81 / 2023-09-20 19:05:18

Luminescent properties of the P,P-bischelate copper(I) complexes on the P2N2-ligands scaffold

copper(I) complexes,cyclic bisphosphines,luminescence

Phosphorus Material Chemistry and Applied Science > 1) Phosphorus chemistry in material science

Copper(I) complexes with P,P-chelate ligands are promising candidates for application in organic light-emitting diodes (OLEDs) or light-emitting cell (LEC) design. The emission of these complexes commonly originates from metal-to-ligand charge transfer (MLCT) transitions. These transitions formally lead to oxidation of Cu(I) to Cu(II) and consequently to distortion of the ligand environment from tetrahedral to planar. Bulky ligands provide rigidity to the copper(I) ligand environment, that allows to prevent the transition on the planar geometry, which results in the increasing of quantum yields of luminescence. [1] In this work, we sythesized P,P-bischelate copper(I) complexes based on the structurally rigid P₂N₂-ligands, namely 1,5-diaza-3,7-diphosphacyclooctanes (Figure 1). [2].





When the complexes are at room temperature, their solid-state emission spectra show two bands at around 350 and 430 nm, but when temperature is decreased to 77 K, a third band appears at around 490 nm. The intensity of this third band then drastically increases, while the intensities of the two other bands only slightly increase. Computational analysis suggests that the emission bands are caused by metal-to-ligand charge transfer (MLCT) transitions. These transitions involve the p-tolyl substituents and the copper(I) ion, which flattens the geometry of the ligand environment. The emission bands are therefore assigned to fluorescence from singlet states with tetrahedral and flattened geometries of the copper(I) ligand environment (350 and 430 nanometers, respectively) and to phosphorescence (490 nanometers).



The research was financially supported by the RSF grant (grant 22-13-00147).



[1] Iwamura, M.; Takeuchi, S.; Tahara, T. J. Am. Chem. Soc. 2007, 129 (16), 5248–5256.

[2] Strelnik, I.D.; Dayanova, I.R.; Gerasimova, T.P. et al. Inorg. Chem., 2022, 61, 16596−16606