TY - JOUR
T1 - Photochemical- and pH-switching Properties of a New Photoelastic Ligand Based Upon Azobenzene. Basicity and Anion Binding
AU - Bencini, Andrea
AU - Bianchi, Antonio
AU - Giorgi, Claudia
AU - Romagnoli, Emiliano
AU - Lodeiro, Carlos
AU - Saint-Maurice, André
AU - Pina, Fernando
AU - Valtancoli, Barbara
N1 - This work has been supported by the Minister0 dell'universita e della Ricerca Scientifica e Tecnologica (MURST, Rome) within the program COFIN 98, in Italy, and Fundagiio para a Cigncia e Tecnologia (FCT) in Portugal. A.S.-M. thanks a grant PRAXIS XXI from FCT.
PY - 2001/1/1
Y1 - 2001/1/1
N2 - 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-.
AB - 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-.
KW - Anion coordination
KW - Chemical switches
KW - Macrocycles
KW - Photoelastic ligands
UR - http://www.scopus.com/inward/record.url?scp=0035564693&partnerID=8YFLogxK
U2 - 10.1080/10610270108027482
DO - 10.1080/10610270108027482
M3 - Article
AN - SCOPUS:0035564693
SN - 1061-0278
VL - 13
SP - 277
EP - 285
JO - Supramolecular Chemistry
JF - Supramolecular Chemistry
IS - 2
ER -