Acute Bite Angle POP- and PSP-Type Ligands and Their Trinuclear Copper(I) Complexes: Synthesis and Photo-Luminescence Properties.

In the current work, the rational synthesis of trinuclear copper complexes, incorporating acute bite angle POP- and PSP-type ligands, is reported. The in situ formation of POP (Ph 2 P-O-PPh 2 ) or PSP (Ph 2 P-S-PPh 2 ) ligands in the presence of a copper(I) precursor gave access to various trinuclear copper complexes of the form [Cu 3 (μ 3 -Hal) 2 (μ-PXP) 3 ]PF 6 [X = O; Hal = Cl ( 1 ), Br ( 2 ), I ( 3 ) and X = S; Hal = Cl ( 5 ), Br ( 6 ), I ( 7 )]. Related iodide-containing complexes and clusters, such as [Cu 4 (μ 3 -I) 4 (Ph 2 PI) 4 ] ( 4 ) and [Cu 3 (μ 3 -I) 2 (μ-I)(μ-PSP) 2 ] ( 8 ), could also be obtained via the variation of the reaction stoichiometry. The investigation of the photo-optical properties by photo-luminescence spectroscopy has demonstrated that the phosphorescence in the visible region can be switched off through the mere change of the heteroatom in the ligand backbone (POP vs PSP ligand scaffold). Theoretical studies have been conducted to complement the experimental photo-optical data with detailed insights into the occurring electronic transitions. Consequently, this systematic study paves the way for tuning the photo-optical properties of transition metal complexes in a more rational way.