Organic heterospin-composite systems based on supramolecular crystal engineering

Abstract

In this study, a novel crystal engineering approach to organic ferrimagnetics is proposed. As a supramolecular heterospin system, we have designed and synthesized a ternary coordination compound of an anionic nitronyl nitroxide biradical and crown–ether derivatives with a closed-shell or an open-shell substituent. The intra-molecular exchange interaction of the anionic biradical in its sodium salt has been determined to be antiferromagnetic from ESR spectra and magnetic susceptibility measurements. The intra-molecular interaction of the anionic biradical, however, has been found to be ferromagnetic in a salt with the closed-shell Na+-crown–ether. A peculiar nonmagnetic (diamagnetic) ground state has been found in a salt of the anionic biradical with the open-shell Na+-crown–ether derivative of nitronyl nitroxide radical. According to our previous prediction based on a theoretical model, the occurrence of the nonmagnetic ground state is attributed to a spin frustration effect inherent in organic molecular assemblages.