The present contribution reviews the synthesis and properties of complexes including redox-active dioxolene ligands as well as its analogues, diiminosemiquinonato, and dithiolene ligands. This review first summarizes the structural and electronic features of new molecular complexes as a building block for constructing electronically labile molecular assemblies. Ligand-based mixed valence (LBMV) state has been realized both in mononuclear chromium and pentanuclear cobalt complexes. Second topic will be on the construction of molecular assemblies integrated by intermolecular stacking or charge-transfer interactions, clusterization, and ligand-unsupported M-M bonds. The formation of a thin film which acts as an active layer of a field-effect transistor will also be described. Final attention is drawn to the use of the redox-active complexes for the construction of stimuli-responsive molecular assemblies. The review will demonstrate recent developments of molecular assemblies that show macroscopic phase transition or phase transformation triggered by intramolecular electron transfer or redox reaction in solid, liquid, and liquid crystals.