A Weakly Antiferromagnetically Coupled Biradical Combining Verdazyl with Nitronylnitroxide Units

Abstract

Probing interacting triplons: Antiferromagnetically coupled verdazyl-nitronylnitroxide heterobiradicals were synthesized via Sonogashira reaction. SQUID measurements revealed that one of the biradical crystal solvates is a promising material for investigating interacting triplons in a magnetic field.An antiferromagnetically (AFM) coupled biradical based on oxoverdazyl and nitronylnitroxide was synthesized in 46 % yield using Sonogashira coupling. The obtained heterobiradical evidenced distinct properties of both radical entities in solution. Depending on the solvent, the prepared biradical crystallized in two different forms. SQUID magnetization measurements on Form II showed coupling constants JintraII/kB=−2.1 K and zJinterII/kB=−11.5 K. Consequently, total intermolecular exchange interactions are five times larger than the intramolecular ones. Further, DFT calculations explained this phenomenon and indicated the advantage of Form I for further in-depth investigations.