Data: 29/07/2026 - Horário: 10:00 - Local: Aud II, DQ, ICEx
Título: Tuning 2-iminoprrrolyl ligands for polymerization catalysis and luminescent complexes
A ser apresentado por: Prof. Pedro T. Gomes - Universidade de Lisboa - Portugal
Resumo
There has been sustained interest in well-defined, aluminum-free homogeneous olefin polymerization catalysts based on late transition metal complexes. The homo- and copolymerization of ethylene using neutral nickel(II) complexes bearing monoanionic bidentate ligands has led to significant advances in this field. In this context, we have developed a ligand framework based on 2-(N-arylimino)pyrrolyl systems. These N,N'-bidentate ligands comprise a neutral imine donor and an anionic pyrrolyl nitrogen, forming five-membered chelate rings upon coordination to the metal center. The first part of the seminar will present the synthetic routes to the ligand precursors, in which electronic and steric modifications are systematically introduced. These ligands are subsequently employed in the preparation of a two family of nickel(II) complexes featuring 5-substituted 2-iminopyrrolyl scaffolds: one N,N'-bidentate1 and the other one C,N,N'-tridentate.2 Their performance in aluminum-free ethylene polymerization will be discussed. Ligands of the same family can also coordinate to boron(III) centers.3The second part of the seminar will address the synthesis, molecular structure, and photophysical characterization of a family of highly luminescent tetracoordinate boron complexes bearing 2-iminopyrrolyl ligands. These bidentate systems can be finely tuned, both electronically and sterically, leading to variations in emission color. The strategies employed to achieve such tuning will be outlined, and selected aspects of their application in the emissive layers of organic light-emitting diode (OLED) devices will also be described.
Data: 12/08/2026 - Horário: 10:00 - Local: AUD II, DQ, ICEx
Título: Supramolecular assemblies of histidine-rich designer peptides with multiple biological functions
A ser apresentado por: Burkhard Bechinger - Université de Strasbourg - França
Resumo
A family of designed histidine-rich peptides will be presented which can assemble in a number of different aggregation states. Interestingly, whereas sequences that occur in soluble form exhibit considerable antimicrobial activities, nucleic acid transfection is best by peptides that form large complexes of tuneable size with nucleic acids (DNA, siRNA, mRNA) and these also exhibit strong cell penetrating activities for large proteins, peptide vaccines, adeno associated viruses and nanodots. Due to the presence of four histidines their membrane interactions are strongly pH dependent. The delivery of cargo by these peptides is complex, involving many steps, which we investigated on a structural and biophysical level. More recently, vectofusin-1, a member of the same family of LAH4 peptides has been shown to spontaneously self-assemble into helical oligomers, spherical aggregates, that further assemble into annular and extended nanofibrils and hydrogels as a function of phosphate concentration and in a pH-dependent manner. This bears considerable interest for the design of biomaterials. Importantly, the peptide has a strong capacity to enhance the gene transfer by lentiviral vectors into the cell interior. Thereby, the fibres formed by this relatively short sequence have therapeutic applications ranging from monogenic and infectious diseases to cancer, by enhancing transduction levels of target cells and reducing the amount of lentivirus for greater safety and reduced costs. Vectofusin-1 associates with viral particles and promotes the entry of several retroviral pseudotypes into target cells when added to the culture medium, without cytotoxicity. The vectofusin-1 fibrils have a unique coiled-coil ?-helical structure whereas most other viral transduction enhancers form ?-amyloid fibrils and are investigated by solid-state NMR and other biophysical approaches. Our observations define vectofusin-1 as a member of a new class of ?-helical lentiviral transduction enhancers. Its coiled-coil fibril formation is reversible which bears considerable advantages in handling the peptide in conditions of gene therapy protocols.
