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

Abstract

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.