Base-mediated alkynyl-cubane to Cu₈-alkynide cluster transformation

Area of Science:

• Coordination chemistry
• Organometallic chemistry
• Materials science

Background:

• Copper cubane clusters are versatile precursors in coordination chemistry.
• Ligand deprotonation is a key strategy for modifying metal cluster structures and properties.
• Acetylene ligands offer unique coordination modes that influence electronic and optical behavior.

Purpose of the Study:

• To investigate the structural and photophysical transformations of a copper cubane cluster upon ligand deprotonation.
• To explore the coordination behavior of terminal and deprotonated acetylide moieties in copper clusters.
• To characterize the solid-state emission properties of the resulting copper complexes.

Main Methods:

• Synthesis and characterization of copper cubane ([Cu4Cl4(LH)4]) and octanuclear ([Cu8L8]) clusters.
• Spectroscopic analysis (e.g., UV-Vis, emission spectroscopy) to determine photophysical properties.
• X-ray crystallography to elucidate the coordination modes and structural differences.

Main Results:

• Successful conversion of the cubane cluster to an octanuclear cluster via ligand deprotonation.
• Differential coordination modes observed: side-on for cubane and both side-on/end-on for octanuclear acetylides.
• Distinct solid-state emission profiles: octanuclear complex emits at ~640 nm, while the cubane shows thermochromic emission (563 nm at RT to 608 nm at 77 K).

Conclusions:

• Ligand deprotonation effectively transforms copper cubane clusters, altering coordination chemistry and luminescence.
• The resulting octanuclear copper complex exhibits unique coordination and emission properties compared to the parent cubane.
• These findings contribute to understanding structure-property relationships in polynuclear copper systems for potential applications in luminescence.