Syntheses, solubilities and oxygen absorption properties of new cobalt(II) Schiff-base complexes

The syntheses, solubilities and oxygen absorption properties of cobalt(II) complexes of N,N'-bis(salicylidene)-2,2'-dimethyl-1,3-propanediimine ligand derivatives, termed CoSaldmpr, are reported. These are homologs of the well-known N,N'-bis(salicylidene)ethylenediiminocobalt(II) (CoSalen) complexes, in which a 2,2-dimethyl-1,3-propanediimino bridging group replaces the ethylenediimino bridging group of CoSalen. Solubility data and limited oxygen-carrying properties bf the complexes in 1-methyl-2-pyrrolidinone (NMP) solution, either alone or in the presence of 2-cyanopyridine (2 M) as an axial base, are reported. Oxygen transport of the solutions is tested with a flow system and a thermal swing process with O-2 absorption conditions of 37 degrees C and desorption conditions of 100-180 degrees C. The two CoSaldmpr complexes that are tested have higher solubilities and oxygen affinities than the CoSalen homologs. In NMP solution with 2 M 2-cyanopyridine axial base, loading of Co(3-methoxy-Saldmpr), measured in (g O-2/g solution) remains about 35% higher than Co(3-methoxy-Salen) for at least four absorption/desorption cycles. (C) 1997 Elsevier Science Ltd.