Thermochromic Phase Transitions of Long Odd-Chained Inorganic–Organic Layered Perovskite-Type Hybrids [(C_nH_2n+1NH₃)₂PbI₄], n = 11, 13, and 15

Abstract

We investigate the last members of a series of inorganic–organic hybrid materials of the general formula [(C n H2n+1NH3)2PbI4] (abbreviated C n PbI). The self-assembly of the inorganic and organic components has a perovskite-like structure as the two-dimensional (2D) inorganic layers have four corners of the lead­(II) iodide octahedra being shared out. The inorganic layers are separated by bilayers of alkylammonium chains, in this case with n = 11, 13, and 15. These materials exhibit complex phase behavior in the temperature range from −20 to + 81 °C. Differential scanning calorimetry and single-crystal X-ray diffraction enabled the phase transition temperatures and enthalpies to be determined and the structural changes that occur at the phase transition temperature. The number of phases is dependent on the chain length: for n = 11 and 15, there are three phases, and for n = 13, there are four phases. Regardless of the number of phases, all three compounds have identical lowest-temperature phases (all stable below room temperature), which have inorganic layers that are staggered, alkylammonium chains that are planar and nonplanar, and yellow crystals. The room-temperature phases for the three compounds differ, but all are orange. C11PbI has staggered layers, and C13PbI and C15PbI have identical room-temperature phases with eclipsed layers. C13PbI and C15PbI also show an additional phase between the lowest-temperature and room-temperature phases.

Manipulation of the Structure and Optoelectronic Properties through Bromine Inclusion in a Layered Lead Bromide Perovskite

“…We also note that the four distinct amine chains in the complex RT phase (phase 3) of [H 3 N­(CH 2 ) 6 NH 3 ]­PbBr 4 all adopt this conformation. Such differences in conformation for differing chain lengths is common in homologous layered perovskite series with differing number of carbons . In the present case, our crystallographic studies show that when bromine molecules are introduced into the perovskite, a significant portion of interlayer space is occupied by the halogen molecule.…”

Toward Understanding the Composition–Structure Relationship of Hybrid Organic Lead Iodide Compounds: Impact from Secondary Structures of Organic Cations

“…Only some qualitative guidelines have been provided from previous studies to predict the dimensionality. For example, flexible primary ammonium ions with a longer main carbon chain and fewer branches generally tend to build up 2D HOLHCs. − Meanwhile, substituted ammonium ions, including secondary, tertiary, and quaternary ammonium ions, are more likely to form 1D or 0D HOLHCs. − Quantitative parameters generated by machine learning algorithms in previous studies of our group also demonstrate a similar trend that 2D structures are preferred when the steric effect around the N atom is small and the eccentricity of the ammonium ion is large . However, an exceptional case that machine learning algorithms failed to predict was also discovered.…”

Hyper Thermostability and Liquid-Crystal-Like Properties of Designed α-Helical Peptide Nanofibers

“…The cooperativity parameter β is a physical quantity defined by β = Δ H VH /Δ H cal and for normal proteins with two-state transition, the value of β is close to 1 (Δ H cal ≈ Δ H VH ). , Hence, this enormous value of β suggests that the CB peptide earns its enthalpy by promoting a bundling of helix molecules to achieve increased heat resistance and then abruptly discharges the stored enthalpy with extremely high cooperativity. Given that endothermic peaks are generally very sharp in molecules with high crystallinity, such as inorganic crystals , and other solid materials, or liquid crystalline materials that combine both fluid and solid properties, − it can be said that CB peptides bear liquid-crystal–like properties with a highly cooperative thermal transition originating from enhanced crystallinity.…”

“…40,41 Hence, this enormous value of β suggests that the CB peptide earns its enthalpy by promoting a bundling of helix molecules to achieve increased heat resistance and then abruptly discharges the stored enthalpy with extremely high cooperativity. Given that endothermic peaks are generally very sharp in molecules with high crystallinity, such as inorganic crystals 57,58 and other solid materials, or liquid crystalline materials that combine both fluid and solid properties, 59−61 it can be said that CB peptides bear liquid-crystal−like properties with a highly Transitions marked in bold correspond to the greatest enthalpy change among the structural transitions. b This value was evaluated graphically based on the graph in Figure 3 cooperative thermal transition originating from enhanced crystallinity.…”