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

A family of robust metal complexes of [Mn(L)X-2] and (LH)(2)[MnX4] type (X = Cl, Br, I) have been synthesized based on xanthene-derived bisphosphine dioxides (L = XantphosO(2) or t-Bu-XantphosO(2)). At ambient temperature, the designed compounds exhibit strong green to yellow phosphorescence with quantum yields as high as 90%. Remarkably, complex [Mn(XantphosO(2))Br-2] reveals polymorphic luminescence, which is a rare phenomenon for Mn compounds. Two polymorphs of this compound, crystallizing in P1 and P2(1)/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 T-4(1) -> (6)A(1) transitions in Mn2+ ions.