title: Synthesis and Aggregation Behavior of Chiral Naphthoquinoline Petroporphyrin Asphaltene Model Compounds.
abstract: The synthesis of structurally relevant compounds that model the chemical behavior and supramolecular aggregation of the asphaltenes, the most polar and metal-rich fraction of heavy petroleum, has been extended to include fusions of important petroleum biomarkers. The synthetic protocol features a multicomponent reaction to form a dyad composed of a fused steroidal naphthoquinoline, followed by a pyrrole cyclocondensation reaction to incorporate the dyad into a chiral triad containing a NiII-porphyrin substituent. This synthetic protocol has been used to prepare large molecules that represent both "continental" and "archipelago" models of asphaltene composition. The steroid-naphthoquinoline-porphyrin triads have been studied by UV/Vis and circular dichroism (CD) spectroscopies, and the results suggest that the naphthoquinoline core, a tetrahydro[4]helicene, adopts a helical conformation, producing a CD signal electronically related to the characteristic Soret absorption band of the porphyrin subunit. Finally, supramolecular aspects of asphaltene aggregation have been examined on a molecular level through analysis of axial coordination of pyridine to the Ni-porphyrin. The relative affinity of pyridine for binding to the Ni center of the porphyrin is evaluated by comparing binding propensities in a series of sterically differentiated substituted porphyrins.
authors: Department of Chemistry and Pharmacy & Interdisciplinary Center for Molecular Materials (ICMM), Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Henkestraße 42, 91054, Erlangen, Germany.
authors: Matthias
authors: M
authors: Schulze
authors: Department of Chemistry and Pharmacy & Interdisciplinary Center for Molecular Materials (ICMM), Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Henkestraße 42, 91054, Erlangen, Germany.
authors: Alexander
authors: A
authors: Scherer
authors: Department of Chemistry and Pharmacy & Interdisciplinary Center for Molecular Materials (ICMM), Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Henkestraße 42, 91054, Erlangen, Germany.
authors: Frank
authors: F
authors: Hampel
authors: Department of Chemistry, University of Alberta, Edmonton, AB, T6G 2G2, Canada.
authors: Jeffrey M
authors: JM
authors: Stryker
authors: Department of Chemistry and Pharmacy & Interdisciplinary Center for Molecular Materials (ICMM), Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Henkestraße 42, 91054, Erlangen, Germany. rik.tykwinski@fau.de.
authors: Rik R
authors: RR
authors: Tykwinski
keywords: cracking; multicomponent reaction; porphyrinoids; steroids; supramolecular chemistry