A series of [Cu(N–N)(P–P)]BF4 complexes: Luminescence quenching caused by electron-configuration transformation in excited state

In this paper, we report a series of [Cu(N–N)(P–P)]BF4 complexes based on two phosphorous ligands and three 1,10-phenanthrolin derived diimine ligands, including their syntheses, characterizations, crystal structures. Their photophysical properties were experimentally measured and theoretically analyzed by time-dependent density functional theory (TD-DFT). It is found that the introduction of too many fused phenyl rings into diimine ligand leads to luminescence absence of corresponding [Cu(N–N)(P–P)]+ complexes at room temperature. A detailed analysis suggests that the thermal activated electron-configuration transformation between the [Cu(N–N)(P–P)]+ triplet metal-to-ligand-charge-transfer (3MLCT) state and the lowest lying excited state of its diimine ligand (3LC) is responsible for the luminescence quenching.

Graphical abstractA series of Cu(I) complexes have been synthesized and studied. It is found that luminescence can be quenched by the thermal activated electron-configuration transformation in excited state Cu(I) complexes.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► A series of [Cu(N–N)(P–P)]BF4 are synthesized and studied in detail. ► Photophysical properties are measured and analyzed in detail. ► Excess phenyl rings in diimine ligand leads to luminescence absence. ► The electron-configuration transformation is the luminescence quencher.