A recyclable dynamic semiconducting polymer consisting of Pauli-paramagnetic diradicaloids promoted and stabilized by catechol-boron coordination.

Coordination between 5,5',6,6'-tetrahydroxyindigo (4OH-ID) and boron tribromide unexpectedly affords a novel dynamic covalent polymer, namely P(ID-O-B), consisting of alternating indigo and indigo diradicaloid units. The catechol-boron dynamic bond plays a vital role in promoting the diradicaloid formation and stabilizing the formed diradicaloid segments. The diradicaloid segment in the polymer has a triplet ground state and a thermally populated doublet state, which has been confirmed by the EPR study. Although not conjugated, the polymer still exhibits an electrical conductivity over 10 S cm. The SQUID study shows that the polymer is Pauli paramagnetic, indicating that the metallic domain exists in this non-conjugated polymer. This diradicaloid-containing polymer is stable toward long-term storage (over 6 months) and thermal treatment over 200 °C, but can be easily depolymerized when treated with methanol.