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Polyviologen Dendrimers as Hosts and Charge‐Storing Devices
Author(s) -
Ronconi Célia M.,
Stoddart J. Fraser,
Balzani Vincenzo,
Baroncini Massimo,
Ceroni Paola,
Giansante Carlo,
Venturi Margherita
Publication year - 2008
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200800773
Subject(s) - viologen , dendrimer , chemistry , titration , eosin , electrochemistry , fluorescence , photochemistry , polymer chemistry , electrode , inorganic chemistry , medicine , staining , physics , pathology , quantum mechanics
Two dendrimers were designed and synthesized that contain a 1,3,5‐trisubstituted benzenoid core and incorporate 9 and 21 viologen (4,4′‐bipyridinium) units in their branches in addition to hydrophilic (aryloxy) terminal groups. For comparison purposes, model compounds containing one and two viologen units were also studied. These polycationic dendrimers form strong host–guest complexes with the dianionic form of the red dye eosin in dilute CH 2 Cl 2 solutions. Titration experiments, based on fluorescence measurements, showed that each viologen unit in the dendritic structures becomes associated with an eosin dianion. Electrochemical (in MeCN) and photosensitization (in CH 2 Cl 2 ) experiments revealed that only a fraction of the viologen units present in the dendritic structures can be reduced. This fraction corresponds to the number of viologen units present in the outer shells of the dendrimers. The reasons for incomplete charge pooling are discussed. Comparison with the behavior of polyviologen dendrimers that are terminated with bulky tetraarylmethane groups and were studied previously enabled the role played by the terminal groups in the redox and hosting properties to be elucidated.