Stable Face-to-Face Singlet Diradicaloids: Triply Linked Corrole Dimer Gallium(III) Complexes with Two μ-Hydroxo-Bridges.

In known singlet diradicaloid molecules, two inherent radicals are interacted antiferromagnetically as a result of delicate energetic balances between closed-shell and open-shell states. Reported herein is that gallium(III) metalations of triply linked corrole dimers provide face-to-face dimers, with two μ-hydroxo-bridges, and they display curved π-planes nearing each other at about 3.24 Å. Based on ESR and SQUID measurements, and theoretical calculations, the dimers have been assigned as singlet diradicaloids that consist of two monoradicals each delocalized on the triply linked corrole dimer planes. Therefore, it is concluded that the dimers have unusual open-shell states stabilized by large through-space spin-exchange interactions.