Pseudohalide Anions Driven Structural Modulation in Distorted Tetrahedral Manganese(II) Hybrids toward Tunable Green-Red Emissions

Abstract

Mn(II)-based halides have recently garnered significant interest as emerging luminescence materials for diverse photonic applications. Generally, Mn(II) hybrids with tetrahedral coordination show green emission, however, ones with octahedral coordination give red emission. Herein, we design the synthesis of tetrahedral Mn(II) pseudohalide hybrids, (RPh3P)2MnBrxNCS4-x (R= phenyl, pentyl or methyl; Ph3P = triphenylphosphine; x = 1 - 3), achieved by gradually substituting bromides with pseudohalides (NCS−). Compared to the green-emitting A2MnBr4 (512 nm), the mixed hybrids exhibit significantly distorted [MnBrxNCS4-X] tetrahedra with high dipole moment, thus leading to the distinct Stokes shift energies and noticeable red shift emission in the range of 549 ~ 613 nm. Furthermore, the photoluminescence quantum yield (PLQY) of these hybrids correlates strongly with the pair correlation function of Mn(II) ions, specifically the Mn···Mn distance. These findings highlight the critical role of dipole moments in determining the emission properties and expand the luminescent family of Mn(II) pseudohalide hybrids.