Topology-Directed Synthesis of Helical Phosphoniums with High Diradical Character and Polar-Dependent Electron Transfer

Abstract

Molecular topology synthesis of polycyclic aromatic heterocycles (PAHs) with diradical character takes root in the intramolecular coupling breakthrough. Herein, we report selectively Mn(III)/Cu(II)-mediated C−P and C−H bond cleavage to obtain robust donorfused phosphoniums with helical or planar geometries and distinct cationic charges. The former helical structures incorporate a common phospha[5]helication acceptor and different arylamines donors, and the latter planar one contains a phospha[6]dication and the same donors. These unprecedented donor-acceptor (D−A) pairs show unique topology-dependent optoelectronic properties. The folded helical radical centers possess an extreme electron-deficient state and throughspace isolation with high diradical character (y0 = 0.989). Moreover, the ingenious charge transfer (CT) and locally excited (LE) transition components facilitate diverse hybridized local and charge transfer (HLCT) in different solvents, endowing the highest emission bandgap variation of 0.78 eV (~217 nm). The cationic emission could also be adjusted from blue to near-infrared regions via topology tailoring and polardependent HLCT, which could output additional circularly polarized luminescence in a compatible chiral menthol matrix with elevated quantum efficiency and retained deep-red glow. It is worth mentioning that an atomically precise Mn(III) halide has been unprecedentedly captured and determined for the C−P bond activation

Hybridized Local and Charge Transfer Modulated Triplet Decay Brightens Ultra-Long Circularly Polarized Afterglow and Chiral Diradical Activity

“…Spectral and HRMS detection data manifest a cyclization product from phosphonium radical species (Figures S43a-i). 75 Recent research has uncovered that this molecular restructuring is a common feature of photochromic phosphines. 25,45,46 On the contrary, P1 is still stable in protecting PMMA (Figure 3g).…”