Synthesis of Functional Aromatic Molecules by 1,3-Dipolar Cycloaddition

Professor Shingo (Nanyang Technological University)

Abstract: Polycyclic aromatic molecules have attracted much attention in a wide range of scientific disciplines as metal-free functional materials. We have been interested in the synthesis of heteroatom-embedded polycyclic aromatic molecules with unique structures and innovative properties. In particular, our synthesis focuses on the use of 1,3-dipolar cycloaddition reactions of polycyclic aromatic azomethine ylides with a variety of dipolarophiles. In the lecture, I would like to present my 10-years journey from the initial discovery of unique azomethine ylide species to recent achievements on the synthesis, properties, and applications of various azacorannulene- and azacoronene-based functional materials.

Design and Synthesis of Highly Fluorescent Phosphorus Heterocycles: Towards the Control of the 3D Organization

Professor Carlos Romero-Nieto (University of Castilla-La Mancha)

Abstract: π-Extended organic architectures are a fascinating class of compounds that plays a fundamental role in the materials science. The efficient overlap of atomic orbitals along an extended network of polyaromatic systems enables outstanding properties such as strong luminescence and high charge mobilities. An efficient strategy to modulate these optoelectronic properties involves embedding heteroatoms into the carbon scaffold. In that context, phosphorus atoms are particular interesting; e.g. they present an electron lone pair that is readily available for a variety of reversible post-functionalization reactions with transition metals, Lewis acids, oxidizing and alkylating agents.[1a] Additionally, incorporating phosphorus centers into -heterocyclic systems prompts a unique hyperconjugation,[1b] leading to electronic characteristics that are inaccessible with other heteroatoms.[2] However, conceiving molecules with new intriguing features is not sufficient. Intermolecular interactions and the resulting spatial arrangement of molecules ultimately define the magnitude of macromolecular properties such as, for example, luminescence and charge mobilities. In fact, the properties of individual molecules cannot be extrapolated to the properties of the materials as a whole. In this context, interest in non-covalent interactions to control molecular arrangement has exponentially increased over the last decades. In particular, our group has successfully demonstrated that phosphorus heterocycles offer extraordinary possibilities for controlling the arrangement of molecules. Within a conjugated scaffold, phosphorus may adopt a tetrahedral-like geometry with two out-of-plane moieties, which could be utilized to control the molecular arrangement through halogen bonds.[3] In this communication, I will present an overview of our research on π-extended six-membered phosphorus heterocycles (6M-PHs). I will describe of the synthesis and properties of the novel phosphaphenalenes derivatives we described a few years ago.[4] Additionally, I will discuss the impact of phosphorus post-functionalizations on their optoelectronic properties. Furthermore, I will introduce the synthesis of recent generations of π-extended architectures based on 6M-PHs and present a detailed investigation of their structural and optoelectronic properties. Finally, I will describe our latest progresses towards controlling the 3D organization of 6M-PHs.

Light refreshments will be served outside of 4-370 at 4:00PM.