Molecular and electronic structure of terminal and alkali metal-capped uranium(V) nitride complexes

Determining the electronic structure of actinide complexes is intrinsically challenging because inter-electronic repulsion, crystal field, and spin–orbit coupling effects can be of similar magnitude. Moreover, such efforts have been hampered by the lack of structurally analogous families of complexes to study. Here we report an improved method to U≡N triple bonds, and assemble a family of uranium(V) nitrides. Along with an isoelectronic oxo, we quantify the electronic structure of this 5f1 family by magnetometry, optical and electron paramagnetic resonance (EPR) spectroscopies and modelling. Thus, we define the relative importance of the spin–orbit and crystal field interactions, and explain the experimentally observed different ground states. We find optical absorption linewidths give a potential tool to identify spin–orbit coupled states, and show measurement of UV···UV super-exchange coupling in dimers by EPR. We show that observed slow magnetic relaxation occurs via two-phonon processes, with no obvious correlation to the crystal field

Ice as a protocellular medium for RNA replication

A crucial transition in the origin of life was the emergence of an informational polymer capable of self-replication and its compartmentalization within protocellular structures. We show that the physicochemical properties of ice, a simple medium widespread on a temperate early Earth, could have mediated this transition prior to the advent of membraneous protocells. Ice not only promotes the activity of an RNA polymerase ribozyme but also protects it from hydrolytic degradation, enabling the synthesis of exceptionally long replication products. Ice furthermore relieves the dependence of RNA replication on prebiotically implausible substrate concentrations, while providing quasicellular compartmentalization within the intricate microstructure of the eutectic phase. Eutectic ice phases had previously been shown to promote the de novo synthesis of nucleotide precursors, as well as the condensation of activated nucleotides into random RNA oligomers. Our results support a wider role for ice as a predisposed environment, promoting all the steps from prebiotic synthesis to the emergence of RNA self-replication and precellular Darwinian evolution