Photoswitchable stable charge-distributed states in a new cobalt complex exhibiting photo-induced valence tautomerism. (16th October 2015)

• Record Type: Journal Article
• Authors: Slota, Michael; Blankenhorn, Marian; Heintze, Eric; Vu, Minh; Hübner, Ralph; Bogani, Lapo
• Is Part Of: Faraday discussions. Volume 185(2015)
• Page Start: 347
• Page End: 359
• Publication Date: 2015-10-16
• Subjects: Chemistry -- Periodicals; Metallurgy -- Periodicals; Electrochemistry -- Periodicals; 540
• DOI: 10.1039/c5fd00088b
• Languages: English
• ISSNs: 1359-6640

Abstract

Abstract : We report the synthesis and magnetic and photomagnetic behaviour of a novel valence tautomeric cobalt complex, [Co(3, 5-dbbq)2 (μ-bpym)] (1 ) (3, 5-dbbq = 3, 5-di- tert -butyl-1, 2-benzoquinone and μ-bpym = 2, 2′-bipyrimidine). The synthesis is performed by reacting Co2 (CO)8 and μ-bpym in the presence of the ligand 3, 5-dbbq in a mixed solvent under inert atmosphere. The magnetic behavior clearly shows the presence of electron transfer from the catecholate ligand to the cobalt center, producing valence tautomers of [Co II (SQ)2 ] with a transition temperature ( T 1/2 ) of 215 K. Photomagnetic studies, performed via both SQUID magnetometry and X-band electron paramagnetic resonance, show the clear presence of photoinduced valence tautomerism, at temperatures considerably higher than previous systems. A metastable charge distribution is observed, strengthening previous investigations on the character of mixed valence ligands. Entropy-driven valence tautomeric interconversion is observed, and drives the transition to the most stable charge distribution. The complex has the ability to coordinate and can be used as a photoswitchable building block, with the photomagnetic characterisation evidencing a metastable state lifetime of the photo-induced valence tautomeric process of ca. 2.9 × 10 4 s below 20 K. The observed yields are higher than ones in similar systems, showing that tiny changes in the molecular structures may have a huge impact.