Tetranuclear Cobalt Complexes as Nano‐Dimensional Template for Inclusion of Nitrophenols

This study describes properties of organized aromatic fluorophores present on two nano‐dimensional cobalt complexes. Two mixed‐valent cobalt tetranuclear oxido‐bridged complexes [(μ 2 ‐Htea) 2 (phen) 2 Co 2 (μ 3 ‐O) 2 Co 2 (phen) 2 ]Cl 2 .5H 2 O ( 1 ) and [(μ 2 ‐Htea) 2 (bpy) 2 Co 2 (μ 3 ‐O) 2 Co 2 (bpy) 2 ]Cl 2 .[Co(H 2 O) 6 ]Cl 2 . 5H 2 O ( 2 ) (Htea=dianion of triethanolamine, bpy=2,2′‐bipyridine, phen=1,10‐phenanthroline) having tetranuclear cations with end to end distance ∼1.69 nm and ∼1.62 nm respectively were characterized. These complexes are weakly fluorescent in solution and fluorescence of respective complexes decreases upon interactions with nitrophenols. Complexes from reactions of 1 and 2 with nitrophenols were isolated and structurally characterized. They also show lower fluorescence in solid state than respective parent complex due to oxygen‐π interactions. Complex 2 underwent cation exchange to form new tetranuclear oxido cobalt complexes possessing [MCl 4 ] 2− ( M=Zn or Cd) anion.