Meeting the challenging magnetic and electronic structure of thiophene-based heterophenoquinones

Two thiophene-based heterophenoquinones, representing a family of molecules that exhibit biradicaloid character, have been studied by a combination of electron paramagnetic resonance (EPR), nuclear magnetic resonance (NMR), Raman, infrared (IR), and synchrotron or singlecrystal X-ray diffraction measurements. This combined approach provided a detailed picture of the previously unknown electronic structure of the molecules in terms of two nearby states: a closed-shell diamagnetic state and a nearby biradical state, which is thermally populated.