[(CH 3 ) 2 NH 2 ] 7 Pb 4 X 15 (X = Cl - and Br - ), 2D-Perovskite Related Hybrids with Dielectric Transitions and Broadband Photoluminiscent Emission.

We have prepared two new lead halides with the novel general formula of DMA7 Pb4 X15 (DMA = [(CH3 )2 NH2 ]+ and X = Cl- or Br- ) by using an easy route under mild conditions at room temperature. These compounds exhibit an unprecedented crystal structure, are formed by layers of distorted [PbX6 ] octahedra, which share corners and faces, and contain intercalated DMA cations. Very interestingly, they display dielectric transitions, which are related to a partial order-disorder process of the DMA cations between 160 and 260 K. Additionally, these new layered hybrids exhibit a broadband photoluminiscent emission, which is related to the structural distortions of the [PbX6 ] octahedra. These findings not only open up large possibilities for future optoelectronic applications of these materials, but they also offer a novel playground for an easy modulation of electrical and optical properties of hybrid organic-inorganic materials. We anticipate that this novel A7 Pb4 X15 formula can be adequate to tune the family of the hybrid lead halides using other alkylammonium cations, such as methylammonium, formamidinium, or ethylammonium, to improve their photoelectronic properties.