Synthesis and Properties of a Through-Space Interacting Diradicaloid.

Knowledge about electronic structures is important to gain an understanding of the unique functional properties of diradicaloids. In this study, we synthesized and characterized a diradicaloid in which two phenalenyl radical sites are coupled antiferromagnetically via a through-space interaction. The results of quantum chemical, physicochemical ((1)H NMR, electronic absorption, cyclic voltammetry, SQUID, ESR), and chemical reactivity studies show that this diradicaloid has singlet diradical character. An assessment of the nature of the bonding interaction between two radical sites in this species using DFT calculations demonstrates that a small spatial overlap between the two SOMOs in this diradicaloid provides an efficient electron exchange path for the singlet state to be substantially lower in energy than the triplet state.