Pyrene derivatives of 2,2′-bipyridine as models for asphaltenes:: Synthesis, characterization, and supramolecular organizations

The behavior of 4,4'-bis-(2-pyren-1-yl-ethyl)-[2,2']bipyridinyl (PBP) was studied as a model for petroleum asphaltenes with a bridged structure. PBP consists of two pyrene groups bridged by a bipyridyl spacer, and exhibits similar solubility and chromatographic properties to some fractions of asphaltenes. On the basis of nuclear magnetic resonance, steady state fluorescence, vapor pressure osmometry, solubility, and adsorption behavior studies, PBP gave self-association in solution. On the basis of these data and single crystal X-ray analysis, this behavior was attributed to pi-pi stacking interactions involving both pyrene rings and the bipyridine spacer. These results demonstrate that bridged aromatic species with up to four fused aromatic rings are capable of self-association in solution.