Structural, spectroscopic and DFT theoretical studies of phosphorescent CuIP₂S-containing cuprous complexes

Area of Science:

• Coordination Chemistry
• Photoluminescence
• Materials Science

Background:

• Luminescent cuprous complexes are valuable due to their availability, cost-effectiveness, and excellent luminescence.
• Cuprous complexes with iodide and phosphine ligands are of particular interest for their unique structural and photophysical properties.

Purpose of the Study:

• To synthesize and characterize two novel CuIP2S-type cuprous complexes: iodido(thiourea)bis(triphenylphosphane)copper(I) ([CuI(TU)(TPP)2]) and (2,3-dihydrobenzimidazole-2-thione)iodidobis(triphenylphosphane)copper(I) ([CuI(DHBIT)(TPP)2]).
• To investigate the UV-Vis absorption and photoluminescence properties of these complexes.
• To elucidate the origin of their phosphorescence emission using computational methods.

Main Methods:

• Single-crystal X-ray diffraction for structural determination.
• UV-Vis absorption and photoluminescence spectroscopy on crystalline powder samples.
• Time-dependent density functional theory (TD-DFT) calculations and wavefunction analysis.

Main Results:

• The crystal structures of [CuI(TU)(TPP)2] and [CuI(DHBIT)(TPP)2] were determined, revealing distorted CuIP2S tetrahedral coordination geometries around the copper(I) centers.
• Both complexes exhibit pale-blue-green phosphorescence.
• Computational analysis indicated that the phosphorescence originates primarily from triplet intra-ligand charge transfer (3(IL+ML)CT) excited states, with a minor contribution from metal-to-ligand charge transfer.

Conclusions:

• The synthesized CuIP2S-type cuprous complexes possess interesting structural and photoluminescent properties.
• The observed pale-blue-green phosphorescence is attributed to a combination of intra-ligand and metal-to-ligand charge transfer transitions.
• These findings contribute to the understanding of luminescence mechanisms in copper(I) coordination compounds.