In the 1 H- K where signal to noise ratios improved and exchange between the two regioisomers slowed on the NMR timescale. The better resolved reduced line-widths for resonances in DAN 6 at the lower temperature consequently revealed additional correlations (Fig. ). Through space correlations observed between H a' and H c' to N II can be attributed to an intermolecular hydrogen bond. A benefit of these experiments is that only hydrogen atoms correlated to nitrogen atoms are observed in the F2 dimension (see ESI). Therefore for complex mixtures the 1 H NMR spectra is simplified to what can be described as "reporter peaks" analogous to PURESHIFT-NMR. The experiment was performed at 243 K, to maximize the population of hydrogen-bonded dimers, with the narrowest peak widths, allowing the observation of intra-and intermolecular hydrogen bonds (Fig. ). It should be noted, however, that spectra obtained at 263K still allow speciation to be determined (see ESI). All observed cross peaks are in agreement with the AUPy•DAN and UPy•UPy speciation. Such analyses usually require multiple spectra to assign and identify shifted resonances whereas the diagnostic cross peaks allow this here in a single experiment.