H3O2–, O22– and O2˙– bridging ligands in cobalt(iii) complexes of an acyclic phenolate-hinged dinucleating ligandElectronic supplementary information (ESI) available: Fig. S1: Raman spectra of [Co2(bpbp)(µ-O2)(µ-CH3CO2)]2+ (top) and the superoxo-bridged complex [Co2(bpbp)(µ-O2)(µ-CH3CO2)]3+ (bottom). Fig. S2: ESI-MS spectra of the peroxo bridged [Co2(bpbp)(µ-O2)(µ-CH3CO2)]2+. Fig. S3: ESI-MS spectrum of the superoxo bridged [Co2(bpbp)(µ-O2)(µ-CH3CO2)]3+. See http://www.rsc.org/suppdata/dt/b2/b210091f/