Photo‐reversible oxygen binding of a cobalt schiff‐base complex with an axially coordinating photo‐isomerizable polymer ligand

The reversible binding of oxygen to N , N ′‐ethylene bis(salicylideneiminato) cobalt(II) (CoS), to which a photo‐isomerizable naphthalenyl vinylpyridine residue of copolymer 1 coordinated, was investigated. The E form of the naphthalenyl vinylpyridine residues coordinating to CoS, ( E )‐ 1 ‐CoS, showed photo‐reversible isomerization into the Z form, ( Z )‐ 1 ‐CoS, on direct ultraviolet (UV) irradiation in a range of 335–345 nm and vice versa on another UV irradiation in a range of 285–295 nm. Reversible change of oxygen‐binding affinity of 1 ‐CoS corresponding to the photo‐reversible E / Z isomerization of the naphthalenyl vinylpyridine residues was also observed in absorption spectra. Steric hindrance of the polymer chain of 1 on the coordination of the naphthalenyl vinylpyridine residue of ( Z )‐ 1 to CoS was thought to cause the decrease of oxygen‐binding affinity of ( Z )‐ 1 ‐CoS.