Cobalt coordination polymers regulated by in situ ligand transformation

A series of cobaltIJII) coordination polymers {; ; [CoIJL1)2(H2O)2]·4H2O·2DMF}; ; n (1 ; HL1 = 4-(3, 5- (dicyano-2, 6- dipyridyl)dihydropyridyl)benzoic acid ; DMF = N, N-dimethylformamide), {; ; [Co(L1a)2(H2O)2]·2H2O}; ; n (2, HL1a = 4-(3, 5-dicyano-terpyridyl)benzoic acid), and [Co3(μ3-OH)2(L1a)2(TP)(H2O)2]n (3, TPA = terephthalic acid) are reported, in which the conformation of the primary ligand L1 − has been regulated by in situ oxidative dehydrogenation into L1a− in different solvent systems. Single crystal structural analyses reveal that compound 1 exhibits a 44 -sql coordination layer structure constructed from cobalt centres and parent L1 − ligands ; compound 2 is constructed from Co2+ cations doubly connected by L1a− anions, which are generated in situ through oxidative dehydrogenation of L1 − ; while compound 3 features a rod-packing 3D network with a pcu-type topology, in which cobalt–oxygen chain units are interconnected by L1a− and TP2− mixed ligands. The formation mechanism of L1a− ligand via an in situ oxidative dehydrogenation reaction has been briefly discussed. This current study confirms that in situ ligand transformation is viable for controlled coordination polymer assembly, and is also adaptable to a more complexed ligand system.