Aggregation‐Induced Emission in a Flexible Phosphine Oxide and its Zn(II) Complexes—A Simple Approach to Blue Luminescent Materials

Abstract

Easily accessible blue-emitting materials are in the focus of ongoing research, as they still lack the efficiency and lifetime of their red and green counterparts. The new multidentate phosphine oxide ligands and two respective ZnCl 2 complexes presented here combine a straightforward synthesis with high yields and show interesting luminescent properties. The free ligand exhibits blue luminescence in the crystalline state, but not in amorphous films or diluted solution. In contrast, the Zn(II) complexes shows intense blue luminescence in the crystalline state as well as in amorphous thin films and in solution. Fluorescence lifetime imaging microscopy measurements show luminescence lifetimes of 3-6 ns indicative of fluorescence. By combining the experimental data with quantum chemical calculations, we propose a model where the conformation of the molecule is restricted, either via the crystal environment, aggregation, or the steric fixation by the coordinating central atom, blocking the nonradiative relaxation from the excited into the ground electronic state. However, this nonradiative relaxation is still possible in the gas phase via elongation of a PC bond. These results may provide a general mechanism to explain the luminescence properties in a whole class of organic phosphine oxides.

Thieno[3,2-b]phosphole-based AIEgens: facile preparation and dual modulation of solid-state luminescence

“…9,10 The exploration of AIE in combination with tuneable solid-state emission has led to the discovery and design of a diverse range of ground-breaking materials. [11][12][13][14] Through careful engineering of molecular structures and intermolecular interactions, researchers have achieved unprecedented control over emission wavelengths, intensity, and polarization in solid-state environments. [15][16][17][18][19][20][21] Numerous stator frameworks have been effectively employed to achieve solid-state fluorescence tunability in aggregation-induced emission luminogens (AIEgens).…”

Access to Strong Thieno[3,2-b]phosphole-Based Solid-State Emitters via Manganese(III)-Mediated Oxidative Annulation

“…As a consequence, smart molecular design has been used to selectively restrict these molecular motions and synthesize strong solid-state luminophores. − Molecules with a rigid stator unit, such as thieno­[3,2- b ]­thiophenes ( TP-TTDO ) , or pyrazines bearing flexible peripheral rotor units, were found to be particularly suitable for this purpose. The incorporation of phosphole, the phosphorus analogue of pyrrole, as a stator moiety into the π-conjugated backbone has been shown to exert various favorable effects on the photophysical properties of the molecule and provides possibilities for facile modifications. − Various arene-fused − and heterocycle-fused phospholes − have received much attention due to their unique optical and electrochemical properties as well as high application potential in optoelectronics and bioimaging. − For example, 1,2,3-triphenylphosphindole-1-oxide ( TPPIO ) exhibits excellent AIE properties and blue emission in the solid state at 478 nm with an emission efficiency of 68%, shows high thermal stability, allows facile chemical modification at the phosphorus atom, and easy synthetic access via a one-pot synthesis with diphenylphosphane oxide ( DPPO ) and diphenylacetylene (Scheme ).…”