Photochemistry of cis,trans-[Pt(en)(I)2(OH)2] complex in aqueous solutions

• Published in: Journal of photochemistry and photobiology. A, Chemistry. Chemistry., 2018-03, Vol.354, p.78-85
• Main Authors: Glebov, Evgeni M., Pozdnyakov, Ivan P., Vasilchenko, Danila B., Zadesenets, Andrey V., Melnikov, Alexey A., Magin, Ilya M., Grivin, Vjacheslav P., Chekalin, Sergey V., Plyusnin, Victor F.
• Format: Article
• Language: English
• Subjects: Aqueous solutions; Chemical compounds; cis,trans-[PtIV(en)(I)2(OH)2]; Coordination compounds; Diiodido Pt(IV) complexes; Drugs; Flash photolysis; Irradiation; Laser flash photolysis; Ligands; Magnetic resonance spectroscopy; NMR spectroscopy; Photochemicals; Photochemistry; Photodynamic therapy; Photoexchange; Photolysis; Photoreduction; Platinum; Prodrugs; Spectroscopy; Spectrum analysis; Ultrafast spectroscopy
• ISSN: 1010-6030; 1873-2666
• DOI: 10.1016/j.jphotochem.2017.06.036

Ligand photoexchange in cis,trans-[PtIV(en)(I)2(OH)2] complex occurs in time interval of 90ps via heterolytic cleavage of Pt − I bond. [Display omitted] •Photochemistry of cis,trans-[PtIV(en)(I)2(OH)2] is a combination of multistage ligand exchange and reduction.•mer-[PtIV(en)(I)(OH)3] is the primary stable product of photolysis.•Characteristic time of photoexchange is about 90ps.•Three successive intermediates were detected in picosecond time domain.•Intermediates were interpreted as the lowest excited state of the complex or pentacoordinated Pt(IV) intermediate. Diiodido Pt(IV) complexes (earlier tested as prodrugs in photodynamic therapy) could be considered as model mixed-ligand platinum complexes. In this work, photochemistry of cis,trans‐[PtIV(en)(I)2(OH)2] complex (1) in aqueous solutions was examined in time interval from hundreds of femtoseconds to hours. UV and NMR spectroscopy, nanosecond laser flash photolysis and ultrafast spectroscopy were applied to study the primary photochemical processes of 1. As it was shown earlier, photolysis of the complex is multistage. On the first stage, mer-[PtIV(en)(I)(OH)3] complex is formed with the quantum yield of 0.06 (irradiation at 282nm). Further ligand exchange and photoreduction occur with much lower quantum yield. The characteristic lifetime of ligand exchange is about 90ps. The spectrum of the key intermediate (KI) was recorded in the picosecond time domain. Depending on the attribution of the KI, two tentative schemes of the primary photophysical and photochemical processes are proposed.