Liquid 1H-1,2,3-Triazole Interpreted as a Continuous, Self-Assembled Hydrogen-Bonded Linear Network

The molecular-level organization of <b>1H</b>-1,2,3-triazole in the liquid state is described as an extended hydrogen-bonded network, reminiscent of linear solution-phase polymer chains. Raman, IR, and no-D NMR spectroscopic data interpreted using density functional theory (DFT) computations reveal no evidence of the lower-energy <b>2H</b>- tautomer or isolated <b>1H</b>- monomers. Spectroscopic and computational results are consistent with an extended network of strong intermolecular hydrogen bonds throughout the pure liquid and explain earlier X-ray and solution-phase studies. Our computations indicate that the Gibbs free energy of ring-like structures for the most part increases with the number of fragments whereas it decreases for extended chain-like structures. These results are contrary to the ring-like structures that would be much more stable in the gas phase, and suggest that in the liquid state this unique molecule possesses long-range structural characteristics that likely play important roles in applications including fuel cells, and could be the origin of its low melting point compared to other nitrogen containing heterocyclic molecules.