Studies on electron spin resonance spectroscopy of biradical molecules containing 14N-O and 15N-O moieties

The biradicals with 14N-Oxide and 15N-Oxide at the both ends of a molecule are synthesized for the molecular ruler of protein structure, and a potential device for quantum computing. We also establish a general synthetic method for reliable biradical formation. ESR spectra are recorded for the biradicals containing 15N-Oxide and 14N-Oxide with various interdistance separations. We find that two types of biradicals yielded different ESR spectra depending upon the distance between the 15N-O and 14N-O moieties in a molecule. This is due to electron spin dipole-dipole interaction occurring between the radicals. We also find that there is an indication of isotopic nuclear effects in the dipole-dipole interactions. The present study implies feasibility of the distance measurement between two different N-Oxides containing 14N and 15N isotopes. We conclude that quantum entanglement effects are observed through the dipolar interactions, which enable application of quantum computing devices operating in the liquid state.