Utilizing an ionic liquid strategy, we report crystal structures of salts of free anionic nucleobases and base pairs previously studied only computationally and in the gas phase. Reaction of tetrabutylammonium ([N-4444](+)) or tetrabutylphosphonium ([P-4444](+)) hydroxide with adenine (HAd) and thymine (HThy) led to hydrated salts of deprotonated adenine, [N-4444][Ad]center dot 2H(2)O, and thymine, [P4444][Thy]center dot 2H(2)O, as well as the double salt cocrystal, [P-4444](2)[Ad][Thy]center dot 3H(2)O center dot 2HThy. The cocrystal includes the anionic [Ad-(HThy)] base pair which is a stable formation in the solid state that has previously not even been suggested. It exhibits Watson-Crick connectivity as found in DNA but which is unusual for the free neutral base pairs. The stability of the observed anionic bases and their supramolecular formations and hydrates has also been examined by electronic structure calculations, contributing to more insight into how base pairs can bind when a proton is removed and highlighting mechanisms of stabilization or chemical transformation in the DNA chains.

We investigated whether the relatively Lewis basic imidazole-2-thiones could be used to substitute water ligands bound to f-element cations and generate f-element soft donor complexes. Reactions of 1,3-diethylimidazole-2-thione (C(2)C(2)ImT) with Nd(NO3)(3)center dot 6H(2)O and UO2Cl2 center dot 3H(2)O led to the isolation of the anhydrous thione complexes Nd(NO3)(3)(C(2)C(2)ImT)(3) and UO2Cl2(C(2)C(2)ImT)(2), characterized by single crystal X-ray diffraction. Differences in the strength of metal-thione interactions have been examined by means of the crystal structure analysis and density functional theory (DFT) calculations. The C(2)C(2)ImT ligands were found to be affected by both coordination and noncovalent interactions, making it impossible to deconvolute the effects of one from the other. Calculated partial atomic charges indicated greater ligand-to-metal charge transfer in the [UO2](2+) complex, indicative of a stronger interaction. The reactivity of C(2)C(2)ImT demonstrates its usefulness in the preparation of f-element soft donor complexes from readily available hydrates that could be useful intermediates for promoting the coordination and studying the effects of soft donor anions.