Luminescence of the Mn ion in non-O and T coordination environments: the missing case of square pyramid.

The first observation of luminescence for Mn(ii) complexes with a square-pyramidal geometry (C) of the metal is reported. The complexes of such type, namely [Mn(L)Hal]X, where L is an O,O'-chelating ligand MeN-CH(PhP[double bond, length as m-dash]O), Hal = Cl or Br, and X = Br, I or [MnCl], show at ambient temperature red photoluminescence (λ≈ 620 nm) with millisecond lifetimes (3.8-7.