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arXiv · 2505.06095

A Piezoelectric Molecular Cocrystal with Unconventional $π$-Stacking

Samuel G. Dunning·Aldo Raeliarijaona·Piotr A. Guńka·Anirudh Hari·Dongzhou Zhang·Ronald E. Cohen·Timothy A. Strobel
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Abstract

We demonstrate the crystallization of a polar octafluoronaphthalene (OFN, \OFN)--phthalazine (Phth, \Phth) cocrystal, formed in a 1:2 ratio by slow evaporation. The crystal structure and vibrational properties of the cocrystal were determined using powder/single-crystal X-ray diffraction (XRD) and Fourier-Transform Infrared (FTIR) spectroscopy, and confirmed with density functional theory (DFT) and density functional perturbation theory (DFPT) calculations. The molecular $π$-stacking of aromatic rings is unconventional compared with other arene--perfluoroarene cocrystals. Phth molecules are offset and misaligned with respect to the major axis of OFN due to electrostatic repulsion between N and F atoms, enabling overall electric polarization attributed to the dipole moment of Phth. Our calculations show that OFN:2Phth is an insulator with a band gap of $\sim$2.4 eV. The electric polarization was calculated to be 7.1 \muC, while the shear piezoelectric coefficient ($d_{34}$) may be as large as 11.4 pC N$^{-1}$.

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Samuel G. Dunning, Aldo Raeliarijaona, Piotr A. Guńka, Anirudh Hari, Dongzhou Zhang, Ronald E. Cohen, Timothy A. Strobel. 2025-05-09. A Piezoelectric Molecular Cocrystal with Unconventional $π$-Stacking. https://arxiv.org/abs/2505.06095

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