They all comprise layers of PbBr6 octahedra separated by layers of organic cations. The aromatic cations interact with the inorganic framework in the terminal mode. The interaction between the NH3 + terminal group and the inorganic framework is known to affect the structure and properties of hybrid halide perovskites. In the case of diammonium cations, it was already reported that some cations cannot give layered perovskite structures. For example, even-membered alkyl chains with ammonium groups at both ends form layered perovskite-type hybrid structures, both in bromide and iodide compounds whereas odd-membered chains do not . The layered perovskite structure is adopted only when the chains are kinked so that the hydrogens on both ends of the organic molecules can hydrogen bond to the halides of the inorganic layers . Moving away from linear chains, it has been shown that cations with fused aromatic rings can give the layered perovskite structure only when the cation is able to tilt and hydrogen bond to the halides . More generally, aromatic cations where the ammonium groups may have no degree of freedom, does not necessarily give the layered perovskite motif and 1D (AEA)PbBr4 form a layered perovskite structure. The XRD powder patterns obtained on the crushed crystals are reported in Figure superimposed to the calculated patterns from the single crystal XRD data. We can further explore the interaction between the inorganic framework and the organic cation using the penetration depth, defined as the distance between the N atom of the amino group and the plane of the terminal halides . The NH3 + penetration affects both the distortion between the octahedra, in term of deviation from 180° of the Pb-X-Pb angle, and within the octahedra, in terms of octahedral elongation length (⟨λoct⟩) and their bond angle variance (σ 𝑜𝑐𝑡 2 ), as defined by Robison et al. (1971) . By comparing the present data for the 2D perovskites, and the above mentioned reported systems including diammonium cations, it is possible to note that the Pb-X-Pb angle increases with increasing penetration with a linear trend from chloride to iodide (Figure ). It is worth noting that (1,4-PDA)PbBr4 falls outside this trend, probably because the PDA cation is short and rigid, and because of the increasing strength of the hydrogen bond from I to Br to Cl. and. It is clear that the octahedral elongation and bond angle variance of this group of compounds decrease as the NH3 + penetration increases. This effect may be a consequence of the flexibility of the organic cation. In fact, the 1,3-PDA cation, where all the atoms except the hydrogens are forced to lie in the same plane, induce the larger distortion among all the (a) (b) investigated halides . Notably, the 1,4-PDA cation induces a distortion within the octahedra similar to the 1,3-PDA cation, whilst the distortion decreases for the 1,4-XDA that is more flexible since the nitrogen atoms are not bound to stay in the same plane as the aromatic ring.