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N,N′-Bis(2,2′-bipyridine-6-ylmethyl)-2,2′-biphenylenediamines: A Tuneable Ligand Scaffold for Room Temperature Fe2+ SCO Complexes



Condensation and subsequent reduction of 2,2′-diaminobiphenyls 5 with 6′- and 5′-substituted 6-carbaldehyde-2,2′-bipyridines 4 yielded N,N′-bis(2,2′-bipyridine-6-ylmethyl)-2,2′-biphenyl-enediamines 7, which were employed as hexadendate ligands with N6 donor sets in the synthesis of dicationic [Fe2+(76N)] complexes 8. Dependent on the substitution pattern the respective complexes are found in the HS state (8b and 8c) or show SCO behaviour. By means of temperature-dependent susceptibility measurements, usingEvans' method, the thermodynamic parameters ΔH, ΔS and T1/2 for the SCO have been determined. T1/2 as well as ΔH are remarkably susceptible to substitution next to the central C–C bond of the biphenyl bridge.