Cobalt(III) promoted ligand fusion reactions of thiobarbituric acid and 4,6-diamino-2-thiouracil (or 4-amino-2-thiouracil)

Novel cobalt(III) complexes containing three kinds of assembled ligands, L1L2=dapymt–tbba(2-), tbba–dapymt(1-) and apymt–tbba(1-) (H3tbba=thiobarbituric acid; Hdapymt=4,6-diamino-2-thiouracil; Hapymt=4-amino-2-thiouracil), were prepared from the mixed ligand systems, where L2 indicates the coordinated ligand to the Co(III) ion and L1 is a pendant ligand bonded to L2. These complexes were characterized by UV–Vis absorption spectra and NMR spectroscopy. The crystal structures of [Co(Htbba)(en)2]ClO4·2H2O (2) (en=ethane-1,2-diamine), [Co{dapymt–tbba(2-)}(en)2]ClO4·3H2O (3) and [Co{apymt–tbba(1-)}(en)2](ClO4)Cl·3H2O (5′) revealed that coordination occurs through the S(1) and N(1) donors of tbba and the latter complexes 3 and 5′ have an assembled ligand; a new bond is formed between the C(5) atom of tbba and the S(2) atom of dapymt or apymt. An intramolecular hydrogen bond between O(1) of tbba and NH of en was found in all crystals. An interesting intermolecular π–π stacking interaction was found in 5′.