Highlight Review The Improved Stability of Molecular Guests by the Confinement into Nanospaces Aranee (Pleng) Teepakakorn, 1 Tetsuo Yamaguchi, 2 and Makoto Ogawa* 2 1 School of Molecular Science and Engineering, Vidyasirimedhi Institute of Science and Technology (VISTEC), 555 Moo 1 Payupnai, Wangchan, Rayong 21210, Thailand 2 School of Energy Science and Engineering, Vidyasirimedhi Institute of Science and Technology (VISTEC), 555 Moo 1 Payupnai, Wangchan, Rayong 21210, Thailand E-mail: makoto.ogawa@vistec.ac.th Makoto Ogawa studied in the Department of Applied Chemistry, Waseda University, supervised by Professor Chuzo KATO. After conducting postdoctoral research at RIKEN, he joined the faculty of Waseda University as a professor, where his work focused on inorganic materials chemistry. In 2015, he moved to Thailand as a founding professor at the School of Energy Science and Engineering, Vidyasirimedhi Institute of Science and Technology (VISTEC), which opened in 2015 in Rayong, Thailand; there, he continues his research activity in materials chemistry. Aranee (Pleng) Teepakakorn was born in Chonburi, Thailand, in 1993. She received her bachelor’s degree in chemistry from Mahidol University, Thailand, in 2015. She is currently a PhD student at Vidyasirimedhi Institute of Science and Technology, Thailand, under the supervision of Professor Makoto Ogawa. Her current research interest is the stabilization of dyes confined in smectites and the interactions of water-soluble polymers and nanoparticles; structural design and applications. Tetsuo Yamaguchi studied in the Department of Chemistry and Biological Science, Aoyama Gakuin University, supervised by Professor Jiro Abe about photochromism of bridged imidazoledimers. He is currently postdoctoral researcher of the research group of Professor Makoto Ogawa at the School of Energy Science and Engineering, Vidyasirimedhi Institute of Science and Technology (VISTEC) and researches about the inorganic-organic hybrid based on supermolecular chemistry. Abstract The stabilities of organic dyes have been controlled by host- guest complexation and the hybrids have been regarded as novel photofunctional materials. In the present review, the dyes encapsulated in smectites and layered double hydroxides are summarized from the viewpoints of the dye stabilization and possible mechanisms for the stabilization toward decolorization are discussed. In addition, the stabilization of photochemically formed isomer of a photochromic spiropyran, by the interactions with smectite isalso presented. Keywords: Photofunctional materials | Dye | Nanoporous materials Introduction Host-guest complexation has been a topicof awide range of scientific and practicalinterests as a possible approach for materials design. By the host-guest complexation, functions of both host and guest are altered, or new functions, which are not available from host or guest alone, may emerge. 1-3 One of the most important examples is enzymes, where a catalytically CL-181026 Received: December 20, 2018 | Accepted: January 22, 2019 | Web Released: January 26, 2019 398 | Chem. Lett. 2019, 48, 398–409 | doi:10.1246/cl.181026 © 2019 The Chemical Society of Japan