New non-aggregating bivalent cis-ML2 (M = Pd, Pt; L = pivaloylcyanoxime)

Abstract

The 1-oximino-1-cyano-3-t-butyl-ketone (pivaloyl-cyanoxime), HPiCO, and its two new bivalent Pd, Pt complexes of the M(PiCO)2 composition were synthesized and characterized using UV-Vis, IR spectroscopic methods, TG/DSC and X-ray analysis. The cyanoxime easily deprotonates upon the addition of a base and forms an anion which exhibits significant solvatochromism: it is pale-yellow in an aqueous solution, but turns pink-red in aprotic DMF with Δλ = 79 nm (3670 cm−1, or 10.3 kcal/M). The ligand HL is an oxime and adopts a trans-anti geometry in a solid state, while in transition metal complexes it is the nitroso anion and has a trans-cis configuration. Both the Pd(PiCO)2 and Pt(PiCO)2 obtained are cis-isomers. All compounds characterized by the X-ray analysis crystallize in centrosymmetric space groups. The Pt(PiCO)2 complex undergoes polymorphic single-crystal-to-single-crystal transition upon cooling: from an orthorhombic crystal system Pnma (#62) at 296 K it becomes monoclinic P21/n (#14) at 100 K. The evaluation of the in vitro cytotoxicity of the new Pd(PiCO)2 and Pt(PiCO)2 complexes (which was the secondary, but rather common and traditional goal during the investigations of these Werner-type complexes) was evaluated against the human solid tumor WiDR colon carcinoma. No aggregation of the compounds was detected in the media or in the presence of the cell culture in the 24-wells plates. An assessment of the cytotoxicity of these new complexes indicated that both metal complexes demonstrate a moderate activity at 6-10% of that of anticancer drug [Pt(NH3)2Cl2] (cisplatin) which was used as a positive control. The Pd(PiCO)2 complex has shown has shown similar - and rather rare for this metal - activity comparable to its Pt-analog, albeit small compared to the conventional anticancer drug

Department(s)

Chemistry and Biochemistry

Document Type

Article

DOI

https://doi.org/10.1016/j.ica.2015.10.040

Keywords

Pt(II) and Pd(II) complexes, cyanoximes, x-ray analysis, uv–vis spectra, pKa

Publication Date

2016

Journal Title

Inorganica Chimica Acta

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