The interconversion between two equivalent configurations of a system via exchange of protons is an important process with implications in areas ranging from chemical dynamics to molecular biology. In this work, we present microwave spectroscopic results and ab initio calculations on the doubly hydrogen bonded complex HNO3-HCOOH. Spectra of eight isotopologues of the system confirm a doubly hydrogen bonded geometry, analogous to that of the well-known carboxylic dimers. Splittings in the a-type rotational spectrum are observed but disappear for HNO3-HCOOD, indicating a tunneling motion of protons across the hydrogen bonds. Ab initio calculations of the binding energy and intermolecular potential surface are compared with those on the more thoroughly studied carboxylic dimers and the role of heavy atom motion is discussed. Spectroscopic constants provide accurate structural information and quantify the degree to which the electronic structure of the HNO3 is altered upon complexation.

Double proton transfer in the HNO<sub>3</sub>-HCOOH complex

247th National Meeting (2014)

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Double proton transfer in the HNO3-HCOOH complex

Double proton transfer in the HNO₃-HCOOH complex