Trygve Helgaker

Hylleraas Centre for Quantum Molecular Sciences, Department of Chemistry, University of Oslo, Box 1033 Blindern, N-0315 Oslo, Norway

Video Recording

Abstract

In a strong magnetic field, chemistry changes: electronic states change their character, atoms and molecules change their shape, and their interactions with radiation are affected, often in a dramatic manner [1–8]. Perhaps most surprisingly, new bonding mechanisms occur, giving rise to molecules that do not exist on Earth but may exist elsewhere such as in the atmospheres of magnetic white dwarfs [4,5]. The exotic chemistry of atoms and molecules in strong magnetic fields provides a fresh perspective on the familiar chemistry on Earth; at the same time, it provides a stress test for quantum chemistry, whose methods have been developed for Earth-like conditions. Density-functional theory, for example, must be re-examined and adapted for the molecules in strong magnetic fields and such modifications have relevance also for the calculation of magnetic properties such as shielding constants and magnetizabilities [7].
In the talk, I give an overview of chemistry in strong magnetic fields and discuss the how the methods of quantum chemistry such as coupled-cluster theory [6] and density-functional theory [7] must be modified and adapted to study molecules and their electronic structure in magnetic fields.

Diego M. Andrada

Faculty of Natural Sciences and Technology, Department of Chemistry, Saarland University, Campus
Saarbrücken, 66123 Saarbrücken, Saarland, Federal Republic of Germany

Video Recording

Video is available only for registered users.

Abstract

In the last decades, there has been continuous excitement surrounding the discovery of unusual types of bonds, which have led in the recent past to fascinating debates on fundamental questions about the definition of chemical bonding. [1] In particular, the heavier low-valent and unsaturated main group compounds have stirred the interest of scientists by exhibiting a diverse range of captivating and unpredictable chemistry, including some unique bond-activating reactions. [2] The use of large, sterically crowded substituents to kinetically and thermodynamically stabilize otherwise reactive motifs represented a landmark achievement. [3] In addition to that, the concept of using strong Lewis bases to stabilize low-valent main group species through the donor-acceptor interaction arose. The idea of using σ-donor ligands (L) like N-heterocyclic carbenes (NHC) turned out to be the key to broaden the scope in this area by blocking reactive sides with a non-oxidative coordination. [4] These concepts prompted the experimental achievement of compounds containing zero-valent atoms (EL 2 ) double and triple bonds (E 2 L 2 ) and cyclic fragments aromatic and non-aromatic (E 3 L 3 ) between elements of the Groups 13, 14 and 15 (Scheme).

Scheme. Low-valent main group compounds scaffolds. E: main group element; L; Lewis base.

The rational design of novel compounds for their synthesis and application in catalysis and inorganic materials as pre-established scaffolds requires a deep understanding of the connection between electronic structure properties and activity. This talk will present our efforts to understand the chemical bonding in order to provide chemical descriptors for addressing different inorganic synthesis.