A family of Mn(ii) complexes exhibiting strong photo- and triboluminescence as well as polymorphic luminescence

Abstract

A family of robust metal complexes of [Mn(L)X₂] and (LH)₂[MnX₄] type (X = Cl, Br, I) have been synthesized based on xanthene-derived bisphosphine dioxides (L = XantphosO₂ or t-Bu-XantphosO₂). At ambient temperature, the designed compounds exhibit strong green to yellow phosphorescence with quantum yields as high as 90%. Remarkably, complex [Mn(XantphosO₂)Br₂] reveals polymorphic luminescence, which is a rare phenomenon for Mn compounds. Two polymorphs of this compound, crystallizing in P and P2₁/n space groups, display green and yellow luminescence, respectively, with the emission quantum yield being 33 and 50%. Moreover, the “yellow” polymorph features bright triboluminescence upon grinding its crystals. An in-depth photophysical study evidences that the observed phosphorescence is due to the ligand-sensitized ⁴T₁ → ⁶A₁ transitions in Mn²⁺ ions.