Light harvesting indolyl-substituted phosphoramide ligand for the enhancement of Mn(II) luminescence

The reaction of N,N,N’,N’-tetramethyl-P-indol-1-ylphosphonic diamide (L) with Mn(II) halides under mild conditions allowed the isolation of tetrahedral neutral complexes having the general formula [MnX2L2] (X = Cl, Br, I). The structures of the new coordination compounds were ascertained by single-crystal X-ray diffraction. The three species exhibited noticeable luminescence in the green region upon excitation with UV light, with emissions related to the Mn(II) 4T1(4G) → 6A1(6S) transition, without appreciable luminescence from the coordinated ligands. Luminescence was caused by both metal and ligand excitations. The good light harvesting features of the indol-1-yl fragment allowed the luminescence enhancement with respect to comparable phenyl-substituted derivatives.