The Department of Applied Chemistry, College of Life Sciences: Professor Hiromitsu Maeda and Lecturer Yohei Haketa, together with Dr. Yuya Bando and Dr. Yoshifumi Sasano, and second-year master’s course student Hiroki Tanaka, in collaboration with researchers from the Japan Synchrotron Radiation Research Institute and Hokkaido University, have reported the successful synthesis of ion pairs¹ (using porphyrin² Au^III complex cations³), and the fabrication of assemblies (i.e., crystals, gels, and liquid crystals) dependent on the shapes and electronic states of coexisting anions⁴.

Professor Maeda’s group focused on porphyrin-Au^III complexes, stable+1 cations with planar geometries, and found they can be paired with several anions. By introducing planar anions to create ion-pairing assemblies based on porphyrin-Au^III complexes with aliphatic substituents, they also found the formation of liquid crystal materials that remain stable up to approximately 300°C.

For their experiments, they used SPring-8, a large synchrotron radiation facility, discovering:

a) Assemblies (liquid crystals) can be stably arranged with regular alternately stacked patterns of cation (porphyrin-AuIII complex) and anion
b) Selecting the appropriate anion enables the fabrication of an array of ions with identical charge

By using freely combined ion pairs to create assemblies, the team discovered interesting features and properties based on the interaction between ions. This research is expected to lead to the fabrication of organic electronic materials (e.g., ferroelectric devices and semiconductors) based on the high density packing of electrons.

The team's findings were published on March 31, 2019 in iScience, an online journal from Cell Press.

The full paper is available via the link below:
https://www.cell.com/iscience/pdf/S2589-0042(19)30093-8.pdf

Definitions

1: Ion pair: A pair of oppositely charged (i.e., positive and negative) species
2: Porphyrin: A class of pigments with a heterocyclic structure formed from four pyrrole rings
3: Cation: A positively charged ion
4: Anion: A negatively charged ion