Supramolecular nanomaterials containing phosphorescent transition metal clusters

• Applicant: Professorin Dr. Sabine Laschat
• Subject Area: Preparatory and Physical Chemistry of Polymers
• Term: from 2018 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 407256071

• Final Report Year: 2023

Final Report Abstract

The multidisciplinary SNAPSTER project developed new phosphorescent hybrid nanomaterials and introduced them in optoelectronic devices. For this purpose metal cluster compounds An[Mo6Qi8Xa6] (A = alkali, Q = chalcogen/halogen, X = halogen) were prepared by high temperature solid state synthesis. Mesogenic crown ethers with different size, heteroatoms, substitution pattern and side chain lengths were synthesized and characterized. An[Mo6Qi8Xa6] and crowns were combined via a supramolecular approach to emissive hybrids showing columnar mesophases. The strong binding of alkali cations by the crowns resulted in the embedding of the clusteranions in the interdigitating hydrophobic alkyl chains. This isolating organic matrix has a beneficial effect on the red-NIR luminescence, resulting in brighter emission and increased lifetimes and emission thermal stability. Moreover, the mesophase widths of these clustomesogens was increased. In addition, ionic liquid crystalline (ILC) clustomesogens were prepared via ionic self-assembly (ISA) approach from wedge-shaped guanidinium salts and An[Mo6Qi8Xa6]. The ISA resulted in change of liquid crystalline behavior from columnar for guanidinium ILCs to undulated lamellar phase for the ILC clustomesogens. Investigation of the ionic and electronic transport of crowns and crown salt complexes revealed that coordination of alkali cations in the crown improved the intracolumnar order, resulting in enhanced hole mobility. Ionic conductivity is dominated by the non-coordinating anions propagating through the anisotropic liquid-like side chain. Charge transport properties have also been investigated using a space charge limited current device on crown bearing two o-terphenyl units and related crown salt complexes. Obtained results demonstrate that metal cluster compounds can enhance the charge carrier mobility by five orders of magnitude compared to the native discotic organic ligand. SNAPSTER is a multidisciplinary German-French project involving 3 research teams with complementary expertise in solid state chemistry (Molard), organic synthesis (Laschat), hybrid materials (Molard), LC (Laschat), physics and electronics (Jacques). Several joint papers were published by SNAPSTER and a follow-up project was recently granted by the bilateral DAAD/PHC Procope program to continue the successful research.

Publications

• Lord of The Crowns: A New Precious in the Kingdom of Clustomesogens. Angewandte Chemie International Edition, 57(36), 11692-11696.
  Guy, Kevin; Ehni, Philipp; Paofai, Serge; Forschner, Robert; Roiland, Claire; Amela‐Cortes, Maria; Cordier, Stéphane; Laschat, Sabine & Molard, Yann
  
• Luminescent liquid crystalline hybrid materials by embedding octahedral molybdenum cluster anions with soft organic shells derived from tribenzo[18]crown-6. Dalton Transactions, 47(40), 14340-14351.
  Ehni, Philipp; Guy, Kevin; Ebert, Max; Beardsworth, Stuart; Bader, Korinna; Forschner, Robert; Bühlmeyer, Andrea; Dumait, Noée; Roiland, Claire; Molard, Yann & Laschat, Sabine
  
• Flavylium Salts: A Blooming Core for Bioinspired Ionic Liquid Crystals. Chemistry – A European Journal, 25(56), 12966-12980.
  Forschner, Robert; Knelles, Jakob; Bader, Korinna; Müller, Carsten; Frey, Wolfgang; Köhn, Andreas; Molard, Yann; Giesselmann, Frank & Laschat, Sabine
  
• Improved Electronic Transport in Ion Complexes of Crown Ether Based Columnar Liquid Crystals. Crystals, 9(2), 74.
  Staffeld, Peter; Kaller, Martin; Ehni, Philipp; Ebert, Max; Laschat, Sabine & Giesselmann, Frank
  
• Novel Luminescent Diazafluorenone Liquid Crystals. Crystal Growth & Design, 19(8), 4436-4452.
  Bader, Korinna; Baro, Angelika; Ehni, Philipp; Frey, Wolfgang; Gündemir, Rafet; Laschat, Sabine & Molard, Yann
  
• Self‐Assembly and Fluorescence of Tetracationic Liquid Crystalline Tetraphenylethene. ChemPhysChem, 20(17), 2210-2216.
  Knelles, Jakob; Beardsworth, Stuart; Bader, Korinna; Bruckner, Johanna R.; Bühlmeyer, Andrea; Forschner, Robert; Schweizer, Kevin; Frey, Wolfgang; Giesselmann, Frank; Molard, Yann & Laschat, Sabine
  
• Electrical Conductivity and Multiple Glassy Dynamics of Crown Ether-Based Columnar Liquid Crystals. The Journal of Physical Chemistry B, 124(39), 8728-8739.
  Yildirim, Arda; Kolmangadi, Mohamed A.; Bühlmeyer, Andrea; Huber, Patrick; Laschat, Sabine & Schönhals, Andreas
  
• Fluorenone imidazolium salts as novel de Vries materials. RSC Advances, 10(40), 23999-24016.
  Bader, Korinna; Müller, Carsten; Molard, Yann; Baro, Angelika; Ehni, Philipp; Knelles, Jakob & Laschat, Sabine
  
• Joint Venture of Metal Cluster and Amphiphilic Cationic Minidendron Resulting in Near Infrared Emissive Lamellar Ionic Liquid Crystals. Chemistry – A European Journal, 28(3).
  Ebert, Max; Carrasco, Irene; Dumait, Noée; Frey, Wolfgang; Baro, Angelika; Zens, Anna; Lehmann, Matthias; Taupier, Gregory; Cordier, Stephane; Jacques, Emmanuel; Molard, Yann & Laschat, Sabine
  
• Chasing Self‐Assembly of Thioether‐Substituted Flavylium Salts in Solution and Bulk State. ChemPhysChem, 23(13).
  Knöller, Julius A.; Forschner, Robert; Frey, Wolfgang; Lang, Johannes; Baro, Angelika; Zens, Anna; Molard, Yann; Giesselmann, Frank; Claasen, Birgit & Laschat, Sabine
  
• Merging liquid crystalline self-assembly and linear optical properties of merocyanines via tailored donor units. Physical Chemistry Chemical Physics, 24(36), 21617-21630.
  Ehni, Philipp; Bauch, Soeren M.; Becker, Patrick M.; Frey, Wolfgang; Zens, Anna; Kästner, Johannes; Molard, Yann & Laschat, Sabine
  
• Luminescent liquid crystals: from supramolecular plant dyes to emissive flavylium salts. Liquid Crystals, 50(7-10), 1310-1323.
  Forschner, Robert; Knöller, Julius Agamemnon; Zens, Anna; Frey, Wolfgang; Molard, Yann & Laschat, Sabine