Homoleptic Tris-Diphosphine Re(I) and Re(II) Complexes and Re(II) Photophysics and Photochemistry.

Area of Science:

• Inorganic Chemistry
• Photochemistry
• Materials Science

Background:

• The ligand-to-metal charge transfer (LMCT) state of [(dmpe)3Re](2+) is a potent oxidant.
• Traditional synthesis of these rhenium complexes yields low quantities.
• Limited optimization of ground and emission properties exists for [(PP)3Re](2+) complexes.

Purpose of the Study:

• To develop improved syntheses for Re(I) tris-homoleptic diphosphine complexes.
• To prepare luminescent Re(II) analogues through single-electron oxidation.
• To investigate the redox and luminescence properties of these complexes.

Main Methods:

• Single-pot reactions of Re(V) oxo-complexes with phosphines at high temperatures.
• Single-electron chemical oxidation using specific oxidizing salts.
• Crystallography to analyze Re-P bond lengths.
• Luminescence spectroscopy and electrochemical measurements.

Main Results:

• Achieved improved syntheses for various [(PP)3Re](+) complexes in good yields.
• Successfully prepared luminescent Re(II) analogues, [(PP)3Re](2+).
• Observed significantly lengthened Re-P bonds in Re(II) complexes compared to Re(I).
• Determined luminescence originates from a P(σ)-to-metal (Re(dπ)) charge transfer ((2)LMCT) state.

Conclusions:

• The developed synthetic routes provide efficient access to Re(II) complexes with tunable properties.
• The luminescence is attributed to a (2)LMCT state, with structured emission at low temperatures.
• The study provides insights into the excited-state redox potentials and charge separation dynamics.