Photon Factory Activity Report 2014 #32 (2015) B

AR-NW2A/ 2014G008

Formation of a nanometer-thick water layer at high humidity on a dynamic
crystalline material composed of multi-interactive molecules

Yumi Yakiyama,‡1 Gil Ryeong Lee,‡1 Sung Yeon Kim,1 Yoshitaka Matsushita,2 Yasushi Morita,3Moon Jeong Park,1,4 and Masaki Kawano*1
1 Division of Advanced Materials Science (WCU), Pohang University of Science and Technology(POSTECH), Pohang 790-784, Korea
2 Research Network and Facility Services Division, National Institute for Materials
Science (NIMS), Sengen 1-2-1, Tsukuba, Ibaraki 305-0047, Japan3 Department of Applied Chemistry, Faculty of Engineering, Aichi Institute ofTechnology, Yachigusa 1247, Yakusa, Toyota 470-0392, Japan
4 Department of Chemistry, Pohang University of Science and Technology(POSTECH), Cheongam-ro 77, Namgu, Pohang 790-784, Korea

1 Introduction
Weak intermolecular interactions like hydrogen bond or
- interaction play a crucial role in biological systems.
Especially, multi-interactivity contribute to stabilizing
meta-stable intermediates, because the multiple
interactions can deepen local minimum potential states
well.
Therefore, we aimed to implement multiinteractivity into a ligand to achieve self-assembled
materials. We designed and synthesized tri(4-pyridyl)
hexaazaphenalenyl (TPHAP) anion. The potassium
salt form of TPHAP showed unexpected crystalline
state under highly hydrated conditions. Here we
describe ionic layered structure with a 1.2 nmthick water layer, and the dynamic structuretransformation revealed by X-ray powder
diffraction analysis. The ion conductivity of thismaterial changed from insulator to 3.4 ×10 -3 S cm 1
depending on humidity conditions.
2 Results and Discussion
We used KTPHAP single crystal powder (1) asan initial material which has 1D-channel structure. The
single crystal of KTPHAP is highly hygroscopic: 1g ofpowder of KTPHAP adsorbs > 70 mL of water.
Therefore KTPHAP powder (1) retained its crystallinity
after hydration.
We measured the XRPD pattern of fully-hydrated
powder (2) which has prepared by hydration of KTPHAP
single crystal (1) at 95% RH and 25 °C, for 1 day. The
XRPD pattern of (2) showed an irreversible change todried powder (3) by keeping at 20% RH and 25 °C for 20s. Notably, the sharp powder pattern of (2) wasrecovered by rehydration of (3).
The structures were determined by the simulated
annealing method in DASH, followed by Rietveld
refinement using RIETAN-FP to refine the position ofeach atom with soft bond-angle restraints for a TPHAP
group. We revealed that 1.2 nm water layer form in thefully-hydrated (2) and that 1D water channels form in (3)by dehydration. The structure solutions of (2) revealed
four possible models that have monoclinic systems thatshow good refinement result between the calculated and(a)(b)

Figure 1 (a) Synchrotron XRPD pattern changes. (b)Reversible structure transformation of KTPHAP system
experimental patterns. Although the precise position
determination of disordered water and potassium cation
was technically very difficult, all of refinement results
showed flat layer structure composed of KTPHAP dimerlike layers forming 1.2 nm-thick water layers. Theselayers are stabilized by the intermolecular interactions
between HAP skeleton and the disorder potassium ions.
In conclusion, we demonstrated high ion conducting
structure under the humid condition and insulator
structure after dehydration. This result can be useful fordevelopment of efficient ionic conductors.
References[1] Y. Yakiyama et al., Chem. Commun., 2015, 51, 68216831.
*mkawano@postech.ac.kr