Dinitrogen complexation with main group radicals

Abstract

In this report we present data from hyperfine sublevel correlation spectroscopy (HYSCORE), an electron paramagnetic resonance (EPR) spectroscopic technique, that reveals weak but distinct interactions between several main group element radicals and physically dissolved dinitrogen in solution. These interactions are the basis for a well-defined coordination of N₂ to the paramagnetic centers. The complexes formed are primarily of the van der Waals-type but also feature a non-negligible orbital overlap between dinitrogen and the radicals' SOMO. Our spectroscopic findings are strongly supported by experiments with isotope-labeled ¹⁵N₂, spectral simulations and quantum chemical and density functional theory (DFT) calculations. Formation of such complexes is unexpected when considering the small polarizability of dinitrogen but steric effects like formation of a binding “pocket” may facilitate their formation. The sensitivity, selectivity, and resolution of HYSCORE with respect to the detection of weak hyperfine couplings is needed to identify such complexes that are probably the result of a subtle interplay of induced van der Waals forces between N₂, the solvent and the dissolved radicals.