Solvent-dependent valence tautomerism and polarization switching in a heterodinuclear [CrCo] complex

Abstract

Macroscopic polarization switching via directional electron transfer has attracted great attention owing to its potential application in data storage devices, sensors, and energy conversion. However, the acquisition of the desired polar crystals is still a huge challenge to realize polarization switching. Here, a heterometallic [CrCo] complex with an enantiopure ligand was successfully obtained by a stepwise synthetic route, which effectively avoids the contamination caused by the lack of recognition of chiral ligands. Both compound 1·sol and its desolvated form, 1, are packed in the polar P2₁ space group. These forms exhibit valence tautomerism to varying degrees and interconversion to each other through single-crystal-to-single-crystal transformation, which enables solvent-dependent polarization-switching behavior. Moreover, both forms show trapping of the photoinduced electron-transferred states upon light irradiation. These findings highlight the effectiveness of using enantiopure ligands in constructing polar crystals with versatile polarization-switching behavior.