Synthesis and characterization of new aromatic tweezers and complex formation with tropylium ion in 1,2‐dichloroethane

Abstract

A series of benzene and pyridine tweezers bearing phenyl, naphthyl and anthryl receptor units was prepared and characterized. The x‐ray crystal structure of the 1,3‐bis(9‐methanolanthracene)methylbenzene ligand (5) is reported. UV–visible and NMR spectroscopy were used to investigate the host–guest chemistry of the new ligands in complexation with tropylium tetrafluoroborate as a model aromatic cationic guest in 1,2‐dichloroethane. The appearance of coloured charge‐transfer absorption bands demonstrates the complex formation with a tropylium ion. The enlargement of aryl receptor size from phenyl and naphthyl to anthryl increases the stability of complexes. Electron donor–acceptor interactions are an important driving force for complexation by molecular tweezers. The results are discussed and compared with those of previously studied systems containing crown ethers and podands. The bisanthracenes 5 and 1,3‐bis(9‐methanolanthracene)methylpyridine (6) are especially interesting in displaying both complexation ability and intramolecular cycloaddition via charge‐transfer excitation. Copyright © 2001 John Wiley & Sons, Ltd.

Tropylium Ion, an Intriguing Moiety in Organic Chemistry

“…The characterization of novel aromatic tweezers and complex formation with the tropylium ion ( 1b ) in 1,2-dichloroethane was discussed by the Lamsa research group [ 88 ]. π-π stacking interactions were found to be crucial in the complexation of benzene-substituted crown ethers with certain electron-deficient ions, such as tropylium pyridinium.…”

“…The structures ( 44a ) and ( 44b ) were synthesized simply by refluxing the reactants with potassium carbonate and acetone as a solvent. The tweezers ( 44c ) were prepared by using sodium hydride in dry DMF with 39% to 78% yields and exhibited properties of complexation and intramolecular cyclization [ 88 ].…”