Supramolecular organization of a H-bonded perylene bisimide organogelator determined by transmission electron microscopy, grazing incidence X-ray diffraction and polarized infra-red spectroscopy

Abstract

An organogelator based on a N,N'-substituted H-bonding perylenebisimide (PBI-C10) self-assembles to form either a green J-type (form I) or a red H-type (form II) aggregate structure. The molecular packing of both polymorphs was determined from a combination of Transmission Electron Microscopy (TEM) (low dose electron diffraction and high resolution), Grazing incidence X-ray diffraction and polarized infrared spectroscopy. To that aim, highly oriented films have been prepared by mechanical rubbing at controlled film temperature and DFT calculations were performed to identify representative vibrational IR bands and their associated polarizations. H-Bonding between amides generates either a rectangular columnar phase (form I) in the dried gel or a hexagonal packing of supramolecular 21/1 helices with a long period of 97 Å (form II) in annealed thin films. In aligned films of form I, polarized FTIR spectroscopy helps determine the orientation of both intermolecular H-bonds and the PBI core with respect to the substrate. In form II, PBI-C10 molecules assemble into pairs to form off-centered 21/1 helices whose helical axis is made of strongly H-bonded amides. TEM investigations show that three 21/1 helices are packed in a frustrated trigonal structure formed by H-bonding. The Form I → Form II transformation implies a redistribution of a single population of strong intra-columnar H-bonds between amides in form I to a mixture of strong and weak H-bonds in the supramolecular helices, the strong H-bonds forming the spine of the helices.

High-Temperature Rubbing: An Effective Method to Fabricate Large-Scale Aligned Semiconducting and Conducting Polymer Films for Applications in Organic Electronics

“…HTR proved also effective for the orientation of small molecular systems including H-bonded perylene bisimide organogelators or acceptor−donor−acceptor triad materials. 120,121 Beyond pure organic systems, HTR is also a very elegant alignment method to fabricate hybrid polymer/nanoparticle systems with the possibility to orient simultaneously anisotropic nanoparticles (nanorods) and polymer chains. 122 Taken altogether, these numerous examples support the versatility and high potential of HTR as a processing method to fabricate complex anisotropic architectures for material science purposes.…”

“…Recent examples concern for instance poly(3-hexylthiophene)- block -peracetylated maltopheptaose or P3HT- b -P(NDI2OD-T2). , Interesting new phenomena resulting from the competing crystallization processes of the two blocks can be analyzed in detail in aligned thin films. HTR proved also effective for the orientation of small molecular systems including H-bonded perylene bisimide organogelators or acceptor–donor–acceptor triad materials. , Beyond pure organic systems, HTR is also a very elegant alignment method to fabricate hybrid polymer/nanoparticle systems with the possibility to orient simultaneously anisotropic nanoparticles (nanorods) and polymer chains . Taken altogether, these numerous examples support the versatility and high potential of HTR as a processing method to fabricate complex anisotropic architectures for material science purposes.…”

Original polymorphism in a naphthalene bisimide π-conjugated organogelator: a complex interplay between hydrogen bonding and heterocycle π-stacking

“…crystalline and liquid crystalline phases, and can also form physical gels in organic solvents. While gelation of p-conjugated systems involving rylene bisimides has been described in the literature, 22 the structures formed in the gels are only marginally described. In most cases, the fibrilar aggregates formed upon gelation are made of columnar or helical supramolecular stacks driven by H-bonding interactions.…”