Abstract
The photoinduced reaction of [Pt(NO3)6]2- with pyridine or its derivatives (L) was found to result in the formation of [PtL4](NO3)2 salts in high yield. This transformation was successfully probed for methyl- and carboxyethyl-substituted pyridines, and the corresponding [PtL4](NO3)2 salts were isolated and fully characterized using single-crystal X-ray diffraction (SCXRD). Anation of the [Pt(py)4]2+ cationic complex with N3- was studied by 1H NMR spectroscopy in aqueous and water/dimethyl sulfoxide solutions of [Pt(py)4](NO3)2. A mixture of cis- and trans-[Pt(py)2(N3)2] complexes was determined as the final product of this interaction with the domination of the trans-isomer (cis to trans ratio is about 1:8) due to its preferable formation from the transient [Pt(py)3(N3)]+ cationic complex. The difference observed for the experimentally determined activation parameters of trans- and cis-paths of anation was supported by DFT calculations. Finally, the new three-stage Ag-free synthetic procedure for the preparation of the trans,trans-[Pt(py)2(N3)2(OH)2] prodrug (potential agent for the photodynamic anticancer therapy) was found using (i) light-induced formation of [Pt(py)4](NO3)2 from (Bu4N)2[Pt(NO3)6] followed by (ii) anation of [Pt(py)4]2+ with azide and (iii) accomplished by oxidation of the resulting mixture of cis- and trans-[Pt(py)2(N3)2] with H2O2. Efficient separation of cis,trans-[Pt(py)2(OH)2(N3)2] and trans,trans-[Pt(py)2(N3)2(OH)2] produced at the last stage was achieved by simple recrystallization from water.
Published Version
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