Photochemical- and pH-switching Properties of a New Photoelastic Ligand Based Upon Azobenzene. Basicity and Anion Binding

Andrea Bencini, Antonio Bianchi, Claudia Giorgi, Emiliano Romagnoli, Carlos Lodeiro, André Saint-Maurice, Fernando Pina, Barbara Valtancoli

Research output: Contribution to journalArticle

14 Citations (Scopus)


The synthesis of a new cylindrical macrotricyclic ligand (L) based upon two 1,4,7,13-tetramethyl-1,4,7, 10,13,16-hexaazacyclooctadecane rings connected via two azobenzene pillars is described. The ligands displays photoelastic properties: light absorption at 366nm produces trans→cis isomerization of the azobenzene moieties with formation of trans-cis (LE-Z) and cis-cis (LZ-Z) isomers. Recovery of the thermodynamically more stable trans-trans (LE-E) isomer can be obtained by thermal back-isomerization or visible light (430nm) absorption. The isomeric composition of L solution depends upon pH: for pH < 5.5 the LE-E form is the unique species in solution, while increasing amounts of Z species are formed at increasing pH. The protonation constants of LE-E have been determined in 0.1 mol dm-3 Me4NNO3 solution at 298.1 ± 0.1 K. The protonated species of L form stable inclusion complexes with anionic species such as [Co(CN)6]3-.

Original languageEnglish
Pages (from-to)277-285
Number of pages9
JournalSupramolecular Chemistry
Issue number2
Publication statusPublished - 1 Jan 2001



  • Anion coordination
  • Chemical switches
  • Macrocycles
  • Photoelastic ligands

Cite this