Dinuclear cobalt complexes with an asymmetric biphenyl bridging ligand, [Co2(LFtBu)(bpqa)2](PF6)2 (H4LFtBu = 5-fluoro-5′-tert-butyl-3,3′,4,4′-tetrahydroxybiphenyl, bpqa = bis(2-pyridylmethyl)(2-quinolylmethyl)amine): Spectroscopic, electrochemical and magnetic characterization

•For [Co2(LFtBu)(bpqa)2](PF6)2, was isolated with a mixed valence of electronic state of lsCoIII-[Cat-Sq]-hsCoII (Cat: catechol, Sq: semiquinone).•The order of strength of electron withdrawing ability is F > H > t-Bu and Fig. 5 shows that the catecholate redox waves with the higher strength of electron withdrawing substituent group are shifted more to the positive direction side. That means that the electronic state lsCoIII-[Cat-Cat]-lsCoIII in [Co2(LFtBu)(bpqa)2](PF6)2, which is due to smaller bulkiness (steric hindrance) of terminal ligand bpqa than that of tqa, easy to change lsCoIII-[Cat-Sq]-hsCoII.