Coordination-Driven Macrocyclization for Locking of Photo- and Thermal cis→trans Isomerization of Azobenzene

• Published in: Chemistry : a European journal Vol. 20; no. 49; pp. 16258 - 16265
• Main Authors: Yamamura , Masaki, Yamakawa, Koji, Okazaki, Yuki, Nabeshima , Tatsuya
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 01.12.2014; WILEY‐VCH Verlag; Wiley; Wiley Subscription Services, Inc
• Subjects: azo compounds; Chemistry; Chemistry, Multidisciplinary; iron; isomerization; macrocycles; Physical Sciences; Science & Technology; supramolecular chemistry; ROTATION; COMPLEX; isomerization; PHOTOISOMERIZATION; azo compounds; INTERLOCKING; BEHAVIOR; INVERSION; MOLECULAR LOGIC; LIGANDS; METALS; macrocycles; CONSTRUCTION; iron; supramolecular chemistry
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.201404620

Both trans and cis isomers of azobenzene‐linked bis‐terpyridine ligand L1 were incorporated in rigid macrocycles linked by FeII(tpy)2 (tpy: terpyridine) units. The complex of the longer trans‐L1 is dinuclear [(trans‐L1)2⋅FeII2], whereas the complex of the shorter cis‐L1 is mononuclear [cis‐L1⋅FeII]. The complex cis‐L1⋅FeII was not only thermally stable but also photochemically inactive. These results indicate a perfectly locked state of cis‐azobenzene. The stable macrocyclic structure of cis‐L1⋅FeII causes locking of the isomerization. To the best of our knowledge, this is first example of dual locking of photo‐ and thermal isomerization of cis‐azobenzene. Doubly locked: Macrocycles in which azobenzene‐bridged bis‐terpyridine ligands are linked by FeII were synthesized. The FeII complex of the trans isomer is dinuclear, whereas that of the cis isomer is mononuclear. The cis complex is not only thermally stable at ambient temperature over 13 months, but also photochemically inactive (see scheme). These observations indicate a perfectly doubly locked state of cis‐azobenzene.