Supramolecular Photochromism of Bis(phenanthrolinylthienyl)-Hexafluorocyclopentene
In this chapter, the chemistry of a novel thermally irreversible photochromic 1,2-bis(3-thienyl)perfluorocyclopentene 1o possessing two 1,10-phenanthroline groups on C-5 of both thiophene rings is described. First, the complex of 1o with Cu(I) was evidenced to be two 1o and two Cu(I) anions forming a C 2-symmetric 2:2 complex. On the other hand, the most stable complex of 1c and Cu(I) was suggested to be the D 2-symmetric 2:2 complex. The 1o 2-Cu(I)2 complex showed an MLCT band at around 450 nm, which remained unchanged during the photochromic reactions. The ring-closing quantum yield decreased dramatically (from 0.75 to 0.026 in acetonitrile) upon complexation. Next, the change in solubility of the salt formed by 1o with oxalic acid by photochromic reactions is described. The crystalline-like 1:1 salt of 1o and oxalic acid (1o-Ox) was hardly soluble in chloroform-acetone. However, upon UV irradiation, the salt became soluble.
KeywordsBisthienylethene Phenanthroline Metal complex Cu(I) Acid–base salt Oxalic acid Solubility switch
I am deeply indebted to the colleagues and students who have been engaged in the research work described in this chapter. I would also like to express appreciation for the financial support from the Grants-in-Aid for Scientific Research on Priority Area “New Frontiers in Photochromism” (471), the Grant-in-Aid for Scientific Research on Innovative Area “Photosynergetics” (2606) of the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan, and the Grant-in-Aid for Scientific Research (B) (23350096) of the Japan Society for the Promotion of Sciences (JSPS). Zeon Corp. is also gratefully acknowledged for their generous donation of the octafluorocyclopentene samples.
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