A highly luminescent tetramer from a weakly emitting monomer: acid- and redox-controlled multiple complexation by cucurbit[7]uril.
The tetrahedral, shape-persistent molecule 1(4+), containing four pyridylpyridinium units connected through a central carbon atom, exhibits unexpected photophysical properties including a substantially redshifted absorption (2350 cm(-1)) and a very strong fluorescence (Φem = 40 %), compared with the monomer 2(+) (Φem = 0.4 %). Density functional theory calculations on the structure and spectroscopic properties of 1(4+) and 2(+) show that exciton interactions, homoconjugation, and orbital nature account for the observed differences in their photophysical properties. The protonated tetramer binds four cucurbit[7]uril molecules and the host/guest interactions can be controlled by chemical (acid/base) as well as redox stimuli.
Dipartimento di Chimica "G. Ciamician" and Interuniversity Center for the Chemical Conversion of Solar Energy (SolarChem), Università di Bologna, Via Selmi 2, 40126 Bologna (Italy), Fax: (+39) 051-2099456.
Giacomo
G
Bergamini
Andrea
A
Fermi
Marianna
M
Marchini
Mirko
M
Locritani
Alberto
A
Credi
Margherita
M
Venturi
Fabrizia
F
Negri
Paola
P
Ceroni
Massimo
M
Baroncini
D001952:Bridged-Ring Compounds / Q000737:chemistry*; D055664:Electrochemical Techniques; D007093:Imidazoles / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D010084:Oxidation-Reduction; D011726:Pyridinium Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D011789:Quantum Theory; D014867:Water / Q000737:chemistry; D047028:Macrocyclic Compounds; D000099246:Cucurbit(n)urils
D001952:Bridged-Ring Compounds; D007093:Imidazoles; D011726:Pyridinium Compounds; D014867:Water; C456276:cucurbit(7)uril; D047028:Macrocyclic Compounds; D000099246:Cucurbit(n)urils
cucurbiturils; electrochemistry; host-guest systems; photochemistry; viologens