Synthesis, structure and phenoxazinone synthase-like activity of three unprecedented alternating Co-Co 1D chains

Three new one-dimensional mixed valence coordination polymers {[Co III (L 1 ) 2 ][Co II (bpy) 2 ]·ClO 4 ·H 2 O} ∞ ( 1 ), {[Co III (L 1 ) 2 ][Co II (phen) 2 ]·ClO 4 ·H 2 O} ∞ ( 2 ) and {[Co III (L 2 ) 2 ][Co II (bpy)(CH 3 OH) 2 ]·ClO 4 ·H 2 O} ∞ ( 3 ) (H 2 L 1 = N -salicylidene- l -alanine, H 2 L 2 = N -salicylidene- l -phenylalanine, bpy = 2,2′-bipyridine and phen = 1,10-phenanthroline) have been synthesized. Structural analysis reveals that the hexa-coordinated Co III unit, [Co III (L 1 ) 2 ] − , formed by two binegative tridentate Schiff base ligands contains uncoordinated oxygen atoms in the pendent carboxylate arm which further link the neighboring [Co II (bpy) 2 ] 2+ units to produce the μ 1,3 syn - anti carboxylato bridged one-dimensional (1D) coordination polymer in complex 1 . Complexes 2 and 3 feature similar syn - anti carboxylato bridged one dimensional coordination polymers formed by joining of alternating Co II and Co III units. Using o -aminophenol (OAPH) as the substrate, the phenoxazinone synthase-like activity of the complexes has been studied and the turnover numbers ( k cat ) have been calculated to be 1.2, 11.5, and 2.7 h −1 for 1-3 , respectively. The mechanism of phenoxazinone synthase-like activity is proposed on the basis of mass spectral analysis, suggesting the cooperativity of Co II and Co III centres, i.e. , the Co II centre binds to the incoming substrate molecule, whereas the Co III centre is involved in electron transfer from the substrate to molecular oxygen. Three new one-dimensional Co II /Co III chains have been synthesized using N -salicylidene- l -alanine/ N -salicylidene- l -phenylalanine and 2,2′-bipyridine/1,10-phenanthroline. All three complexes exhibit phenoxazinone synthase-like activity.