μ-Polymethylene bridged dicobaloximes: Structural, photolysis and thermal decomposition properties

A series of μ-polymethylene bridged dicobaloxime complexes py(dmgH)2Co(CH2)nCo(dmgH)2, where n = 4, 5, 6, and 12 (1–4) were synthesized and characterized. Crystal structures of py(dmgH)2Co(CH2)4Co(dmgH)2py · 2CH2Cl2 (1 · 2CH2Cl2), py(dmgH)2Co(CH2)5Co(dmgH)2py (2), and py(dmgH)2Co(CH2)6Co(dmgH)2py · CH2Cl2 (3 · CH2Cl2) have been determined by X-ray diffraction. Their structural features are compared with those reported for monocobaloxime complexes and oligomethylene-bridged vitamin B12 dimer. 2-D layers or 3-D nets formed through intermolecular C–H⋯O interactions are observed in the molecular packing structures of 1 · 2CH2Cl2, 2, and 3 · CH2Cl2. The photolytic kinetic rates of the dicobaloximes were determined by UV–Vis spectroscopy and the products of photolytic solutions were characterized by ESI-MS. The results indicated that lengths of polymethylene have a little effect on the observed rate of the Co–C bond cleavage in our dicobaloxime complexes, while changing the solvent from methanol to ethanol has shown significant rate enhancement. In addition, TGA experiments for solid dicobaloxime complexes were performed to exam their thermal decomposition behaviors.