Dipole-Orientation-Dependent Förster Resonance Energy Transfer from Aromatic Head Groups to MnBr₄^2– Blocks in Organic–Inorganic Hybrids

The understanding and visualization of dipole–dipole interaction on molecular scale are scientifically fundamental and extremely of interest. Herein, two new zero-dimensional (0D) Mn hybrids with aromatic head groups and alkyl tails as organic spacers are selected as models. It was found that the dipole interaction between head groups and Mn blocks could have a huge impact on their crystalline structures as well as the luminescent properties. The parallel-oriented dipoles of the head groups and MnBr₄^2– blocks contribute to an efficient Förster Resonance Energy Transfer (FRET) in cetylpyridinium manganese bromide ([C16Py]₂MnBr₄), while the process is absent in 1-methyl-3-hexadecylimidazolium manganese bromide ([C16mim]₂MnBr₄) with perpendicular-oriented dipoles. This work gives insight into the influence of organic spacers on the geometry and the dipole interaction of Mn polyhedron in the hybrids, which could be of great interest in the future optical regulations and structural design.