Organic heterospin-composite systems based on supramolecular crystal engineering

摘要

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 intramolecular 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. (C) 2003 Elsevier Science Ltd. All rights reserved. [References: 31]