Alkynyl triphosphine copper complexes: synthesis and photophysical studies.

Area of Science:

• Organometallic Chemistry
• Coordination Chemistry
• Materials Science

Background:

• Copper(I) complexes with alkynyl ligands are of interest for their electronic and photophysical properties.
• Designing ligands that control the nuclearity and structure of metal complexes is crucial for tuning their functions.

Purpose of the Study:

• To synthesize and characterize a series of copper(I) alkynyl complexes with a rigid triphosphine ligand.
• To investigate how the ligand structure influences the nuclearity (mono-, di-, or trinuclear) of the resulting copper complexes.
• To explore the solid-state photophysical properties, including luminescence, of these novel copper(I) complexes.

Main Methods:

• Reaction of a rigid triphosphine ligand with Cu(I) and terminal alkynes under basic conditions.
• Single crystal X-ray diffraction for structural determination of selected complexes.
• Nuclear Magnetic Resonance (NMR) spectroscopy (31P, 1H, 1H-1H COSY) to confirm structural integrity in solution.
• Photophysical studies (luminescence spectroscopy) at variable temperatures (298 K and 77 K).
• Time-Dependent Density Functional Theory (TD-DFT) calculations to elucidate electronic transitions.

Main Results:

• A family of copper(I) alkynyl complexes with varying nuclearities (mono-, di-, trinuclear) was successfully synthesized.
• The nuclearity of the complexes was controlled by the number of terminal alkyne groups on the ligand.
• X-ray diffraction confirmed distorted tetrahedral coordination geometry around Cu(I) centers, achieved through tridentate ligand coordination and alkynyl σ-bonding.
• NMR spectroscopy verified the stability of the complexes in solution.
• Moderate to weak orange luminescence was observed, with mononuclear complexes showing potential for thermally activated delayed fluorescence (up to 19% quantum yield).
• Emission quantum yields were sensitive to the nature of the alkynyl ligand, as supported by TD-DFT studies.

Conclusions:

• The rigid triphosphine ligand effectively controls the nuclearity of copper(I) alkynyl complexes.
• These complexes exhibit interesting structural and photophysical properties, with potential applications in luminescence.
• The electronic transitions and luminescence behavior are influenced by both the copper center and the alkynyl substituents, offering avenues for further tuning.