%0 Journal Article
%T Structurally Diverse Metal Coordination Compounds, Bearing Imidodiphosphinate and Diphosphinoamine Ligands, as Potential Inhibitors of the Platelet Activating Factor
%A Alexandros B. Tsoupras
%A Maria Roulia
%A Eleftherios Ferentinos
%A Ioannis Stamatopoulos
%A Constantinos A. Demopoulos
%A Panayotis Kyritsis
%J Bioinorganic Chemistry and Applications
%D 2010
%I Hindawi Publishing Corporation
%R 10.1155/2010/731202
%X Metal complexes bearing dichalcogenated imidodiphosphinate ligands (E = O, S, Se, Te), which act as (E,E) chelates, exhibit a remarkable variety of three-dimensional structures. A series of such complexes, namely, square-planar , tetrahedral , E = O, S, and octahedral , were tested as potential inhibitors of either the platelet activating factor (PAF)- or thrombin-induced aggregation in both washed rabbit platelets and rabbit platelet rich plasma. For comparison, square-planar , X = Cl, Br, the corresponding metal salts of all complexes and the ligand were also investigated. showed the highest anti-PAF activity but did not inhibit the thrombin-related pathway, whereas , with also a significant PAF inhibitory effect, exhibited the highest thrombin-related inhibition. and inhibited moderately both PAF and thrombin, being more effective towards PAF. This work shows that the PAF-inhibitory action depends on the structure of the complexes studied, with the bulkier being the most efficient and selective inhibitor. 1. Introduction Extensive research work over the last few years has revealed a remarkable structural variability of transition metal compounds bearing dichalcogenated imidodiphosphinate type of ligands, that is, , E = O, S, Se, Te; R, = various aryl or alkyl groups. These ligands have been shown to display great coordinating versatility, producing both single and multinuclear metal complexes, with a variety of bonding modes [1¨C3]. The coordinating flexibility of these (E,E) chelating ligands is attributed, mainly, to their large ( 4£¿£¿) E E£¿bite, which would accommodate a range of coordination sphere geometries. For instance, it was recently shown that the [ P(Se)NP(Se) ligand affords both tetrahedral and square-planar complexes of Ni(II) [4], in agreement with an earlier observation on the analogous [Ph2P(S)NP(S)Ph2 ligand [5]. Moreover, the nature of the R and peripheral groups of the [R2P(S)NP(S) ligand has been shown to affect the geometry of the complexes formed upon its coordination to Ni(II) [6, 7]. In a more general sense, depending on the nature of the metal ion, the chalcogen E atom and the R peripheral group, complexes bearing the above type of ligands were shown to contain rather diverse coordination spheres [8]. Such structural differences are of significant importance, as they are expected to lead not only to different stereochemical characteristics, but also to varied electronic properties of the metal site, which, in turn, could potentially result in significant biological reactivity [9]. The aim of this work was to investigate a
%U http://www.hindawi.com/journals/bca/2010/731202/