Bistable complex formation systems consisting of biphenylene (BP) and redox-active organic molecules such as chloranil (CL) and TCNE have been experimentally and theoretically investigated, based on an intermolecular interaction which characteristically occurs in the electrogenerated dianions forming a π−π type charge-transfer (CT) complex. Initially, we examined the CT complex formation of CL2- and TCNE2- with hydrocarbons (BP, hexamethylbenzene (HMB), and anthracene (AN)). Spectroelectrochemistry evidently gave the intermolecular CT spectra in the CL2-−BP and TCNE2-−BP systems at 500 and 550 nm, respectively. The CT interaction between the dianions and BP was measured as the positive shift of the second reduction potential with increasing concentrations of BP. This behavior allowed the formation constants to be estimated as 33.9 and 20.3 dm3 mol-1 at 25 °C for the CL2- and TCNE2- complexes in CH2Cl2 containing 0.5 mol dm-3 tetrabutylammonium perchlorate, respectively. Temperature dependence of the forma...