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Multidentate Pyridyl‐Based Ligands in the Coordination‐Driven Self‐Assembly of Palladium Metallo‐Macrocycles
Author(s) -
Brusilowskij Boris,
Schalley Christoph A.
Publication year - 2011
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.201001368
Subject(s) - chemistry , supramolecular chemistry , palladium , denticity , ligand (biochemistry) , stereochemistry , pyridine , bipyridine , self assembly , nuclear magnetic resonance spectroscopy , crystallography , combinatorial chemistry , crystal structure , organic chemistry , biochemistry , receptor , catalysis
In the current study, a convenient way is presented to synthesize one ditopic and two tetratopic pyridine‐based ligands, which are then used to construct metallo‐supramolecular polygons. The tetratopic ligands offer two different metal‐binding sites, one central 2,2′‐bipyridine, which can act as a chelate ligand, and two separate pyridine rings, which mediate assembly formation. The three ligands differ with respect to their conformational flexibility. While a biphenyl core allows the ligand to adjust its conformation as needed, a bipyridine core strongly prefers a divergent arrangement of the additional pyridine binding sites, but can be fixed in a cisoid conformation by metal complexation to the bipyridine.Instead, a phenanthroline core already fixes the pyridinylethynyl substituents in a cisoid structure without any metal coordinated to it. Upon mixing each one of the ligands separately with the appropriate amount of dpppPd II triflate, discrete self‐assembled metallo‐macrocycles are formed which are characterized by 1 H and 31 P NMR spectroscopy and mass spectrometry. Mixing all three ligands simultaneously with the metal complex leads to the formation of a statistical dynamic combinatorial library (DCL) of all possible homo‐ and heterodimeric metallo‐supramolecular assemblies. This underlines the conformational differences between the three ligands not to impact significantly on the self‐assembly process.