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

The biradicals with (14)N-Oxide and (15)N-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 (15)N-Oxide and (14)N-Oxide with various interdistance separations. We find that two types of biradicals yielded different ESR spectra depending upon the distance between the (15)N-O and (14)N-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 (14)N and (15)N 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.