Hydrogen and Nitrogen
The hydrogen economy represents a way of fulfilling our need for energy by using molecular hydrogen as an energy carrier and using reactions in which polluting products like greenhouse gases are avoided. The prospects of such an economy require the development of clean and efficient ways of producing and storing molecular hydrogen, or, in an extended sense, of molecules by which energy is stored in their chemical bonds. We have investigated a catalytically active nickel-bis-dithiolate complex by theory and spectroscopy and conclusively identified the energetically most favourable energetic pathway.
In addition, we have performed similar investigation for the naturally occurring enzymes, [NiFe] hydrogenases. A recurring theme is the binding of the substrate, electron donation into empty metal d orbitals, and backdonation into antibonding orbitals of the ligand, thus doubly weakening the chemical bond in the substrate.
Nitrogen is one of the most inert molecules on the planet. It features a triple bond. Presently, nitrogen is turned into ammonia in the Haber-Bosch process, which requires high temperature and pressure. In nature, nitrogenase enzymes, featuring an iron-molybdenum (FeMoCo) active site are able to catalytically turnover N2 into ammonia in an impressive 8-electron reduction process, in which additionally an H2 molecule is produced. We investigated a simplified molecular complex that features some of the structural elements of the FeMoCo, bound NO+, which is iso-electronic to N2, and derived on the electronic level how the weakening of the NN triple bond occurs.
 Das, R.; Neese, F.; van Gastel, M. Phys. Chem. Chem. Phys. 2016, 18, 24681-24692.
 Kalläne, S.I.; Hahn, A.; Weyhermüller, T.; Bill, E.; Neese, F.; DeBeer, S.; van Gastel, M. Inorg. Chem. 2019, 58, 5111-5125.