A new zwitterionic, water soluble, Re(I) complex: Synthesis, spectroscopic and computational characterization

作者：Martinez Saavedra Hector H; Franca Carlos A; Petroselli Gabriela; Erra Balsells Rosa; Ruiz Gustavo T; Wolcan Ezequiel^*

来源：Journal of Organometallic Chemistry, 2013, 745: 470-478.

DOI：10.1016/j.jorganchem.2013.08.038

• Re(I) complex
• Zwitterionic
• MLLCT
• TD-DFT
• Acid-base equilibriums

A new water soluble Re(I) complex with a zwitterionic structure, Bu4N[(bpy)Re(CO)(3)(dcbpy)] (where Bu = butyl; bpy = 4,4'-bipyridine; dcbpy = 2,2'-bipyridine-5,5'-dicarboxylate), was successfully synthesized and characterized by elemental analysis, H-1 NMR, FTIR and ESI. Protonation studies in aqueous solutions of the Re(I) complex showed three acid-base equilibriums with pK(a1) = 5.0, pK(a2) = 3.0 and pK(a3) = 2.0. pK(a1) was assigned to the protonation equilibrium at bpy while pK(a2) and pK(a3) could be ascribed to protonation/deprotonation of the two carboxylates groups in the dcbpy ligand. With the aid of TD-DFT calculations the nature of the electronic transitions responsible for the pH-dependent UV-vis spectroscopy of the Re(I) complex was identified. At pH = 7 the lower energy band of the complex has MLLCTRe(CO)3 -> dcbpy character while at pH < 2 it switches to MLLCTRe(CO)3 -> bpy. This change in the nature of the lower energy band is responsible for the overall spectral changes in the 350-500 nm range after protonation of the Re(I) complex.

• 出版日期2013-11-15