Modulating the Room Temperature Phosphorescence by Tweaking SOC and P = X Interactions (X = O, S, and Se) in Phosphoramides: Magnetic Circularly Polarized Luminescence from Achiral Phosphoramides

Abstract

AbstractHerein, the synthesis, structure, room temperature phosphorescence, and magnetic chiroptical properties of phosphoramides 1‐6 with donor–acceptor architecture are reported.5). The electronic interactions between donor phenothiazine (PTZ) and acceptor (C6H5)n‐P = X (n = 1, 2; X = O, S, and Se)moieties in 1–6 are modulated by varying the number of donor units. The Lewis acidity of the phosphorus center is controlled by the nature of heteroatoms and the number of phenyl moieties attached to it. All compounds exhibit phosphorescence in the solid state under ambient conditions with a photoluminescence lifetime in the millisecond range (≈8–40 ms). The energy of the phosphorescence bands and their excited state lifetimes are governed by the P=X units. The phosphorescence features observed for 1–6 are in complete contrast to the observations noted for (PTZ)3P = X (X = O, S, and Se), where the phosphorescence process is completely controlled by the PTZ moiety, and there is a negligible contribution from the P = X moiety. Thus, the present and earlier studies together reveal that the steric crowding and the number of C6H5 moieties around the P = X unit play a crucial role in controlling the electronic coupling between the donor and acceptor moieties in phosphoramides containing non‐planar donor moieties. Furthermore, for the first time, the magnetic chiroptical properties of achiral phosphoramides 1–6, exhibiting a luminescence dissymmetry factor (gMCPL) in the order of 10−3 (≈4.0 × 10−3–7.4 × 10−3) are demonstrated.