Scaling Approach for Intramolecular Magnetic Coupling Constants of Organic Diradicals

Abstract

The intramolecular magnetic coupling constants (<i>J</i>) of 9 diradicals (<b>i</b>–<b>ix</b>) coupled with an aromatic ring were investigated by means of unrestricted density functional theory (DFT) calculations [UB3LYP/6-311++G­(d,p)]. For these diradicals, a remarkable linear relationship between the calculated and experimental <i>J</i> values was found. In this study, we suggest that the slope (0.380) of the linear relationship can be utilized as a scaling factor for estimating <i>J</i> values. By applying this scaling factor and calculating <i>J</i> values, we could predict the reliable <i>J</i> values of four dithiadiazolyl (<b>DTDA</b>) diradicals coupled with an aromatic ring. It was also found that this scaling scheme shows a dependence on the length of a coupler. Nevertheless, this scaling approach could be used to estimate <i>J</i> values for diverse diradical systems coupled with a particular coupler by DFT calculations