2D Cocrystallization from H‑Bonded Organic Ferroelectrics

Authors

Donna A. Kunkel, Univeristy of Nebraska-LincolnFollow
James Hooper, Jagiellonian UniversityFollow
Benjamin Bradley, University of Nebraska-Lincoln
Lisa Schlueter, California State University at San Bernadino
Tom Rasmussen, University of Nebraska-Lincoln
Paulo Costa, University of Nebraska-LincolnFollow
Sunit Beniwal, University of Nebraska-LincolnFollow
Stephen Ducharme, University of Nebraska-LincolnFollow
Eva Zurek, State University of New York at BuffaloFollow
Axel Enders, University of Nebraska-LincolnFollow

Date of this Version

1-2016

Citation

Journal of Physical Chemistry Letters 7:3 (January 2016), pp. 435−440.

doi: 10.1021/acs.jpclett.5b02472

Comments

Copyright © 2016 American Chemical Society. Used by permission.

Abstract

The synthesis of 2D H-bonded cocrystals from the room-temperature ferroelectric organics croconic acid (CA) and 3-hydroxyphenalenone (3-HPLN) is demonstrated through self-assembly on a substrate under ultrahigh vacuum. 2D cocrystal polymorphs of varied stoichiometry were identified with scanning tunneling microscopy, and one of the observed structural building blocks consists of two CA and two 3-HPLN molecules. Computational analysis with density functional theory confirmed that the experimental (CA)₂(3-HPLN)₂ tetramers are lower in energy than single-component structures due to the ability of the tetramers to pack efficiently in two dimensions, the promotion of favorable electrostatic interactions between tetramers, and the optimal number of intermolecular hydrogen bonds. The structures investigated, especially the experimentally found tetrameric building blocks, are not polar. However, it is demonstrated computationally that cocrystallization can, in principle, result in heterogeneous structures with dipole moments that exceed those of homogeneous structures and that 2D structures with select stoichiometries could favor metastable polar structures.