CHARACTERIZATION OF INTERMOLECULAR AND INTRAMOLECULAR HYDROGEN-BONDING IN THE SOLID-STATE USING VARIABLE-TEMPERATURE IR SPECTROSCOPY

A study is presented of the molecule NN'dihydroxyethyldithiooxamide (NN'DHEDTO) in the solid state by means of FT-IR at different temperatures, where the inter- and intramolecular hydrogen bonds present are distinguished in the solid state, and where some of the properties of the hydrogen bond are demonstrated clearly. It is shown that a weakening of the hydrogen bond results in a stronger O-H bond, which is what a shift towards higher wave-numbers in the IR spectrum means. When no hydrogen bond is present at all, the band can be found at the highest frequency, as for NN'DHPeDTO in CS2, where the free vOH vibration is found at 3636 cm-1. The fact that only one vOH band is found in solution clearly demonstrates that the two vOH bands observed in the solid-state IR spectrum are due to crystal effects. The assignments for the vNH and vOH vibrations in NN'DHEDTO can be done by comparison with NN'DHPeDTO.