Synthesis, characterization, and photophysical properties of a new 2,5-di(aryl)phosphole derivative and their trigonal copper–phosphole complexes

A new phosphole derivative, 2,5-di(2-quinolyl)-1-phenylphosphole (1), was synthesized by using the Fagan–Nugent method. Phosphole 1 was obtained as an air-stable solid in high yield (73%). Additionally, two new copper–phosphole complexes, [CuX(Phosphole)₂] (X = Cl (2a), I (2b), Phosphole=1), have been synthesized by reaction of CuX (X = Cl, I) and 1. All compounds were characterized by NMR, ESI-MS, UV–Vis, and fluorescence spectroscopy. The photophysical properties of all compounds were analyzed. UV–Vis spectra of 2a-b show π–π* transitions with shifts very similar to the free phosphole due to that their symmetrical structures inhibiting an efficient intraligand charge transfer, ILCT. Compounds 1, 2a-b exhibit fluorescence between 460 and 583 nm with quantum yields of Φ_f =0.04 − 0.11. The emission energy of 2b is higher than 2a, suggesting that λ _max is affected by the ligand-field strength of the halide in the complexes (I^¯ < Cl^¯). The suggested structures of 2a-b were analyzed computationally at the PBEPBE/def2svp level of theory. The rotation barrier of the quinolyl group was analyzed by a scan analysis. Then, the 3 D structures of 2a-b were obtained in good agreement with the experimental results.