Comprehensive Vibrational Spectroscopic Investigation of trans,trans,trans-[Pt(N3)2(OH)2(py)2], a Pt(IV) Diazido Anticancer Prodrug Candidate

We report a detailed study of a promising photo-activatable metal-based anticancer prodrug candidate, trans,trans,trans-[Pt(N-3)(2)(OH)(2)(py)(2)] (Cl; py = pyridine), using vibrational spectroscopic techniques. Attenuated total reflection Fourier transform infrared (ATR-FTIR), Raman, and synchrotron radiation far-IR (SR-FIR) spectroscopies were applied to obtain highly resolved ligand and Pt-ligand vibrations for Cl and its precursors (trans[Pt(N-3)(2)(py)(2)] (C2) and trans-[PtCl2(py)(2)] (C3)). Distinct IR- and Raman-active vibrational modes were assigned with the aid of density functional theory calculations, and trends in the frequency shifts as a function of changing Pt coordination environment were determined and detailed for the first time. The data provide the ligand and Pt-ligand (azide, hydroxide, pyridine) vibrational signatures for Cl in the mid- and far-IR region, which will provide a basis for the better understanding of the interaction of Cl with biomolecules.