oligomeric compounds as a result of partial oxidation and axial stacking of planar Pt monomers [2][3][4][5][6][7][8][9][10][11][12]. This assumption is consistent with X-ray diffraction studies of a crystalline PDDa-a-pyridone system [6].…”

“…The Pt pyrimidine "blues" exhibit paramagnetism [3,[7][8][9][10][11]13] which can be detected by means of electron spin resonance (ESR) spectroscopy. The ESR results are consistent with the assumption that the unpaired electron spin is located in the 5d2 2 -orbital.…”

ESR Study on Complexes Formed on Reaction of cis-Dichlorodiammineplatinum(II) with Cytosine and Cytidine

“…higher reaction temperature and/or higher concentrations of PDD and cytosine or cytidine dark blue solutions occur after relatively long reaction times. These solutions contain several platinum complexes, including paramagnetic species [5,6], If the preparation procedure is changed only slightly, new types of paramagnetic platinum complexes are formed giving some insight into their molecular structure by means of electron spin resonance (ESR) spectroscopy. The presented results may be a useful contribution to the relatively complicated chemistry of the formation of platinum pyrimidine blue complexes which have also been shown to possess antitumor potency [7].…”

Interactions du Cu(II), du Hg(II) et du Pt(II) avec les formes monomères et dimères de la thymine, de la thymidine et de l'acide orotique

“…Les bases puriques et pyrirnidiques rnonomkres cornposant des acides nuclgiques sont susceptibles de cornplexer de nombreux cations tels que H~~+ , Pt2+, Cu2+, ~i~+ , z n 2 + , c o 2 + , Mg2+, Ca2+ et Pb2+ bien que les constantes de stabilite correspondantes ne soient pas calculCes (1,2,(5)(6)(7)(8). Excepte les travaux que notre laboratoire a publies nous n'avons repertori6 aucune donnCe bibliographique relative a la deprotonation et aux stabilitts thermodynarniques de ces rn&rnes bases sous forme dimCrisCe.…”