"On-off" Au(I)...Cu(I) interactions in a Au(NHC)2 luminescent vapochromic sensor

Area of Science:

• Coordination Chemistry
• Materials Science
• Luminescent Materials

Background:

• Gold(I) and copper(I) complexes are known for their diverse coordination chemistry and luminescent properties.
• N-heterocyclic carbenes (NHCs) are versatile ligands that stabilize metal centers and influence their electronic properties.
• Vapochromism, the change in optical properties upon exposure to vapors, is a desirable characteristic for sensor development.

Purpose of the Study:

• To synthesize and characterize novel heterometallic gold-copper complexes with NHC ligands.
• To investigate the vapochromic behavior of these complexes, focusing on luminescence changes induced by solvent vapors.
• To elucidate the structural and electronic factors governing the observed vapochromism.

Main Methods:

• Synthesis of a tricationic gold(I)-copper(I) complex ([Au(NHC)(2)](+)[Cu(MeCN)(2)](2+)) and its methanol adduct.
• Single-crystal X-ray diffraction to determine the molecular structures of the synthesized compounds.
• Luminescence spectroscopy to monitor emission color changes upon exposure to various solvent vapors (MeOH, MeCN, acetone, H2O).

Main Results:

• The gold(I)-copper(I) complex and its methanol adduct exhibit distinct luminescence colors (blue and green, respectively).
• The structures reveal changes in Au-Cu interactions and coordination environments upon solvent coordination/dissociation.
• Reversible color changes from blue to green, yellow, and orange were observed upon exposure to different solvent vapors, demonstrating vapochromism.

Conclusions:

• The synthesized gold(I)-copper(I) complexes are effective molecular vapochromic materials.
• Ligand substitution reactions triggered by solvent vapors induce significant changes in luminescence, attributed to "on-off" Au-Cu interactions.
• These materials show promise for applications in chemical sensing and responsive materials.