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Axial chiral bisbenzophenazines: solid-state self-assembly via halide hydrogen bonds triggered by linear alkanes.

ABSTRACT: An axial chiral tetrachlorinated bisbenzo[a]phenazine has been discovered that undergoes an alkane-induced shift in the solid state from a disordered amorphous form to an ordered polycrystalline form. This phase transition is caused by the formation of pores that accommodate linear alkanes of varying lengths with a very strong affinity as judged by differential scanning calorimetry. Single crystal X-ray structure analysis revealed that a series of weak phenolic OH···Cl hydrogen bonds dictates the pore structure. These weak interactions can be disrupted mechanically, causing the material to revert to the amorphous form. Notably, the interchange between the amorphous and crystalline forms is readily reversible and is easily observed by characteristic colorimetric changes. Measurements via photoimage processing reveal that the degree of color change is dictated by the type of alkane employed.

SUBMITTER: Metz AE

PROVIDER: S-EPMC4353019 | biostudies-literature | 2014 Jul

REPOSITORIES: biostudies-literature

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Axial chiral bisbenzophenazines: solid-state self-assembly via halide hydrogen bonds triggered by linear alkanes.

Metz Alison E AE Podlesny Erin E EE Carroll Patrick J PJ Klinghoffer Ariel N AN Kozlowski Marisa C MC

Journal of the American Chemical Society 20140718 30

An axial chiral tetrachlorinated bisbenzo[a]phenazine has been discovered that undergoes an alkane-induced shift in the solid state from a disordered amorphous form to an ordered polycrystalline form. This phase transition is caused by the formation of pores that accommodate linear alkanes of varying lengths with a very strong affinity as judged by differential scanning calorimetry. Single crystal X-ray structure analysis revealed that a series of weak phenolic OH···Cl hydrogen bonds dictates th ...[more]

PMID: 25019179

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Project description:Hydrogen bonds (HBs) play an important role in the rotational dynamics of organic cations in hybrid organic/inorganic halide perovskites, thus affecting the structural and electronic properties of the perovskites. However, the properties and even the existence of HBs in these perovskites are not well established. In this study, we investigate HBs in perovskites MAPbBr3 (MA+ = CH3NH3+), FAPbI3 (FA+ = CH(NH2)2+), and their solid solution with composition (FAPbI3)7/8(MAPbBr3)1/8, using ab initio molecular dynamics and electronic structure calculations. We consider HBs donated by X-H fragments (X = N and C) of the organic cations and accepted by the halides (Y = Br and I) and characterize their properties based on pair distribution functions and on a combined distribution function of the hydrogen-acceptor distance with the donor-hydrogen-acceptor angle. By analyzing these functions, we establish geometrical criteria for HB existence based on the hydrogen-acceptor (H-Y) distance and donor-hydrogen-acceptor angle (X-H-Y). The distance condition is defined as d(H - Y) < 3 Å for N-H-donated HBs and d(H - Y) < 4 Å for C-H-donated HBs. The angular condition is 135° < (X - H - Y) < 180° for both types of HBs. A HB is considered to be formed when both angular and distance conditions are simultaneously satisfied. At the simulated temperature (350 K), the HBs dynamically break and form. We compute the time correlation functions of HB existence and HB lifetimes, which range between 0.1 and 0.3 ps at that temperature. The analysis of HB lifetimes indicates that N-H-Br bonds are relatively stronger than N-H-I bonds, while C-H-Y bonds are weaker, with a minimal influence from the halide and cation. To evaluate the impact of HBs on the vibrational spectra, we present the power spectrum in the region of N-H and C-H stretching modes, comparing them with the normal mode frequencies of isolated cations. We show that the peaks associated with N-H stretching modes in perovskites are redshifted and asymmetrically deformed, while the C-H peaks do not exhibit these effects.

Dataset Information

Axial chiral bisbenzophenazines: solid-state self-assembly via halide hydrogen bonds triggered by linear alkanes.

Publications

Axial chiral bisbenzophenazines: solid-state self-assembly via halide hydrogen bonds triggered by linear alkanes.

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