title: Solvent-tunable morphology and emission of pyrene-dipeptide organogels.
abstract: Two pyrene based organogelators in which the pyrene moiety has been linked to the diphenylalanine dipeptide have been synthesized. We show how the solvent can tune both the morphology and the optical properties of the organogels: spherical aggregates with quenched emission were obtained in acetonitrile, whereas an entangled fibrillar network with enhanced emission was formed in o-dichlorobenzene. Fourier transform infrared spectroscopy, circular dichroism and nuclear magnetic resonance spectroscopy experiments suggest that both π-π stacking and hydrogen bonding contribute to the formation of the supramolecular networks. Ultraviolet-visible and steady state emission studies demonstrated the formation of I-aggregates in acetonitrile. In contrast, in o-dichlorobenzene, the formation of J-type aggregates leads to assemblies with enhanced emission. These results give some insight into the important role of the gelling solvent in the morphology of the supramolecular gels and may help in the design of new soft-materials.
authors.affiliation: Department of Chemical Sciences, University of Padova, Padua, Italy.
authors.forename: S
authors.initials: S
authors.lastname: Bartocci
authors.affiliation: Department of Chemistry, University of Parma, Parma, Italy.
authors.forename: I
authors.initials: I
authors.lastname: Morbioli
authors.affiliation: Department of Chemical Sciences, University of Padova, Padua, Italy.
authors.forename: M
authors.initials: M
authors.lastname: Maggini
authors.affiliation: Department of Chemical Sciences, University of Padova, Padua, Italy.
authors.forename: M
authors.initials: M
authors.lastname: Mba
mesh_terms: D002942:Circular Dichroism; D004151:Dipeptides / Q000737:chemistry*; D005782:Gels / Q000737:chemistry*; D006860:Hydrogen Bonding; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D011721:Pyrenes / Q000138:chemical synthesis* / Q000737:chemistry; D012997:Solvents / Q000737:chemistry; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D004151:Dipeptides; D005782:Gels; D011721:Pyrenes; D012997:Solvents
keywords: dipeptides; low molecular weight gelator; organogel; pyrene; self-assembly; supramolecular gel