title: Photoluminescence and conductivity of self-assembled pi-pi stacks of perylene bisimide dyes.
abstract: The self-assembly of a new, highly fluorescent perylene bisimide dye 2 into pi stacks, both in solution and condensed phase, has been studied in detail by NMR spectroscopy, vapor pressure osmometry (VPO), UV/Vis and fluorescence spectroscopy, differential scanning calorimetry (DSC), optical polarizing microscopy (OPM) and X-ray diffraction. The NMR and VPO measurements revealed the formation of extended pi-pi stacks of the dye molecules in solution. The aggregate size determined from VPO and DOSY NMR measurements agree well with that obtained from the concentration and temperature-dependent UV/Vis spectral data by employing the isodesmic model (equal K model). In the condensed state, dye 2 possesses a hexagonal columnar liquid crystalline (LC) phase as confirmed by X-ray diffraction analysis. The columnar stacking of this dye has been further explored by atomic force microscopy (AFM). Well-resolved columnar nanostructures of the compound are observed on graphite surface. A color-tunable luminescence from green to red has been observed upon aggregation which is accompanied by an increase of the fluorescence lifetime and depolarization. The observed absorption properties can be explained in terms of molecular exciton theory. The charge transport properties of dye 2 have been investigated by pulse radiolysis-time resolved microwave conductivity measurements and a 1D charge carrier mobility up to 0.42 cm(2) V(-1) s(-1) is obtained. Considering the promising self-assembly, semiconducting, and luminescence properties of this dye, it might serve as a useful functional material for nano(opto)electronics.
authors.affiliation: Universität Würzburg, Institut für Organische Chemie and Röntgen Research Center for Complex Material Systems, Am Hubland, 97074 Würzburg, Germany.
authors.forename: Zhijian
authors.initials: Z
authors.lastname: Chen
authors.forename: Vladimir
authors.initials: V
authors.lastname: Stepanenko
authors.forename: Volker
authors.initials: V
authors.lastname: Dehm
authors.forename: Paulette
authors.initials: P
authors.lastname: Prins
authors.forename: Laurens D A
authors.initials: LD
authors.lastname: Siebbeles
authors.forename: Joachim
authors.initials: J
authors.lastname: Seibt
authors.forename: Philipp
authors.initials: P
authors.lastname: Marquetand
authors.forename: Volker
authors.initials: V
authors.lastname: Engel
authors.forename: Frank
authors.initials: F
authors.lastname: Würthner
mesh_terms: D002152:Calorimetry, Differential Scanning; D004553:Electric Conductivity; D005456:Fluorescent Dyes / Q000138:chemical synthesis / Q000737:chemistry*; D007094:Imides / Q000737:chemistry*; D050866:Liquid Crystals / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D018625:Microscopy, Atomic Force; D008859:Microscopy, Polarization; D008958:Models, Molecular; D008968:Molecular Conformation; D015394:Molecular Structure; D010569:Perylene / Q000031:analogs & derivatives* / Q000737:chemistry; D012666:Semiconductors; D013050:Spectrometry, Fluorescence; D013053:Spectrophotometry; D013696:Temperature; D014961:X-Ray Diffraction
chemical_list: D005456:Fluorescent Dyes; D007094:Imides; C510697:perylene bisimide; D010569:Perylene