Functionalized triphenylphosphine oxide-based manganese(ii) complexes for luminescent printing

Abstract

Three novel neutral manganese(II) complexes (TPhPONMe₂)₂MnBr₂, (TPhPOOMe)₂MnBr₂, and (TPhPOCF₃)₂MnBr₂ have been designed and synthesized based on a functionalized Ph₃PO ligand. These structures are clarified by single crystal X-ray diffraction analysis, which reveals that they crystallize in centrosymmetric space groups and feature an isolated mononuclear structure with Mn²⁺ in a tetrahedral environment. The photoluminescence spectra and emission lifetime decay curves of three manganese(II) complexes show distinct green emission (λ_em = 498–512 nm) and phosphorescence lifetime (τ = 362.0–663.0 μs). The results of DFT calculations indicate that the energy levels of (TPhPONMe₂)₂MnBr₂ and (TPhPOOMe)₂MnBr₂ are higher than that of (TPhPOCF₃)₂MnBr₂ due to the electron-donating effect of the NMe₂ or OMe group, which explains the blue-shift of the emission wavelength and the increase of emission lifetime. Furthermore, the prepared neutral manganese(II) complexes can be used for high-resolution luminescent printing.