Dual emission from Mn(II) complexes with carbazolyl-substituted phosphoramides

The carbazolyl-substituted phosphoramide N,N,N’,N’-tetramethyl-P-carbazol-9-ylphosphonic diamide (L) was successfully coordinated to MnX2 halides (X = Cl, Br, I), obtaining tetrahedral complexes having general formula [MnX2L2]. The structures were ascertained by means of single-crystal X-ray diffraction. The three complexes show appreciable luminescence in the visible range upon excitation with UV radiation, attributed to the Mn(II) 4T1(4G)→6A1(6S) transition superimposed to the emission from coordinated ligands. The different contributions are particular evident for the chloro-complex and the relative intensity depends upon the excitation wavelength. The correlation between the two emitting levels is highlighted by the luminescence decay curves of the three compounds.