Foreword
Authors: Micheau Jean‐Claude , Yokoyama Yasushi 
Published: October 2007

AbstractThis Special Issue contains a selection of invited papers and reviews published at the occasion of the Japanese–French Joint Seminar on Organic Photochromism‐Switches and Memories held in Hayama, Japan from 15 to 18 October 2006. This seminar was the first scientific manifestation occurring within the framework of the Groupe de Recherches International ‘Photoswitchable Organic Molecular Systems and Devices’ recognised by the French CNRS under the acronym ‘Phenics’ or GDRI n° 93. For this reason, several papers from Russia and China (these two countries are also involved in the GDRI ‘Phenics’) have been welcomed.The last 10 years witnessed a substantial expansion of the chemistry of photoswitchable molecules. Today, very large application prospects are conceivable. Variable transmission photochromic glasses already belong to the daily life. However, the involvement is much wide from optoelectronics (rapid switches, organic microelectronics, 2D or 3D optical memories…) to life sciences (ion transport modulation, imaging, photoactive or photoluminescent probes, protein folding…). The conception of such molecular photoswitches is a long task because it needs synthesis of new compounds, mechanistic studies and the achievement of specific devices.The purpose of this seminar was to gather the participants in a very stimulating atmosphere to discuss the state of the art in the field of organic photochromism and to make projections for the future establishment of new international relationships. Obtaining organic photochromic materials able to find many potential applications in various photonic devices is the bottle‐neck of our domain. Several papers in this Special Issue fulfil this aim by illustrating the considerable achievements in the rational design and synthesis of new photochromic derivatives (such as cyclophanes, new types of functionalised olefins, diarylethenes, dihydroindoles, spiro‐compounds with thienopyrrolines …) and their use to phototrigger phase transitions, aggregation, complexation, gelation, peptide conformation, specific ion‐sensing… All these rapid developments would not be possible without the help of careful mechanistic and theoretical investigations using the most advanced spectroscopic techniques (NMR, ESR, SERRS, AFM, femtosecond transient absorption spectroscopy …) combined to high‐level numerical modelling (ab initio, DFT …) and structure photochromic behaviour relationships (SPBR) for a better understanding of the photochromic elementary act. Several clever attempts to achieve a practical photonic molecular or supramolecular solid‐state systems (PMMA films, single crystal, organic–inorganic nanohybrids …) or devices were also presented. Among them, are the diarylethene based nano‐devices and multiphotonic systems able of second‐harmonic generation (SHG) or non‐destructive read‐out of a previously recorded photonic signal.Worth to be mentioned is the paper: Fedorova OA, Maurel F, Chebun'kova AV, Strokach YP, Valova TM, Kuzmina LG, Howard JAK, Wenzel M, Gloe K, Lokshin V, Samat A. Investigation of cation complexation behaviour of azacrown ether substituted benzochromene. J. Phys. Org. Chem. 2007; 20: 469–483, doi: 10.1002/poc.1181, which should have been included in this Special Issue but because of an unfortunate human error, it was already published in issue 7 of this journal. The Wiley's editing staff who wants to apologise to the authors has created a hyperlink in order to make obvious that this paper belongs to the present Special Issue.As Honorary Editors, we thank all the contributors of this Japanese–French Joint Seminar that made this meeting a frank success and all the authors for their timely contributions. Pr. J. Lambert (Evanston) and Dr M. F. Ruasse (Paris), and all other associate editors and office staffs of this journal, are gratefully acknowledged for their editorial efficiency. Last, but not least, it is of our great pleasure to thank Pr. K. Nakatani (Cachan) for his indispensable help and Pr. M. Irie (Fukuoka and Tokyo) for his perfect organisation in Shonan Village, Hayama, his kind hospitality, and especially for the unforgettable closing banquet of this Japanese–French Joint Seminar on Organic Photochromism.