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Synthesis and Binding Properties of Dendritic Oxybathophenanthroline Ligands towards Copper( II )
Author(s) -
Stephan Holger,
Geipel Gerhard,
Bernhard Gert,
Comba Peter,
Rajaraman Gopalan,
Hahn Uwe,
Vögtle Fritz
Publication year - 2005
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.200500176
Subject(s) - chemistry , copper , bromide , ligand (biochemistry) , chromophore , fluorescence , electron paramagnetic resonance , fluorescence spectroscopy , photochemistry , crystallography , inorganic chemistry , organic chemistry , receptor , nuclear magnetic resonance , biochemistry , physics , quantum mechanics
Dendritic oxybathophenanthroline ligands (generation 0 to 3) have been synthesized by treatment of 4,7‐bis(4′‐hydroxyphenyl)‐1,10‐phenanthroline with the corresponding Fréchet‐type dendrons carrying a benzylic bromide function at the focal point. The complexation of copper( II ) has been studied by liquid–liquid extraction using the radioisotope 64 Cu and time‐resolved laser‐induced fluorescence spectroscopy (TRLFS) in organic media indicating the formation of 1:3 complexes (Cu:dendritic ligand). Electronic and EPR spectroscopy were used to characterize the copper( II ) chromophore, which is shown to have the expected distorted square‐planar geometry with two phenanthroline donors coordinated to the copper( II ) center. The third dendritic ligand therefore is proposed to be bound by secondary interactions. The stability constants of the 1:3 complexes were found to be in the order of log K ≈ 16 in CHCl 3 . On the other hand, increasing generation of the dendritic Fréchet‐type branches leads to enhanced shielding of the copper ion from the environment. Additional information about this behaviour was obtained by the fluorescence lifetimes, which are much less influenced upon addition of copper( II ) salt to solutions of the higher generation ligands. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)