A Switchable Complex Ligand Exhibiting Photoinduced Valence Tautomerism

The crystal of a valence tautomeric cobalt complex, [Co(dbbq) 2 (bpym)]( 1 ) (dbbq = 3,6‐di‐ tert ‐butyl‐1,2‐benzoquinone and bpym = 2,2′‐bipyrimidine), have been obtained by reaction between Co 2 (CO) 8 and dbbq in the presence of the ligand bpym in a mixed solvent under an N 2 atmosphere. The magnetic behavior of complex 1 clearly indicates that electron transfer from the catecholate ligand to the Co III center occurs, which results in valence tautomers of [Co II (SQ) 2 (bpym)] with a transition temperature ( T 1/2 ) of 232(1) K. Photomagnetic studies show that complex 1 exhibits photoinduced valence tautomerism. The complex has the ability to coordinate and can be used as a photoswitchable building block.