Short hydrogen bonds in 2,4-dinitrobenzoic acid complexed with pyridine

The aim of this work was to describe the vibrations connected with the short hydrogen bonds of differing geometries in 2,4-dinitrobenzoic acid and in 2,4-dinitrobenzoic acid complexed in two ratios with pyridine. All three compounds contain short hydrogen bonds either between two acid molecules (OH-O bond) or between acid and pyridine (NH-O bonds) or both. We selectively deuterated the proton of the 2,4-dinitrobenzoic acid molecule involved in the proton transfer to aid in the assignment of the H-bond protonic modes. The compounds have been characterized with single crystal X-ray diffraction, CHN elemental analysis, FT-IR and IINS spectroscopy. We show that our combination of analytical methods with DFT calculations represents a fruitful approach to observe the relationship between the geometries of hydrogen bonds and their dynamics.